Evaporation Pond Hydrology

by M. E. Grismer, Univ of California, Davis, United States,
F. Karajeh, Univ of California, Davis, United States,
H. Bouwer, Univ of California, Davis, United States,

Document Type: Proceeding Paper

Part of: Management of Irrigation and Drainage Systems: Integrated Perspectives


Drainwater evaporation ponds are impoundment facilities designed for drainwater disposal by evaporation. In California, these ponds are typically constructed on the clay soils of the western San Joaquin Valley whereas in Australia, many of these 'ponds' are natural depressions in the Murray River Basin. Pond water evaporation rates of roughly 1.4 m/year far exceed the average annual rainfall of roughly 0.2 m the San Joaquin Valley. Pond water seepage is spatially variable within the ponds and the overall rate decreases dramatically within the first one to two years of pond operation apparently due to 'bottom sealing' from microbial activity in pond bed materials. Seepage rates on the order of several mm/day are common. Seasonal variations and changes in pond water salinity have a relatively small effect on pond water seepage rates. Evaporation rates on the order of 5 mm/day and seepage rates tend to decrease with increasing water salinity. The impact of pond seepage on shallow groundwater appears to be limited to the locality of the pond, particularly when perimeter drainage systems are operational or groundwater cutoff walls are employed. Groundwater degradation from pond seepage is probably similar to that resulting from excess deep percolation not collected by drainage systems on adjacent irrigated lands.

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