Salt Loading in Disturbed Watershed°Field Study

Salt loading of waters receiving drainage from lands disrupted by mining is estimated from nearly 3 yrs of field data on a strip-mined watershed in Western Colorado. Observed salt loading is separated into approximate contributions from mined land, undisturbed land, ground-water runoff, and overland runoff. The inorganic composition of mine drainage is found to be very similar to that obtained in saturation and 1:1 extracts prepared from the disturbed material. Calcium, magnesium, and sulfate dominate the dissolved solids content of the water. In water years 1974 and 1975, the salt loading from mined land was estimated to be 2.37 tons/acre (5,330 kg/ha) and 2.13 tons/acre (4,790 kg/ha), respectively. It is estimated that 56% of the total observed salt loading is attributed to mined lands that comprise 17% of the contributing watershed area.