ILLINOIS WATER AND CLIMATE SUMMARY
April 2011
Illinois State Water Survey
2204 Griffith Drive, Champaign, IL 61820 • Tel (217) 333-2210 • Fax (217) 333-6540
April 2011 Overview
Temperatures and precipitation in Illinois during April were above
average. Mean streamflows were above median values for the month.
Shallow groundwater levels were above long-term average depths.
Temperatures across Illinois (Figure 1) for April were above
average (a +0.6-degree departure). Crop Reporting District (CRD)
temperatures ranged from 3.6 degrees above average (Southeast
CRD) to 1.8 degrees below average (Northwest CRD).
Precipitation amounts for Illinois in April were above average
(Figure 1). The statewide average of 7.59 inches represented a
3.79-inch surplus or 200 percent of average for the month. The West
CRD received the least amount of rainfall, 4.78 inches (131 percent
of average), while the Southeast CRD recorded the greatest rainfall
total with 13.30 inches (298 percent of average).
Mean provisional streamflow statewide was above the median
flow in April, 230 percent of median (Figure 1). Rivers throughout
Illinois recorded monthly mean discharges from normal to much
above normal for April. Monthly mean flows recorded on some far
southern and southeastern Illinois streams were the highest on record
for the month of April. The Illinois, Mississippi, and Ohio Rivers all
exceeded flood stage. The Ohio River was approaching record high
stage at Cairo at the end of the month.
Water surface levels at the end of April were below full pool/
target operating level at two of 31 reporting reservoirs. (Water levels
at these two reservoirs are actively managed.) At the end of April,
Rend Lake was 7.5 feet above spillway level, Lake Shelbyville was
5.6 feet above May 1 target level, and Carlyle Lake was 12.1 feet
above May 1 target level. Lake Michigan’s mean level remains below
the long-term average.
Shallow groundwater levels statewide were above normal
with an average departure of +1.9 feet. Combined with the change
in normal monthly groundwater levels between March and April,
an increase of 1.1 feet in departures was observed from last month
(Figure 1). Levels averaged 1.4 feet higher than March levels and
were approximately 0.9 feet above April levels of last year.
#/,,#510&,(/#
Figure 1.
Statewide departures from normal
Water and Atmospheric Resources Monitoring Program | www.isws.illinois.edu/warm
Illinois State Water Survey | Prairie Research Institute | University of Illinois at Urbana-Champaign
Contact Jim Angel: (217) 333-0729, email: [email protected]
Weather/Climate Information (Jim Angel)
Temperatures across Illinois for April were above average (Figure 2 and Table 1). The highest temperature
reading for the month was 93° F at Kaskaskia on April 11. The lowest temperature reading for the month was 18° F
at Streamwood and Marengo on April 1.
Precipitation for April was above average statewide (Figure 2 and Table 1). The largest daily precipitation
total was 4.75 inches at Du Quoin. The largest monthly precipitation total was 15.29 inches at Brookport Dam. This
was the wettest April (one month), second wettest February–April (three months), and ninth wettest May–April
(12 months).
Snowfall in April occurred in the far northern counties. Amounts were generally less than 2 inches; however,
Spring Grove reported 2.9 inches.
Severe weather was widely reported for April. Approximately 26 tornado, 111 significant hail, and 135 wind
damage reports were filed for the month. Many of those events were reported on April 19 for the southern half of
the state and are too numerous to mention here.
Illinois Climate Network (ICN) Data. Average daily wind speeds across Illinois for April (Figure 3) ranged
from 5.4 mph at Dixon Springs to 14.2 mph at Stelle. The highest wind speed for the month was 80 mph recorded at
Carbondale on April 19. The prevailing wind direction was from the west across Illinois. Wind speeds in excess of
8 mph varied from 167 hours at Dixon Springs to 568 hours at Stelle. Average air temperatures ranged from 47.0° F
at DeKalb to 60.6° F at Carbondale.
Solar radiation totals in April ranged from 359 Mega-Joules per meter squared (MJ/m 2) at Freeport to 528
MJ/m2 at Belleville. Potential evapotranspiration observations ranged from 2.7 inches at Freeport to 4.9 inches at
Belleville. Soil temperatures in Illinois ranged from 47° F at DeKalb to 60° F at Carbondale (4-inch level) and from
47° F at DeKalb and Freeport to 59° F at Carbondale (8-inch level).
Extended climate outlooks are issued by the U.S. Department of Commerce, National Oceanic and
Atmospheric Administration, Climate Prediction Center and are available at http://www.cpc.noaa.gov/.
Figure 2. Illinois temperature and precipitation during April 2011
2
Table 1. Illinois Precipitation (inches) and Temperature (ºF) by Crop Reporting District
Crop Reporting
District
Last Month
Apr 11
%
Temp
Amount Avg
Dev
Last 3 Months
Feb 11%
Temp
Apr 11
Avg
Dev
Last 6 Months
Nov 10%
Temp
Apr 11
Avg
Dev
Last 12 Months
May 10%
Temp
Apr 11
Avg
Dev
Northwest
4.97
141
-1.8
9.85
131
-1.3
14.61
108
-1.9
44.83
Northeast
5.22
142
-1.1
10.72
139
-1.0
15.74
108
-1.6
42.19
West
4.78
131
-0.3
8.79
108
-0.5
12.87
87
-1.2
50.33
Central
5.86
163
-0.4
10.65
129
-0.6
16.31
106
-1.8
43.84
East
7.20
204
0.2
12.32
149
-0.2
18.50
118
-1.8
41.60
West-southwest
5.94
156
1.3
11.78
130
0.2
17.73
104
-1.1
47.31
East-southeast
10.66
268
2.0
18.29
185
0.9
26.51
138
-1.0
51.14
Southwest
12.38
294
3.1
21.22
197
1.1
28.24
134
-0.7
48.23
Southeast
13.30
298
3.6
22.79
195
1.6
31.70
140
-0.4
48.69
State Average
7.59
200
0.6
13.73
153
-0.1
19.87
118
-1.3
46.44
________________
Note: Data are provisional. Complete, quality-controlled data are available about six months after a given month.
Surface Water Information (Bill Saylor and Amy Russell)
124
115
134
118
111
125
125
113
109
120
0.0
0.2
0.2
-0.1
0.1
0.3
0.6
0.9
1.2
0.3
River and stream discharge and stage data are obtained from gaging stations operated by the U.S.
Geological Survey (USGS) or the U.S. Army Corps of Engineers (USACE). The USGS gaging station network is
supported, in part, by the Illinois Department of Natural Resources Office of Water Resources, the Illinois State
Water Survey (ISWS), and the USACE. Provisional discharge data are obtained from the USGS.
Table 2 lists the provisional peak stage for the current month compared to flood stage at selected streamgaging
stations located on the Illinois, Mississippi, and Ohio Rivers. The peak stage is determined from the daily morning
readings posted by the National Weather Service and/or the USACE. The Illinois, Mississippi, and Ohio Rivers
all exceeded local flood stages in April. At the end of the month, the Ohio River stage at Cairo was still rising,
approaching the highest water surface level recorded in the station’s period of record.
Provisional monthly mean flows for 26 streamgaging stations located throughout Illinois are shown in
Table 3. Mean values posted by the USGS are listed if available; otherwise, daily mean discharge data posted by the
USGS are used to estimate the mean flow for the month. Long-term mean flows for each month are published by
the USGS. The month’s median flow for each station listed in Table 3 was determined by ranking the April mean
flow for each year of record and selecting the middle value, 50 percent exceedence probability.
The statewide percent of historical mean flow and percent of historical median flow are calculated by dividing
the sum of the average flows this month at stations in Table 3 by the sum of the historical mean and median
flows calculated for the month, respectively, at the same stations. This method is intended to weight individual
observations proportionately in the aggregate comparison. (The Illinois River and Rock River stations are excluded
from the statewide calculation because other rivers listed in Table 3 contribute to their flow.)
Mean provisional flow statewide was above the median value for April (230 percent of the median) and above
the long-term mean for the month (190 percent of the mean). Monthly mean streamflow conditions throughout
Illinois, as represented by Table 3 stations, ranged from normal to much above normal for April. Skillet Fork at
Wayne City, the Little Wabash River below Clay City, and the Cache River at Forman monthly mean streamflow
values this month were the highest values for April for the respective periods of record of each gage. The April
2011 monthly mean streamflow of the Cache River at Forman was the second highest of any calendar month in the
period of record of that gage.
Water-Supply Lakes and Major Reservoirs. Table 4 lists reservoirs in Illinois, their normal pool or target
water surface elevation, and other data related to observed variations in water surface elevations. Reservoir levels
are obtained from a network of cooperating reservoir operators who are contacted each month by ISWS staff for
3
4
7.7
9.2
6.9
9.8
9.3
5.4
6.7
8.3
8.2
7.6
13.3
14.2
11.6 9.4
464.64
429.3
528.04
470.33
493.38
502.15
481.18
436.56
412.6
417.85
384.15
482.76
487.22
509.34
470.74
421.96
404.15
358.6
Total Solar Radiation (MJ/m*m)
7.8
12.9
10.4
7.4
Average Wind Speed (mph)
265
223
214.7
220.9
236.4
201.4
224.8
220.4
235.3
202
96.7
172.5
115.7296.3
3.94
4.4
4.06
4.33
3.76
4.21
4.14
4.75
4.22
4.85
3.84
4.05
3.28 3.26
321
356
266
568
327
285
546
167
244
313
401
440
468 419
55.5
49.3
58.1
58.9
57.1
58.2
56
51.6
49.3
47.2 49.2
60.2
53.1
51.9
55.7
54.7
50
48.9
Average 4 Inch Soil Temperature (deg F)
329
548
478
263
Hours Wind Speed Above 8 mph
Figure 3. April monthly averages and totals as collected by the Illinois Climate Network
3.98
4.31
3.63
2.71
Total Potential Evap. (in)
188.3
209
96.3
307
Average Wind Direction (deg)
49.4
59.5
58.3
52.6
60.3
60.1
57.2
60.6
55.2
57.8
54.4
52
47 47.8
53
47.9
58.5
57.4
57.4
57.3
50.8
50.8
46.6 47.4
55.1
59
49.7
55.1
56
52.9
48.3
46.6
Average 8 Inch Soil Temperature (deg F)
54.8
50.5
49.3
47.1
Average Temperature (deg F)
Table 2. Peak Stages for Major Rivers during April 2011
River
Station
River
mile*
Flood stage
(feet)*
Peak stage
(feet)**
Date
Morris
La Salle
Peoria
Havana
Beardstown
Hardin
263.1
224.7
164.6
119.6
88.6
21.5
16
20
18
14
14
25
16.4
25.3
22.4
20.4
21.9
31.8
28
28
30
30
30
30
Dubuque
Keokuk
Quincy
Grafton
St. Louis
Chester
Thebes
579.9
364.2
327.9
218.0
180.0
109.9
43.7
17
16
17
18
30
27
33
22.8
18.9
22.8
25.8
34.8
39.6
44.0
20
23
24
30
30
30
29
Illinois
Mississippi
Ohio
Cairo
2.0
40
59.1
30
________________
Notes:
* River mile and flood stage from River Stages in Illinois: Flood and Damage Data, Illinois Department of Natural Resources,
Office of Water Resources, August 2004 (and Addendum, February 2007).
** Peak stage based on daily a.m. readings, not instantaneous peak. Stage data obtained from U.S. Army Corps of Engineers.
the current water levels. Reservoir levels are reported in terms of their difference from normal pool (or target
level). The average of the month-end readings for the period of record is reported in terms of the difference from
normal pool or target level (column 6 of Table 4), and the number of years of record for each reservoir also is given
(column 7). Most reservoirs serve as public water supplies, with the exceptions noted in the last column.
Compared to end-of-March water levels at 30 reservoirs, reported end-of-April water levels were lower at
four reservoirs, higher at 23 reservoirs, and the same as at the end of last month at three reservoirs. For the 31
reservoirs with observations reported at the end of April, water levels at two reservoirs were below normal target
pool or spillway level, five reservoirs were at normal pool or spillway level, and 24 reservoirs were above normal
pool or spillway level. (Note that some operators do not measure water level when higher than full pool.) The
two lakes reporting water levels below normal seasonal pool, Lake Decatur and Raccoon Lake, are both actively
managed to control water levels, in part considering predicted inflow. Also, New Mt. Olive Lake is drawn down
for spillway repairs.
Major Reservoirs. Compared to water levels at the end of March, at the end of April, the Rend Lake water
level was 4.5 feet higher, Lake Shelbyville was 11.2 feet higher, and Carlyle Lake was 14.0 feet higher. At the end
of April, Rend Lake was 7.5 feet above spillway level, Lake Shelbyville was 5.6 feet above May 1 (summer) target
level, and Carlyle Lake was 12.1 feet above May 1 target level.
Great Lakes. Current month mean and end-of-month values are provisional and are relative to International
Great Lakes Datum 1985. The April mean level for Lake Michigan was 577.1 feet, compared to a mean level
of 577.8 feet in April 2010. The long-term average lake level for April is 578.7 feet, based on 1918–2010 data.
Historically, the lowest mean level for Lake Michigan in April occurred in 1964 at 576.1 feet, and the highest level
occurred in 1986 at 581.5 feet. The month-end level of Lake Michigan was 577.6 feet.
5
Table 3. Provisional Mean Flows, April 2011
Station
Drainage Years
area
of
(sq mi) record
2011
Long-term flows
mean flow Mean* Median
(cfs)
(cfs) (cfs)
Flow condition
Percent Days of
chance of data this
exceedence month
Rock River at Rockton
6363
75
10,650
7570
6870
above normal
23
Rock River near Joslin
9549
67
15,290
11,010
9898
above normal
23
Pecatonica River at Freeport
1326
91
1791
1257
1016
above normal
20
Green River near Geneseo
1003
72
1501
1073
960
above normal
23
Edwards River near New Boston
445
72
786
545
422
above normal
26
Kankakee River at Momence
2294
93
4052
3480
3508
normal
33
Iroquois River near Chebanse
2091
86
5254
3190
3054
above normal
14
Fox River at Dayton
2642
91
5017
3305
2770
above normal
14
Vermilion River at Pontiac
579
66
1372
813
673
above normal
18
Spoon River at Seville
1636
93
3294
1871
1532
above normal
17
LaMoine River at Ripley
1293
87
1756
1555
1279
normal
39
Bear Creek near Marceline
349
66
279
411
313
normal
54
Mackinaw River near Congerville
767
61
1191
1057
949
normal
33
Salt Creek near Greenview
1804
68
3524
2407
1955
above normal
21
Sangamon River at Monticello
550
98
1399
798
682
above normal
15
South Fork Sangamon near Rochester 867
60
1804
1053
770
above normal
19
Illinois River at Valley City
26,743
71
36,070
37,440
33,650
normal
45
Macoupin Creek near Kane
868
81
1460
1117
579
above normal
29
Vermilion River near Danville
1290
88
4161
1852
1599
much above normal
6
Kaskaskia River at Vandalia
1940
40
5974
2500
1960
much above normal
7
Shoal Creek near Breese
735
66
2680
959
630
much above normal
4
Embarras River at Ste. Marie
1516
96
6190
2211
1702
much above normal
3
Skillet Fork at Wayne City
464
90
3062
784
627
much above normal
1
Little Wabash below Clay City
1131
95
6393
1636
1114
much above normal
1
Big Muddy at Plumfield
794
39
3033
1495
1159
above normal
12
Cache River at Forman
244
86
2737
564
499
much above normal
1
________________
Notes:
Source streamflow data are obtained from the U.S. Geological Survey.
N/A = not available (due to ice or equipment problems).
Much below normal flow = 90-100% chance of exceedence.
Below normal flow = 70-90% chance of exceedence.
Normal flow = 30-70% chance of exceedence.
Above normal flow = 10-30% chance of exceedence.
Much above normal flow = 0-10% chance of exceedence.
*As reported in U.S. Geological Survey (USGS) Water Resources Data, Illinois, Water Year 2009.
6
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
Table 4. Reservoir Levels in Illinois, April 2011
Reservoir
County
Current level
Normal pool difference from
or target
normal or target
level (feet)
(feet)
Monthly
change
(feet)
Average
difference from
normal or target
(feet)
Years
of
record
March
reported
pumpage
(million gallons)
Altamont
Effingham
582.0
+0.1
+0.4
-0.5
25
6.8
Bloomington
McLean
719.5
+0.2
+0.2
-0.8
23
330.6
Canton
Fulton
577.5
0.0
0.0
-0.4
20
63.5
Carlinville
Macoupin
571.1
+0.3
+0.3
0.0
27
28.1
Carlyle(1)
Clinton
445.0
+12.1
+14.0
+0.6
33
N/A
Coulterville
Randolph
515.9
N/A
N/A
-0.5
12
N/A
Macon
614.3
-1.1
-0.1
-0.4
27
1,064.8
Decatur(1,3)
Evergreen(4)
Woodford
720.0
+0.2
+0.2
-1.1
20
No pumpage
Glenn Shoals(2)
Montgomery
590.0
+0.8
+0.3
+0.3
17
w/Hillsboro
Greenfield
Greene
566.2
+0.4
+0.4
-0.3
16
2.6
Highland
Madison
500.0
+0.2
+0.2
+0.1
22
31.9
Montgomery
589.0
0.0
-0.3
+0.2
17
28.3
Hillsboro(2)
Jacksonville(2)
Morgan
644.0
0.0
N/A
-0.1
16
w/Mauvaise Terre
Kinkaid
Jackson
420.0
+1.5
+1.4
+0.3
22
61.3
Lake of Egypt
Williamson
500.0
+1.3
+1.2
+0.2
17
N/A
Mattoon
Coles
632.0
+0.1
0.0
-0.2
15
w/Paradise
Mauvaise Terre(2) Morgan
588.5
0.0
-0.1
+0.1
17
no meter
Mt. Olive (new) Macoupin
600.0
N/A
N/A
0.0
8
w/Mt. Olive (old)
Mt. Olive (old)
Macoupin
654.0
0.0
0.0
-0.3
14
6.4
Nashville(3)
Washington
503.8
+1.0
+0.7
-0.1
26
15.5
Pana
Christian
641.6
+0.1
+0.1
-0.5
26
N/A
Paradise
Coles
685.0
+0.1
+0.1
-0.2
21
59.8
Paris (east)
Edgar
660.0
+0.2
+0.1
-0.1
26
Not PWS
Paris (west)
Edgar
660.1
+0.2
+0.1
+0.2
16
w/Paris (east)
Pinckneyville
Perry
445.0
N/A
N/A
+0.1
16
N/A
Pittsfield
Pike
596.0
N/A
N/A
+0.3
22
18.6
Marion
477.0
-0.6
-0.6
N/A
N/A
115.8
Raccoon(1)
Rend
Franklin
405.0
+7.5
+4.5
+3.7
33
N/A
Salem(3)
Marion
546.5
+0.3
+0.6
-0.6
16
30.1
Shelbyville(1)
Shelby
599.7
+5.6
+11.2
-0.7
33
Not PWS
Randolph
497.0
+0.1
+0.9
-0.7
14
21.1
Sparta(3)
Spring(4)
McDonough
654.0
N/A
N/A
+0.2
27
53.9
Springfield(1,3)
Sangamon
560.0
+0.5
+0.9
0.0
27
621.0
Taylorville
Christian
590.0
+0.7
+0.8
0.0
18
56.0
Vermilion(4)
Vermilion
581.7
+0.1
+0.1
-0.3
25
244.5
Virginia
Cass
575.0
+0.1
+0.1
0.0
24
Not PWS
_______________
Notes:
Normal pool and target level datum is NGVD 1929.
Current levels reported represent water surface levels at the end of the month, not the monthly average.
Average difference from normal or target level is the arithmetic average of reported month-end values for the period of record
indicated.
Years of record = total number of monthly readings included in month-end average. Total period of record may be longer.
Not PWS = not a public water supply.
N/A = not available.
(1)
Target operating level may vary. Seasonal target levels this month represent May 1 values.
(2)
Instrumentation not available to measure height of water elevation above spillway.
(3)
Natural inflow can be supplemented by other sources.
(4)
Normal pool elevations have changed during period of record reported.
7
Groundwater Information (Ken Hlinka)
Comparison to Average Levels. Shallow groundwater levels in 15 observation wells, which are remote from
pumping centers, were above average for the month of April. Levels were 1.9 feet above normal and ranged from
0.2 feet to 5.6 feet above normal levels (Table 5).
Comparison to Previous Month. Shallow groundwater levels were above those of last month. Levels averaged
1.4 feet above and ranged from 0.4 feet below to 3.7 feet above levels of last month.
Comparison to Same Month, Previous Year. Shallow groundwater levels in April were above levels
measured one year ago. Levels this month averaged 0.9 feet above and ranged from 2.5 feet below to 3.7 feet above
April 2010 levels.
Table 5. Month-End Shallow Groundwater Level Data Sites, April 2011
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Well name
County
Galena
Mt. Morris
Crystal Lake
Cambridge
Fermi Lab
Good Hope
Snicarte
Coffman
Greenfield
Janesville
St. Peter
SWS #2
Boyleston
Sparta
SE College
Dixon Springs
Bondville
JoDaviess
Ogle
McHenry
Henry
DuPage
McDonough
Mason
Pike
Greene
Cumberland
Fayette
St. Clair
Wayne
Randolph
Saline
Pope
Champaign
________________
Notes:
N/A - Data not available
* Data not used in analysis
Deviation from
Period of
Previous
record avg.
month
(feet)
(feet)
Well depth
(feet)
This month’s
reading (depth
to water, feet)
15-year
avg. level
(feet)
25.00
55.00
18.00
42.00
17.00
30.00
40.30
28.00
20.70
11.00
15.00
80.00
23.00
27.00
10.19
8.63
21.00
17.85
13.50
2.92
9.05*
3.43
3.67
35.42
7.66
7.07
1.19
0.77
7.77
1.39
NA
0.04
0.48
2.56
+2.07
+3.74
+0.93
NA
+1.42
+0.64
+1.47
-0.18
+1.06
+3.61
+1.27
+4.39
+1.33
NA
+2.73
+1.82
+0.43
+2.84
+4.08
+1.11
NA
+1.32
+1.48
+1.18
+0.41
+0.18
+3.36
+1.39
+5.59
+1.40
NA
+2.34
+1.27
+0.21
+1.20
+1.16
+0.41
NA
+1.76
+1.20
+0.35
+0.94
-0.35
+3.65
+0.95
+2.98
+1.24
NA
+2.40
+2.08
+0.88
-0.17
-0.41
-0.07
NA
+3.51
-0.22
-0.01
-2.50
-0.96
+3.63
+0.72
+3.68
+1.66
NA
+1.92
+1.15
+1.47
Averages
+1.78
+1.88
+1.39
+0.89
Addendum (Nancy Westcott)
Previous
year
(feet)
Imperial Valley Precipitation. Precipitation for April 2011 was heavy (Figure 4a). Monthly gage totals were
greatest along the northwestern border of the network and least in the central region. Individual gage amounts
ranged from 7.11 inches at Site #8 to 4.83 inches at Site #6. The 1971–2000, 30-year average precipitation amounts
for April at Havana and Mason City are 3.45 and 3.34 inches, respectively. The April 2011 network average of 5.85
inches is about 169 percent of the 18-year (1993–2010) IVWA April network average of 3.49 inches.
Cook County Precipitation. April 2011 total precipitation was above average (Figure 4b). Precipitation
amounts were greatest in the southwestern portion of the county and lightest in the northern portion of the network.
Precipitation values ranged from 6.63 inches at Site #20 (Orland Park) to 4.29 inches at Site #2 (Winnetka). The
April 2011 network average of 5.10 inches is about 145 percent of the 21-year (1990–2010) April network average of
3.51 inches.
8
+ORGTKCN8CNNG[9CVGT#WVJQTKV[
2TGEKRKVCVKQP
KPEJGU
a. Imperial
Valley
#RTKN
5ECNGQH/KNGU
b. Cook County
#RTKN
Figure 4. Long-term raingage network precipitation totals (inches) for April 2011
Data sources for information in this publication include the following:
CPC - Climate Prediction Center, http://www.cpc.ncep.noaa.gov/index.php
ISWS - Illinois State Water Survey, http://www.isws.illinois.edu/
MRCC - Midwestern Regional Climate Center, http://mrcc.isws.illinois.edu/
NCDC - National Climate Data Center, http://www.ncdc.noaa.gov/
NWS - National Weather Service, http://www.nws.noaa.gov/
USACE - U.S. Army Corps of Engineers, http://rivergages.com, http://www.lre.usace.army.mil/greatlakes/hh/
USGS - U.S. Geological Survey, http://waterdata.usgs.gov/il/nwis
WARM - Water and Atmospheric Resources Monitoring Program, http://www.isws.illinois.edu/warm/
9