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United States Department of Agriculture

Agricultural Research Service

Title: Experiences in Instrumentation and Conducting Investigations of Drastic Land Disturbances in Small Watersheds

Author
item Bonta, James

Submitted to: International Instrumented Watershed Symposium
Publication Type: Proceedings
Publication Acceptance Date: March 15, 2004
Publication Date: June 22, 2004
Citation: Bonta, J.V. 2004. Experiences in instrumentation and conducting investigations of drastic land disturbances in small watersheds. International Instrumented Watershed Symposium, Edmonton, Alberta, Canada.Available: http://www.osern.rr.ualberta.ca/Downloads/IIWS/bonta_paper.pdf

Interpretive Summary: Conducting watershed research in land areas drastically disturbed to mining and reclamation activities while mining for coal is difficult, and challenges faced by researchers into such projects need to be highlighted to minimize problems that may be faced by future researchers. Furthermore, flow measurement in streams draining mined areas that produce much sediment can be difficult. A seven to 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 (12 to 20 ha) in Ohio were monitored before mining, during mining and reclamation, and after reclamation for hydrology and water quality. The planned experimental design of the project, the actual conditions during the mining and reclamation activities, and challenges in conducting the research are discussed. Watershed research in surface-mined areas is considered long term, high risk research. It is long term because mining activities take a while to occur, and because watersheds will respond slowly to these drastic changes. It is high risk because researchers do not have control of weather occurrences, market conditions for coal, labor-management relations, etc. Some of the major factors contributing to the challenges in conducting this type of watershed research are listed. Control watersheds must be free from previous disturbances, which is difficult to document for sites that do not have long hydrologic runoff records. It was not economically feasible to quantitatively characterize the watersheds during the rapid and transitory periods of watershed disturbance. Undisturbed and reclaimed watersheds can be visually undisturbed, but hydrologically disturbed. Surface and ground water hydrology and water chemistry processes may not reach a dynamic equilibrium until many years have passed. This study addressed the immediate and most apparent impacts of surface mining and reclamation, but not the more subtle impacts. The utility of, and recent research into, a flow-measuring device called the "drop-box weir" is also presented. This weir is not well known, but works well where commonly used weirs would fail because flows are sediment-laden with large particles expected from erosion-vulnerable landscapes draining drastically disturbed areas. Recent hydraulic research with the weir extends its utility to small erosion plots and small, steep watersheds. Sampling devices for use with the weir have been developed. The design of the project led to many useful results, in spite of the challenges during the project. Project results are useful to university and federal researchers, and to regulatory agencies and research funding organizations.

Technical Abstract: A seven to 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 (12 to 20 ha) in Ohio were monitored before mining, during mining and reclamation, and after reclamation for hydrology and water quality. The planned experimental design of the project, the actual conditions during the mining and reclamation activities, and challenges in conducting the research are discussed. Watershed research in surface-mined areas is considered long term, high-risk research. Control watersheds must be free from previous disturbances, which is difficult to document for sites that do not have long hydrologic runoff records. It was not economically feasible to quantitatively characterize the watersheds during the rapid and transitory periods of watershed disturbance. Undisturbed and reclaimed watersheds can be visually undisturbed, but hydrologically disturbed. Surface- and ground-water hydrology and water chemistry processes may not reach a dynamic equilibrium until many years have passed. This study addressed the immediate and most apparent impacts of surface mining and reclamation, but not the more subtle impacts. The utility of, and recent research into, a flow-measuring device called the "drop-box weir" is also presented. This weir is not well known, but works well where commonly used weirs would fail for sediment-laden flows with large particles that are expected from erosion-vulnerable landscapes draining drastically disturbed areas. Recent hydraulic research with the weir extends its utility to small erosion plots and small, steep watersheds. Sampling devices for use with the weir have been developed. The design of the project led to many useful results, in spite of the challenges during the project.

Last Modified: 11/28/2014
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