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Ecology Publications & Forms |
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Ecology Publications & Forms |
| Title | Spokane River and Lake Spokane Dissolved Oxygen Total Maximum Daily Load 10-Year Effectiveness Study |
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Spokane River and Lake Spokane Dissolved Oxygen Total Maximum Daily Load 10-Year Effectiveness Study (Number of pages: 186) (Publication Size: 11451KB)
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| Author(s) | Tighe Stuart and Joseph Zimbric | ||||
| Description | Ecology adopted the Spokane River and Lake Spokane Dissolved Oxygen Total Maximum Daily Load (TMDL) in 2010 to address low dissolved oxygen (DO) levels in the Spokane River and Lake Spokane, as well as harmful algal blooms in Lake Spokane. The TMDL identified that Ecology would conduct an interim assessment of conditions approximately 10 years into the TMDL implementation period. Ecology assessed dissolved oxygen and nutrients in the Spokane River and Lake Spokane using data we collected during an October 2021 – October 2022 field study, along with a variety of other data collected by Ecology and partner organizations. In recent years, point source dischargers have substantially reduced their phosphorus discharges to the Spokane River. As a result, since 2021, summertime total phosphorus (TP) levels entering Lake Spokane have typically been less than 0.01 mg/L. Although tributary and nonpoint sources have also decreased over recent decades, nonpoint sources, particularly Hangman Creek, remain as the largest sources of phosphorus. For example, during March – May 2022, Hangman Creek contributed 74% of the total load entering the Spokane River. As of 2022, it is likely too soon to draw conclusions about Lake Spokane DO response. When a large phosphorus reduction occurred during the 1970s, Lake Spokane DO took at least five years to fully respond. Furthermore, during the 2022 field study, large Hangman Creek phosphorus loads during June may have complicated conditions in Lake Spokane for that year. We recommend continued monitoring of Lake Spokane over the next several years to assess the lake response. We also recommend continued efforts to reduce nonpoint phosphorus pollution in the tributaries, especially Hangman Creek. |
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The mission of the Department of Ecology is to protect, preserve, and enhance Washington’s environment. To help us meet that goal, please consider the environment before you print or request a copy.
ADA Accessibility The Department of Ecology is committed to providing people with disabilities access to information and services by meeting or exceeding the requirements of the Americans with Disabilities Act (ADA), Section 504 and 508 of the Rehabilitation Act, and Washington State Policy #188. Visit Ecology’s website for more information. |
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| Contact | EAP Publications Coordinator at 564-669-3028 or EAPpubs@ecy.wa.gov | ||||
| Keywords | Nonpoint Pollution, Spokane River TMDL, Hangman Creek, TMDL Effectiveness, discharges, Lake Spokane, Wastewater Treatment Facilities, effectiveness monitoring, wastewater treatment plant, algae control, Spokane River, water quality, wastewater discharge, TMDL, Total Maximum Daily Load, phosphorus, point source, pollution, pollution control, discharge, Discharge Monitoring, dissolved oxygen, total phosphorus, DO | ||||
| WEB PAGE | Spokane River multi-parameter TMDL | ||||
| WATERSHED | Water Resource Inventory Areas (WRIA 54,WRIA 55,WRIA 56,WRIA 57) |
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| DATA | Environmental Information Management (EIM) #tist0003 |
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| RELATED PUBLICATIONS | Title:
Quality Assurance Project Plan: Spokane River and Lake Spokane Dissolved Oxygen Total Maximum Daily Load 10-Year Effectiveness Monitoring Study Erratum Spokane River and Lake Spokane Dissolved Oxygen Total Maximum Daily Load Water Quality Improvement Project Spokane River and Lake Spokane Dissolved Oxygen Total Maximum Daily Load: Water Quality Improvement Report Errata: Spokane River and Lake Spokane Dissolved Oxygen Total Maximum Daily Load Water Quality Improvement Project |
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