Laserfiche WebLink
12 <br />• loss on the nontopsoiled spoils by 84°6. Interestingly, the sediment <br />production from the bare topsoil was far greater than the nontopsoiled <br />spoils - an average of 74,000 kgjha. Straw mulch reduced sediment yield <br />by 93 percent for the topsoil. The relatively low erodibility of the <br />nontopsoiled spoils compared to that of the topsoil was attributed tb <br />the formation of a soil crust on the sodic spoils (spoils 5AR = 35, <br />topsoil SAR = 3). Rototilling broke the crusts of the nontopsoiled spoils <br />and increased surface roughness, increasing infiltration from what it was <br />on the noncultivated nontopsoiled spoils. <br />Physical features of spoils which affect thermal properties can also <br />have an impact on the hydrologic characteristics of regraded coal mined <br />land. Changes in albedo, for example, could change evaporation losses <br />and freeze-thaw cycles, both of which could influence infiltration and <br />• erosion. Verma (1477) observed snowfall immediately melting on spoils in <br />northeast Arizona while snow accumulated on adjacent undisturbed land. <br />He believes this was probably due to subsurface oxidation of coal left in <br />the regraded spoils. The impact of a reduced snowpack or a more rapid <br />melting of snowpack caused by this oxidation process in Colorado, where <br />much of the erosion on regraded surface mined land may occur from snow- <br />melt, could be substantial. <br />Verma continued his study at the same mine in Arizona through the <br />summer and he observed the regraded watershed responded to thunderstorms <br />with higher and sharper peak flows which produced more runoff than an <br />adjacent, undisturbed watershed. Furthermore, the concentration of <br /> suspended solids in the runoff from the regraded watershed was 300 to <br />• 1300 percent greater than the suspended solids in the runoff from the <br />