Mining water use includes water for the extraction of naturally occurring materials (including petroleum), dewatering, milling, and other preparations that are a part of mining activities. All water is self supplied and saline water is significant.
Water used in mining is difficult to quantify. Except for some washing and milling, water used at mining sites tends to be an impediment to or a byproduct of the extraction process. Unless water is needed for the mining operation, little attention is paid to quantities withdrawn. Estimates for mining withdrawals were obtained from State agencies that regulate discharges, or by estimating a coefficient for the relation between the quantity of water withdrawn and the quantity of material extracted. Consumptive-use estimates were based on coefficients, ranging from 10 to 100 percent of withdrawals, depending on the type of mining activity.
The quantity of water withdrawn for mining during 1990 was an estimated 3,310 Mgal/d of freshwater, and an additional 1,650 Mgal/d of saline water. (See table 21: water-resources regions and table 22: State.) Mining freshwater use during 1990 was 24 percent more than during 1985, and represents 1 percent of total freshwater use for all offstream categories. Some of the increase can be attributed to a more complete inventory of mines in some States.
The source and disposition of water for mining purposes are shown in the pie charts below (or as a GIF file or PostScript file (94Kb)). Ground water was the source for about 65 percent of mining withdrawals, and surface water was the source for the remaining 35 percent. Saline water accounted for approximately one-third of total mining withdrawals. The consumptive use of freshwater and saline water for mining during 1990 was about 1,550 Mgal/d or 31 percent of total withdrawals.
The most water withdrawn for mining use during 1990 was in the Ohio water-resources region, followed by the Texas-Gulf, the South Atlantic-Gulf, and the Mid Atlantic regions, as shown in figure 23 (GIF file)(or as a PostScript file (620 Kb)). By State, Texas and West Virginia had the most freshwater and saline water withdrawn for mining (figure 24 (GIF file), or PostScript file (508 Kb)), and accounted for about 23 percent of the Nation's total mining withdrawals. West Virginia and Florida had the most freshwater withdrawn for mining (figure 25 (GIF file), or as a (PostScript file (508 Kb)).