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Okanogan River Tributaries pH 303(d) Listing Verification Study

Publication number Date Published
16-03-036September 2016
VIEW NOW Okanogan River Tributaries pH 303(d) Listing Verification Study (Number of pages: 84) (Publication Size: 2121KB)

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Author(s) Carroll, J.
Description A total of 19 reaches on 11 tributaries to the Okanogan River are on the Washington State Department of Ecology’s 303(d) list for pH impairment. Because the listings were based on older unverified pH data, Ecology re-monitored the 11 tributaries for verification of pH impairment in 2015-16.

Verification monitoring determined that 18 of the 19 listed reaches were meeting the pH standards. Monitoring showed pH levels were either meeting pH numeric criteria, or when above criteria, were in equilibrium with the pH saturation potential. A model of pH saturation showed that pH levels in tributaries of the Okanogan River often exceed (do not meet) pH criteria due to naturally high alkalinity levels in the water resulting from local geology.
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Keywords Okanogan River, 303(d), pH
WATERSHED Water Resource Inventory Area 49 Okanogan
DATA Environmental Information Management (EIM) #JICA0003


Quality Assurance Project Plan: Okanogan River Tributaries 303(d) pH Listings Verification Study