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CONTROLS ON WATER CHEMISTRY OF AN OREGON COAST RANGE STREAM
Citation:
Church, M R., J E. Compton, AND S T. Larned. CONTROLS ON WATER CHEMISTRY OF AN OREGON COAST RANGE STREAM. Presented at Department of Geosciences, Corvallis, OR, January 25, 2001.
Description:
Numerous factors may control losses of dissolved nutrients from forested basins in the Oregon Coast Range. Potentially important factors include forest composition, stand age, forest management, grazing, agriculture, sewage inputs and bedrock types, as well as others perhaps not previously appreciated. With understanding of processes and controls may come the ability to model, predict and extrapolate current and future conditions across the Coast Range. To better understand the controls on nutrient losses from coastal watersheds, we sampled over 45 sites on the main stem and tributaries of the Salmon river in the Oregon Coast Range monthly since January 2000. The Salmon river basin is characterized by old soils with large stores of soil nitrogen, presumably resulting from long-term inputs by nitrogen-fixing red alder. We measured all major chemical constituents, with a focus on organic and inorganic nitrogen, and also determined instantaneous stream flow at approximately two-thirds of our sites.
Nitrate concentrations in these streams ranged from zero to nearly 3 ppm nitrate-N. Our data to date show a surprising correlation between losses of nitrate from the basin and losses of chloride, indicating that the inputs of chloride from sea spray play a role in nitrogen losses from these watersheds. In addition, at equal chloride concentration, areal coverage of alder within subbasins is positively related to stream nitrate concentration. Phosphorous losses appear to be related mainly to bedrock type (sedimentary vs. volcanic).