Final Evaporation Control in reservoirs

6.7
 
Short Term Measures 
Short-term measures are employed in the drought and scarcity conditions especially for crisis 
management. Since these are cost prohibitive, the use of chemical retardants can be restricted to 
crisis management to tide over the periodic and acute shortages of water when even drinking 
water may not be adequately available. This method, however, is not cost effective for mass 
scale use. This method is also not suitable under following conditions : 
(i)
When the wind velocities are more than 10-16 km/hr. 
(ii)
When the temperature rises above 40-42
o
C. 
(iii)
The size of reservoir/ water body is relatively large. 
Fatty alcohols can be used for the purpose having following properties : 
(i)
The chemical selected should have cohesive property which can maintain the monolayer 
on the surface of the body irrespective of the effect of wind. Even if the layer is broken 
due to occasional high wind velocities, the material should have the property of reuniting 
and forming the layer.
(ii)
The chemical selected for use should have no effect on the quality of water , especially no 
toxic effect on aquatic and human life. 
(iii)
The chemical should also be such that the film should allow enough passage of air through 
it so that the aquatic life is not affected.
6.7.1
 
Merits of Chemical WERs 
Use of evaporation control techniques requires a small capital investment. Locally constructed 
rafts can be used in its application, and skilled labour is not required, except for operation of 
motorized boats. Fatty alcohols cause no hazards in handling, and are non-inflammable, non-
toxic, and non-irritating. There perhaps may be no known harmful effects, making this 
technology safe for application on drinking water lakes and reservoirs. There are also no 
known ecological ramifications, as the alcohols contain straight chain carbon compounds, 
which are biodegradable and permeable to oxygen.