GROUND-WATER DRAINAGE TO SURFACE MINES REFINED.

Changes in seepage flux and hydraulic head (ground-water level) resulting from ground-water drainage into the first and subsequent cuts of a surface coal mine can be estimated by a technique that considers drainage from the unsaturated zone and drainage effects of the advancing mine. A 'single-layer' technique is used, in which each layer of a stratified aquifer system is considered separately. Use of the technique requires knowledge of some aquifer characteristics at the proposed mining site and an estimate of the rate of approach of the advancing surface mine.