PREDICTING GROUND-WATER DRAINAGE TO SURFACE MINES.

A two-dimensional, finite-difference numerical model is used to simulate the drainage of ground water into a surface coal mine. Graphs of dimensionless head as a function of dimensionless distance, and dimensionless seepage flux as a function of dimensionless time are developed from results of the numerical modeling. Changes in seepage flux and ground-water levels can be estimated from the dimensionless hydrographs, from knowledge of aquifer characteristics prior to mining, and by means of several 'simple-to-use' equations. The technique is an improvement on previous experimental, analytical, and other numerical solutions because drainage from the unsaturated zone also is considered. The procedure is applicable to a wide range of hydrogeologic settings, but is especially applicable to hydrogeologic conditions typically encountered in the coal strip-mining regions of Illinois.