Infiltration rates and erosion associated with reclaimed coal mine spoils in west central New Mexico

Abstract

Large quantities of coal are extracted in New Mexico by surface mining that results in large areas of surface disturbance. Some goals of reclaiming these disturbances are to control erosion and consequent sediment yields by recontouring and revegetation. This study investigates the rates of infiltration and sediment removal on successfully reclaimed coal mine areas, and their relationship with analogous undisturbed rangeland. Reclaimed areas that had been revegetated for one, three and five years, and a nearby natural rangeland, were subjected to simulated rainfall. Ponding time and runoff time were similar between the non-disturbed lands and the areas reclaimed one and five years before for both dry and wet soil moisture scenarios. The area revegetated three years before required substantially longer time to pond and yield runoff than the rangeland. The reclaimed areas with three and five growing seasons displayed greater infiltration rates than the rangeland area on dry soils and wet soils. Infiltration rates for the reclaimed area with one growing season were similar to the natural rangeland area for both soil moisture conditions. Sediment production and concentrations on the newly reclaimed areas were equal to, or greater than, that for the rangeland on dry and wet soils, respectively. The reclaimed area with the most established vegetation yielded the least sediment of all the reclaimed sites, and significantly less than the rangeland site, regardless of soil moisture situations. Various vegetation, rock, soil, and surface roughness variables were found to influence ponding and runoff times, infiltration rates, sediment production, and sediment concentration. These variables include, in decreasing importance: foliar grass cover, grass production, bulk density, foliar shrub cover, shrub production, horizontal roughness, litter cover, vertical roughness, rock cover and organic matter content.