Geochemical Mass-Balance in a Small Forested Watershed in Southwestern Pennsylvania

by Emitt C. Witt, III, U.S. Geological Survey, Harrisburg, United States,
Michael Bikerman, U.S. Geological Survey, Harrisburg, United States,

Document Type: Proceeding Paper

Part of: Structures for Enhanced Safety and Physical Security


An intensive hydrologic investigation of the North Fork Bens Creek Watershed on Laurel Hill in southwestern Pennsylvania was made during 1984-85. Precipitation was sampled weekly, and stream water was sampled monthly and during selected storms for discharge and chemical composition. The watershed is underlain by sandstone and sandy shale consisting of quartz, feldspar, muscovite, chlorite, calcite, and kaolinite. Watershed chemical flux for the sum of Ca++, Mg++, Na+, and K+ shows that solutes from wet deposition account for 19 to 21 percent of the load in runoff from the watershed. Cation exchange and weathering account for the net changes in the chemistry of streamflow. Alteration of orthoclase, muscovite, chlorite, and albite to kaolinite accounts for 36 percent of the neutralization of H+ resulting from precipitation input and carbonic-acid weathering. Dissolution of calcite accounts for 34 percent of H+ neutralization. Dissolution of aluminum-bearing minerals in the soil matrix accounts for 25 percent of H+ neutralization.

Subject Headings: Watersheds | Weathering | Surface water | Hydrology | Rivers and streams | Precipitation | Water discharge | Chemicals | Pennsylvania | United States

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