EFFECT OF DYE ON SOLAR EVAPORATION OF BRINE
C . G . K E Y E S , Jr. ( * ) a n d N . N . G U N A J I (**)
ABSTRACT
Solar evaporation as a disposal process is not a new concept. The process of evaporation has been used on an industrial scale in many arid and semi-arid regions. The
investigation reported herein describes studies of the effect of dyes (Methylene Blue
and Congo Red) on solar evaporation of brine at the Roswell Saline Water Conversion
Plant Effluent Ponds, near Roswell, in Southeast New Mexico. This study represents
part of the first phase of a disposal of brine by solar evaporation research program.
This program, initiated in the spring of 1965, observed the effect of Methylene Blue,
Congo Red, Nigrosine, Bismark Brown, and 2-Naphthol Green dyes on solar evaporation of brine. To evaluate the efficiencies of increases evaporation and the economic
feasibility of the addition of dyes, evaporation must be determined accurately. Two
basic methods for evaluating the effect of dye on the solar evaporation of brine in
Modified Cummings Radiation Integrators have been reported in this investigation.
They are: (1) Energy-budget, and (2) Water Budget. The addition of Methylene Blue
dye affected the following Energy-budget Method parameters: (1) short-wave reflectivity, (2) Bowen's Ratio, and (3) the evaporated depth. The addition of Congo Red dey
affected the surface temperature and the Bowen's Ratio of the brine. The study shows
that the Water Budget Method for determining evaporated depth in a Modified Cummings Radiation Integrator is more reliable than the Energy-budget Method. The
calculations of evaporated depth by this method support the hypothesisthat the Methylene Blue dye will increase the solar evaporation of brine while the Congo Red
dye has little or no effect on the evaporation of brine.
RÉSUMÉ
Le procédé d'évaporation par la chaleur solaire a souvent été utilisé sur une base
industrielle dans plusieurs régions arides. Nous rapportons ici certaines études sur
l'emploi de colorants tels que le bleu de méthylène et le rouge Congo dans Pévaporation
des eaux salines par la chaleur solaire au Roswell Saline Water Conversion Plant
Effluent Ponds, près de la ville de Roswell, dans le sud-est du Nouveau-Mexique, aux
États-Unis d'Amérique. Ces essais, qui représentent une première étape dans notre
programme de recherche, ont débuté au printemps 1965 et avaient pour but de déterminer les effets des colorants bleu de méthylène, rouge Congo, nigrosine, brun de
Bismark, et vert 2-naphthol, sur l'évaporation des eaux salines par la chaleur solaire.
Afin d'apprécier l'augmentation dans l'évaporation et l'application économique des
colorants, l'évaporation doit être mesurée correctement. Deux méthodes pour évaluer
l'effet des colorants sur le taux d'évaporation des eaux salines par la chaleur solaire,
tel que mesuré par des intégrateurs de radiations Cummings modifiés, ont été utilisées
dans ce travail. Elles sont : (1) le bilan-énergie, et (2) le bilan-eau. L'addition de bleu de
méthylène a modifié les facteurs suivants du bilan énergétique; (1) la réflectivité des
ondes courtes, (2) le rapport de Bowen, et (3) la profondeur de la couche évaporée.
L'addition de rouge Congo a modifié la température de la surface des eaux salines ainsi
que le rapport Bowen. Cette étude a démontré que la méthode du bilan-eau pour déterminer la profondeur de la couche évaporée dans un intégrateur de radiations Cummings
modifié est plus exacte que la méthode du bilan-énergie. Les calculs de la profondeur
de la couche évaporée selon cette méthode confirment l'hypothèse que le bleu de méthylène accélère l'évaporation tandis que le rouge Congo n'a que peu ou pas d'effet.
INTRODUCTION
Extensive use of inland saline water conversion plants is anticipated in arid regions
of the southwestern United States where abundant deposits of brackish water are
(*) Assistant Professor of Civil Engineering, New Mexico State University.
(**) Professor of Civil Engineering, New Mexico State University.
338
available in ground water basins. In the arid southwest where good quality water spells
the difference between life and death, the water obtained from inland saline water
conversion plants will be the basis of future economic and industrial development.
Therefore, the disposal of brine water from saline plants is as vitally important as the
saline water plant itself.
The increase of evaporation by using dyes requires the determination of evaporation
as accurately as possible to evaluate the efficiencies of increased evaporation and the
economic feasibility of the addition of dyes.
REVIEW OF PREVIOUS INVESTIGATIONS
Lee( 12 )(*), in 1927, presented a chart showing that up to a certain limit the ratio of
evaporation of Owen's Lake brine to that of distilled water decreased about one per
cent for a change in specific gravity of 0.01.
Observations by Rohwer ( 14 ), in 1933, on the evaporation from solutions of sodium
chloride of different strengths showed that the evaporation from 10 and 20 per cent
solutions is definitely less than that from water.
In 1934, Adams C1) reported the results of laboratory experiments conducted to
determine the ratio of evaporation from Great Salt Lake brine to evaporation of fresh
water.
Young ( 18 ), in 1947, presented the results of an experiment using varying concentrations of sodium chloride. His findings did not differ greatly from those of Lee.
In 1951, Bloch, Farkas, and Spiegler (3) reported the results of studies of solar
evaporation of salt brine from the Dead Sea, which is used on a large scale by the
Palestine Potash Co., Ltd., for the manufacture of chloride of potassium, sodium, and
magnesium. In this study, solar evaporation of saturated salt brine, colored and uncolored, in layers eight to 27 inches deep was measured in mirror-lined vessels in order to
determine the influence of depth of the brine and dye concentration on the rate of
evaporation.
In 1955, Harbeck( u ) reported the results of a study of the effect of salinity on
evaporation. He stated that because of many variables, of which some are interrelated,
it is difficult to determine a simple relationship between salinity and the decrease in
evaporation.
Bonython ( 4 ), in 1956, compared the temperature salinity gradient on a chain of
saltfield ponds. He found that his measured gradient was higher than the calculated
values using his steady-state energy balance evaporation equation.
De la Rue and Lapple ( 8 ), in 1959, reported on the evaporation rates from the
Leslie Salt Co. ponds in California. They stated that the addition of dyes for the purpose
of increasing evaporation rates of low concentration brines (lower than saturated
brines) should be studied in more detail before they could arrive at an economic
evaluation of the addition of dyes to brine waters.
METHODS OF DETERMINING EVAPORATION
Energy-budget
Method
The importance of the energy-budget in evaporation was probably first recognized
by Angstrom ( 2 ), in 1920. During the 1920's, the theory was further developed by
(*) Numbers in parentheses refer to the bibliography.
339
Bowen ( 5 ), and Cummings, and Richardson ( 7 ). The investigation showed that a study
of evaporation consists of a balance of energy existing between the gain and the loss of
heat at the interface of the liquid and the air layer above the liquid surface. Beginning
in April 1950, at Lake Hefner, Oklahoma, several federal agencies jointly participated
in a rigorous energy-budget evaporation study ( 16 ). The investigators used the most
recent developments in instrumentation and proved, for the first time on a large scale,
the soundness of the energy-budget method in determining evaporation for a week or
longer. The Lake Hefner Project provided a basis for using the energy-budget as a
control for the Lake Mead water-loss studies (17) conducted by the same federal
collaborators in March, 1952.
The depth of fluid (centimeters) evaporated in one day, dE/dt, can be written in
terms of flux units. The expression is:
(dE/dt) = (VJA, t) = ^'.-Qr + q'a-i'ar-9'is + çi'u-qo)
QlL(l+R) + CpT0-}
(1)
where As is the surface area of evaporated liquid, in square centimeters; Ve represents
the evaporated volume in cubic centimeters; t is the time period in days; ?'sis the
incoming short-wave radiation in calories per square centimeter-day; q V represents the
reflected short-wave radiation in calories per square centimeter-day; q'a is defined as the
incoming long-wave radiation in calories per centimeter-day; q'ar is the reflected longwave radiation in calories per square centimeter-day; q'ts represents the back radiation
in calories per square centimeter-day; q'v represents the net advected energy in calories
per square centimeter-day; q'0is defined as the net stored energy in calories per centimeter-day; g is the mass density of the evaporated water, in grams per cubic centimeter; L is the latent heat of vaporization at the water surface temperature (T0, in °C),
in calories per gram; i? represent Bowen's ratio—the ratio of sensible heat to the energy used by evaporations;and Cv represents the specific heat at constant pressure, in
calories per gram- °C.
The above equation should produce adequate results when applied to thermally
insulated pans. The terms ç'^and <?'0in this investigation were small as compared to
the evaporation term, since a period of measurement, called a Thermal Survey Period
(TSP), is seven days or more.
Water Budget Method
The Water Budget Method for determining evaporation is based on the Law of
Conservation of Mass flow into and out of a pan or pond. The volume of evaporated
water, in cubic centimeters, can be expressed as:
Ve = (QB VB -QEVE + QP VP - QS0 VS0)lQe
(2)
where QBVB represents the mass of liquid at the beginning of a Thermal Survey Period,
in grams; QEVE represents the mass of liquid at the end of a Thermal Survey Period, in
grams ; Qp Vp represents the mass of precipitation in grams, and QSO VSO represents the
mass of surface outflow in grams.
This method should adequately meet the limitations for comparisons of the
evaporation volume, Ve. The volume constituents of equation 2 are measured directly
with care. The densities of the brine are measured indirectly with a conductivity bridge
for each Thermal Survey Period.
340
INSTRUMENTATION
The experimental investigation was carried out near the Saline Water Conversion
Demonstration Plant located near Roswell, New Mexico, as shown in figure 1. The
Roswell plant site was an ideal field site for this investigation, but involved travel at
least every ten days from Las Cruces, New Mexico, to Roswell, New Mexico.
H
Control pond
O
Liquid level recorder
a
Inflow recorder
Û Meteorological station
0
Saline water conversion plant
Fig. 1 — Pond layout and location of experimental sites.
8
&$•.„.
;--r^^r^^^
;m
Fig. 2 — Meteorological Station, Roswell, New Mexico.
341
The meteorological and other pertinent data used for determining various parameters in the two methods of this investigation can be divided into the following groups :
A. Field instrument data:
1.
2.
3.
4.
5.
6.
7.
8.
Incoming short-wave radiation;
Reflected short-wave radiation ;
Total radiation flux;
Precipitation;
Wet- and dry-bulb temperatures and relative humidity;
Air temperature;
Water surface temperature;
Temperature profiles in each insulated pan.
B. Laboratory data—conductivity of samples.
A centrally-located meteorological station, figure 2, was maintained on the south
central dike between the 30-acre ponds (numbered 1 and 2 in fig. 1)..
DATA ANALYSIS
The analyses of data embodying the various parameters of the evaporation equations in this investigation were divided into 14 computation intervals. Each interval,
called a "Thermal Survey Period" (TSP), averages about 10 days. Table I defines the
data and time of beginning and ending of each TSP.
The Energy-budget and Water Budget Methods were used for the determination of
the effect of dye on solar evaporation of brine and other objectives of the investigation.
Following is the list of variables required for evaporation determination:
A. For Energy-budget studies;
1.
2.
3.
4.
5.
6.
7.
Short-wave radiation;
Long-wave radiation;
Surface temperature of liquid;
Volumes and densities of rainfall, inflow, and outflow for the integrators;
Thermal stratification and density gradients of the insulated pans;
Air temperature;
Area and capacity of each MCRI (Modified Cummings Radiation Integrator);
B. For Water Budget studies:
1.
2.
3.
4.
Surface temperature of the liquid;
Volumes and densities of rainfall, inflow, and outflow for the integrators;
Capacity of each MCRI with the varying depths;
Density gradients of the insulated pans.
Energy-budget Method for the Determination of Evaporation
In the analyses of the data, estimation of evaporation over a given TSP required
integrated values of the various parameters for that period. The Amsler Integrator was
used to evaluate each record at two-day intervals, as outlined by Glover and Hamburg ( 9 ). Mean values were obtained by combining all two-day intervals constituting the
Thermal Survey Period and then averaging. In the case of the potentiometric recorder
chart paper, the mean radiation values were recorded and calculated in calories per
square centimeter-minute. Because of the functional variation of the temperature
recorders' chart paper, simultaneous equations were calculated for each temperature
342
TABLE I
Thermal survey period dates and intervals in hours and days
Thermal
Survey
Period
Beginning
Date
Time
End Date
Time
Time
Interval
in hours
Time
Interval
in days
Blue Dye Used in MCRI* #1
1
2
3
4
5
6
7
8
July 14, 1965
21
Aug. 2
12
22
Sept 1
10
20
3:00
2:00
7:00
10:45
9:30
4:00
6:00
2:00
pm
pm
pm
am
pm
pm
pm
pm
July 21, 1965
Aug. 2
11
21
Sept 1
9
19
Oct. 2
11:30
10:45
12:30
3:30
10:00
10:15
12:30
8:00
am
am
pm
pm
am
am
pm
am
164.50
284.75
209.50
220.75
228.50
186.25
210.50
282.00
6.854
11.865
8.729
9.200
9.521
7.760
8.771
11.750
8:00
5 00
10 00
11 00
8 15
8 30
am
pm
am
am
am
am
187.50
216.50
210.50
168.25
257.75
163.25
7.813
9.021
8.771
7.010
10. 740
6.802
Red Dye Used in MCRI #1
9
10
11
12
13
14
Oct.
2
10
20
30
Nov. 6
17
12:30
4:30
3:30
10:45
2:30
1:15
pm
pm
pm
am
pm
pm
10
19
29
Nov. 6
17
24
"(Modified Cummings Radiation Integrator.)
reference axis and used to arrive at an evaluation of the mean temperature values. The
following paragraphs include the variables which were calculated in a different manner
than the Elephant Butte study ( 10 ).
The long-wave back radiation, q-bs, emitted by the liquid body was computed according to the Stefan-Boltzmann Law for black-body radiation and corrected with an
emissivity factor, e, which is the ratio of radiation emitted by a body with a surface
temperature, T0, to the black-body radiation at the same temperature. The total emissivity used for brine in this investigation only varied with temperature. Chapmanf 6 )
states, "When two values are given for both the emissivity and temperature, they correspond and linear interpolation is permissible." Chapman's values of the total emissivity for water are: 0.950 at 32 °F and 0.963 at 212 °F.
The reflected long-wave radiation, q'ar, was computed by multiplying (1 -emissivity)
by the long-wave radiation of each Thermal Survey Period. The values of (1 -emissivity)
varied with each TSP instead of a constant value of 0.03 as used in the Lake Hefner ( 16 )
and Elephant Butte (10) studies.
The change in energy content of the pans during a Thermal Survey Period was
computed from corrected temperature profiles taken at the beginning and end of each
TSP. A relationship, density (in gm/cm 3 at 25 °C) = (6.796 x 10 " 4 ) (conductivity in
mmhos/cm at 25 °C) + 0.9800, was obtained by a least-squares analysis of a number of
samples tested for the density and the conductivity of the brine. Specific heat of the
brine that was used in this research could not be easily determined, since the brine did
not have the exact characteristics or composition of either sea water or an aqueous
sodium chloride solution. Corrections for the brine weights as compared to sea water
weights were obtained using the sea water density versus temperature curve in Office of
Saline Water Handbook ( 15 ). Also, the aqueous sodium chloride versus heat capacity
curve was used for a correction to the brine. With these two correction factors, an
approximate specific heat versus temperature curve for various concentrations were
drawn and were used in this study.
The density of evaporated water, p, was assumed to be the same as the density of
pure water, ppui, at the temperature of the evaporation surface or the surface tempera-
343
ture, To- Also, the specific heat of the evaporated water (Cp) and the latent heat of evaporation was assumed to be that of fresh water.
Values of the saturated vapor pressure of pure water (e0p), saturation vapor pressure
at the wet-bulb temperature (emo), and the change Ae were obtained by equations given
in tables 94 and 98 of the Smithsonian Meteorological tables ( 13 ).
Water Budget Method for the Determination of Evaporation
In this investigation, the water budget method was the simplest method of determining the effect of dye on solar evaporation of brine. Volume parameters on the righthand side of equation 2 were measured directly. The densities were determined from the
figures and tables of given temperatures versus densities and conductivities, as described
in the energy-budget data analysis.
RESULTS
The calculations for the first 14 Thermal Survey Periods of the Roswell Saline
Evaporation Research Project were performed by laborious procedures on desk calculators in conjunction with the Amsler Integrator. Computer programs using a CDC
3300 Computer were later used to evaluate and facilitate the data reduction.
The values of incoming short-wave radiation, reflected short-wave radiation, incoming long-wave radiation, reflected long-wave radiation, long-wave back radiation adverted energy, net energy stored, and Qnet. which is the algebraic sum of the above, are
listed for each MCRI by Thermal Survey Periods in table II.
TABLE II
Results of the energy values (calories* 107, unless otherwise noted).
Ufa
a
v
5
(xKT)
(xlO 6 )
MCRI #1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
9.99
16.19
13.51
13.22
13.14
8.79
9.36
12.21
8:12
8.68
8.37
6.32
6.84
4.22
3.49
2.65
1.90
1.93
1.89
1.28
1.30
1.70
1.24
1.28
1.26
1.04
1.08
0.789
18.61
29.11
21.60
22.78
22.42
17.62
18.90
23.01
15.11
17.48
16.03
12.87
20.63
12.73
1
2
3
4
5
ô
7
8
9
10
11
12
13
14
9.88
16.02
13.36
13.07
12.99
8.69
9.26
12.08
8.03
8.59
8.28
6.25
6.77
4.18
3.44
2.45
1.86
1.89
1.93
1.26
1.10
1.55
1.04
1.37
1.28
1.03
1.00
0.737
18.41
28.79
21.36
22.53
22.17
17.42
18.70
22.76
14.94
17.29
15.85
12.73
20.40
12.59
0.869
1.36
1.01
1.07
1.05
0.829
0.893
1.10
0.727
0.840
0.775
0.624
1.00
0.618
15.78
27.01
19.95
20.70
21.55
17.37
19.24
24.06
15.55
18.13
17.07
13.45
20.50
12.91
2.99
12.19
2.51
4.02
0.00
4.72
6.34
-0.119
-0.216
0.409
-0.109
-0.113
3.11
-0.088
9.55
5.35
10.54
0.00
11.52
4.30
8.17
19.34
10.63
5.62
8.59
6.45
-0.637
5.46
7.53
13.86
11.21
12.35
9.91
6.54
6.07
6.42
4.65
5.36
4.44
3.44
4.99
2.09
15.50
26.58
19.60
20.33
21.25
17.15
19.11
23.90
15.21
17.92
16.87
13.30
20.25
12.74
2.96
12.06
2.48
3.98
0.00
4.67
6.27
-0.198
-0.245
0.411
-0.123
-0.10.7
3.15
-0.054
9.77
3.92
8.43
-4.86
9.24
2.55
8.15
1.75
8.99
5.77
8.26
5.95
0.352
5.20
7.54
14.16
11.44
12.85
10.02
6.68
6.11
6.54
5.11
5.18
4.39
3.45
4.93
2.16
MCRI #2
344
0.862
1.35
1.00
1.06
1.04
0.820
0.882
1.09
0.721
0.831
0.767
0.617
0.990
0.612
To determine the effect of dye on the solar evaporation terms of the different
equations used in this investigation, rate units, such as calories per square centimeterday, were used.
Short-wave Reflectivity of Energy-budget
Method
When the short-wave reflectivity of the brine with blue dye was compared to the
short-wave reflectivity of the brine, a least squares analysis yielded the following
equation:
Yb =0.85 + 0.98 X
(3)
where Yi, (the independent variable) is the short-wave reflectivity of the brine with blue
dye, in per cent, and X (the dependent variable) is the short-wave reflectivity of thebrine,
in per cent. The correlation coefficient, which measures the degree of association of
Yb to X, is 0.988.
Short-wave reflectivity of the brine with red dye equalled the brine short-wave
reflectivity with a probability of approximately 79%. This would explain the correlation
coefficient of only 0.71, which was obtained for the least squares line involved.
Bowen's Ratio of the Energy-budget
Method
Bowen's Ratio may have the greatest percentage effect from the addition of dyes
since it is normally a small number, such as 0.1 to 0.3. Bowen's Ratio of the brine was
not equal to the Bowen's Ratio of the brine with dye liquid. If this relation was assumed,
it could be rejected with a probability of 39% for both dyes used. A polynomial
relationship might exist between the Bowen's Ratio of the brine to the Bowen's Ratio
of each brine with dye. A polynomial expression, however, was not used in this study.
Evaporated Depth
Using the Energy-budget Method, the evaporated depth of the brine was greater
than the evaporated depth of the brine with blue dye, with a coefficient of correlation
of 0.99. The range of the standard error of estimate for the least squares line of the
evaporated depth of the brine with blue dye as a function of the brine is 11.6%.
Assuming the hypothesis that the evaporated depth of the brine with red dye was
equal to the evaporated depth of the brine, it was shown that, with a probability of
approximately 85%, the Congo Red dye brine solution evaporated at the same rate as
the brine.
As a result of this study, it appears that the Water Budget Method for determining
evaporated depth is more reliable than the Energy-budget Method. This inference is
based on the observations that the estimated probable errors in the Water Budget
Method are smaller than those estimated probable errors in the Energy-budget Method.
Comparing the depth of evaporated water by the Water Budget Method between two
thermally insulated pans with Methylene Blue dye in MCRI # 1, the hypothesis that
the depth of evaporated brine with blue dye equals the evaporated depth of the brine
can be rejected at a 19.2% confidence interval. Table III shows that the ratio of the evaporated depth in MCRI #1 (brine with blue dye) to the evaporated depth in MCRI # 2
(brine) has a maximum value of 1.14 and a minimum equal to 0.98. The mean value of
this ratio over the seven Thermal Survey Periods is 1.06.
It appears from table III that the effect of the Congo Red dye on the evaporated
depth by the Water Budget Method would be the same as the effect that this dye had on
the Energy-budget Method of determining the evaporated depth.
345
TABLE III
Volume of and depth of evaporated liquid
{Energy-budget and Water Budget Methods)
MCRI #2
MCRI #1
:SP
V,
E
V
, 3 e 5,
(cm xlO )
(cm)
l
2
3
4
5
6
7
8
1.35
2.40
1.87
5.16
9.17
7.14
1.76
1.08
1.08
1.05
6.73
4.13
4.13
4.01
9
10
11
12
13+
14
0.846
0.959
0.773
0.538
0.848
0.380
3.23
3.67
2.95
2.06
3.24
1.45
E .
wb
, 3 ?\
(cm XlO ) (cm)
V
, 3 e 5,
(cm xlO )
(cm)
V
, 3 w \
(cm xlO )
wb
(cm)
5.44
9.86
7.73
9.66
7.42
4.41
4.10
4.02
1.92
2.54
2.05
1.75
1.77
1.21
1.34
1.56
7.42
9.82
7.92
6.76
6.84
4.68
5.18
6.03
4.06
3.61
2.98
2.08
3.30
1.57
1.01
1.29
0.976
0.701
-0.062
0.686
*
<Wl
<Ewb>2
Blue Dye
*
-k
2.08
2.92
2.03
7.95
11.15
7.75
1.90
1.32
1.33
1.70
7.26
5.04
5.08
6.49
*
1.41
2.55
2.00
2.50
1.92
1.14
1.06
1.04
0.988
1.24
1.01
0.752
0.134
0.606
3.78
4.74
3.86
2.87
0.512
2.33
1.05
0.935
0.770
0.539
0.855
0.405
*
1.07
1.14
0.98
1.06
1.08
0.98
1.08
Red Dye
3.90 0.97
4.99
0.95
3.79
1.02
2.71
1.06
-0.239 +
2.67 0.87
* No final hook gage reading.
Rain filled integrators to the point that overflow occured.
+
ACKNOWLEDGEMENTS
This investigation was supported by the Office of Saline Water, U. S. Department
of the Interior, under Contract No. 14-01-001-511. Sincere appreciation is expressed to
Dr. Frank C. Diluzio, U. S. Department of the Interior, and the officials at the U. S. Saline Water Conversion Demonstration Plant at Roswell, New Mexico, for their
valuable assistance in this investigation. The staff and students of the Engineering
Experiment Station, New Mexico State University, are gratefully acknowledged for
their cooperation and contributions to this project.
BIBLIOGRAPHY
0
2
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(3)
(4)
(5)
(6)
(7)
(8)
346
ADAMS, Thomas C , Evaporation from Great Salt Lake, Bulletin of American
Meteorological Society, Vol. 15, No. 2, February, 1934, pp. 35-39.
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7, and 11.
CUMMINGS, N.W., and RICHARDSON, Burt, Evaporation from Lakes, Physical
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(9) GLOVER, R.E. and HAMBURG, G.R., New Methods for Evaluating Recorded
Charts, Water-Loss Investigations, Lake Cachuma, 1961, Evaporation Reduction
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10
( ) GUNAJI, Narendra N., et al, Evaporation Reduction Investigation, Elephant Butte
Reservoir, New Mexico, 1963-65, Technical Report No. 25, Engineering Experiment Station, New Mexcio State University, University Park, November, 1965.
n
( ) HARBECK, G. E., Effect of Salinity on Evaporation, Geol. Survey Professional
Paper, 272-A, U.S. Printing Office, Washington, D.C., 1955.
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Trans. American Society of Civil Engineers, Vol. 90, 1927, pp. 340-343.
(13) LIST, Robert J., Smithsonian Meteorological Tables, Sixth Edition, Smithsonian
Institution, Washington, D.C., 1963, Table 92, p. 343.
(14) ROHWER, Carl, Evaporation from Salt Solutions and from Oil-covered Water
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( 15 ) U. S. Department of the Interior, Saline Water Conversion Engineering Data Book,
July 1965, by M.W. Kellog Co., for Office of Saline Water.
( 16 ) U.S. Geological Survey, 1954a, Water-loss Investigations—Lake
Hefner Studies,
Technical Report: U . S . Geol. Survey Prof. Paper 269.
17
( ) U.S. Geological Survey Professional Paper 298, Water-loss Investigations—Lake
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DISCUSSION
5) Discussion by TIXERONT: Does the coloring change with fluctuating depth or is it
completely mixed in the brinemass?
6) Discussion by C.G.
KEYES, Jr. and
N.N.
GUNAJI:
Dye concentrations have been measured by the use of a spectro-photometer. The
wavelength range of the three spectrophotometers used was between 0.2 to 16/x. The
amount of absorbance and. the concentration of the dye at each depth in the radiation
integrators was calculated from the above data. No consistent correlation was obtained
on the changing dye concentration with respect to depth. However, of the 1000 odd
samples taken at the Roswell site, there was a definite change of dye concentration
with respect to time. This fact has been also investigated at New Mexico State University in a Dye Stability Study by Winans (*). Morton Salt Co. and Leslie Salt Co. in the
United States have also investigated the evaporation rates on their salt producing
ponds.
(*) WINANS, D.C., " T h e Relative Stability of Six Dyes in a Saline Brine of Constant
Salinity", Master of Science in Civil Engineering Thesis, New Mexico State University,
Las Cruces, July 1967.
347