Water Quality Improvement Project
Middle Yakima River Area:

Water quality issues

Cowiche Creek, Wide Hollow Creek, and Moxee Creek/Drain are three tributaries to the Naches and Yakima Rivers, between Union Gap and Selah Gap in Washington State. All three creeks flow through areas dominated by three land use types: irrigated fields and orchards, fruit and vegetable packing facilities, and low-to-medium density urban development. These tributaries are on the Washington State 303(d) list for impaired water quality because water temperatures exceed standards that have been established for healthy streams. (Study area map)

Why this matters

Water temperature influences how many other types of organisms can live in a water body. Cooler water can hold more dissolved oxygen that fish and other aquatic life need to breathe. Warmer water holds less dissolved oxygen. Many fish need cold, clean water to survive. Temperatures in the Yakima River Watershed have been found to exceed standards by more than 5°C (41°F).

The Yakima River Watershed is designated as one of several critical links in the network of streams and rivers that comprise the Evolutionary Salmonid Units (ESUs) for five Salmonid species of the Columbia River. The Yakima has also been designated habitat for steelhead and bulltrout, both listed as endangered under the federal Endangered Species Act. If water temperatures exceed survivable limits for these species, their populations either die out, or they fail to use their natal waters for spawning and rearing.

Status of the project

Ecology will complete field studies on these streams in Fall of 2014. When preliminary studies are complete, a water quality improvement report (WQIR) will be submitted to the EPA for approval. After EPA acknowledges the WQIR, a water quality implementation plan (WQIP) will establish specific actions for reducing water temperatures.

The current projects will also expand upon an earlier project, the Upper Naches River and Cowiche Creek Temperature TMDL, approved in 2011.

Technical information

Unless otherwise specified, the following documents are Ecology publications.

Quality Assurance Project Plan: Mid-Yakima River Tributaries Temperature Study

Related information

Unless otherwise specified, the following documents are Ecology publications.

Wide Hollow Creek Water Quality Study for Aquatic Life Use Water Quality Study Design (Quality Assurance Project Plan)

WRIA 37: Lower Yakima Watershed Information (Environmental Assessment Program web site)



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Last updated June 2015
  Water resource inventory area (WRIA) 37 map, Washington State.


#37 (Lower Yakima)
#38 (Naches)

Water-body Name:
Cowiche Creek
Moxee Creek/Drain
Wide Hollow Creek


# of TMDLs: ---

Status: TMDL in development

Contact Info:
Laine Young
Phone: 509-575-2642
Email: Laine.Young@ecy.wa.gov

Central Region
Department of Ecology
1250 West Alder Street
Union Gap, WA 98903-0009