Public Disclosure Authorized LATENDissemination Note # 5 An Analysisof Flooding in the ParaniYParaguay River Basin September1993 Public Disclosure Authorized Public Disclosure Authorized 19820 September 1993 Public Disclosure Authorized ..N . ... ,a,g-X Z S~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~. RobertJ. Anderson,Jr. Nelsonda FrancaRibeirodos Santos HenryF.Diaz The World Bank Latin America TechnicalDepartment EnvironmentDivision t LATEN Dissemination Note # 5 An Analysis of Flooding in the Parana'/Paraguay River Basin September 1993 Robert J. Anderson, Jr. Nelson da Franca Ribeiro dos Santos Henry F. Diaz The World Bank Latin America & the Caribbean Technical Department Environment Division FOREWORD Late in 1991, unusually heavy rain began to fall in the catchment areas of the Parana, Paraguay, and Uruguay Rivers. In 'normalH years, the average precipitation in this basin varies between 200 mm per year in the western part, the mountain range of the Andes, and 2,000 mm in the southeasternpart, consisting of the Iguazu River basin. The rains are almost incessant during the year in the southern and southeasternparts of the basin. This rainfall distributionproduces high river flows in the basin that begin in October/Novemberand peak between February and June/July. As in most flood years, torrential downpoursin the Brazilian part of the Paran; River Basin between January and May 1992 produced massive flows in the Parana River. In addition, heavy rains in the middle to lower Paraguay River basin during March and May led to peak flows in this river that were coincident with the peak flows of the Parana River. The Parana thus peaked in April/May 1992 at almost four times the yearly average. The initial data on the 1992 flood indicate that the peak flow was about 56000 m3/s. This caused serious infrastructure damage and forced the evacuation of about 120,000 people from seven Argentine provinces - Buenos Aires, Chaco, Corrientes, Entre Rios, Formosa, Misiones, and Santa Fe. Although it is too early to attempt a precise estimate, indications are that the damage may be on the same order of magnitudeas that caused by the 1983 flood, which cost about US$ 1 billion to repair. Apart from the capital stock damage, Argentina will also face substantialeconomic losses (e.g., lost production of grains, livestock, and cotton). Losses in Paraguay and Brazil were also severe. In September, 1992, the World Bank approved a loan to Argentina to cover a portion of the costs of repairing the damage due to this flood. The Bank also initiated the identification of a possible subsequent operation that would aim at improving Argentina's preparedness to deal with severe flooding. During the processing of the rehabilitation operation, the Bank became aware of satellite imagery evidence that heavy siltation appears to be occurring along stretches of the Parani that are bordered by agriculture. This led the senior managementof the LAC Region to question whether deforestation may be making the basin more prone to floods. Regional senior management asked the Region's Technical Department to examine this issue. Disentangling the impact of deforestationfrom other factors on flooding is a difficultundertaking under the best of circumstances. The quantity and quality of historical data on land-use changes and other interventions affecting the hydrology of the basin and basic hydrologic data are reasonably good by developing country standards. Records of Parana River flows exist since 1901 and land-use data extend back perhaps 40 years. There are, however, serious gaps in meteorologicalinformation, and the hydrology of this large basin is extremely complex. This paper, writtenby a team led by RobertJ. Anderson,Jr., formerlyof LATEN,and comprisedby Dr. Nelsonda Franca Ribeiro dos Santosof the Organizationof AmericanStates,and Dr. Henry F. Diaz of the NationalOceanicand AtmosphericAdministration,draws upon these data to reach preliminaryconclusionsabout the recent frequencyand severityof flooding,and about the possiblerole that land use changesmay be playing. Duringthe preparationof the paper, Drs. Anderson,da Franca Ribeirodos Santos,and Diaz benefittedfrom the commentsof workshopin whichseveral distinguishedscientistsand practitionersparticipated.' While the data are far from perfect, the evidenceexaminedindicates basin has indeedbeen both more that floodingin the ParanAfParaguay frequentand more severein recent years. Ten-yearflood dischargerates are now over 15%greater than they were in the early years of the 20th century. Mean dischargerates and extremelow dischargerates are higher too. The analysisalso showsthat changesin precipitationrates and patterns are by far the mostimportantexplanatoryfactorsin these observedchangesin streamflow. Recentprecipitationhas been higherin the wet season,and lowerin the dry season. Reservoirson the Upper Parandhavealso playeda role, particularly in increasinglow flows. When these other factorsare held constant,there is no systematicevidencethat any other factorsuch as land use changesin the upperbasin is playinga significantrole in flooding. Theseconclusionsnotwithstanding,the apparentlack of association betweenfloodingand land use changesis no reason to be complacentabout these changes. Data examinedduring the course of the researchparticularlythe satelliteimagerysuggestiveof heavy sedimentloads suggestthat land use changesin the upper basins maybe exactinglarge privateand socialcosts in terms of lost productivityin agricultureand infrastructure,and lost biodiversity. Like other papers in this 'DisseminationNoteswseries, the findings, interpretations,and conclusionsexpressedare entirelythose of the author(s) and shouldnot be attributedto the WorldBank, membersof its Board of ExecutiveDirectors,or the countriesthey represent. DennisJ. Mahar Division Chief EnvironmentDivision Latin American& the Caribbean TechnicalDepartment (Orgaiion includedDr. KirkRodgers in additonto theauthors, Workshop participants, of American States), Professor Rafael Bras (Massahusetts Instituteof Technology), Mr. StephenOliver(IBRD),Mr. ArmandoAraujo(IBRD),and Mr. Sri-RamAiyer (IBRD). AN ANALYSISOF FLOODING IN TIHE RIVER BASIN PARANA/PARAGUAY Robert J. Anderson, Jr. Nelson da Franca Ribeiro dos Santos Henry F. Diaz' 'The authors are respectively Principal Sector Economist, India Country Department, The World Bank, Water Resources Senior Specialist, Department of Regional Developmentand Environment, and Climatologist,National Oceanic and AtmosphericAdministration. Dr. Anderson led the team and was prinarily responsiblefor analysis and for preparation of the main body of the paper. Dr. da Franca Ribeiro dos Santos was primarily responsible for the preparation of Annexes A and C. Dr. Diaz was primarily responsible for preparation of Annex B. The views expressed in this paper are solely those of the authors and do not necessarily reflect the views of organizations with which they are associated. AN ANALYSISOF FLOODINGIN THE RIVER BASIN PARANAIPARAGUAY Introduction 1. Torrentialdownpoursin the Upperand MiddleParanaRiver BasinbetweenDecember 1991and May 1992and in the Middle and Lower ParaguayRiver BasinbetweenMarch and Mayproducedmassivefloodingin Argentina,Brazil, and Paraguay.These floodscaused seriousinfrastructuredamageand forcedthe evacuationof about 120000 peoplefrom the Argentineanprovincesof BuenosAires, Chaco, Corrientes,Entre Rios, Formosa, Misiones, and SantaFe, as shown. In Paraguay,more than 70 000 peoplewere evacuatedin the cities of Asunci6n,Concepcion,Alberdi,and Pilar. In Brazi, heavyrains and the floodsin these basinsforcedthe evacuationof thousandsof peopleand also causedseriousinfrastructure damage. TableI: MostSevereMaximumFloods,1901-92 ParanA-Posadas Year 1905 1983 1992 1990 1936 1987 1966 1923 1929 1982 date 45 000 May 25 m 3 /s 43 330 41 850 37 500 34 500 34 500 33 900 33 750 32 450 31 350 July 12 June 25 Jan 25 June 12 May 23 Feb 23 June 21 March 5 Dec 5 Paraguay-Asunci6n Year 1983 1905 1992 1919 1982 1988 1931 1912 1979 1913 m3/s date 11 740 May 29 11 170 10 530 8 770 8 730 8 500 8 240 7 820 7 580 7 420 June 23 June 1 June 13 July 29 June 10 July 1 Jan 15 June 14 May 15 Parang-Corrientes Year 1983 1992 1905 1966 1990 1982 1912 1929 1987 1923 date 54 700 July 18 m 3 /s 50 800 50 000 43 800 43 800 42 600 39 100 39 100 38 900 38 100 June 8 June 5 March 1 Feb 1 Dec 11 Jan 7 March 10 May 30 June 27 The 1992floodscappeda decadeof unusual(by historicalstandards)flood activity. 2. Five (5) of the ten (10) most severe (measuredin terms of annualdaily peak discharge) floodsrecordedin the Parani/ParaguayRiver Basinduring this centuryhave occurredsince 1982 (TableI). This apparentrecent "bunching"of relativelyseriousflood eventshas led to 3. speculationthat some systematicstructuralchanges(as opposedto purely randomvariations) may have occurredthat may have made/bemaldngthe basin more prone to flooding. Any such changes,if present, clearly wouldhave far-reachingimplicationsfor the future developmentof the central-easternregionof SouthAmerica. The larger La Plata Basin, whichis comprisedby the Parand, Paraguay,and UruguayRiver Basinswith an area of 3.1 millionkm2 in Argentina,Bolivia,Brazil, Paraguay,and Uruguayconstitutesthe economic River Basin encompasses2.6 million km2 (84% heart of this region. The ParanA/Paraguay of the totalarea of the La Plata Basin)in the four countriesexcept Uruguay. It containsa multitudeof naturalresources: water, minerals,and arable soils. As a result, the area has the most developedagriculturaland industrialzonesof the continent;it holds some of the moreimportanthydroelectricdams in Latin America(Itaipuand Yacyreta);it containsan extensiveriverine and terrestrialtransportationnetwork;it generatesaround 80% of the Gross DomesticProductof the countriesand it is home to some 100 millionpeople.' Three majorchangeshave occurredsincethe 1960sthat potentiallycould affect the 4. hydrometeorology of the region: o Agriculturaland industrialproductionin the basin has grownrapidlyand the frontierof agricultureand livestockproductionexpanded. In Brazil, land in the UpperParana Basinhas been convertedfrom coffeeplantationsto soybeansand sugar canefor alcoholfuel production. In the ParaguayBasin, deforestationand the expansionof the agriculturalfrontier to establish croplandand pasture, have been extensivein both the Brazilianand Paraguayanportionsof the basin. These land use changesmay have increased runoff, streamflow,siltationand may be implicatedin recent flood episodes. O Hydroelectricdevelopment,mostlyin the Upper Parara Basin, has expanded significantly. Some20 hydroelectricpowerplants of more than 1000MW includingbinationalplants for Brazil-Paraguayand Argentina-Paraguayhave been installedor are under construction. Overallpotentialin the basin is now approximately42,000 MW and the total amountof water stored in the reservoirsis approximately350,000hm3 , of which 120,000hm3 are active storage. Reservoiroperationmay have increasedthe flow of the ParanaRiver at the confluencewith the Paraguayat the time that the ParaguayRiver peaks. o Wet season rainfallin the region of the Paranaand ParaguayBasinshas been relativelyhigh sincethe early 1980s,raising the possibilitythat a changein climate (as opposedto simplerandomvariationin precipitation)may have occurred. It also begs the questionwhetherany suchchangecould be due to humaninfluenceson the environment(e.g., increasedconcentrationsof atmospheric'greenhouse' gases, worldwidedeforestation,stratosphericozone depletion,and increasesin anthropogenicaerosol loadingof the atmosphere could be contributingto these recent precipitationextremes). Basinis containedin AnnexA. 'A basicdescriptionof the ParanL/Paraguay 2 This paper examines some of the evidence bearing on these developments and their 5. possible effects on the hydrometeorologyof the Basin. In particular, it considers two questions' i Has flooding in the basin become more frequent and/or more severe? ii Can observed variations in streamflow in the basin be explained by random variations in precipitationalone, or do other factors such as changes in climate, land use, or operations of reservoirs also appear to have played a role? Definitive answers to these questions are beyond the reach of the paper given the present state of the data. This limitation notwithstanding,however, the evidence is reasonably strong that flooding was significantly(in a strict statistical sense) more frequent and more severe in recent years, and that this was due primarily to unusually concentrated (in time and space) precipitation. There is no strong statistical evidence to indicate that any other factor played a significant role in flooding. There is, however, some evidence that when precipitation is not extremely high, some change has taken place that causes streamflow to be greater than otherwise would have been expected. Has Flooding Become More Frequent or Severe? 6. The data presently available only permit a partial and preliminary analysis of the frequency and severity of flooding in the Basin. This analysis is based on examination of discharge/stage extrema (i.e., maxima and minima) and mean discharges at a limited number of stations Annual Maximum Daily Discharges/Stages Since 1900 Data on annual maximum daily discharge rates/stages at Corrientes are shown in 7. Figure 1.2 Other things being equal, if flooding were no more frequent in the latter years of the sample than in the early years, the proportion of the time that peak discharges exceed a given level would be about the same as in the earlier years of the sample. Visual inspection of the data shown in Figures 1 is not conclusive, but does suggest some bunching of relatively high peak discharge rates toward the end of the sample period. A statistical analysis of the data in Annex C for Corrientes and other stations (based on binomial probability distributions estimated from the data in these tables) rejects the hypothesis that the frequency of extraordinary (i.e.. ten-year) floods was the same in the latter years of the sample (Table II). This conclusion is not sensitive to the point at which the sample is divided in the cases of Corrientes, Posadas, and Porto Murtinho. The frequency of extraordinary 2Annualmaximumdaily dischargerates/stagesat Corrientes,Posadas,Asuncidn,Porto Murtinho, Ladario,Guaira,and Jupia are reportedin AnnexC. 3 60000 50000 AII 40000 20000 t0000 0 i: :IiI,,ii:nt itt uuuu:i tt uu: uI 111111: Wtn F"igure1: Corrientes - Annual MaximumDaily Discharge Rates (m3Is) floodsis significantlyhigherin each of theseplaces over all divisionsof the sample,while floodingin Guaira,Asunci6n,and Ladaniois significantlymore frequentpi Ix when the sampleis split at 1980. Splittingthe data at 1970or 1960yieldsinconclusiveresults at these latter sites. 8. To determinewhetherthe seveity o loo~dsappearsto be increasing,log normal cumulativedistributionfunctionswere fitted to the maximumdischargedata over two sample periods of equal length (1901-46and 1947-92)for Posadasand Corrientesand the resulting fits testedto determinewhetherthe distributionshad changedsignificantlybetweenearly and later sampleperiods.3 The tests reject the null hypothesisthat the post-1947cumulative 3Thecumulative distribution functions werefittedby estimating thefollowingexpression by ordinary regressionmethods, N+1 whereF, is the reportedmaximumdailydischargerate in yeart, N is the totalnumberof yearsin the subsample,R, is the rank in the subsampleCinorder of decreasingdischargerates,withthe highest dischargeraterankedfirst, andso forth)of thete observation,ande, is an errorterm. An analysisof variancetest wasperformedin the contextof theseregressions.Thistest partitionsthe data intotwo 4 Table II: Probability Analysis of Frequency of Extraordinary Floods River SampleSplit Station Asuncion 0.00972 0.07492 0.22555 0.00001 0.00001 0.00177 Ladario 0.02095 0.01069 0.25724 Corrientes Posadas Guaira 0.00318 0.00021 0.16540 0.02346 0.01193 0.71984 0.00120 0.00133 0.37953 Porto Murthinho Parana 1960 1970 1980 Paraguay At Table m: Estimated Flood Discharges (m31s) Corresponding to Alternative Return Periods (years) StationlSample Significance Subperiod Level of Test Posadas 1901-92 1901-46 1947-92 Corrientes 1901-92 1901-46 ; 1947-92 l Return Period (Years) 10 20 50 100 32700 32653 33653 36986 36968 38273 42653 42672 44382 46939 46987 49002 39204 37542 44584 42659 51696 49423 57076 54540 41734 47694 55574 61535 0.0990 0.0000 distribution function is the same as the pre-1947 distribution function, although the significance level of the test at Posadas is only about 10% (Table Im). At both sites, higher flood peaks were associated with any given level of probability in the post-1947 period, or equivalently, the flood for any given return period was more severe. 9. While the samples of data analyzed as described above span relatively long time periods (i.e., 92 years in Corrientes and Posadas, and between 49 and 89 years at other locations), it should be kept in mind that a longer sample period might well lead to different subperiods(in this case of equal length)and tests whetherthe estimatedcoefficientsare, for statistical purposes,identicalover the two subperiods. 5 conclusions.There exist referencesto extraordinaryfloodsthat occurredin Corrientesin 1612and 1748(stage< 10.50 m), as well as in 1812, 1858, and 1878. Table IV reports extraordinaryfloodsin Corrientesprior to 1905in comparisonwith the floodsof 1983and 1992. It is not clear whetherthis is a completerecord of extraordinaryfloods during the 1800s.However,these three large floodsduringthe 1800sunderscorethe point that, if the statisticalrecord could be extendedback into the 1800s,the conclusionsconcerning frequencyand severitystatedabove mightnot stand. TableIV:ExtraordinaryFloodsin CorrientesBeforePrior to 1905Comparedto the Floodsof 1905 and 1992 Stage lGM1 m m m3 /s 1812 1983 1858 1878 9.53 9.02 8.93 8.65 50.93 50.42 50.33 50.05 58 000 54 700 52 000 51 000 1992 8.64 50.04 50 800 1905 8.57 49.94 50 000 Year Discharge sboveswalevel-Instituto I-Gage-dacUm Gcog~iSco MiIk, Aretn Other StreamflowCharacterisics 10. Two other streamflowcharacteristics,annualminimumdaily dischargerates and mean monthlydischargerates were examinedto determinewhetherchangesappearto have occurredin theseparametersas well. Figure 2 suggeststhat annual minimumdischargerates have tendedto increase. Regressionestimationfittinglog normalcumulativeprobability distributionsto the annual minimumdaily dischargerate data for Corrientesand Posadasand statisticaltestingconfirmsthat minimumdaily flowswere significantlyhigherat these stationsduring the latter part of the sampleperiod.4 'Data on annualminimumdaily dischargerates/stagesat Corrientes,Posadas, Guaira, Asunci6n, Porto Murtinho, and Ladario are reported in Annex C. Estimationand testing was carried out in accordancewith the proceduredescribedin footnote3 above. 6 258000- 20000 15000 10000 5000 20.1n a Flgure 2: Annual Minimum Discharge Rates (m3Is) at Corrientes 4 1910-92,g ".0 190_ -9 5.0 Jan Feb Mar Apr May Jun Jul Aug Gep Oct Nov Dec at Corrientes Figure 3: Monthly Mean DischargeRates (m3 /sec) 7 11. Figure 3 showsa distinctshift in the patternof mean monthlyflowsin Corrientes over two subperiods(1901-67and 1968-92).5Visualinspectionof the figure suggeststhat two changeshave occurred. First, mean dischargesseemgenerallyto have increased. Mean annualdischargewas between15 and 20 percent higherduring the secondsubperiod(196892) than in the earlier period. Second,there was a shift in the intra-annualpatternof discharges,with mean monthlyflows becomingmore uniformover the year due to significantlyhigher (in the secondsubperiod)mean flowsin the monthsof May through December. This latter shift in the distributionis what wouldbe expectedto occur as a result of the operationsof reservoirsin the UpperBasin. 12. In sum, the analysesdescribedabove suggestthat the entire streamflowdistribution was shiftedtowardhighervaluesin the later years of the sampleperiod. Maximumannual daily dischargerates, minimumannualdaily dischargerates, and mean annualdaily dischargerates all were higherin the later years of the sampleperiod. Thereis also some evidenceof a changein the intra-annualdistributionof streamflow. What Accountsfor Greater FloodFrequency and Severity? 13. The dischargedata reviewedabovethus are generallyconsistentwith the hypothesis that floodswere both more frequentand more severein the latter years of this centurythan in the earlier years. It is of fundamentalimportancefor the future developmentof the Basin to try to understandwhetherthis is due to purelyrandomvariationsin precipitationor of the basin. whetherit representsa structuralchangein the hydrometeorology 14. This is a complexundertaking. Runoffwithina basin dependsnot only on the amountof rainfall but also upon its temporaldistribution,vegetal cover, evapotranspiration, infiltrationrates, soil moisturestoragecapacity,the amountof moisturein storage, surface storage,rate of groundwateroutflow,lossesdue to deep percolation,and a host of other factors. Many of theseparametersare interrelated. An extensiveprogramof reservoir constructionover the sampleperiodon the UpperParara introducesadditionalcomplications. For thesereasons, the analysispresentedhere is indicative,but not conclusive. UnusuallyHeavyPrecipitation 15. The most obviouspossibleexplanationfor recent heavy floodingis that it could have been"causedby too much rain fallingin too short a period, or prolongedrain fallingon land that is already saturatedwith water."6 Figure 4 showsan annualtime series of precipitation anomalies(i.e., deviationsof precipitationfrom its meanvalue) over the region of the Basinsduring a three-monthperiod (March-May)derivedfrom stationdata ParanA/Paraguay 'Data on mean monthlyflowsare presentedin AnnexA. LawrenceS. *TheRecentBangladeshFlood Disaster Was No Causedby Deforestation %Hamilton, Alone." EnvironmentalConservation,1988,pp 369-370. 8 4 ma 2- .~~~~~a iO 20 30 40 50 60 70 |_PRECIP Figure4: March-May Preupitation Anomalies and Annual Maximum 80 90 .MAXFLOW| Daily Dischages at Corrientes (Normnalized) within this region.' Clearly, the temporal behavior of the rainfall anomaly sen'es agrees quite closely with that of the peak annual flow series. The correlation between the two series, weighted by the number of station at which measurements were taken for each observation, is roughly 0.95. This means that variations in weighted precipitation explain about 90% of the variation in the annual weighted maximum daiy discharge rate series. The correlation between the two unweighted series is about 0.67. Ilhe March-May period was chosen because five of the ten maximum discharge rates recorded at Corrientes occurred in May, June or July. Two others occurred in March. See Table I. 9 TableV: RegressionResultsfor MonthlyPrecipitationand MeanMonthlyDischargeRateData Regression1 Coefficient Constant PRECIP PRECIP(-1) PRECIP(-2) PRECIP(-3) PRECIP(4) PRECIP(-S) PRECIP(-6) AR(1) R2 Dubin-Watson Observations 0.6241 0.0256 0.0423 0.0228 0.0113 0.0129 0.0140 0.0202 0.8004 0.6520 1094 Regression2 t-statistic 0.8821 7.9090 12.6846 6.7791 3.3709 388398 4.1640 6.3313 Coefficient t-statistic 11.4019 0.0107 0.0325 0.0136 0.0029 0.0038 0.0027 0.0039 0.7889 0.9048 2.0502 1093 13.5376 5.0276 15.8547 6.5997 1.4015 1.8169 1.3181 1.8969 40.3219 16. Monthlydata on precipitationand streamflowalso shedsome light on the extent to which precipitationaccountsfor apparentdifferencesin streamflowcharacteristics. Two regressionsreportedin Table V suggestthe samerelativelytight relationshipbetween precipitationand streamflowevidentin the annualdata describedabove.' In the first regression,monthlymean dischargerates are regressedon monthlyprecipitationanomaliesin the current monthand six precedingmonths. The multiplecorrelationbetweenthe estimated linear combinationof explanatoryvariablesand streamflowis a little greaterthan 0.7. The secondregressioncorrects for autocorrelationin residuals,increasingthe multiplecorrelation coefficientto about 0.9. of the Basin Changesin the Structureof the Hydrometeorology 17. It is clear that variationsin precipitationexplaina great deal of the apparentshift in streamflowdistributionparametersand, more specifically,the recent spate of severeflooding in the Basin. This does not mean that other factors were unimportant. Three possibilities merit consideration:(i) climatechangesleadingto increasedprecipitation,particularlyin cntical monthsfor flooding;(ii) reservoirconstructionand operation;and (iii) changesin land use that increaserunoff. reportedin paragraph15basedon annual 'Tle regressionsreportedin TableV, likethe correlation wasthe numberof data, are weightedregressions.The weightingfactorappliedto eachobservation stationsreportingprecipitationobservationsin eachmonthdividedby the meannumberof stations reportedherebasedonmonthlydataalsoholdfor regressionsdonewith reporting.Alloftheconclusions data. unweighted 10 440.00 40. 00 20.00 l0.00 Jan Pab Mar APr way Jun Ju I Aug Sep OCt Nov Des Figure 5: Mean MonthlyPrecipitation (mm) 18. Climate Change. Monthly precipitation data suggest that the rainy season has become somewhat wetter and the dry season slightly drier (Figure 5). Also note that relatively large positive March-May precipitation were more frequent in the 1980s and early 1990s than in earlier periods (Figure 3). These changes may represent a purely random perturbation (a statistically unlikely one, to be sure), a cyclical fluctuation, or a change in the climate of the region. 19. The climate change hypothesis is broadly consistent with extensive recent work on predicting global climate change and analyzing large scale atmospheric disturbances. Global climate models, developed to study the effect of accumulationof greenhouse gases in the earth's atmosphere, generally predict that precipitationin the vicinity of the basin will increase in the early and late months of the calendar year, as seems to be occurring (Figure 5). These models also predict that the El Nino phenomenon, which is empirically closely related to flooding in the ParanA/ParaguayBasin,' will intensify. However, due to the high variability present in precipitation data, considerably more data would be needed to discriminate statistically among the random perturbation, cyclical fluctuation, and structural climate change hypotheses. 20. Reservoirs. There has been a considerable expansion of active storage capacity in the Upper Parana River Basin over the last 40 years. Active storage has increased from 2500 hm3 in 1956, to over 150,000 hm3 today (see Table VI). Much of this capacity (approximately 125,000 hm3) came on line during the 1970s and 1980s. These reservoirs 'AnnexB describesthe relationshipbetweenEl Ninophenomenaandfloodingin theParanTlParaguay Basin. 11 reducepeak floodsby roughly 10-20%during heavyrainfall months,and increaseninimum flows during the dry months. This may accountfor the fact that the statisticalresults on the stabilityof maximumdischargerates as betweenearly and late periods are weakerat Posadas than they are at Corrientes, whichreceivesunregulatedflows from the ParaguayRiver and is well belowthe last reservoiron the ParanaRiver.10 The effectof reservoirsis also reflectedin the data on low flowextrema: most of the extremelow flows recordedfrom 1901in Posadasand Corrientesoccurredprior to 1970. Table VI: Brazilian Reservoirs - Upper Parana River Basin' Active Year Storge hm' 1956 1958 1962 1963 1963 1966 1968 1969 1970 1971 1973 1973 1973 1974 1975 1975 1975 1976 1978 1979 1980 1980 1980 1982 1982 1982 1983 1984 2500 0 2890 16089 2556 04 1250 IS0 045 1295 12866 296 233 50 00 310 Name of hm' the Dam 2500 2960 850 1939 2449 24999 249 6399 9444 0739 3605 3901 134 C84 S1994 2434 1134 924 124 5724 9974 74 700 790 204 13600 250 600 300 12700 00 800 80 1. DmimCauhw tmulated 108S74 110874 111674 1S954 Pizoto C o lurann Furnas Bar Bonita raninha upin Esiruito Xavates 'puar( SolIhrn PoateNova Pto Colombia Voha Grand PrDmiuJo ixndo ahoono aprn Sio Smbo AguaVermIelba InhiPrn Faz do Atia T874 ru Inrbc. E io NovaAvanhandava River Grande Grand0 PSapn net. randc paner g iota rnd u runde guaqu ne Mt. Santiago ag 21. Prior to 1970, mean monthlydischargesof the ParanaRiver at Posadaswere considerablylower during the monthswhen meanmonthlydischargesof the ParaguayRiver reached their highestlevels. Since 1970, however,mean monthlydischargerates at Posadas have increasedaround 15 to 30% during the mid monthsof the year, and hencecoincide with the period of high average dischargerates in the ParaguayRiver. This changein the "MThe resultson extremelow flows are equallystrongat both sites,however. 12 monthly distribution of streamflow could also be due to a change in the monthly distribution of precipitation, or in the intertemporal relationship between precipitation and streamflow in the Upper Parana Basin. Deforestation/Land Use Changes. Significant changes in land use have taken place 22. over the last 100 years in the upper and middle basins of both the Parana and Paraguay Rivers. Most of the land use changes in the Upper Paranr Basin took place in the 1930s and 1940s when land was put into coffee production, and again in the late 1960s when land was converted from coffee plantations to production of soybeans and sugar cane. In the Paraguay River Basin, particularly in Western Brazil and Eastern Paraguay where agricultural potential is greatest, there has been a progressive conversion of forest to agricultural land. In Paraguay in 1945, approximately 55% of the land area of the Eastern Region was forested. During the 1960s, the Paraguayan Government, under pressure to respond to growing demands for employment and income, began to encourage the expansion of the agricultural frontier to the east. As a consequence, forested areas in this region declined to about 45% by the mid-to-late 1960s, 35% by the mid-1970s, 25% by the mid-1980s, and only about 15% by the early 1990s.1' Other things being equal, one would expect to observe an increase in streamflow 23. associated with deforestation and/or other land use changes that tend to increase runoff.'2 The results on flooding frequency and severity reported above are thus broadly consistent with the land use effect hypothesis. They are, however, also consistent with the heavy rainfall hypothesis. Some additional examination of the data is thus necessary to discriminate between these hypotheses. Consistent time series data on land use in the Basin are not presently available. It is not possible, therefore, to proceed directly by introducing land use variables into the regression analysis to determine whether or not they contribute significantly to explaining streamflow variations. Inferences of the possible effect of land use changes can only be drawn indirecty by analyzing whether the rainfall-runoff relationship seems to have changed in ways that could be explained by land use changes. To this end, note that if land use change were an important contributor to streamfiow, the relationship between precipitation and streamflow should differ between early and late subsamples: in particular, the same rainfall should generate more streamflow in the later part of the sample period than in the early part. This possibility was investigated using the two sets of data (i.e., annual and monthly) 24. on precipitation and streamflow analyzed above. First, the annual data on March-May "Bozzano,BernadoandJorg H. Weik.El Avancede la Deforestaciony el ImpactoEconomico.Serie N. 12. Proyectode Planificaciondel Manejode los RecursosNaturales(MAG/GT-GTZ).Asunci6n, Noviembre1992. 'A detaileddiscussionof hypothesesconcerningrelationshipsbetweenland use changesand runoff is availablein Hamilton,LawrenceS. TropicalForestedWatersheds:Hydrologicand Soil Responseto MajorUses or Conversions,(Boulder: WestviewPress), 1983. 13 Table VII: Analysis of Variance Test for Stability in the Relationship Between Precipitation Anomalies and Annual Maximum Daily Discharge Rates (F-test Significance Level) Sample Period 1901-92 Sample Break Point 1930 1940 1950 1960 1965 1970 1975 1980 1985 Regressions CONSTANT PRECIP R2 Durbin Watson 0.3481 0.0986 0.0344 0.0126 0.0314 0.0025 0.0003 30581.507 112.189 0.8538 1.5397 1901-60 i 1961-92 0.7863 0.5517 0.8292 0.2996 0.1717 0.8691 27670.084 35.020 0.6270 1.9169 31295.372 123.705 0.5668 1.5566 precipitationanomaliesand amual maximumdischargerates were split into early and late subsamplesand examinedto see whetherthe relationshipbetweenprecipitationanomaliesand maximumdischargediscussedin paragraph15 is stableC(ableVIU).Three differentsample periods (1901-92,1901-60,and 1961-92)are considered. The first columnof the table reports results obtainedanalyzingthe data from the full sampleperiod. The numbers reportedin the upper sectionof the table (i.e., the rows in the 'Break Point' sectionof the table) are F-statisticprobabilitiesassociatedwith an analysisof variance test like that describedin footnote3. The numbersreportedin the lower sectionof the table are 3 regressionsummarystatistics." 25. The probabilitiesshownin Table VII are interpretedas follows. Considerthe period 1901-92. When the 1901-92sampleis dividedinto two subsamples- for example 1901-79 1 Theresultsreportedin TableVIIarebasedon weighted regressionsinwhichthenumberofstations reportingprecipitation observations is relativeto the meannumberof stationsoverthe wholesample period(i.e., 1901-92)is usedas the weightingfactor. Thisgivesmoreweightto observations that are basedon moremeasurements of precipitation.An analysis(notreportedin detailhere)parallelingthat in Table VII was carried out using unweighted regressions. The results and conclusions of this unreported analysis are exactly the same as those reported here. 14 and 1980-92- the probabilityis only 0.0003of gettingan F-statisticas large as was obtainedin the analysisof variancetest if the relationshipbetweenprecipitationanomalies and maximumdischargeswere in fact the samein both subsamples. 26. Three conclusionsflowfrom the results (and, moreimportantly,the pattern of results) summarizedin the table. First, the data stronglyreject the hypothesisthat the relationship betweenMarch-Mayprecipitationanomaliesand maximumdischargerates was unchanging. For break pointsat 1960or after, the test rejects the null hypothesis(i.e., no change)at the 0.035 level of significanceor better. Second,the changein the relationshipappearsto occur sometimein the 1950sor 1960s. As can be seenin the columnheaded"1901-92",the null hypothesiswouldbe rejectedonly at muchlower levelsof significance(i.e., higher probabilityvalues)if the samplewere splitat 1950or 1940. This conclusionis confirmedby two additionalcuts of the data. In the columnof the table headed"1901-60",stabilityof the regressionrelationshipwithinthe 1901-60subperiodis examined. As can be seen, the test fails to reject the null hypothesisat any reasonablelevel of significance(i.e., the highest level of significanceobtainedis 0.55). The sameresult is obtainedfor tests of splits within the subsample1961-92(i.e., the highestlevel of significanceobtainedis 0.17). Third, the regressioncoefficientsbehavequalitativelyas they wouldbe expectedto if some changehad occurredwhichincreasedthe runoffproducedby any givenquantityof rainfall: the coefficientof the precipitationvariable(PRECIP)is muchhigherin the secondsubsample (1961-92)than it is in the first (1901-60),taldnga valueof "123" versus "35". 27. The relationshipbetweenmonthlyprecipitationand averagestream flowsexhibitsthis samegeneralpatternof -instability (TableVmI). The relationshipis significantlydifferent in the latter part of the sampleperiod. However,analysisof the post-1960data indicates significantdifferencesin the relationshipwithinthe post-1960samplesubperiod. 28. The statisticalrelationshipbetweenprecipitationand streamfiowis widelyheld to be highlynonlinearand to dependcruciallyon the temporalpatternof precipitationas well as its amount. At higherprecipitationrates, other thingsbeing equal, streamflowshouldincrease more than in proportionsince the other ways in whichprecipitationcan be 'dissipated" (e.g., infiltration,evapotranspiration,surfaceretention)have very definitemaxima. The results reportedin Tables VII and VIII could thus simplybe a reflectionof the fact that precipitation has been far above "nonnal"throughoutmuch of the 1980sand early 1990s. In the annual data, the fact that the coefficientof the precipitationvariablein the secondsubperiodis over three times as large as it is in the first subperiod(i.e., 123versus 35), whichwouldbe an implausiblylarge effectto attributeto structuralchangesin rainfall-runoffrelationships, suggeststhat nonlinearitymay be at work. In the monthlydata, the instabilityof within subsampleregressioncoefficientin the post-1960periodcould also be associatedwith nonlinearity. 29. If nonlinearitywere Ie explanationfor apparentchangesin the relationshipbetween precipitationand streamflow,we shouldexpectto find significantdifferencesbetween relationshipsfitted to subsamplesclassifiedby precipitationranges, and little if any 15 Table VIII: Test of Stability of Statistical Relationship Between Monthly Precipitation and Mean Monthly Mean Discharge Rates at Corrientes (F-test Significance Level) SamplePeriod 1901.01-92.08 SampleBreakPoint 1930.01 1940.01 1950.01 1960.01 1975.01 1980.01 1985.01 0.1183 0.0333 0.0001 0.0000 1901.01-59.12 1960.01-92.08 0.9737 0.0374 0.4341 0.0000 0.0000 0.0000 Table IX: Test of Stability of Statistical Relationship Between Precipitation Anomalies and Annual Maximum Discharge Rates: Marimum Flood and Non-Maximum Flood Years Nul Hypothesis F-test Levelof Significance Relationshipbetweenprecipitation anomaliesand maximumdischagerates fittedto datafor 1905,1912, 1923,and 1929is statisticaUyindisinguihablefrom the elationshipfittedto datafor 1966, 1982, 1983,1987, 1990,and 1992. 0.9998 Relationshipbetweenprecipitation anomaliesand maximumdischargerates fitted to pre-1960years otherthan 1905, 1912, 1923,and 1929is stadsticaly indistinguishable from the relationship fittedto post-1960yearsother than 1966, 1982, 1983, 1987, 1990and 1992. 0.5757 difference between early and late subsamples within precipitation ranges. If nonlinearity were an explanation, along with some time varying factor such as land-use change, then significant differences would be expected both between subsamples defined by precipitation ranges and within subsamples defined by precipitation ranges across time. 16 30. Supportfor the "nonlinearityhypothesis"is providedby further analysisof both annual maximumand monthlymeandata alongthese lines. Table IX reports the results of analysisof variancetests for differencesbetweensubsampleswhen the annual data are partitionedinto 4-subsamples:(i) pre-1960years in whichone of the ten highestmaximum dischargerates occurred(i.e., 1905, 1912, 1923, 1929); (ii) other pre-1960years; (iii) post1960years in whichone of the ten highestmaximumdischargerates occurred(i.e., 1966, 1982, 1983, 1987, 1990,and 1992);and (iv) otherpost-1960years. If nonlinearitywere responsiblefor the apparentstructuralinstabilityin the annualrainfall-runoffrelationship, relationshipsfitted to the data thusly disaggregatedmightnot show significantdifferences betweenearly and late periods. In fact, tests fail to reject the null hypothesesthat pre- and post-1960relationshipsbetweenprecipitationanomaliesand maximumdischargerates were the samein the pre- and post-1960periods. Table X: Test of Stability of RelationshipBetween monthly Precipitation and Monthly Mean DischargeRates - Data Grouped by Three-MonthCumulativePrecipitation Precipitation ThroeMonthCumulative CP < 190 190 <= CP < 240 240 <= CP < 290 290 <= CP < 330 330 <= CP < 370 370 <= CP < 410 410 <= CP <460 460 <= CP < 520 520 <= CP F-testLevelof Significance 0.0120 0.0000 0.0087 0.0232 0.0106 0.9077 0.1634 0.5812 0.0393 31. Monthlyprecipitationand mean dischargedata, when disaggregatedby level, also fail to show consistentlysignificantdifferencesbetweenrelationshipsfitted to pre- and post- 1960 data. Two differentdisaggregationswere examined. In the first, the 12 monthsleadingup to the flood eventsat Corrientesshownin Table I are separatedfrom the other observations(TableX). The test fails to reject the null hypothesisthat pre- and post- 1960 relationshipsare identicalin this subsample. The hypothesisof stabilityis stronglyrejected, however,in the complementarysubsample. The seconddisaggregation(TableXI) divides the sampleinto 9 subsamplesbased on the cumulativeprecipitationover three months(i.e., the current and two precedingmonths). In general,tests show significantdifferences betweenearly and late periods at lower cumulativeprecipitationlevels, but differences betweenearly and late periods at highercumulativeprecipitationlevelstend to become insignificant. 17 Table XI: Test of Stability of Relationship Between Monthly Precipitation and Monthly Mean DischargeRates - Data Grouped by Three-Month Cumulative Precipitation ThreeMonthCumulative Precipitation F-testLevel of Significance CP < 190 190 <= CP < 240 0.0120 0.0000 240 <= CP < 290 0.0087 290 <= 330 <= 370 <= 410 <= 460 <= 520 <= 0.0232 0.0106 0.9077 0.1634 0.5812 0.0393 CP < CP < CP < CP < CP < CP 330 370 410 460 520 Conclusions 32. Takentogether,these results tend to suggestthat the unusuallyheavyprecipitationof the 1980sand early 1990swas the most importantfactoraccountingfor the floodingof these years. There is no consistentstatisticalevidencein the data examinedhere that any other factor playeda significantrole. This conclusionis not surprising. When precipitationis concentratedin timeand space, as it typicallyis during flood years, it simplyoverwhelms other factors: floodingwill occur other factorsnotwithstanding.There is some evidencein the data examinedhere that, at less extremelevels of precipitation,the basin may be producingmore runoff todayfor a given quantityof precipitationthan it did in the early years of the century. 33. In sum, the conclusionsthat emerge from the previousanalysisare as follows: o Floodingwas both morefrequentand more severein the latter part of the 1900s than previously; o Extremelow flows were both less frequentand less extremein the latter part of the 1900sthan previously; o Total streamflowwas greaterand its intra-annualdistributiondifferentthan in the latter part of the sampleperiodthan during the early years; o Variationsin precipitationexplainmuchof the variationin streamflowsand flooding; 0 Changes in intra-annual variation in streamflow appear to be due to some combinationof changesin the intra-annualdistributionof precipitation,and to 18 the operationof reservoirson the Paranawhichdelay the propagationof floods;and o There is no consistentevidence,statisticalor otherwise,that changesin rainfall-runoffdynamicsassociatedwith land use changeshave playedan importantrole in recentfloodingin the Basin. 19 Annex A: Description of the Parana/Paraguay River Basin This annex summarizesbasic information and data on the Parana/Paraguay River 1. Basin. Much of this information derives from international compacts established to manage the basin's resources. Intergovernmental Cooperation on Hydrometeorology in the La Plata Basin In 1969, the Foreign Affairs Ministers of Argentina, Bolivia, Brazil, Paraguay and 2. Uruguay signed the Plata Basin Treaty in an effort to institutionalize the Plata System. An IntergovernmentalCoordinating Committee-CICwas created to promote, coordinate, and implement the multilateral actions as defined by the Ministers including the hydrometerology and floods in the Basin. Several resolutions dealing with floods have been approved by the Ministers. (Table A. 1) Furthermore, expert Groups and Ad hoc Working Groups on Hydrometeorology and 3. Flood Warning System were formed and have met with the CIC periodically since 1982, in order to exchange information and recommend actions to be considered by the Foreign Affairs Ministers. Consequently, the countries have established an information exchange network, especially for periods of flood warning. Selected stations of the flood warning system are shown in Table A.2. Table A. 1: Plata Basin Resolutions Dealing with Hydrology and Floods ResolutionNo. Meeting Year network 1977 Paraguayriver hydrometeorological IX 88 informationamongthe Plata 1977 Exchangeof Hydrometerological IX 91 Basincountries 1980 Floods in the ParaguayRiver XI 153 1981 Floodsin other internationalrivers XII 174 network 1981 Plata Basinhydrometerological XII 176 1986 Plata Basinfloodwarningsystem XVI 195 1986 Technicalcooperationactionsincludingwaterresources flEx 2Ex 1987 Flood warningsystemand water quality XVII 302 The Paranf River Basin The Parana River Basin is the most important in the La Plata Basin system due to the 4. magnitude of its discharges, the extension of its area, and its overall length. It encompasses 1 510 000 km2 (excluding the area of the Paraguay River Basin, its most important tributary). Of this area, 890 000 km2 is located in Brazil, 565 000 km2 in Argentina, and 55 2000 km2 in Paraguay. The total area including the Paraguay River extends to 2 605 000 km2 . Its length from its origins at the Paranaiba River until the confluence with the Uruguay River reaches 3 740 km. The ParanAis divided into the Upper Parana ( 972 050 km2 upstream of its confluence with the Paraguay River), the Middle Parana (between the confluence with the Paraguay River and the Salado River) and the Lower Parana (from the confluence with the Salado River to the confluence with the Uruguay River) Table A.2: Parand-Paraguay Flood Warning System-Selected Stations River Parana Parana Parana Iguagu Parana Parana Parana Paraguay Paraguay Paraguay Paraguay Paraguay Tebicuary Paraguay Bermejo Parana Parand ParanE Station Area km2 478 000 Jupia 670 000 Sao Jos6 802 150 Guafra SaltoCataratas 67 300 901 545 R-8 Itaipu 910 000 Libertad 933 600 Posadas 258 000 Ladario Porto Esperanga 363 500 Porto Murtinho 474 500 600 000 Concepcidn 797 000 Asunci6n 21 000 V. Florida 925 000 Pilar 91 950 El Colorado 2 067 050 Corrientes 2 457 050 SantaFe 2 480 000 Rosario Observations Country since 1926 1963 1921 1915 1976 1931 1901 1900 1963 1939 1910 1904 1945 1917 1969 1903 1925 1884 Brazil Brazil Brazil Brazil Brazil Argentina Argentina Brazil Brazil Brazil Paraguay Paraguay Paraguay Paraguay Argentina Argentina Argentina Argentina 5. The distinguishing feature of the Upper Parana is its delineation in "stepped' plateaus, creating 'saltos" in the river channel, now flooded by the reservoirs of hydroelectric dams. Other smaller falls and the presence of rapids, the majority of which are now also flooded by the reservoirs of around 40 hydroelectric dams, characterize the landscape. Most of the reservoirs were constructed between 1960 and 1990 in the Braziian portion of the basin. The width of the Paran River vaies dramaticaly from 4 000 m north of town of 6. Guaira in Brazil to 60 m below Itaipu Dam. Near Posadas, in Argentina, its width ranges Annex A - September 2, 1993 -2- between 150 and 2 500 m. Downstream of Posadas, the river flows through a series of islands, covering a 25 km-wide area. The river is 4 200 m wide at Corrientes, 2 600 m at Bella Vista, and 2 300 m near Santa Fe. However, its flood plain gradually spreads out, especially over its right bank, which is lower than its left bank. The width of this flood plain varies between 13 km near Corrientes to about 56 km near Rosario-Victoria. The delta of the river is 18 km wide at its beginning, growing to a width of about 60 km. Then through its numerous branches, the Parana flows into the La Plata.. The Paraguay River Basin 7. The Paraguay River Basin encompasses 1 095 000 km2 , of which nearly 365 000 km2 are in Brazil, 365 000 km2 in Paraguay, 182 500km2 in Argentina, and 182 500 km2 in Bolivia. The origin of the Paraguay is found in Brazil, and the river, after flowing 2 800 km (Table A.3) reaches the Parana river, north of the Argentinean cities of Corrientes and Resistencia. In its northeast portion (i.e., the Bafiadosof Izozog in Bolivian territory), the basin boundaries are not clearly defined. Excluding the headwaters of the Pilcomayoand the Bermejo, which descend from the 8. Argentine-Bolivianplateau in the Andes, and in the southern part of the left banks of the Paraguay River, between the Apa River and its confluencewith the Parana - which presents a wavy relief with slopes of certain magnitudes- the rest of the river basin extends over an immense alluvial plain, very slight slope and extensive flood plains. In the Upper Paraguay, the river banks are low and prone to floods, creating a zone 9. known as the 'Pantanal' , a vast flood plain that covers close to 100 000 knmand that is periodically covered by water. The terrain slope is very slight, as is the slope of the river channel. The river bed is sandy, very unstable, and the river meanders. There are some rocky stretches, but they do not affect the general character of the river. In the area that extends from the Apa River to the confluence with the Tebicuary, the 10. flood plain is restricted to a width that varies from 5 to 10 km, occupying mainly the right bank. The mouth of the Paraguay river extends from this point until its confluence with the ParanA (approximately 130 km). During floods, water rises over both banks in this region, occupying a strip of land 10 and 15 km wide. The major characteristics of the Paraguay river in this section are the enormous amount of sediments carried from the Bermejo River, and the backwater phenomena produced by the waters from the Paranr at its confluence with the Paraguay River. Annex A - September 2, 1993 -3- Table A.3: Limits and Slopes- Paraguay River' Limits Zones Distances Lower Paraguay Confluence-Tebicuary River (260km south of Asuncion) 130 km Middle Parguay Tebicuary-Apa River (an 927, bordering 797 km Brazil-Paraguay) Upper Paraguay ApaRiver-headwaters (km2 800) 1 873 km MedianSlopes/ Observations 5 cm/km. Sufferseffect of the Parana whenthe river is rising. The BermejoRiveris at km 87 and Pilar is at km 89. 6 cm/km. Asunci6nis at km 390 and Concepcidn at km 700. 3,1 cm/km.Includesthe Pantanal.Porto Murtinho is at kan999, Porto Esperancaat km 1395, andLadariois at km 1 530. 1I-AS, 1992 Basic Basin Parameters 11. The concluding section of this annex (previous studies) contain a listing of data sources and of relevant previous studies of the hydrometeorologyand floods of the ParanA and Paraguay river basins'. Many of these have been utilized in the preparation of this paper. A wealth of information remains to be exploited, however. 12. The hydrometeorolgy of the Paranr-Paraguay River Basin is very complex. Several small sub-basins have particular hydrological characteristics. Previous studies of the basin have divided it into seven major sub-basins (EBY,1979): 'Datapresentedin AnnexC on annualmaximumandminimumdailyfloodsandstages,meanmonthly flowand stages, and annualandmonthlyprecipitationat selectedstationswereprovidedby the Instituto Nacionalde Cienciay TecnicaHidricas(Argentina),Departamento Nacionalde Aguase EnergiaEletrica (Brazil),and Direccionde Meteorologiae Hidrologiaand AdminsitracionNacionalde Navegaciony Puertos(Paraguay). Annex A - September 2, 1993 -4- Upper ParmnfRiver upstreamGuafa (802 150 kn2) * Upper ParaguayRiver UpsreamPorto Esperan(363500 km) * * Middle ParaguayRiver betweenP. Esperanzaand Asunci6n (433 500kmn) * Upper PamnrRiver betweenGuain and Confluence(169 900 km: * Lower ParaguayRiver betweenAsunci6nand Confluence (29S000 km) * MiddleParani RiverbetweenConfluenceand Santa Fe/ Parani (390 000 kin) * Lower ParaniRiver downam (197 950 km2) SantaFeI Pararn Precipitation The runoff basins of the Parana and Paraguay Rivers are located in a region of heavy 13. precipitation that is prevalent almost throughout the year. Situated east of the Andes, between approximately 150 S and 30 0 S, the region is subject to rain-producing systems of both tropical and extratropical (frontal-type)origins. The annual mean rainfall in the Parana basin varies from 1100 to 1600 mm, except in the upper basins of the Tiete, Paranapanema and Iguacu with the annual mean reaching 2 200 mm. In the Paraguay Basin, it varies from 400 to 1800 mm. Mean Discharges 14. The Parana river system, shows a predominance of summer-fall discharges over those of winter-spring. The variability is more evident in the upper portion -due to the tropical regime of rains- with high waters between December and April, pealing in February, and a period of low waters in the winter, with minimumsin August and September. South of Guaira, the tributaries of the Parant, like the Iguagu, exhibit a somewhat different seasonal pattern: lower waters in the summer, and high waters in the winter and spring due to the greater persistence of rains during the entire year. After its confluence with the Paraguay, which also exhibits increased flows during the winter (June, July) due to the retardation effect created by the Pantanal, the flows in the Parana exhibit less seasonal variability. Table A.4 summarizes the mean monthly and mean annual discharges for 1901-1992, 19011967 and 1968-1992. An analysis of the origin of the Parani River flow is shown in Table A.5. Roughly 15. 78% of the mean annual flow originates in the Upper Parand. From Corrientes to the confluence with the Uruguay River (around 540 000km2) the discharge of the Parani River increases only 10%, less than 2 000 m3 /s. Generally, the rainfall in the Upper Parana (i.e., upstream of.Guaira) is the main source of the flows in the Middle and Lower Parana river, but in some years torrential rains between Guafra and the confluence with the Paraguay River (including the Iguacu River Basin) and between Asunci6n and Confluence are the main cause of the floods registered in Asunci6n, Posadas, Corrientes and downstream. AmnexA - September 2, 1993 -5- Table A.4: Mean Montly Discharge in Posadas and Corrientes-ParandRiver 1OOm3Is M A M I Jl A S 0 16.5 15.7 13.6 12.0 12.0 10.5 9.0 9.3 14.5 16.3 16.1 13.6 11. 11.2 9.6 8.1 1968 1992 16.1 16.8 14.7 13.7 13.5 13.9 12.9 Corrients 19011992 17.6 20.3 20.3 18.6 16.7 17.0 Corrientes 19011967 16.7 19.6 20.S 18.5 15.8 Corentes 19681992 20.1 22.1 19.8 19.0 19.1 Station Period I F Poudas 19011992 14.9 Poaadas 19011967 Pouda 16. N D AVG 10.8 11.0 11.9 12.3 8.3 10.1 10.2 11.1 11.7 11.4 12.0 12.9 13.1 14.1 13.8 15.1 11.6 12.2 13.8 14.2 15.0 16.1 15.8 13.8 11.3 10.7 12.5 13.1 13.0 15.2 20.2 18.6 16.1 16.1 17.2 17.1 18.0 18.6 An analysis of the ozigin of the Parand River flow is shown in Table A.5. Roughly 78% of the meanannual floworiginatesin the UpperParani. From Corrientesto the confluencewith the UruguayRiver (around540 000km2) the dischargeof the ParandRiver increasesonly 10%, less than 2 000 m3/s. Generally,the rainfallin the Upper Parari (i.e., upstreamof Guaira)is the main source of the flowsin the Middle and Lower Parandriver, but in some years torrentialrains betweenGuafraand the confluencewith the ParaguayRiver (includingthe IguacuRiver Basin) and betweenAsunci6nand Confluenceare the main cause of the floodsregisteredin Asunci6n,Posadas,Corrientesand downstream. 17. The hydrologicalregimeof the Upper Paraguayin Cuiabais similarto the Upper Parand, but the principalcharacteristicof the ParaguayRiver regimeis the intra-annual variationwhich occurs along its course. In the Upper Paraguay,before reachingthe lower and flood-pronearea of the Pantanal,the maximumlevelsare reached in February and the minimumsin August-September.Howeverin Corumba,Ladario,and in the Middle Paraguayin Asunci6nand Concepci6n,the period of high flowsis practicallyreversed, with the maximumin June-July,and the minimumin December-January.This waterflowpattern variationis causedby the storageeffectproducedby the Pantanal,which createsa delay of about 3 monthsin the flood propagation,beforearriving in Asuncionand at the confluence with the Parana. Annex A - September 2, 1993 -6- Table A.5: Origin of the Dischargesof the Paranf River in Posadas and Corrientes Flowin Posadas' Corrientes' AreaKm2 Percent Originatedfrom 933 600 78% UpstreamGaufra 12% IguaquRiverBasin 10% Intermediatearea 2 067 050 72% Upstream Posadas 16% UpstreamAsunci6n 12% Intermediatearea CorrienteS2 2 067 050 61 % Upstream Guafra 17% betweenGuafraand the ParaguayRiver 22% I-ELETROBRAS, 1978 ParaguayRiver Basin Area km2 802 150 68 000 63 450 933 600 797 000 336 450 802 150 169 900 1 095 000 2-EBY, 1979 Minimum Discharges 18. The percentage of the occurrence of annual extreme low flows and stages in selected stream flow gauging stations of the Paraguay and Parana rivers are shown in Table A.6. Most of the extreme low flows occurs in November, December, in the Paraguay river. From August to October, November, and even December, and January in the Parana River. In the Iguacu River they may occur during the whole year especially in January, May, and August. Maximum Discharges Most of the maximumannual floods in the Upper Parana (Guafra and Posadas) occur 19. in January, February and March while in the Middle and Lower Paraguay (Asunci6n), they occur in May, June, and July.2 In the Middle Parana (Corrientes), they occur in February and March. In the Iguacu River Basin (Cataratas) floods occur generally in October, November and in June and July. The percentage of the occurrence of annual maximum floods in each month of the year for those stations is shown in Table A.7. High precipitation in the lower part of the Upper Parani Basin is more effective in 20. producing peak discharge at Guaira (and Posadas) than the same average basin rainfall spread uniformly over the basin or concentrated in the upper end. 21n the ParaguayRiverBasinthe volumeanddurationof the floodsare as importantas the peak flood due to the area, shapeand topographyof the basin. AnnexA - September2, 1993 -7- Table A.6: Percentage of Occurrenceof Eitreme Low Flows and Stages by Month River Station J F M Paraguay Ladario 19 2 * 0 0 * ParanA Guafra 4 0 0 0 * Iguagu Cataratas 14 6 21 Parana Posadas 9 * Parana Corrientes 12 0 A 4 1 9 0 1 0 M J JI A S O N 2 7 13 29 % 28 100 1 16 40 28 7 4 100 6 1 13 7 7 4 8 100 4 2 5 21 24 16 11 7 100 4 1 10 28 22 12 12 100 O N D % 1 22 4 4 3 2 12 6 6 9 6 12 100 100 100 100 100 0 0 D Table A.7: Percentage of the Occurrence of Annual Maximum Floods by Month' River Station J M A M Parang Iguagu Parana Paraguay Parand Guaira Cataratas Posadas Asunci6n Corrientes 19 2727 * 5 5 19 29 19 13 7 2 8 23 25 7 8 5 5 9 6 2 5 i-It should be notedth F 7 3 J JI A S 4 0 1 0 14 15 6 5 10 2 0 2 30 10 i 2 1 11 4 0 5 3 1 the mots ezxtorimay floodsin Poadas and Comfent occurrd in May, June, and July. The most criticalconditionsfor floodsat Guafra,(Posadasand Corrientes),wouldbe with storms over the wholeParandBasinfor the first few months,givinghigh base flowsand peak discharges from the upper part of the basin, followedlater by stormsconcentratedin the lower part of the Upper Basin. This combinationshouldproducethe greatestpeak dischargeat Guafra,Posadasand 1972). This is whatoccurredin 1982, 1983,and 1992,for Corrientes(ELETROBRAS/ANDE, example. 21. The flood-travel time in the ParanARiver between Jupia and Corrientes, and Salto Osorio and in the Iguagu River between Salto Cataratas is shown in Table A.8. (ELETROBRAS, 1978). According to EBY, 1979 the flood-travel time between Posadas and Corrientes in the Parna river is 5 days and between Corrientes and Rosario 30 days (i.e., 788 km at 0.3 mls). AnnexA - September2, 1993 -8- 22. Table A.9 presents the difference between ordinary and extraordinary floods according to EBY, 1979 (An extraordinary flood is considered equal or superior to a 10 year recurrence flood.) Table A.8: FloodTravel rime in Parana and IguaguRivers Zone Distance km Flood Travel days Jupia-Guarfa Guafa-Posadas Posadas-Corrientes S. Osorio-S.Cataratas 499 664 376 270 4 2 5 1 River Parana Parana Parana Iguagu Velocity m/s 1.4 3.8 0.9 3.1 Table A.9: Ordinary and Extraordinary Floods in the Parana and Paraguay Rivers River Station Paraguay Paraguay Paraguay Parana Parana Parana Ladario P. Murtinho Asunci6n Guafra Posadas Corrientes Warning Extraordinary Floods Ordinary Floods m m31s m m3/s 4.0 6.0 6.3 6300 4.5 4000 2.0 15000 2.8 24000 3.5 21000 6.0 30000 5.5 24000 7.0 35000 Gauge Datum abovesea level m 82.15 70.15 53.09 218.00 73.09 41.40 23. In the Iguagu Basin, due to its area, topography, and shape, the peak floods are high, but for shorter periods of time. The maximum peak floods recorded since 1926 in the Iguacu river basin are: 1983July 31 000 m3 /s 1936June 28 600 m31s 1992May 18 700 m3/s Annex A - September 2, 1993 1987May 17 500 m3/s 1928May 17 500 m3/s 1932April 16 000 m'/s 1938July 15 500 m3/s 1937Nov 15 000 m 3 /s 1989June 14900 m3/s -9- Table A.10: Sedimentsin the ParanA- Paraguay river basins Mean Sedimementston/year Annual (*106) Flow 1977' 1992 River Site ParanA Guaira Observations W/s3 23.72 Since 1982, most 9350 12000 26.5 6* 2750 4.3 4.5* Paraguay ConfluenceParang 4000 100.9 100* Parana Corrientes 16000 126.1 106* Parana Confluence Paraguay Paraguay Asunci6n of the sediments are depositedin the reservoirof Itaipu dam. Includesthe contributionof the Iguaguriver basin and other tributaries Mostof the sedimentsof the Brazilianportion are depositedin the Pantanal Includesthe contributionof the Bermejoriver basin Most of this sedimentreaches the port of Buenos Aires I-EBY, 1979 2-ELETROBRAS, 1992 *-Estiriated Sedimentation At present, data for only two years (1977 and 1992) have been obtained and 24. examined. These are shown in Table A.10. 25. In 1992 ELETROBRASpublished an updated report on the sedimentological conditions of the most important Brazilian rivers. This report shows three areas of higher production of sediments in the Paran6/Paraguay River Basin, mainly caused by the erosion of sedimentary rocks, mostly sandstone. In the Parand River Basin, the areas are located in the upper part of the Araguari river (Paranaiba basin) and between the Paranapanema and Ivaf rivers (Caiud sandstone). Both areas are upstream from Guaira and the Itaipu dam. In the Annex A - September 2, 1993 -10- Paraguay River Basin the area of high production of sediments is located in the upper part of the Pantanal. As far as the Paraguay River Basin is concerned most of the sediments in the 26. Brazilianportion are deposited in the Pantanal. The same occurs with the production of sediments in the Parana River that remain deposited in the reservoirs of the hydroelectric dams. The most important production of sedimentsin the Parana/Paraguay River Basin 27. occurs in the Bermejo River Basin (94 350 km2 ) that originates in the Andean slopes of Argentina and Bolivia. Almost 100 000 000 tons of sediments are transported each year into the Paraguay and Parani Rivers. Previous Studies The La PlataBasin AISIKS,E.G. 1985. 'La Gran Crecidadel Rfo Paranade 1983".BuenosAires CIC. 1982. 'Reunionesde las ContrapartesTecnicaspara el Programade AlertaHidrol6gicadela Cuencadel Plata". Alsothe reportsfrom 1984,1989, and 1991meetingsheld in BuenosAires. Quantitativoe Qualitativo COIMBRA,R.M., OLIVEIRA,E., CUDO,K.J. 1992. "Monitoramento das Aguasda Bacia do Prata' (ProjetosAlertaHidrologicoe Qualidadedas Aguasdo CIC - Comit6 Coordenadorda Baciado Prata). Brasfia. Intergovernamental DIAZ, H.F. 1993. 'TemporalPatternsof Precipitationin the Paranaand ParaguayRiver Basinsand its Relationshipto the El NinloPhenomenon".NationalOceanicand AtmosphericAdminstration. EnvironmentalResaearchLaboratories.Boulder.Colorado. Brasilia DNAEE. 1987. 'Inventariodas Estac6esPluviom6tricas". Brasilia DNAEE. 1987. 'Inventariosdas EstacoesFluviometricas". EBY. 1979. "Estudiode CrecidasRfos Paranay Paraguay. Estudiorealizadopor MOTOR COLOMBUSY Asociadospara EntidadBinacionalYacireta.BuenosAires-Asunci6n. dosPrincipaisRios Brasileiros". ELETROBRAS.1992'Diagn6sticodas Condi06esSedimentologicas Institutode PesquisasHidraulicas-IPH.Rio de Janeiro. OEA. 1969. 'Cuenca del Plata. Estudiopara su Planificaci6ny Desarrollo.Inventariode Datos Informedel estudiollevadoa cabopor la Unidadde Recursos Hidrol6gicosy Climatol6gicos". Naturalesen 1967y 1968.Washington,D.C. OEA. 1971. 'Inventarioy Analisisde la Informaci6nBasicasobre RecursosNaturales". Cuencadel Rfo de la Plata. Estudiopara su Planificaciony Desarrollo.Washington,D.C. AnnexA - September2, 1993 -11- OEA. 1969. " Indice Anotado de los Trabajos Aerofotograficosy de los Mapas Topograficos y de Recursos Naturales". Cuenca del Rio de la Plata. Estudio para su Planificaci6n y Desarrollo. WashingtonD.C. OEA. 1985. 'Infraestructura y Potencial Energetico en la Cuenca del Plata'. Washington, D.C. The Paraguay River Basin ANNP. 'Anuarios Hidrograficos". Asunci6n ARMADA NACIONAL. "Anuarios Hidrograficos'. Asuncidn ARMADA NACIONAL. 1979. 'Estudio del Comportamientodel Rfo Paraguay y su Litoral Desde Concepcidn Hasta Confluencia'. Asuncion. CARVALHO, N. de O., AYRES R.M., ROCHA, J.P.G. 1992. 'Estudos Sedimentoldgicosda Bacia do Sao Lourengo, MT'. ELETROBRAS/UniversidadeFederal de Mato Grosso. Cuiaba. CARVALHO, N. de O., MONTEIRO, A.E. 1991. 'Sistema de Alerta e Provisao de Cheias do Pantanal'. ELETROBRAS/Companhiade Pesquisas de Recursos Minerais. Rio de Janeiro. DMH. 1992. 'Balance Hidrico Superficialde Paraguay". Asunci6n. DNPVN. 1973. 'Estudo Hidrologicodo Rio Paraguai. Perfodo 1966-1972Relat6rios Parciais e Relat6rio Final'. Hidrologia Comercial Ltda. Rio de Janeiro DNOS. 1974."EstudosHidroldgicos da Bacia do Alto Paraguai%.4 Volumes. Rio de Janeiro. GIUSTI, E. V., LOPEZ M.A., 1984. 'On the Hydrology of the Paraguay River'. USGS. Selected Papers in the Hydrologic Sciences. Reston. HALCROW AND PARTNERS. 1973. 'Estudio de Navegabilidaddel Rfo Paraguay al sur de Asuncicn'. Asunci6n. JICA. 1985. 'Storm Drainage System. Improvementin Asuncion City'. Asunci6n. LOPEZ, M.A. et alli. 1983. 'Hydrologic Hazards in Paraguay with Special Reference to the floods of 1983.' USGS. Reston. OEA. 1974. 'Alta Cuenca del Rio Bermejo. Argentina-Bolivia'. Estudio de los Recursos Hidricos. Washington, D.C. OEA. 1977. "Cuenca Inferior del Rfo Bermejo. Argentina". Programaci6n para su Desarrollo. Washington, D.C. OEA. 1975. ' Proyecto Aquidaban. Desarrollo de la Regi6n Nororiental del Paraguay". Washington, D.C. AnnexA - September2, 1993 -12- OEA. 1979. "Caracteristicas da Vegetacio da Bacia do Alto Paraguai" Informe preparado por el consultorJorge AdAmolipara o 'Estudo de DesenvolvimientoIntegrado da Bacia do Alto Paraguai (EDIBAP)". Brasilfa. OEA. 1992. "Proyecto de Reconstrucci6ny Desarrollo Integrado del Area Meterol6gica de Asunci6n y de los Entidades de Concepci6n, Alberdf, Pilar Afectadaspor Inundaciones." Informe de las Misi6n Preliminar de la OEA/DDRMA. Washington. PNUD. 1975. "Proyecto de Mejoramientode la Navegaci6ndel Rfo Paraguay". PAR/TS/006. Asunci6n. PNUD. 1979. "Estudio de Inundacionesdel Rfo Paraguay". Asunci6n. PNUD. 1980. 'Modelos Estadlsticospara Previsi6n de Niveles del rfo Paraguay". PAR1801002. Asunci6n. SUDECO. 1979. "Estudo de DesenvolvimentoIntegrado da Bacia do Alto Paraguai-EDIBAP". Convenio Governo Brasileiro PNUD-OEA Brasfia. USCE. 1972. 'Application of the SSARRmodel to the Upper Paraguay River Basin". Portland, Oregon. UNESCO/UNDP. 1973."Hydrologicalstudies of the Upper Paraguay River Basin (Pantanal) (19661972) Technical Report". Bra. 66.521. Paris. Parang River Basin AyEE/DNCPyVN/CONCAP. 1973. "Estudio Hidrol6gico y Sedimentol6gicodel rio Alto Parand." Buenos Aires. AyEE. 1970. "Resumen de la EstadfsticaHidrol6gica Hasta 1967". Buenos Aires. AyEE. 1960. "Estudio Hidrol6gico del Rio Alto Parana". Buenos Aires. AHLQUIST, 0. 1906. "La Gran Creciente de 1905 del Rio Parana y sus Afluentes". Buenos Aires. BERGER-BROKONSULTA.B. 1973. "Mejoramientode la Navegaci6n del Rfo Parana. Buenos Aires. BRAZILIUNDP.1966. "Power Study of South Central Brazil-SaoPaulo Group-Hydrometerology Report."Appendix No. 8. Canambra Engineering ConsultantsLimited. Montreal. CARVALHO, N. de O., CATHARINO, M.G. 1992. 'Avaliacao do ssoreamento do Reservatorio da UHE Itaipu". ELETROBRAS, Diretoria de Planejamento e Engenharia. Rio de Janerio. CARVALHO, N. de O., 1991. 'Producbo de Sedimentosda Area de Contribuisao ao Reservat6rio de Itaipu". I Reuniao sobre Erosao e Sedimenta§bo,Curitiba. Annex A - September 2, 1993 -13- COMIP. 1977. 'Aprovechamiento del Rfo Paranl en el Tramo Limitrofe Comprendido Entre la Desembocaduradel Rfo Iguazd y la Seccidn Encanaci6n-Posadas, con particular atenci6n a la zona de Corpus-FaseI" . Lahymer-Harzay Asociados. Buenos Aires. CONCAP. 1970. 'Modelo Matematico de la Cuenca del Plata - Informe Preliminar de la Fase I Factibilidad Tecnica de las Fases 2-3". Buenos Aires. CONCAPlDNCPyVN/AyEE. 1973. 'Estudio Hidrol6gico y Sedimentol6gicodel rio Alto ParanA". Buenos Aires. COTTA, D. 1973. "Influencia Sobre el Rfo Parana del Material Sdlido Transportado por el Rfo Bermejo. Buenos Aires DNCPyVN. 'Anuarios Hidrograficos". Ministerio de Economfa de la Replblica Argentina. Buenos Aires. EBY. 1973. "Estudio de Factibilidad Tecnica, Econ6mica y Financiera para el Desarrollo del Rfo Parand en el Area Yacyreta - Apipe". Consorcio Harza y Asociados. Asuncidn. Buenos Aires. ELETROBRAS/ANDE. 1972. "Rio ParanAStudy. Appendix A. Hydrology and Meterology", prepared by EECO-International EngineeringCompany of San Francisco, California and ELCElectroconsult of Milan, Italy. Rio de Janeiro/Asunci6n. ELETROBRAS. 1978. "Estudo da Genese das Vaz6es do Rio ParanA".5 volumes realizados pelo Consorcio Nacional de Engenheiros Consultores SA. Sao Paulo. ELETROBRAS/GCOI. 1992. "AnAliseda Operacao de Controle de Cheias para as Bacias dos Rios Parana e outros na Estagao Chuvosa 1991/1992". Subcomite de Estudos Energeticos. Rio de Janeiro. ELETROBRAS/GCO1.1992 'Analise da Operacao Hidraulica dos Aproveitamentosda Bacia do Rio Iguagu durante a Cheia Maio-Junhode 1992." Grupo de Trabalho de Hidrologfa Operativa. Rio de Janeiro. EINSTEIN, H.A. 1972. -Report on the Sediment Problems Connected with the Apip6 Project on the ParanARiver. Buenos Aires. FESQUET, H.B. 1975. 'Pron6stico de la Fecha de Culminaci6n de las crecientes del Rio Parana". Publicaci6n N°15, Serie Hidrometeorol6gica.Buenos Aires. INCyTH. 1975. 'Cuenca Superior del Rfo Parana - Estudio de la Crecida Maxima Probable". Buenos Aires. OEA. 1973. *Noroeste do Estado do Parana-Brasil. Estudo para o Controle da Erosao". Washington, D.C. PNUD. 1977. 'Proyecto Mejoramiento de la Navegacidn del Rio Parana, Mediciones de Transporte de Sedimentos en el rfo Parana a altura de Corrientes", por J. Lelievre y E. Navntoft. Buenos Aires. PNUDIINCYTH. 1974. "Estudio del Sistema Fluvial Parang-SantaFe' SFIARGI66I521. Buenos Aires. Annex A - September 2, 1993 -14- RAFFO, J.M. 1951. 'Pron6stico de las Crecientesdel Rfo Parana, S.M.N., Publicaci6n N0 2. Serie Hidrometeoroldgica.Buenos Aires. STUCKRATH, T. 1969. 'Movement of Ondulationon the Bed of the Parang River". Buenos Aires. VANONI, V. 1967. "Review of SedimentationProblems of the Proposed Parana-Fe Tunnel". Buenos Aires. ACRONYMS ANNP Administaci6nNacional de Navegacidny Puertos (Paraguay) AyEE Agua y Energia Electrica (Argentina) CFI Consejo Federal de Inversiones (Argentina) CIC Comite IntergubernamentalCoordinadorde la Cuenca del Plata COMIP ComisionMixta Argentina Parguaya del rfo Parang CONCAP Comisi6nNacional de la Cuenca del Plata (Argentina) DEPVN Departamientode Puertos y Vfas Nagigables (Aregentina) DRDE Departmentof Regional Developmentand Environment ELETOBRAS Centrais Eletricas Brasileiras SA DMH Direcci6n de Meteorologfae Hidrologfa (Paraguay) DNAEE DepartamentoNacional de Aguas e Energia Eletrica(Brazil) DNCPyVN DepartamentoNacional de ConstruccionesPortuarios y Vfas Navigables (Argentina) DNPVN Departamento Nacional de Portos e Vias Navegaveis (Brazil) DNOS DepartamentoNacional de Obras de Saneamento(Brazil) EBY Entidad BinacionalYaciretA(Argentina/Paraguay) EDIBAP Estudo para o DesenvolvimentoIntegrado da Bacia do Rio Paraguai (Brazil) GCOI Grupo Coordenadorpara a OperagaoInterligada (Brazil) JICA Japan International Cooperation Agency IECO/ELC Consultoras "Intemational Engineering*San Francisco / "Electroconsult" Milan IGH Instituto Geogrlfico Militar (Argentina) Annex A - September 2, 1993 -15- INCyTH Instituto Nacional de Ciencia y Tdcnica Hfdricas (Argentina) IPH Instituto de Pesquisas HidrAulicas(Brazil) LAC Latin America and the Carribbean MIT MassachusettsInstitute of Technology NOAA National Oceanic and AtmosphericAdministration OAS Organizationof American States SMN Servicio Meterol6gicoNacional (Argentina) SUDECO Superintendenciado Desenvolvimentoda Regiao Centro Oeste (Brazil) SUCCE Subunidad Central de Coordinacidn para la Emergencia del Ministerio del Interior (Argentina) UNDP United Nations DevelopmentProgramme (PNUD in spanish) UNESCO United Nations Educational, Scientific, and Cultural Organization USAID United States Agency for InternationalDevelopment USCE United States Corps of Engineers, North Pacific Division USGS United States Geological Survey AnnexA - September2, 1993 -16- Annex B: Large Scale Atmospheric Disturbances and Flooding in the Parana/ParaguayRiver Basin 1. Large-scale atmospheric disturbancesand their temporal variability may play a role, via precipitation, in producing year-to-year changes in streamflow in the Parana\Paraguay Basin. In particular, a characteristic feature of the climate of the tropical Pacific Ocean is a biennial tendency in equatorial sea surface temperature (SSI) and associated atmospheric fields such as the surface winds, sea-level pressure, and rainfall. In general, conditions along the equatorial Pacific are such that warm surface waters and heavy rainfall are restricted to its western areas (west of the International Dateline). During so-called El Nifio events, warm equatorial Pacific waters are found much further east than usual, heavy rainfall shifts eastward, and between about December and March, can become excessive along the normally dry coasts of southern Ecuador and Peru. 2. The shifts in rainfall pattems in the tropical Pacific perturb large scale atmospheric circulation patterns all over the globe. Because the weather patterns associated with El Nino events can persist for about one year, the anomalous weather conditions that can be experienced in those regions affected by the phenomenon can also be long-lasting. 3. In 1991-92, a moderate El Nifo event occurred in the Pacific. In the last decade, we have experienced three moderate to very strong El Nifio events - in 1982-83, 1986-87 and in 1991-92. The 1982-83event is considered the strongest such event in this century. The type of climatic anomalies experienced in any one part of the world depends on its geographic location, and it also tends to be seasonally dependent. 4. The pattern of anomalously high and low precipitation is quite characteristic of the typical season response to El Nino events in this region (Kiladis and Diaz, 1989'; Diaz and Kiladis, 19922). In particular, heavier than normal rainfall is experienced in the Parana/Paraguary Basin and along the northern coast of Peru, and dryer than normal weather is experienced in the Nordeste region of Brazil. Although this is the typical or characteristic response of the precipitation regime in South America, it does not necessarily occur in every El Nifio event to the same degree, whether in its spacial features or in its seasonal distribution. Nevertheless, the frequency with which this typical response is observed, and the fact that significant alterations of the normal climatologicalfeatures in the affected regions can occur, suggest that having knowledge of the expected climatic patterns when an El Niinoevent is underway would be helpful in planning for the safety of life and property. 'Kiladis,G.N. andDiaz, H.F., 1989:Globalclimaticanomaliesassociatedwiththe extremesof the 2:1069-1090. SouthernOscillation.Journal of Calimate, 2Diaz,H.F. andKiladis,G.N., associatedwiththeextremephases 1992:Atmosphericteleconnections of the Southern Oscillation.In Diaz, H.F. and Markgraf, V. (eds.), El Mflo: Historical and PaleoclimaticAspectsof the SouthernOscilation, CambridgeUniversityPress, Cambridge,pp. 7-28. Table B. 1 shows a close correspondence between El Nino events and the occurrence of extraordinary floods'. Table B.1: El Niiio Episodes and Floods in the ParanDIParaguay River Basin' El Nifno Year of Yearof Occurrence Extraordinary (warmevent) FloodsRecorded 1992 1991 1986 1987 1982-83 1982 1976 1977 1972 1974 1965 1965-66 1963 1957 1953 1951 1939 1932 1930 1925 1923 1918 1913 1911 1904 1877 1963 1957 1954 1951 1939 1932 1931 1926 1923 1919 1913 1912 1905 1878 3Extraordinary flood years are years in whichan extraordinaryflood (i.e. 10-yearsflood)occurred at one or more of the folowing sites: Jupia, Guafra, Posadas,Corrientes,Ladario,Porto Murtinhoor Asunci6n. ANNEX B -AugUSt 31, 1993 -2- The warm events in the Pacific are not the only critical feature of this phenomenon. 5. The Southern Oscillation (SO), a large scale "seesaw" of atmospheric mass between the western and eastern tropical Pacific, is also an important tropical feature. In essence, the SO defines two predominantclimate regimes in the tropical Pacific 6. Ocean. In one mode, sea-level pressures (SLP) are relatively high over the subtropical South Pacific and the Southeast Trades are strong, upwellingalong the equator is well developed, and rainfall is heavier than usual in the western tropical Pacific, while very dry conditions prevail along the equator east of the dateline and along the Peruvian coast. In the other mode, pressure gradients are weaker, and, in response, the Southeast Trades are also weakened resulting in anomalously warm water along the Equator from the coast of South America to the dateline, and anomalously heavy rainfall over these same areas. The El Nino is the manifestationof the latter extreme phase, whereas, so called "La Nifia" events comprise the opposite phase of the SO. Some of the great droughts of this century in parts of the Parana/Paraguay Basin have occurred in associationwith La Nina events. Table B.2 summarizesthe impact of the extremes in the El Nihio/SouthernOscillation 7. (ENSO) in terms of the average percent of normal annual peak flow measured during warm and cold ENSO events in this century for the available streamflow record at the three recording sites. The figures show that the climatic patterns associated with the extreme phases of the ENSO phenomenon have resulted in about a 20% differential in peak flows on the Upper Parand-ParaguayRiver Basin. The data displayed in Figures of the main text suggest that since the about the early 1980s wet season rainfall and annual peak streamflow in the region of the Parana and Paraguay River Basins have been relatively high. The question thus arises as to whether the recent increase in wet season rainfall represents a change in climatic conditions (i.e., a structural change), or whether it is simply a random perturbation within the same climatic structure. Indeed, if this increase to a higher level of runoff is real and climatically driven, this would have serious implications for the planning of development projects that are affected by streamflow levels. Table B.2: Mean Deviationfrom Long Term Mean Annual MaximumDaily Discharge(percent of normal) ANNEX B-August La NifiaYear GaugingSite El Nifno Posada 110 93 Corriente 113 89 Asuncion 118 94 31, 1993 _3. ANNEX C: DATA TABLES This annex presents in tabular fonn the data that were used in the analyses reported in the text of the paper. These data are available in Lotus format on request from Robert J. Anderson, Jr. Table C.1 Parana River in Posadas: Mean Monthly Discharges Table C.2 Parana River in Corrientes: Mean Monthly Discharges TAbleC.3 Parana River: Extreme Annual Low Flows Table C.4 Paraguay River: Extreme Annual Low Flows/Stages Table C.5 Parana River: Annual Maximum Daily Discharges Table C.6 Paraguay River: Annual Maximum Daily Discharges/Stages Table C.7 Monthly Precipitation in the Parana/Paaguay Basin I Table C.1 Parana river in Posadas Mean monthly dischargs m/s *1000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 21.6 15.3 13.6 17.5 20.1 19.7 17.2 18.6 13.6 23.9 14.8 16.3 16.9 23.8 23.3 17.6 22.4 13.7 21.2 19.9 16.9 12.1 20.4 23.5 19.9 16.7 13.4 20.5 16.7 10.7 9.0 19.7 22.4 12.5 12.1 11.4 16.3 14.4 9.7 7.7 29.4 13.5 10.6 10.7 9.5 12.2 16.0 9.6 7.9 25.5 13.4 12.0 10.4 9.8 10.2 10.7 9.0 11.0 17.1 10.2. 12.9 9.2 7.7 14.7 7.6 8.6 8.1 14.7 7.7 9.9 8.8 5.7 9.2 9.2 6.2 9.8 12.5 7.2 15.9 8.3 5.7 7.9 10.8 9.2 12.8 10.7 7.7 17.3 13.4 7.6 6.4 12.4 9.5 16.6 9.1 7.9 17.1 14.2 9.6 10.6 17.7 9.7 13.9 13.1 9.7 16.3 15.5 9.8 14.5 13.8 10.7 11.8 18.0 13.8 14.9 13.3 9.7 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 10.9 7.7 21.5 16.9 8.5 10.8 10.7 12.4 8.9 12.5 15.6 10.4 22.1 14.9 12.4 8.4 13.7 14.6 15.6 19.4 14.9 9.0 23.8 13.8 13.0 7.7 12.0 15.3 12.9 15.2 12.1 11.2 16.9 11.9 9.5 9.5 12.0 12.8 9.3 14.2 9.1 10.1 13.1 9.3 6.8 10.4 8.8 9.6 8.4 13.7 10.2 8.7 11.7 8.7 8.7 13.7 8.3 7.2 12.1 14.5 8.8 9.9 8.8 7.3 12.8 8.1 8.4 7.0 9.0 10.8 8.1 10.1 8.9 6.6 8.6 6.6 6.2 5.5 8.0 7.5 7.2 13.0 9.1 6.8 8.4 9.7 8.4 5.5 7.2 8.2 8.7 18.9 10.6 5.9 10.1 16.3 8.9 8.7 10.5 10.7 7.3 14.8 12.8 5.6 12.8 10.5 5.1 6.7 11.0 17.3 6.2 22.1 12.3 5.6 12.7 9.8 7.9 6.3 12.3 16.7 9.9 12.2 14.2 9.4 10.3 10.1 9.2 9.3 10.4 13.3 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 18.0 18.7 11.4 13.0 11.6 13.4 19.1 18.3 6.6 21.5 17.9 23.0 17.8 15.5 16.0 9.5 22.6 15.9 11.7 27.0 17.7 17.0 20.9 17.0 17.5 8.3 17.3 17.0 13.9 27.1 13.3 13.6 18.9 16.9 13.4 8.8 21.5 13.1 16.2 18.2 10.0 9.0 18.7 13.9 11.6 9.7 16.1 9.3 13.4 12.3 9.7 8.5 18.1 19.7 12.3 7.6 15.4 9.2 17.7 13.2 11.3 8.6 14.4 12.4 8.8 6.6 15.5 7.7 11.7 9.2 8.5 7.8 12.6 8.4 6.7 4.9 9.8 6.0 11.6 8.1 8.9 11.0 10.1 11.6 5.8 4.5 8.7 13.0 11.1 14.2 9.5 12.9 10.7 13.9 4.8 7.2 7.1 9.2 17.7 16.2 11.6 7.2 9.6 16.9 5.5 11.2 8.6 12.7 9.3 13.8 14.0 6.1 9.8 11.4 7.2 13.8 10.7 7.1 11.5 12.4 12.5 11.9 14.4 14.2 10.1 8.8 14.1 11.5 12.7 16.0 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 16.4 19.6 15.6 17.8 12.6 14.4 16.5 19.1 15.5 14.6 20.6 19.2 19.5 16.6 12.3 15.5 9.5 15.0 17.1 16.0 15.6 24.6 17.8 14.1 11.4 17.1 13.5 14.6 12.3 12.7 11.6 19.3 19.3 11.0 9.9 13.7 10.9 13.3 11.7 10.6 10.6 19.9 14.6 9.5 8.9 10.6 10.6 10.9 12.8 11.7 8.5 17.9 15.1 7.1 6.2 11.0 16.5 9.8 14.2 10.0 7.0 13.0 11.9 6.5 5.1 9.5 8.9 7.1 15.7 9.3 7.4 8.8 9.2 5.5 4.3 12.2 9.7 6.1 8.7 6.6 7.5 10.8 9.0 5.4 4.7 10.6 10.3 6.3 6.7 7.0 12.4 10.4 13.6 7.1 6.2 24.8 8.6 9.5 6.5 6.8 13.4 8.8 9.7 6.9 4.3 14.7 7.6 15.2 8.3 12.8 14.1 12.6 15.8 8.3 9.0 12.3 9.9 13.9 9.6 19.4 12.0 15.4 14.2 9.6 7.9 13.9 11.0 11.7 11.6 11.4 1940 1941 1942 1943 1944 1945 1946 1947 17.3 13.8 14.6 16.1 10.6 7.1 20.0 14.8 17.5 15.9 16.5 18.8 10.5 14.9 23.1 18.0 18.1 11.3 19.3 17.7 15.0 15.3 24.4 21.7 15.0 10.1 18.6 12.6 10.4 14.7 16.7 18.6 12.9 14.1 15.6 9.0 7.5 9.6 13.6 13.8 10.1 9.9 14.3 11.5 5.8 7.5 13.1 12.2 8.0 8.9 11.7 7.9 4.7 10.3 16.5 9.7 7.0 12.1 9.3 7.0 3.7 5.8 9.6 9.4 5.3 9.2 8.3 6.0 3.6 4.7 7.3 12.4 5.0 10.9 9.7 9.3 3.1 5.5 10.7 12.9 8.7 11.8 7.6 11.4 6.7 7.3 10.1 9.4 10.2 17.8 9.6 10.1 7.5 12.2 11.8 10.4 11.2 12.1 12.9 11.4 7.4 9.5 14.7 13.6 Page 1 Table C.1 Parana river in Posadas Mean monthly dischargs mI/s *1000 1948 1949 Jan 14.4 10.8 Feb 16.4 15.5 Mar 16.3 15.0 Apr 13.6 10.8 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 11.2 14.3 7.7 9.0 11.7 9.2 12.5 13.0 10.5 14.5 17.9 21.4 13.0 8.5 12.2 9.0 8.7 17.6 16.6 18.9 18.1 23.0 18.1 8.5 12.2 8.3 10.7 16.0 14.4 14.4 14.3 15.8 13.7 11.2 8.3 10.3 14.3 15.4 13.1 14.7 10.9 9.4 7.9 8.1 16.4 9.5 15.2 11.4 10.1 10.4 8.7 8.1 9.2 8.2 18.4 15.2 17.6 9.6 11.3 9.3 8.1 7.2 7.6 5.7 12.4 14.1 12.7 15.0 8.5 7.2 5.8 5.5 5.2 4.4 7.4 8.2 14.9 18.9 8.6 7.2 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 11.2 17.6 12.1 18.8 7.9 32.0 22.0 17.2 14.0 12.5 16.6 16.9 16.5 17.2 13.5 19.4 23.6 18.8 13.2 10.3 15.2 23.8 18.4 13.7 12.5 23.5 21.3 19.8 12.6 9.3 12.5 18.8 12.8 11.4 10.9 16.5 15.3 13.0 9.1 10.6 9.7 15.2 9.5 8.5 9.5 19.6 11.3 9.3 8.3 8.5 8.9 11.6 8.8 7.4 7.5 14.1 10.6 9.5 6.4 13.2 8.1 8.7 6.5 5.7 7.6 17.8 9.8 8.9 6.0 9.1 8.7 6.5 5.6 4.9 8.4 11.4 7.6 8.0 5.6 5.8 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 11.8 18.0 11.7 18.4 19.4 15.6 15.3 22.7 15.9 13.0 13.2 9.5 16.9 19.6 15.9 13.5 16.7 24.6 12.6 15.3 15.5 10.6 16.5 15.3 14.8 12.6 15.0 11.6 12.6 13.6 9.3 9.7 12.9 14.4 18.5 12.4 13.1 14.4 9.2 10.5 8.5 12.1 8.5 12.3 12.5 9.7 9.8 10.7 8.0 15.3 9.1 13.7 10.5 12.7 12.5 9.2 16.1 10.5 9.0 10.2 11.1 12.4 10.7 13.7 13.6 9.0 10.7 9.4 10.5 9.5 5.7 9.5 12.1 11.6 9.8 9.5 12.9 8.7 10.6 11.0 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 15.7 18.9 18.7 24.9 21.6 13.5 9.9 10.4 13.9 15.0 22.0 16.5 19.1 29.9 17.1 19.3 12.3 15.4 14.1 21.5 19.8 10.9 16.8 31.7 12.0 17.5 12.8 12.5 16.2 16.3 13.3 10.0 18.2 24.1 12.4 16.7 13.0 13.8 13.3 13.5 13.3 11.0 11.5 30.7 11.9 15.9 14.2 20.5 16.5 13.8 11.1 9.6 15.0 34.6 14.1 13.1 13.0 18.0 16.8 12.5 11.2 0.6 21.6 33.7 11.5 12.2 12.4 15.0 12.2 12.4 1990 1991 1992 26.9 11.2 13.5 16.7 17.9 17.8 11.6 13.1 15.0 13.2 19.6 17.5 14.5 14.7 24.8 19.0 13.4 24.8 15.6 12.9 16.3 May 9.2 9.6 Jun 8.3 8.8 Jul 6.4 6.1 Page 2 Aug 8.4 6.1 Sep 5.9 6.3 6.3 6.5 6.4 7.4 7.5 8.9 10.3 21.1 11.3 6.5 Oct 7.5 6.3 Nov 10.8 5.8 Dec 9.5 7.7 Ann 10.5 9.0 9.5 9.7 11.7 11.7 11.0 5.8 8.2 13.9 10.1 7.0 8.9 9.1 12.5 14.0 7.8 7.2 7.3 12.3 11.3 7.1 12.7 10.2 7.9 10.8 7.5 7.7 7.3 12.8 12.1 9.7 11.0 11.7 10.1 8.9 11.1 9.4 11.6 14.7 11.4 10.5 9.7 9.4 12.5 8.0 8.0 16.6 10.8 7.1 7.0 11.9 12.9 12.0 9.8 16.0 8.5 14.0 13.5 8.0 8.4 13.4 11.1 10.4 11.0 10.2 10.1 20.1 11.4 11.5 8.6 10.6 11.0 13.2 10.9 10.5 9.4 16.2 13.8 11.5 8.7 10.0 7.6 7.5 15.3 14.2 10.5 10.2 12.8 8.8 10.9 12.8 11.7 9.4 22.0 15.2 8.3 15.6 13.0 9.5 8.6 13.9 7.6 7.2 17.0 12.6 11.2 12.5 15.7 10;3 10.0 15.8 9.6 10.2 17.2 12.0 11.2 16.0 17.6 14.7 9.9 15.0 10.0 10.8 14.3 14.3 13.1 12.1 14.0 12.9 10.7 13.0 10.8 8.4 13.2 19.7 14.0 12.6 12.3 11.6 11.2 15.3 13.4 8.. 11.1 19.7 12.6 12.3 12.8 10.8 12.5 20.6 13.3 9.9 9.3 24.9 13.3 10.3 12.8 12.2 8.8 14.6 12.3 11.0 19.3 22.1 15.1 11.0 11.3 15.4 11.4 12.7 13.5 19.7 27.0 19.8 15.3 10.2 12.1 13.2 9.9 12.8 14.1 11.9 16.7 26.3 14.2 13.7 12.4 14.0 13.0 15.1 16.7 11.2 15.0 20.5 10.0 15.0 18.9 12.7 16.2 16.2 11.S 17.0 13.7 14.3 17.9 16.9 13.5 17.6 8.4 8.3 7.5 4.6 8.2 9.9 8.6 8.1 5.2 4.8 Table C.2 Parana river in Corrientes Mean monthly dischargs m/a *1000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Ann 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 17.0 15.2 13.1 20.1 25.1 21.5 16.5 21.7 18.2 17.9 14.4 15.9 19.2 27.0 24.7 17.4 26.4 16.5 16.6 19.2 20.4 14.4 29.0 24.5 21.8 22.9 16.9 15.9 19.3 14.3 11.1 25.1 26.0 13.3 17.2 16.1 13.5 15.0 12.5 9.2 31.7 15.6 11.0 14.2 13.5 10.6 16.6 12.3 9.4 40.3 15.0 12.0 17.2 13.8 9.4 12.8 11.1 12.9 28.3 13.0 12.7 14.3 10.1 12.4 8.6 10.2 10.3 24.0 10.4 10.0 11.7 7.4 9.6 9.7 7.5 11.4 19.7 9.4 14.6 9.2 6.6 7.9 10.7 8.5 15.1 17.5 8.8 17.2 15.4 8.1 6.7 11.4 11.2 20.2 15.5 7.8 19.6 18.5 10.4 9.5 18.7 13.1 21.8 17.4 9.1 17.2 20.7 11.6 12.2 14.3 12.5 14.6 25.0 15.4 15.3 17.4 12.4 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 11.9 7.7 33.8 18.9 9.7 15.1 11.5 12.4 9.1 14.2 16.7 11.5 28.7 20.3 13.8 11.8 17.5 15.6 16.6 20.9 18.6 11.8 31.7 18.8 16.6 9.9 14.5 17.8 16.3 20.6 16.7 14.3 23.8 19.9 15.3 15.7 14.1 15.2 13.2 16.9 14.9 13.9 18.0 18.2 12.9 15.4 11.5 12.4 12.0 18.1 12.8 12.7 16.0 15.8 11.9 18.4 12.3 9.4 17.4 23.6 10.2 12.4 12.7 13.3 14.8 10.7 11.7 9.0 14.9 20.6 9.6 12.9 11.8 11.4 11.4 7.5 9.1 8.0 10.5 11.5 7.6 14.0 11.1 11.3 10.3 10.0 9.4 7.5 8.2 10.2 8.9 21.9 13.2 10.3 12.1 17.2 9.6 10.8 10.9 11.2 8.2 16.9 14.5 9.3 16.2 12.0 6.5 8.8 13.1 20.0 7.6 30.2 15.1 7.5 20.7 11.8 7.6 6.6 14.9 25.5 12.0 15.0 19.2 14.6 13.8 13.0 11.3 11.1 13.1 17.7 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 25.8 25.2 12.4 15.8 16.8 14.6 20.2 20.4 8.5 24.3 24.3 33.1 23.1 20.7 18.2 12.9 30.9 20.9 12.5 33.6 25.9 27.3 26.7 20.4 21.0 10.4 23.2 20.3 15.3 35.5 20.1 25.2 26.4 21.7 17.4 11.8 25.3 16.5 21.7 25.4 15.1 17.1 26.5 19.2 13.5 15.1 22.2 12.8 21.1 16.5 15.0 14.5 27.2 24.4 15.8 11.9 20.4 11.5 24.0 16.4 17.4 14.7 24.0 21.9 12.8 9.0 16.0 10.4 18.3 12.8 15.1 13.2 19.9 12.8 9.1 7.2 13.2 8.5 13.9 11.2 13.7 14.2 15.7 14.5 8.2 6.3 12.1 13.5 14.5 16.8 16.3 22.2 13.9 18.8 6.9 8.4 10.4 11.0 22.4 23.6 17.2 13.8 13.1 24.4 6.9 13.2 11.2 14.6 15.7 19.5 22.3 9.3 12.4 19.0 8.0 16.9 13.0 8.8 13.1 14.6 19.0 19.1 20.1 19.4 12.9 11.5 18.1 14.0 16.7 20.7 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 21.0 25.5 19.1 22.1 13.9 16.1 21.3 19.2 16.2 14.7 26.1 23.5 23.1 22.6 14.9 17.2 12.4 18.5 21.9 16.8 23.5 32.3 23.8 20.6 13.8 22.1 14.5 16.7 15.1 15.6 15.4 27.0 25.7 15.9 13.2 16.7 12.2 15.0 13.4 15.1 14.7 28.9 22.7 13.9 12.8 13.6 12.7 13.4 13.5 14.8 13.5 29.1 22.5 11.7 8.9 13.7 20.1 12.4 16.8 14.2 10.7 22.0 19.8 10.6 7.7 13.4 12.6 9.0 19.6 12.2 10.4 14.4 15.4 9.5 7.1 16.7 11.5 7.5 9.9 8.4 10.6 14.6 13.9 8.8 6.9 13.6 10.9 7.6 7.2 8.4 13.1 15.3 19.3 9.9 7.6 29.0 9.6 9.1 6.7 9.4 18.2 14.5 15.6 9.8 6.3 23.2 8.2 14.2 8.4 14.8 16.7 16.3 20.1 9.3 9.0 17.6 9.5 15.4 9.5 26.5 16.1 21.9 20.1 13.7 10.2 17.8 13.0 13.1 13.1 14.2 1940 1941 1942 1943 1944 1945 1946 1947 22.2 14.7 18.4 15.9 12.9 7.3 21.1 17.4 20.6 19.0 17.9 20.9 11.7 14.7 28.0 21.5 23.4 14.8 22.2 20.6 17.3 18.4 31.1 24.8 22.5 19.8 23.5 16.1 13.2 17.4 25.0 26.1 19.8 17.6 23.2 11.1 9.4 12.0 19.3 19.4 18.1 13.8 22.8 14.5 7.7 9.2 21.1 18.7 14.7 12.0 18.5 12.3 6.7 12.1 21.9 15.4 13.6 14.0 13.9 9.8 5.6 8.6 16.1 13.8 10.8 10.5 11.4 8.5 12.1 13.3 11.2 4.7 7.9 12.5 17.4 10.5 12.4 10.7 14.3 6.7 8.7 13.9 12.3 12.9 20.9 10.5 14.1 8.0 11.8 14.8 10.8 16.5 15.1 17.2 14.1 9.1 11.3 19.5 17.7 Page 1 8.4 4.9 7.5 10.3 14.9 Table C.2 Parana river in Corrientes Mean monthly dischargs m/s *1000 Aug 9.6 8.0 Sep 7.3 7.5 Nov 11.7 6.4 Dec 10.4 8.3 Ann 12.4 11.0 11.1 7.6 13.8 13.2 15.6 7.3 13.4 22.8 16.6 13.7 10.6 10.9 16.4 19.9 12.5 8.4 13.1 16.1 17.6 12.7 14.7 12.5 11.6 14.4 8.7 8.3 10.9 16.4 20.6 15.4 14.6 14.7 13.6 12.0 15.6 12.0 16.9 19.9 16.6 17.7 12.3 11.4 8.5 7.7 10.1 12.9 10.2 9.2 6.6 6.1 13.3 12.8 14.2 8.8 9.3 19.6 10.8 8.2 8.1 12.7 19.1 15.3 11.6 18.8 9.5 19.6 15.7 8.6 11.1 16.0 15.0 15.8 11.2 14.2 11.3 23.2 13.2 11.6 9.0 14.9 15.8 19.1 13.5 14.2 11.6 21.8 19.6 13.9 10.4 12.5 7.4 11.8 12.9 14.1 14.9 12.6 15.3 12.7 14.8 18.6 8.1 8.8 18.2 17.0 15.5 13.1 15.9 12.3 13.8 20.4 13.7 10.1 26.3 18.3 11.7 19.7 16.0 12.8 11.8 22.0 9.3 8.6 20.1 15.1 14.2 16.8 20.0 12.9 13.0 23.7 9.1 10.2 25.8 14.8 14.3 21.4 20.3 18.7 13.2 22.3 11.5 14.0 17.2 18.4 18.3 16.2 17.8 17.7 14.1 19.7 18.3 13.9 32.2 48.2 16.4 18.9 18.0 22.2 20.3 18.0 17.6 12.7 25.5 33.5 16.8 20.2 15.3 16.4 18.2 19.6 19.5 12.1 20.2 25.4 15.7 19.5 14.2 13.6 17.6 28.4 19.4 13.0 17.7 33.3 16.9 14.8 16.4 13.4 13.0 23.2 18.7 13.6 24.9 29.1 19.4 14.1 13.7 17.9 13.4 18.7 18.9 22.7 40.6 25.7 21.5 11.7 14.1 16.6 10.6 14.8 20.6 17.3 25.2 37.8 19.2 19.9 16.2 18.8 17.3 19.9 21.7 18.0 27.4 21.4 14.1 21.5 28.1 12.5 20.7 25.6 15.4 23.5 22.5 13.6 26.8 17.3 16.4 26.6 22.4 16.7 25.5 1948 1949 Jan 15.3 11.9 Feb 18.1 17.1 Mar 19.5 18.7 Apr 17.7 13.2 May 12.3 12.3 Jun 10.7 12.0 Jul 8.5 10.0 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 14.1 15.0 9.2 10.3 14.4 10.3 14.0 14.2 15.0 22.6 21.0 25.3 15.2 10.1 15.2 11.3 12.4 21.7 19.9 29.3 23.9 30.5 21.5 9.9 16.9 10.5 12.8 23.4 19.1 22.9 21.4 25.4 20.4 13.3 11.6 14.2 19.6 20.9 18.6 22.4 14.9 13.5 12.1 12.7 19.0 13.0 23.0 17.4 16.1 18.2 13.2 11.2 13.5 13.6 27.7 17.9 25.6 15.4 15.7 16.4 13.0 9.9 11.8 10.3 21.5 20.8 20.3 19.3 12.9 14.1 9.3 8.1 9.1 7.4 13.5 10.6 22.3 24.1 13.0 12.8 8.1 7.2 8.8 8.6 11.1 11.6 15.7 26.4 14.2 13.2 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 17.3 20.6 14.8 20.8 9.7 17.1 33.3 20.2 14.0 16.1 22.7 21.2 19.2 22.7 13.7 24.5 33.4 22.3 17.4 12.6 20.9 30.1 23.3 18.5 16.9 31.1 36.6 26.0 14.7 11.1 17.9 30.5 18.0 16.7 15.0 25.1 26.6 18.4 11.0 12.6 13.8 26.1 12.7 12.9 15.5 26.1 17.9 11.6 9.8 10.9 13.2 19.5 11.5 12.0 10.3 25.0 15.0 10.9 8.3 17.4 12.8 15.4 8.9 10.2 9.0 22.3 13.1 10.6 7.7 12.5 11.7 11.1 7.9 8.4 9.0 15.2 10.1 9.6 7.1 7.6 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 12.5 22.4 12.5 23.8 23.1 19.9 20.6 28.5 19.1 15.8 15.3 16.7 16.6 26.3 24.7 17.9 22.1 34.0 18.3 19.8 17.7 15.2 20.7 21.5 19.7 16.2 20.1 18.9 16.5 19.4 12.1 15.3 15.8 18.5 26.7 16.4 17.6 18.6 13.1 16.2 9.9 16.9 10.5 17.4 18.0 14.9 12.8 15.8 11.0 21.3 10.0 16.5 13.6 16.6 18.2 12.7 20.0 13.8 12.0 19.0 13.0 16.0 13.1 18.4 19.1 12.3 13.9 14.4 12.7 17.5 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 21.1 25.7 27.0 38.3 27.3 18.8 10.9 15.0 16.4 14.4 29.4 27.5 24.7 40.4 22.9 24.2 13.1 19.0 16.5 25.6 28.9 18.6 22.5 45.3 15.6 24.0 16.9 18.5 19.4 23.0 18.3 15.5 27.6 38.2 17.6 25.3 19.8 18.7 16.4 19.4 18.8 17.6 18.0 46.5 19.6 24.7 21.0 26.0 20.8 18.4 18.6 15.0 21.4 50.2 20.7 22.8 20.3 28.5 24.7 16.6 1990 1991 1992 26.3 13.0 18.9 27.2 19.7 21.0 13.8 16.3 19.7 16.8 23.6 23.3 21.2 21.0 34.2 27.8 17.1 42.3 Page 2 Oct 8.4 6.9 Table C.3 Parana River Extreme Annual Low Flows Year Guaira Date Discharge 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 Dec 1 Jan 1 Sept 29 Sept 1 Sept 1 Aug 14 Sept 30 Oct 1 3850 5100 3350 2500 2550 4600 3500 3600 Date Posadas Discharge Nov Aug Oct Aug Nov Sept Aug Sept Aug 5699 6949 5520 6097 8061 6686 8376 7983 5378 Dec Jan Aug Dec May Aug Nov Sept Sept Oct 5026 5061 7404 4991 5096 5096 4271 4102 5735 6724 Sept Dec Jan Aug Nov Sept Oct Aug Jan Aug 7175 5307 6464 7519 4169 3539 6097 5879 5807 7213 Corrientes Date Discharge Nov Aug Oct May Nov Nov Aug Sept Sept 6154 7902 5962 8330 14107 7291 8851 8477 6096 Dec Jan Sept Dec Jan Aug Nov Dec Sept Oct 6115 6077 10216 6531 8452 6470 5962 5962 7181 8501 Sept Dec Jan Aug Oct*NoV Sept Oct Dec Jan Aug 2302 8477 9107 11452 6271 5812 9316 8138 7902 10762 8927 12662 12795 7203 5431 11238 7269 6674 5906 6756 Sept 30 Oct 1 Sept 24 Nov 24 Nov 16 Sept 1 oct 13 Sept 28 Oct 1 Sept 4 3600 3900 4450 3350 2500 2700 3800 3350 3400 3350 Oct Aug Aug*Sep Sept Nov July Nov Sept Oct Oct 5735 7634 7299 4749 3572 7519 6464 5378 5237 5166 Oct Sept Sept Dec Nov June Nov Oct Oct Sept Sept 29 Oct 1 Sept 1 Sept 12 Oct 10 Oct 1 Oct 1 Oct 1 2900 2900 4450 3400 3500 2600 3200 4800 Oct Nov Nov Sept Oct Sept Sept Dec 4474 7404. 6649 5166 2928 4406 6538 6986 Oct Jan Nov Sept Oct Jan Sept Dec Page 1 8306 8526 9529 8019 4552 6154 9475 9030 Table C.3 Parana River Extreme Annual Low Flows Year 1948 1949 Guaira Date Discharge Oct 10 3200 Oct 20 2000 Date Sept Oct 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 Sept 7 Sept 1 Sept 1 Aug 24 Nov 11 Oct 6 Oct 1 Dec 1 Aug 31 Oct 1 2700 2700 2950 2700 2950 2600 2800 4100 4200 3250 Aug Aug Sept Aug Nov Oct*Dec Dec June Aug Oct 5378 5378 4338 3836 5520 5378 5378 8376 6170 5413 Sept Oct Sept Aug Dec Oct Dec Jan Sept Nov 7763 6390 7603 6592 8090 6861 9965 10762 10674 11118 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 Oct 2 Oct 16 Aug 29 Sept 22 Sept 28 Oct 1 Aug 30 Sept 1 Oct 10 Sept 24 3250 3900 4300 3600 3800 4350 5000 5050 3750 3150 July Aug Sept Sept Jan Sept Sept Oct Sept Sept 6060 6097 5202 3935 6097 9176 6686 6464 4852 4440 Aug Oct Sept Sept Sept Sept-Oc Oct Oct Sept Sept 9992 9882 7313 7181 7856 11982 8725 7763 6430 5868 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 Sept 1 Aug 29 Sept 1 Sept 1 Sept 29 Sept 5 Aug 1 Aug 25 Sept 1 Aug 19 3630 4500 4500 5750 5500 5600 5900 6200 6400 6500 Aug Nov May Aug Oct Sept May Aug May July 4957 5988 7789 9748 7213 7289 8653 7827 7289 8455 Sept Nov*Dec May Aug Oct Sept May Sept Oct Jan 6430 7247 9691 12400 10998 10558 11329 11856 10674 12761 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 Aug 1 Sept 23 Sept 1 Oct 1 July 5 Nov 29 Nov 8 Jan 1 Jan 1 Dec 6900 5800 6600 8050 7000 7800 6400 6900 7130 June July Oct Sept July Dec Jan Jan Oct Jan 9790 7062 5520 13944 10205 8894 7673 8336 6761 8693 May Sept Oct Sept Aug Dec Jan Oct Dec Jan 16862 11793 13193 23124 13787 10329 9609 12206 9772 9449 1990 1991 1992 Dec 31 7950 Aug 7300 March Sept Jan 10457 9339 11526 March Nov Jan 12465 11028 15708 - Posadas Discharge 5026 5378 Page 2 Corrientes Date Discharge Sept 6674 Nov 6000 Table C.4 Paraguay River - Extreme Annual Low Flows and Stages Year 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 Ladario Date Discharge Jan 1 Nov 4 Novl Oct 3 0.79 1.12 1.17 0.31 Dec Nov Dec Jan 28 11 1 1 1.90 0.85 1.10 1.50 Nov Nov Dec Jan Jan 2 1 1 1 1 0.00 0.02 0.33 0.78 0.79 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 Nov Dec Nov Dec Nov Dec Jan Nov 1 31 23 1 1 1 1 11 1.36 1.45 1.02 1.14 0.34 0.46 0.68 0.50 Jan 1 0.85 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 Jan Nov Jan Dec Feb Dec Nov Sept 4 Sept 9 1.05 1.67 1.90 1.18 0.00 1.44 0.00 0.12 0.00 0.00 1940 1941 1942 1943 1944 1945 1946 1947 Oct Oct Nov Jan 1 16 1 1 0.05 0.00 0.14 0.73 Sept 1 0.07 Dec 24 0.86 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1 1 1 7 28 1 11 Porto Murtinho Date Discharge Oct 10 1.13 Oct 1 Nov 4 Nov 1 Nov 1 Sept 28 Oct 10 Jan 1 Dec 1 1.30 1.57 1.60 2.26 1.01 1.08 1.90 2.26 Page 1 Asuncion Date Discharge Paraguay River Ladario Discharge Year 1948 1949 Date 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 Nov 21 Dec 6 1.02 0.87 Nov 17 Nov 1 Nov 30 0.57 0.70 0.07 Jan 1 Jan 1 Dec 30 0.64 1.63 1.53 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 Dec 1 - Table C.4 Extreme Annual Low Flows Porto Murtinho Date Discharge Oct 4 1.28 Oct 1 1.26 Dec Nov Dec Dec Dec Dec Dec Jan Feb Dec 1 14 29 26 30 3 1 1 8 22 1.86 2.17 2.19 2.04 1.80 1.51 1.92 1.94 3.17 3.00 Dec 30 Nov 27 2.72 2.15 Sept 26 Oct 1 Oct 16 Oct 18 Nov 1 Sept 28 0.81 0.87 1.28 0.80 0.94 0.86 Oct 1 Sept 25 Oct 1 Oct 5 Oct 1 Nov 23 Dec 12 Jan 1 Dec 25 Dec 16 0.98 0.73 0.77 1.25 1.31 2.80 3.10 3.11 3.96 3.78 Dec Dec Dec Feb Jan Dec 3.99 3.66 3.43 3.54 3.91 2.82 0.16 Oct 11 Sept 6 Oct 3 Aug 8 0.00 0.00 0.00 0.00 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 Nov 11 0.00 Oct 12 Oct 1 Dec 1 0.00 0.08 1.30 Dec 5 1.95 1980 1981 1982 1983 1984 1985 Dec 1 Dec 6 1.89 1.71 12 4 1 1 1 31 Page 2 and Stages Asuncion Date Discharge Table C.5 PARANA RIVER - ANNUALMAXIMUM DAILY DISCHARGES Year Jupla m/s Guaira date m/s Posadas date m/a Corrientes date m/s date 1901 1902 1903 1904 1905 1906 1907 1908 1909 25800 24500 20100 21100 45000 26150 23650 26600 15450 Feb 17 Dec 1 Feb 24 Jan 31 May 25 April 1 March 6 Feb 7 June 1 19400 23000 22100 25700 50000 27800 24300 29400 21300 Feb 22 April 10 March 25 Dec 31 June 5 April 17 March 14 Feb 12 Jan 2 1910 1911 1912 1913 18850 29550 29800 20800 17050 24650 18100 19850 21850 27550 March 2 Dec 30 Jan 2 Jan 27 Nov 17 Oct 11 Feb 7 Mar 8 June 21 Nov 29 22000 33200 39100 24200 22500 24100 20100 22100 24800 31000 March 3 Dec 31 Jan 7 Feb 1 Dec 16 June 6 Feb 12 March 13 June 26 Dec 6 1914 1915 1916 1917 1919 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 22000 19000 11600 26300 1930 1931 1932 1933 18900 25500 14600 14700 April 7 March 12 Feb 12 Feb 19 23700 19800 19600 19000 11400 25700 21000 15300 34900 Feb 11 April 2 March 18 March 9 Nov 28 April 15 Jan 21 March 26 March 3 23450 25800 25050 33750 18850 17250 27000 21000 29600 32450 Jan 7 Feb 13 April 2 June 21 March 10 Dec 15 Jan 30 Jan 28 Oct 22 March 5 30000 36000 30500 38100 22200 18600 33400 24300 31000 39100 Jan 13 Feb 20 July 5 June 27 March 14 Dec 19 Feb 5 Feb 3 Oct 27 March 10 Feb Feb Jan Jan 21300 32800 20200 19400 Feb 11 March 1 Feb 5 Jan 23 23600 29900 26750 19700 Feb 15 March 3 April 24 Jan 26 30100 36000 32100 24600 Feb 22 March 10 April 29 Feb I 8 22 30 31 Page 1 Table C.5 PARANA RIVER - ANNUALMAXIMUM DAILY DISCHARGES Year Jupia Guaira 1934 1935 1936 1937 1938 1939 m/a 11200 17000 13700 14900 12800 15100 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 17400 12800 15300 19700 11900 15900 19500 21800 14600 15500 Feb 22 Jan 8 March 14 Jan 31 Feb 23 Feb 14 Jan 10 March 21 March 21 Feb 17 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 15000 17700 19300 9740 12500 9740 12600 17400 17000 15600 Feb 14 Jan 30 March 18 March 28 Feb 22 Jan 27 Jan 7 March 1 Jan 29 March 26 18000 20200 1960 1961 1962 1963 1964 15000 20200 15200 16600 13200 Jan 28 Feb 25 March 22 Jan 2 Feb 26 17900 25300 18400 21200 20300 1965 1966 1967 19300 20100 15000 March 11 Feb 13 Feb 17 25800 27400 20100 date Jan 18 Feb 20 March 8 Jan 20 Dec 24 Jan 4 m/a 13600 19000 16700 24700 15200 16800 Posadas date Dec 31 March 12 Jan 9 Jan 19 Jan 29 Jan 10 14650 27650 34500 25800 25100 26600 20900 16400 20000 21000 15700 17700 25900 26500 17400 17300 Feb 28 Feb 11 March 21 Feb 3 March 21 Feb 19 March 5 March 28 Feb 25 March 6 21550 23750 22000 21700 17400 17800 28500 2i500 18800 17300 20300 23000 21400 11100 17900 13100 March 6 Feb 5 March 25 Apr1l 4 May 24 June 23 June 15 Feb 38 Feb 4 Feb 9 1850o i18oo e/ 22300 25800 20900 19450 23900 22900 22050 26150 17800 23800 Feb 2 March 6 March 22 Jan 25 Feb 23 March 8 Feb 22 Feb 22 17800 26650 20700 21750 20500 30300 33900 21700 Page 2 date Jan 27 Oct 13 June 12 Nov 21 July 4 Dec 7 Corrientes r/s 16300 33500 31900 25800 26800 31000 date Feb 2 Oct 23 June 17 Jan 27 July 9 Dec 12 Jan 21 Feb 13 April 19 Feb 8 March 24 Feb 22 March 6 March 30 Feb 25 March 8 25600 25500 25700 23000 20000 20100 33700 29600 21500 20400 April 7 April 27 March 29 Feb 13 March 28 March 8 March 12 April 9 March 4 March 20 March 9 March 22 March 28 Nov 4 June 19 June 24 June 7 Sept 27 Feb 7 Feb 12 26800 March Feb 5 March 18 Feb 27 Nov 9 Feb 25 Dec 23 Feb 23 March 9 33200 25700 23200 30600 27300 29200 32400 23300 33800 23500 35100 24500 24400 22700 36400 43800 27200 15 March 27 March 31 Nov 8 June 24 July 1 June 13 oct 4 Dec 31 Feb 19 Feb 24 March 25 March 11 Feb 1 March 2 Dec 29 March l March 14 Table C.5 PARANA RIVER - ANNUAL MAXIMUM DAILY DISCHARGES Corrientes Posadas Guaira Jupia Year 1968 1969 rn/a 11600 8680 date March 3 Nov 19 m/s 18300 13900 date Jan 23 Nov 24 m/s 18800 23100 date Jan 39 Jan 1 m/s 21300 23500 date Feb 3 Jan 16 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 14800 11500 12400 13400 18soo 11000 14100 21270 l8830 15180 March 3 Dec 12 Dec 12 April 6 March 26 Jan 9 Dec 17 Feb 6 Jan 1 Jan 29 17100 16800 20000 22130 22880 16250 19770 28250 19890 17400 March 7 Jan 10 Oct 17 Jan 28 April 2 Jan 6 Dec 31 Feb'13 Jan 29 Feb 27 17100 23450 24600 25050 23500 22850 21050 28000 19700 25500 March 12 Jan 3 Oct 10 Jan 31 Jan 27 Dec 11 June 10 Feb 15 Jan 31 May 17 19600 27200 29800 29900 30400 26600 24400 36700 25000 29800 March 19 Jan 19 Dec 11 Feb 9 Feb 2 Dec 17 June 17 Feb 21 Feb 5 May 23 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 19000 13070 21220 28160 16080 16040 7920 7350 13970 12520 Jan 31 Dec 21 March 27 Feb 12 Jan 7 Feb 15 April 3 Jan 1 March 10 Feb 19 26380 21250 27190 39850 19840 19550 15140 21310 17020 March 7 Dec 29 Dec 1 June 15 Aug 9 Feb 18 May 21 May 23 March 14 26850 25900 31350 43330 23100 21750 21000 34500 23450 31250 March 8 Dec 30 Dec 5 July 12 Jan 6 Feb 19 May 22 May 23 May 27 Sept 16 34100 31000 42600 54700 28800 28300 27200 38900 26900 35200 March 15 Feb 5 Dec 11 July 18 Jan 19 Feb 23 May 28 May 30 June 3 Sept 23 1990 1991 1992 16040 22380 16680 Jan 9 Jan 13 May 6 34180 21390 22520 Jan 19 April 11 May 9 37500 22800 41850 Jan 25 April 14 June 25 43800 27500 50800 Feb 1 April 22 June 8 Page 3 I PARAGUAY RIVER Ladario Year 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 4.32 4.39 5.00 2.71 5.00 6.62 5.61 3.69 3.69 2.77 date June 25 June 10 June 4 May 16 June 3 May 11 May 6 July 13 July 23 May 27 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 2.00 2.17 5.10 6.39 3.57 1.51 3.26 5.13 3.45 3.00 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 m - Table C.6 ANNUAL MAXIMUM DAILY STAGES AND DISCHARGES Asuncion Porto Murtinho date m W/s m date 6.40 8.80 5.38 3.60 5.96 5.31 6320 11170 4980 3320 5730 4900 Dec 11 June 23 Jan 1 Dec 31 March 21 Jan 1 March 23 June 21 June 17 April 8 July 10 April 12 July 25 June 18 July 22 July 8 3.31 7.00 7.30 7.08 5.84 4.84 4.85 3.89 5.40 7.78 3110 7280 7820 7420 5540 4400 4410 3550 5010 8770 March 19 Dec 31 Jan 15 May 15 Nov 30 June 9 Feb 20 Oct 16 June 18 June 13 6.37 6.07 4.26 5.50 3.41 2.30 5.47 4.07 2.87 5.31 May .12 April 7 June 12 June 14 July 4 July 20 June 18 July 2 July 9 June 4 6.14 6.02 5.99 5.85 3.57 4.94 4.85 3.42 5.46 4.35 5950 5780 5740 5560 3300 4500 4410 3190 5080 3940 Dec 6 July 18 Jul 30 Nov 19 Jan 1 May 13 May 28 May 5 June 17 Oct 16 5.20 5.50 5.98 5.11 June 6 June 3 May 27 May 16 4.80 7.52 5.91 4.96 4360 8240 5630 4520 Feb 17 July 1 July 4 Feb 1 Page 1 PARAGUAY RIVER Year 3.99 5.74 2.25 2.43 1.60 2.01 July June June July June June date 1 11 12 12 9 16 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 5.03 1.96 5.25 5.03 2.05 5.24 4.15 4.57 1.92 5.32 June 12 May 28 June 28 June 23 June 13 June 19 July 15 July a June 26 May 3 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 5.07 4.15 4.64 2.86 4.42 2.64 4.30 4.19 5.01 5.91 June 8 June 26 July 3 July 1 July 14 July a August 3 July 22 June 25 May 9 1960 1961 1962 1963 1964 1965 1966 1967 Table C.6 ANNUAL MAXIMUM DAILY STAGES AND DIScHARGEs Ladario m 1934 1935 1936 1937 1938 1939 - 4.92 4.34 2.25 4.47 1.33 2.74 2.48 1.63 May 25 June 21 June 10 June 19 April 1 April 8 May 22 April 24 Porto Murtinho m date 3.16 6.49 3.94 6.06 5.46 3.98 5.64 5.79 6.04 2.78 5.83 June 6 May 25 April 1 Oct 5 Aug 12 May 25 Aug 24 July 21 May 24 June 19 Auq 13 5.65 4.90 5.49 4.27 4.96 3.66 6.16 5.60 6.20 7.75 Aug 19 March 24 May 26 June 17 June 4 July 12 Sept 21 Aug 10 Oct 1 Aug 5 5.42 6.20 June 29 July 1 2.60 4.80 4.66 3.06 April 17 May 22 April 9 March 14 Page 2 Asuncion m m/s date May 12 Aug 23 June 21 May 21 Feb 18 June 14 2.87 5.03 5.04 3.52 3.26 4.60 2800 4600 4610 3260 3070 4170 6.36 4.50 5.06 5.07 3.11 3.02 6.50 5.43 1.48 3.61 6260 4080 4630 4640 2970 2900 6470 5040 1910 3330 June 10 April 23 June 22 Nov 28 Jan 1 Sept 13 June 1 June 3 May 3 July 1 4.12 5.27 4.52 4.87 6.38 3.01 6.45 5.45 6.02 5.80 3740 4860 4100 4430 6290 2890 6400 5060 5780 5500 April 22 June 6 June 11 June 6 June 18 July 15 May 17 April 11 oct 23 Oct 17 5.20 6.05 2.28 4.09 4.40 6.77 4.85 2.62 4780 5820 2420 3710 3980 6900 4410 2640 Jan 1 May 20 May 28 June 27 May 2 June 1 Jan 26 April 1 PARAGUAYRIVER Year - Table C.6 ANNUAL MAXIMUM DAILY STAGES AND DISCHARGES Ladario. m 1969 1969 2.05 1.80 date June 6 May 31 1970 1971 1972 1973 1974 1975 1976 1977 1979 1979 2.13 1.11 1.97 2.09 5.46 4.33 4.95 5.52 5.36 6.25 June 16 May 4 May 25 June 19 June 5 June 16 June 22 April 20 May 2 April 1 2.96 2.77 3.18 4.86 6.87 4.98 5.59 6.97 6.41 9.15 1980 1981 1982 1983 1994 1985 1986 1997 1988 1989 6.14 5.46 6.52 5.36 5.07 April 18 May 19 April 21 May 10 June 1 Porto Murtinho m date Jan 30 May 9 Asuncion m m/e 2.34 4.50 2450 4080 date Feb 2 May 12 July 11 May 11 May 12 Dec 31 Aug 15 Aug 13 May 29 July 29 July 20 June 6 1.60 6.35 3.96 3.33 4.98 4.20 3.65 4.74 3.75 7.17 1980 6250 3610 3120 4550 3810 3360 4300 3440 7580 Jan 28 June 17 Jan 8 Feb 8 Dec 14 June 10 Jan 31 May 31 June 14 8.54 6.64 9.71 9.08 5.95 9.20 July 1 July 16 June 29 May 29 July 20 June 7 6.53 4.40 7.76 9.01 5.55 6.95 4.69 5.90 7.65 6.42 6520 3980 8730 11740 5180 7200 4260 5620 8500 6350 July 10 Jan 1 July 29 May 29 May 12 June 7 June 10 June 6 June 10 Sept 25 June 31 5.75 4.73 5430 4290 June 22 July 8 8.55 10530 4.36 3.82 1990 1991 5.49 6.64 1992 5.38 7.90 Page 3 June 1 I Table C.7 Monthly Precipitation in the ParanafParaguayBasin (mm) Year Jan Feb Jun JuL 54.33 53.00 90.25 69.50 65.50 103.75 44.00 70.75 69.75 66.75 63.67 125.33 51.25 114.00 60.25 102.75 28.25 153.50 146.00 128.75 104.68 93.82 162.05 80.80 33.35 76.25 97.38 75.15 73.70 30.40 62.40 72.28 15.28 60.98 99.40 130.32 45.86 66.48 79.70 74.52 49.72 129.22 108.92 70.14 42.02 36.72 114.68 40.10 112.64 132.52 30.00 83.57 52.00 37.33 64.75 135.00 95.75 56.00 69.75 130.75 50.00 68.50 83.67 36.67 30.75 111.75 47.50 82.50 80.25 68.75 61.33 95.75 41.00 76.68 54.25 14.67 29.12 85.95 22.50 66.38 68.12 51.12 26.36 59.24 8.74 15.08 108.08 87.08 54.38 33.92 43.62 225.00 58.34 47.58 53.40 18.50 89.94 79.60 85.52 103.50 37.78 45.22 10.86 43.29 Mar Apr 91.33 116.33 195.25 99.00 118.75 74.50 111.00 86.50 115.25 121.50 105.50 51.00 171.25 203.00 172.00 46.75 83.25 217.00 107.00 125.25 185.40 109.45 78.57 85.88 39.33 78.57 188.57 129.68 119.97 155.88 96.24 176.16 39.72 107.40 80.56 90.40 168.02 107.20 180.40 178.68 213.62 181.66 111.94 102.86 143.30 207.30 90.12 174.38 212.76 186.82 220.86 142.00 131.33 100.33 92.75 97.00 175.25 109.25 129.00 79.75 88.00 215.00 133.00 136.33 146.67 201.33 281.00 69.00 123.75 122.75 89.33 104.00 105.75 133.45 146.93 104.30 263.80 104.50 101.25 270.15 27.73 93.22 213.36 187.20 73.26 66.04 59.40 146.34 95.12 125.70 89.94 140.34 241.56 104.26 39.06 56.26 64.58 98.62 146.56 163.42 74.66 82.52 45.14 62.71 90.00 81.00 49.75 108.50 263.50 62.75 57.50 119.00 67.25 94.50 113.67 115.33 61.75 127.00 170.25 220.25 36.25 206.00 142.50 104.75 51.10 168.52 146.77 93.25 184.15 129.10 28.20 175.62 71.68 114.40 143.34 103.22 56.62 77.88 33.16 96.28 54.54 128.22 125.86 160.62 135.10 127.36 101.20 29.06 62.76 165.60 176.08 68.78 43.68 116.14 57.29 119.29 150.50 168.67 116.71 196.Q0 163.14 108.43 180.50 137.62 187.41 138.60 100.90 158.90 176.50 124.82 33.31 72.35 131.97 71.71 119.17 128.17 125.09 71.83 229.33 95.33 157.67 101.00 85.43 143.86 80.00 81.00 92.29 72.S7 34.14 110.29 106.75 69.12 74.00 79.25 97.54 92.20 27.61 69.46 69.43 74.45 34.20 64.63 127.87 89.26 70.97 85.63 86.12 30.97 43.U 46.92 54.31 144.36 95.28 99.08 72.00 113.36 98.54 80.77 116.50 118.78 51.67 131.00 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 151.33 198.67 117.00 120.50 96.75 25.25 183.50 122.75 75.75 160.25 156.00 112.67 97.67 142.50 154.50 117.50 8.00 162.50 98.75 214.50 155.45 251.15 160.50 65.97 143.12 223.68 179.82 116.60 185.55 155.77 206.22 133.86 86.32 83.80 118.68 142.68 80.38 218.00 109.08 152.68 150.66 203.16 104.10 101.22 134.74 238.32 177.22 135.56 168.36 216.90 170.57 130.86 118.33 66.67 211.25 90.25 129.00 49.00 86.25 84.00 213.25 191.25 101.25 196.00 104.00 182.00 92.25 144.00 139.75 134.25 143.25 157.50 194.35 117.55 86.57 132.90 83.10 51.92 108.28 142.05 50.05 150.82 126.98 164.52 142.12 165.12 99.96 71.90 102.48 152.76 182.68 141.68 168.34 118.40 121.56 122.58 154.46 202.00 166.10 209.86 94.12 155.54 182.86 238.00 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 175.67 238.33 107.43 253.86 227.29 87.71 165.00 161.00 119.94 151.93 190.62 90.21 168.50 190.33 222.46 213.94 204.63 143.73 204.70 155.91 212.77 183.45 96.17 81.67 171.17 106.00 103.86 216.29 117.14 166.14 70.00 170.43 201.71 121.29 202.25 122.38 69.12 150.75 168.84 200.06 88.69 123.94 142.11 144.19 169.30 179.17 87.28 203.S2 167.94 202.56 218.92 154.96 75.46 105.80 129.00 105.08 138.04 148.81 143.73 200.82 185.27 128.45 114.85 191.08 166.18 143.17 May 26.67 90.83 57.00 137.57 98.57 67.14 66.88 45.12 42.90 24.24 28.49 37.08 86.37 41.43 74.32 46.58 26.93 39.77 91.62 57.08 65.67 33.91 1 Aug 105.67 72.33 127.00 85.75 104.00 64.00 103.50 65.75 34.50 31.50 77.33 52.00 36.67 93.75 90.75 68.00 28.25 23.25 41.00 41.00 56.25 74.03 53.33 21.55 33.12 40.28 27.88 56.00 96.72 118.05 33.52 59.46 26.66 48.48 122.22 73.10 52.80 24.24 74.46 99.40 90.72 66.04 24.82 33.56 23.78 42.46 54.80 41.00 30.10 15.70 21.29 33.29 29.83 30.50 36.43 50.57 79.71 35.71 62.50 92.75 33.26 35.56 20.49 8.86 65.61 40.38 39.70 87.56 12.93 48.63 39.00 106.38 88.82 86.10 Sep Oct Nov 73.00 81.33 45.75 141.75 108.00 71.75 104.75 76.25 97.25 103.33 141.00 65.67 103.50 77.75 73.25 66.25 127.00 71.75 37.00 140.00 189.05 89.03 80.40 75.47 140.80 99.90 95.22 219.90 163.75 50.88 52.80 98.46 60.60 74.56 117.16 83.76 93.02 66.32 143.72 66.98 120.10 83.16 54.46 49.52 95.54 86.88 132.64 101.30 75.38 85.64 49.14 92.14 99.67 137.00 194.00 204.25 274.50 75.25 112.00 198.50 80.75 61.00 108.33 76.67 166.25 224.50 137.00 59.50 104.00 124.25 176.00 118.25 153.80 108.00 171.80 33.53 182.30 99.12 109.70 211.25 183.32 124.68 187.54 149.42 164.02 81.86 165.82 108.16 87.40 116.40 202.48 98.02 51.22 88.70 112.06 116.84 108.76 176.30 95.32 123.18 88.04 116.92 160.86 143.43 137.33 212.33 84.75 119.25 151.00 76.50 129.75 119.00 68.75 104.00 213.33 159.33 133.25 189.50 69.25 72.50 44.75 216.00 205.00 136.67 49.75 97.57 102.43 119.35 196.43 185.10 215.45 97.40 102.22 106.20 79.12 167.88 63.16 119.58 172.56 66.20 176.98 103.76 193.78 147.80 197.16 59.98 142.12 102.28 125.32 161.36 41.06 162.66 121.26 145.06 132.43 157.00 136.83 121.00 21.86 57.86 163.29 119.71 75.62 72.00 104.53 94.62 89.21 88.13 94.13 49.02 40.76 72.12 93.21 159.74 50.92 87.58 64.42 32.27 201.00 237.17 104.71 197.71 144.14 103.14 147.25 206.62 158.90 134.09 95.40 70.30 230.91 160.73 97.90 164.73 200.61 130.76 96.83 138.33 169.00 148.18 140.83 32.67 68.57 42.00 116.00 238.71 119.00 174.00 223.21 96.11 182.79 119.46 133.69 107.02 100.08 82.72 212.14 93.90 78.75 257.40 125.73 119.73 Dec 67.33 240.67 280.25 147.75 148.00 115.00 231.00 228.25 109.00 69.67 230.67 154.00 68.50 133.50 143.75 139.50 94.00 197.50 134.00 186.50 105.85 100.78 228.35 71.25 112.65 148.50 111.32 104.75 131.25 178.15 166.56 124.66 143.54 137.98 226.50 125.58 81.62 93.92 175.00 152.74 141.90 84.36 110.48 64.84 132.20 180.52 66.18 52.06 196.54 179.28 131.14 67.17 116.83 133.83 152.14 96.57 169.00 271.14 172.75 135.75 136.17 116.72 125.65 177.30 281.30 158.90 99.59 165.61 73.99 162.02 99.64 145.25 247.45 155.Q0 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 95.50 202.21 255.80 127.00 123.93 149.57 180.64 72.29 252.64 203.33 66.29 111.69 109.54 89.60 103.80 136.71 122.00 155.40 195.50 178.80 100.27 148.54 194.54 128.20 137.47 73.43 78.00 126.00 117.47 145.83 189.20 196.20 163.36 184.15 131.73 68.80 32.67 139.14 95.23 109.33 80.13 225.13 110.53 137.10 32.42 119.27 81.29 67.91 129.85 134.36 60.08 79.33 268.20 104.20 115.53 84.38 35.87 64.64 33.21 23.92 58.14 73.47 165.21 72.29 52.71 30.57 69.62 26.14 42.29 63.50 57.00 33.60 13.71 57.62 94.27 11.93 89.64 61.54 64.29 50.36 50.50 90.29 68.73 43.40 94.00 10.27 60.13 57.86 1987 1988 1989 1990 1991 1992 195.86 139.54 227.50 220.21 157.18 118.78 179.00 104.17 139.69 111.50 109.89 279.00 96.86 128.38 178.92 163.00 138.00 186.83 162.92 145.92 142.08 256.08 144.15 207.00 135.86 84.50 34.69 138.43 122.83 174.80 85.00 28.42 80.85 87.31 99.71 54.12 82.15 8.83 53.25 72.82 26.22 42.00 39.77 12.23 106.70 84.64 19.17 100.38 1986 141.23 151.08 237.69 193.62 174.07 44.09 2 37.92 61.00 84.85 145.36 101.00 178.23 51.21 67.23 99.50 140.00 125.64 152.36 117.40 134.00 40.86 105.27 99.79 151.29 98.87 144.67 92.27 103.93 71.67 63.31 202.00 107.75 234.58 158.29 155.93 179.07 164.14 340.93 162.07 222.4 78.60 175.54 1K4.29 138.50 144.67 252.77 154.27 186.29 209.29 110.80 182.53 86.50 38.00 54.50 86.42 142.17 94.10 -1.00 149.00 97.83 102.71 136.69 129.82 -1.00 164.92 163.55 147.31 153.31 250.00 -1.00 88.93 125.21 175.07 170.82 129.83 119.15 130.93 142.85 98.00 -1.00
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