| Study ID | JICA0003 |
| Study Name | Okanogan River Tributaries 303(d) pH Listings Verification Study |
| EIM Data Entry Review Status | Reviewed |
| Study Type | General environmental study |
| Study Purpose | Ecology will conduct an assessment of pH in select tributaries to the Okanogan River during summer months to verify pH 303(d) listings.
Data loggers with pH sensors will be used to continuously measure pH for 24-hour periods. Data collection is planned for July 2015 to May 2016. |
| Field Collection Date Range | 8/15/2015 - 4/27/2016 |
| Data First/Last Loaded Date |  |
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| Ecology Program or Other Responsible Entity | Ecy Environmental Assessment Program |
| Ecology Contact | Jim Carroll |
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| Study QA Planning Level | LEVEL 4: Approved QAPP or SAP. |
| Study QA Project Plan Description | Ecology will conduct an assessment of pH in select tributaries to the Okanogan River during summer months to verify pH 303(d) listings.
Data loggers with pH sensors will be used to continuously measure pH for 24-hour periods. Data collection is planned for July 2015 to May 2016. |
| Study QA Assessment Level | Level 5: Data Verified and Assessed for Usability in a Peer-Reviewed Study Report |
| Study Result Description | During 2015-2016, Ecology monitored 11 tributaries to the Okanogan River for verification of pH impairment. A total of 19 reaches on the 11 tributaries are on the Washington State 303(d) list for not meeting pH criteria. The 303(d) listings were based on pH measurements made by the Okanogan Conservation District during a 3-year Ecology grant project from 2000 to 2003 (EIM Study ID G0000225). Ecology’s review of the older pH data showed a bias for the pH measurements. Ecology conducted verification monitoring during August and October 2015, and April 2016. Eighteen of the 19 listed reaches met pH standards. In several cases, levels were above the pH criteria but were determined to be in equilibrium with the pH saturation potential. A model of pH saturation showed that the pH of tributaries in the Okanogan River basin was often higher than the pH criteria due to high alkalinity levels in the water. The high alkalinity is the result of natural carbonate geology in the Okanogan basin. Data collected for this study were sufficient to show that most of the Okanogan River tributaries do not have pH impairment due to anthropogenic influences. |
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