Most water used for fish farms is required to maintain acceptable pond levels and water quality. The quantity of surface water and ground water withdrawn for use by livestock was estimated from the numbers of animals in a county. The livestock and poultry numbers are available in most States from the U.S. Department of Agriculture Crop and Livestock Reporting Service or the Cooperative Extension Service. The number of each type of animal in each county was multiplied by an average water use per animal to obtain the water-use estimate. The Crop and Livestock Reporting Service or the Cooperative Extension Service generally have pond acreage for fish farms.
Water use is estimated by multiplying pond acreage by an application rate.
In some States, water use for fish farms is reported under a permit system. The uncertainties in the livestock water-use estimates include difficulties in determining the sources of water and great variations in estimates of consumptive use. Consumptive use estimates generally were based on co efficients ranging from 10 to 100 percent of withdrawals. Several States, including Louisiana and North Carolina, reported a significant increase in animal specialties water use, primarily fish farming. Idaho reported a significant decrease based on more reliable information.