USGS Washington Water Science Center
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The Issue: Phosphorus from many different sources has caused water quality problems for Lake Spokane in eastern Washington by promoting the growth of algae and aquatic plants. Phosphorus comes from municipal and industrial point-sources upstream of Lake Spokane, as well as non-point sources like septic tanks, agricultural fields, and wildlife. Lake Spokane was listed by the Washington State Department of Ecology as an impaired waterbody for low levels of dissolved oxygen and developed a Total Maximum Daily Load for phosphorus. Current loads delivered by groundwater are not well defined.
How the USGS will help: To help resource managers reduce sources of phosphorus to Lake Spokane, the USGS will estimate the groundwater input of phosphorus, including seasonal variations. Quarterly groundwater-quality measurements and groundwater-discharge rate estimates will be used to estimate seasonal variations.