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Approaches to Identify Exceedances of Water Quality Thresholds Associated with Ocean Conditions
Citation:
BROWN, C. A. AND W. G. NELSON. Approaches to Identify Exceedances of Water Quality Thresholds Associated with Ocean Conditions. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-10/128, 2010.
Impact/Purpose:
present an application of logistic regression models to predict the probability of exceedance of water quality thresholds using flood-tide nutrient and dissolved oxygen data from the Yaquina Estuary.
Description:
WED scientists have developed a method to help distinguish whether failures to meet water quality criteria are associated with natural coastal upwelling by using the statistical approach of logistic regression. Estuaries along the west coast of the United States periodically have high nutrient, high chlorophyll a, and low dissolved oxygen levels due to the intrusion of oceanic water into the estuaries. These chemical and biological conditions are generated by the physical process of upwelling which occurs near the coast. As a result, this oceanic water during upwelling periods often has water quality conditions which fail to meet water quality standards. In order to be able to correctly identify water bodies experiencing impairments due to human actions, these natural events need to be distinguished. Temperature and salinity characteristics of the water sampled in the estuary during flood tide can be used to help identify the likelihood that upwelling sources have contributed to the values of water quality parameters that fail to meet water quality criteria.