Georgia Water Plan - Water Resources Information and Data
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The distinction between the amount of water withdrawn for use and the amount of water consumed during use is important for water planning and management. Water data are reported as total water withdrawals or as consumptive water use. Consumptive water use is the part of withdrawn water that is not returned to the immediate source waters. Consumptive water use is the part of water withdrawn that is evaporated, transpired, lost to leakage, incorporated into products or crops, consumed by humans or livestock, transferred to another area, or otherwise removed from the immediate water environment (Hutson and others, 2004). For many withdrawals, data on the amount withdrawn that was returned to the immediate water environment (either a ground- or surface-water system) are not available.
Consumptive water use may be determined from measurements of water withdrawals and return discharges for a specific source; or may be estimated from consumptive-use coefficients. Data on the amount of withdrawn water that is returned to the immediate water environment (either a ground-or surface-water system) are not available for many withdrawals. Because of the difficulties in obtaining and compiling data on the amount of water returned to the environment for each withdrawal, consumptive use was estimated from the withdrawal amounts and consumptive-use coefficients by water-use category. Although estimates derived using coefficients can provide insight into consumptive water use, the results are not as accurate as metered data on withdrawals and return flows.
Consumptive-use coefficients vary for each of the water-use categories. Because public supply delivered water to domestic, commercial, industrial, and thermoelectric-power users, consumptive use is estimated for those use categories and not for public supply. The total water used in the categories is the sum of water withdrawn (self-supplied water) and water delivered from public suppliers.
For domestic water use, consumptive use was estimated at 18 percent of the total use (Atlanta Regional Commission, written commun., 2007). The consumptive-use coefficient for commercial use was developed by the Georgia Water-Use Program and supported by calculations using withdrawal and discharge data for some commercial users and estimated to be 18 percent. For industrial and mining use, consumptive-use coefficients were determined by industry type and type of mining activity. Irrigation and livestock water uses are considered to be 100 percent consumed. Consumptive-use coefficients for thermoelectric-power ranged from 0 to nearly 70 percent, and is determined by the type of plant cooling (once-through cooling, cooling towers, or ponds). Consumptive use is negligible for instream hydroelectric-power generation.