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Caption: Orthophosphate was measured at twelve locations, with varying frequencies, in the Stemple Creek watershed by the North Coast Regional Water Quality Control Board (NCRWQCB) from 1990-1994. The graph shows data collected at five locations (going downstream from left to right) from 1992-1993. The maximum concentration found among all stations and monitoring events was 9.6 mg/L, and the minimum concentration was 0.08 mg/L. It seems that orthophosphate (as well as total phosphate) generally decreases as you go downstream. Orthophosphate, the form of phosphorus most readily available to algae, made up a high proportion of the total phosphate concentration. In addition, NCRWQCB notes that total phosphates were strongly correlated with TKN and total ammonia concentrations, which gives evidence to common nutrient sources in the watershed. Orthophosphate objectives have not been established for Stemple Creek. See Picture for monitoring locations and Info Links for more information.
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