Final Evaporation Control in reservoirs

7.1.3
 
Institute of Hydraulics and Hydrology, Poondi, Chennai 
The studies on evaporation control with chemical WER were conducted from 1959 to 
1965 in Buderi tank situated near the institute. The tank had a water spread area of 
about 11.34 ha and depth of 3.66 metres. There were no withdrawals from this tank 
for irrigation or for other purposes. The inflows into the tank were only from 
monsoon rains. Regular meteorological observations and pan evaporimeters studies 
were conducted at the location of study. Cetyl Stearyl alcohol was used for the study.
Cetyl Stearyl alcohol was applied on water surface at the rate of 0.05 kg to 0.25 kg in 
the form of solution and emulsion and at the rate of 0.36 kg in the powder form.
Applications were made during the daylight hours for short periods ranging from 7 to 
10 days. 
Film pressure was tested by indicator oils of standard strength. It was maintained at 
40 dyne/cm, which is the equilibrium value at which the film was found to offer 
maximum resistance to the escape of water molecules. 
The inference drawn on the basis of the study were: 
i)
From economic considerations and facility of operation, application in the 
form of emulsion appeared to be the best, under local conditions. 
ii)
Layer is found to break due to wind velocity above 8-16 km per hour and also 
due the presence of bacteria and protein in water. 
iii)
The efficiency of the layer decreases with increase in temperature 
iv)
The saving in water was to the tune of 20% 
7.1.4
 
Karnataka Engineering Research Station, Krishnaraja Sagar 
This Research Station, then known as Mysore Engineering Research Station, had 
conducted evaporation control studies on field and semifield scales in four tanks 
during 1962. The salient features of these tanks and the details of the studies 
conducted are given in Table 7.3. The studies conducted in each tank are discussed 
below: 

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TABLE 7.3 Details of Studies Conducted by Karnataka Engineering Research Station, Krishnaraja Sagar 
S. No 
Name of Reservoir 
Average 
water 
spread area 
in Ha 
Maximum 
depth in m 
Meteorological 
observations 
Method of 
application 
Surface film 
pressure 
maintained 
1.
Kukkarahalli Tank, 
Mysore.
66.77 
10.67 
Temperature, 
wind direction, 
its velocity & 
rainfall
Solution, 
emulsion & 
powder form
24-40 dyne/cm
2.
VarunaTank, Mysore.
69.61 
3.66 
— do—
—do— 
— do—
3.
Kadavinahosahalli 
Tank,, Hassan Distt.
Karnataka
0.4 
— do— 
—do— 
Emulsion & 
solution form
40 dyne/cm
4.
Lingambudhi Tank, 
Mysore.
67.99 
5.61 
—do— 
Solution, 
emulsion & 
powder form
—do— 

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a)