USGS Washington Water Science Center
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The Issue - During the 2004-07 irrigation season, nutrient concentrations in the lower Yakima River were high enough at certain times and locations to support the abundant growth of periphytic algae and macrophytes which resulted in large daily fluctuations in dissolved oxygen concentrations and pH levels that exceeded the Washington State water-quality standards for these parameters. The nutrient concentrations in the lower reaches of the Yakima River during this time were almost always greater than the reference conditions suggested by the U.S. Environmental Protection Agency to protect water bodies from the negative effects of nutrient enrichment. To date, an efficient and effective way of determining where nutrient loads are elevated throughout the Yakima River Basin and what factors are responsible for these elevated loads does not exist
How the USGS will help - In close cooperation with the Washington State Department of Ecology, the USGS will develop a model to estimate mean annual total phosphorus loads throughout the Yakima River Basin, and to estimate the relative contribution from various sources of phosphorus to the River.