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| Title | A Suspended Sediment and DDT Total Maximum Daily Load Evaluation Report for the Yakima River | |||
| Month-Year Published | July 1997 | |||
| Online Availability |
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| Short Description |
The Washington State Department of Ecology (Ecology) conducted a total maximum daily load (TMDL) evaluation of the lower Yakima River basin in 1994-1995. The TMDL was conducted in cooperation with the USEPA and the Yakama Indian Nation, who are also water quality managers in the basin. The TMDL evaluation focused on total suspended sediment (TSS) and DDT loads from irrigated agricultural areas during the irrigation season. (Also see abstract below) | |||
| Publication Number | 97-321 | |||
| Author(s) | Joy, J. and B. Patterson | |||
| Print Availability | ||||
| Number of pages | 87 + app (121 total) | |||
| Keywords | basin, DDT, evaluation, irrigation, report , river, sediment, suspended sediment, TMDL, Total Maximum Daily Load, toxic, toxicity, TSS, water, Water Quality | |||
| Subject Waterbodies |
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| Related Publications | Title | Relationship | ||
| Lower Yakima River Suspended Sediment Total Maximum Daily Load: Effectiveness Monitoring Report | similar topic | |||
| Abstract | Long Description |
The Washington State Department of Ecology (Ecology) conducted a total maximum daily load (TMDL) evaluation of the lower Yakima River basin in 1994-1995. The TMDL was conducted in cooperation with the USEPA and the Yakama Indian Nation, who are also water quality managers in the basin. The TMDL evaluation focused on total suspended sediment (TSS) and DDT loads from irrigated agricultural areas during the irrigation season. Historical and TMDL data indicated significant correlations between TSS and turbidity, and between TSS and total DDT (t-DDT= DDT+DDE+DDD). Turbidity targets for main stem and tributary sites were recommended with an implementation schedule spanning 15 years. The Washington State Class A turbidity criterion was applied to the main stem to control TSS loading. Turbidity will be limited to a 5 NTU increase in the 86.4 mile reach between the confluence of the Yakima and Naches River and Benton City. A 90th percentile turbidity target of 25 NTUs (56 mg/L TSS) for the tributaries and return drains was recommended to significantly reduce t-DDT loads and to protect aquatic communities from TSS effects. The target will require the largest return drains to reduce TSS loads 70% or more during an irrigation season with normal water availability. Based on the current correlation equation, tributary TSS concentrations will need to be further reduced to 7 mg/L to meet the 1 ng/L DDT chronic toxicity criterion for protection of aquatic life. However, more data from tributaries for TSS and t-DDT at lower TSS concentrations are needed to confirm this target. |
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