Service biologist floating an egg to determine stage of developement

Photo: W. Beckon

Evaporation Ponds

In the Tulare Basin of California some farm operators have constructed large basins to evaporate drainwater high in salts. These basins have provided highly productive feeding and nesting habitat for shorebirds in this wetland-sparse region, but the water also contains toxic amounts of selenium and boron, which cause severe embryonic deformities and reproductive failure in this population of birds.

In 1996, the Service and others won a petition to the State Water Resources Control Board (State Board) resulting in the preparation of new Waste Discharge Requirements by the Central Valley Regional Board (Regional Board) for operators who had not earlier settled with the Service. In addition, those operators were directed to rectify their previously inadequate Environmental Impact Reports (EIRs).

The pond owners which have settled with the petitioners are using Service developed protocols to determine the acreage of mitigation needed for each evaporation pond system. The protocols use selenium concentration in shorebird eggs, evaporation pond size and attractiveness, and other parameters to determine the appropriate wetland acres needed. The results of nearly 10 years of research by the Service and others were used to develop the protocols. It provides incentives to pond owners to make their ponds less attractive to shorebirds thus reducing the risk of exposure and then providing for alternative habitat to draw birds away from the ponds. Compensation habitat is then determined to address any remaining unavoidable impacts. Depending on the variables used in the protocols as many as 2,000 acres of alternative habitat and 900 acres of compensation habitat may be created in the Tulare Basin.