Methodology for evaluating premining hydrology and postmining effects of mining and reclamation on the hydrology of an area is presented for a potential mine-permit area of 1,680 acres in the Warrior Coal Field, northwestern Alabama.
Information is included on climate, geology, soil-water relations, vegetation, surface water, ground water, and quality of water. Estimation techniques are used to develop data for reconstructed topography, soil-water relations, vegetation cover, peak flows, flow volumes, soil losses, and sediment yields.
Streamflow response of the basin is described by the variable-source-area concept; nearly all water moving from slopes flows through coarse-textured soils and unconsolidated sand and gravel deposits that are underlain by an impermeable clay zone. The resultant peak discharges per unit area are small to moderate, and there is very little erosion of slopes or channels. Susceptibility of the soils to compaction by heavy machines and the effects of compaction on soil-water relations are demonstrated.
Regression and empirical methods for evaluating streamflow characteristics are compared. Estimates of peak discharges made with four methods are divergent, particularly for recurrence intervals of 2, 5, and 10 years; divergence is less for 25-, 50-, and 100-year discharges.
The Universal Soil Loss Equation (USLE) and sediment-delivery ratios are used to estimate sediment yields for various land and cover conditions from premining until 20 years after reclamation would begin. A premining estimate of sediment yield made with the Universal Soil Loss Equation and a sediment-delivery ratio is about 2.5 times larger than an estimate made with the sediment rating curve-flow duration method.
Research and data needs are discussed regarding: (1) An improved understanding of the hydrology of small, very ,permeable, upland basins; (2) alternative methods for estimating streamflow and sediment yield of such basins; (3) field evaluation of permeability and erodibility of soils on reclaimed areas; and (4) better understanding of ground-water hydrology and geochemistry of the coal-bearing Pottsville Formation before and after mining.
