Investigations of Water Supply and Water Quality Issues Related to Inland Shrimp Farming in Western Alabama

Abstract

Examination of data on chloride concentrations in well waters revealed that an area in Greene, Sumter, Hale, Marengo, and Wilcox Counties had the greatest potential for inland culture of marine shrimp. A few places in Tuscaloosa and Lowndes Counties also have access to groundwater of adequate salinity. Highly saline groundwater in Washington, Clarke, and Choctaw Counties did not appear as acceptable for shrimp culture. Studies conducted at an existing inland shrimp farm in Greene County showed that potassium applied to ponds as fertilizer to correct a potassium deficiency in pond waters was lost from ponds by bottom soil adsorption, seepage, and discharge of water for harvest. Estimates of potassium adsorption by bottom soil revealed that the capacity of the soil to exchange other ions for potassium in the water was mostly filled during a single shrimp crop. However, the bottom soils contained 2:1 type clay minerals with high capacity to fix potassium through noncationic exchange processes. Pond soils likely will remove added potassium from water for several years, and the only reliable way to determine when potassium fertilizer should be applied to inland shrimp ponds in Alabama is to monitor potassium concentrations in the water. The salt input to the shrimp farm in Greene County was saline well water, fertilizer, feed, rainfall, and runoff was 1,980.8 tonnes of salt over a 5-year period. A total of 1,588 tonnes of the added salt was lost to the environment with almost equal amounts lost exiting ponds in seepage and effluent (overflow and draining). The salinity of water in a small creek flowing through the farm and in the shallow aquifer beneath the pond area was elevated by saline water discharged from the ponds. However, chloride concentration in the receiving stream, Needham Creek, only exceeded the Alabama Department of Environmental Management “in stream” standard of 230 mg/L when water was discharged from ponds to facilitate shrimp harvest in the fall. Greater water reuse or more gradual release of pond effluents during harvest would reduce the peak in chloride concentration in Needham Creek during shrimp harvest.