Minimizing contamination hazards to waterbirds using agricultural drainage evaporation ponds |
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Authors: | David F Bradford Lynda A Smith Deborah S Drezner J David Shoemaker |
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Institution: | (1) Environmental Science and Engineering Program School of Public Health, University of California, 90024 Los Angeles, California, USA |
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Abstract: | In much of the San Joaquin Valley, California, USA, inadequate drainage of applied irrigation water and accumulating salts
in the soil have necessitated the installation of subsurface tile drainage systems to preserve crop productivity. At present,
these subsurface drainage waters are disposed of by means of evaporation ponds or discharges into the San Joaquin River. Unfortunately,
most of these agricultural drainage waters contain high concentrations of salts and naturally occurring trace elements, such
as selenium, and recent evidence indicates that substantial numbers of waterbirds are exposed to contamination by selenium
in the evaporation ponds. In order to avoid, minimize, or mitigate the adverse impacts on wildlife using the ponds, alternative
pond management methods must be identified and evaluated for implementation. A number of methods have the potential to be
cost-effective in significantly reducing the contamination hazard to birds using agricultural evaporation ponds. Twenty general
methods were evaluated in this study, and four methods are recommended for implementation: remove levee vegetation, remove
windbreaks, deepen the ponds, and haze birds. A number of other methods are recommended for further consideration because
they appear to have good prospects for reducing the contamination hazard: steepen interior levee slopes, apply herbicides
and insecticides, place netting on pond shorelines, and provide freshwater habitat adjacent to evaporation ponds. It may be
necessary to use a combination of methods to effectively control selenium contamination of aquatic birds because it is unlikely
that a single affordable pond management method will be able to entirely eliminate the contamination hazard. |
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Keywords: | Agricultural ponds Birds Evaporation ponds Selenium Selenium contamination Shorebirds Subsurface drainage Waterfowl |
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