Challenges in conducting hydrologic and water quality research in drastically disturbed watersheds

ABSTRACT:

A nine-year investigation was conducted on the impacts of drastic land disturbances in small watersheds due to coal mining and reclamation activities on surface and subsurface hydrology and water quality. Three small watersheds in Ohio (12 to 18 ha) were monitored before mining, during mining and reclamation, and after reclamation for hydrology and water quality, resulting in many publications. The current increased interest in coal mining may require additional watershed-scale studies on the short- and long-term effects of drastic land disturbances on watershed hydrology, water chemistry, and sedimentation. Conducting watershed-scale studies in drastically disturbed areas is expensive, long-term, high-risk, and difficult research. The challenges and experiences of conducting the nine year study are identified so that other investigators may efficiently plan and conduct similar watershed-scale research in mines. The experimental design of the project, actual conditions during the project, and challenges in conducting the research are discussed. Hydrological instrumentation must be dependable and operational to collect data from the short duration disturbances because these periods are not repeatable, and watersheds require many years to approach a new equilibrium. Control watersheds must be free from previous disturbances. It was not feasible to quantitatively characterize the watersheds during the rapid and transitory periods of disturbance. Undisturbed and reclaimed watersheds can be visually undisturbed, but hydrologically disturbed. Surface- and groundwater hydrology and water chemistry processes may not reach a dynamic equilibrium until many years have passed. Association of data with periods of disturbance is not precise, depends on available data, and requires scientific judgment. The “drop-box weir” works well for sediment-laden flows with large rocks expected from drastically disturbed areas. Many recommendations are presented for future watershedscale research on drastic land disturbances. This paper addresses challenges in researching the impacts of mining and reclamation activities but is applicable to studying other land disturbances such as urbanization.