Snake River (Middle) - Succor Creek Subbasin - Idaho Department of Environmental Quality

Snake River (Middle) - Succor Creek Subbasin

Subbasin at a Glance

Hydrologic Unit Code	17050103
Size	2,002 square miles
§303(d) Listed Stream Segments	Snake River (3 segments), Birch Creek, Brown Creek, Castle Creek, Corder Creek, Cottonwood Creek, Hardtrigger Creek, Jump Creek, McBride Creek, North Fork Castle Creek, Pickett Creek (2 segments), Poison Creek, Rabbit Creek, Reynolds Creek, Sinker Creek, South Fork Castle Creek, Squaw Creek, Squaw Creek Unnamed Tributary, Succor Creek (2 segments)
Beneficial Uses Affected	Cold water aquatic life, salmonid spawning, primary contact recreation, drinking water supply, special resource water
Pollutants of Concern	Bacteria, dissolved oxygen, flow alteration, nutrients, pH, sediment, temperature
Major Land Uses	Rangeland, irrigated agriculture
Date Approved by U.S. EPA	January 2004
Date Approved by U.S. EPA	December 2007 EPA Approval Letter

Overview

This document addresses the water bodies in the Mid Snake River/Succor Creek Subbasin that have been placed on the §303(d) list of impaired water bodies. Within the Mid Snake River/Succor Creek Subbasin, 23 segments were identified on the §303(d) list and were assessed to determine if TMDLs were warranted. TMDLs were established for six of these segments.

The Mid Snake River/Succor Creek watershed is an arid watershed characterized by hot summer temperatures. The tributaries to the Snake River are generally low volume streams that have a combination of high ambient temperatures, poor shading, low flow volume, flow alteration, and naturally warm springs, which often leads to exceedances of the temperature standard. Even with maximum potential shade, some of the streams in the watershed cannot meet the cold water temperature standard. These streams were evaluated to determine the best achievable temperature based on the maximum potential shade.

Nutrient loading to the Snake River comes from the upstream segment of the Snake River, drains, tributaries, and point sources. The primary nutrient impairing beneficial uses is phosphorus. A total phosphorus target of 0.07 milligrams per liter has been set for the Mid Snake River, based upon the work done in the draft Snake River-Hells Canyon TMDL.

In-stream channel erosion is the primary source of sediment loading in Castle Creek, Sinker Creek, and Succor Creek. Land management practices contribute to unstable banks and this resultant instability leads to sediment delivery to the stream channel. Eighty-percent bank stability was selected as a surrogate target to achieve 28% depth fines in the creek.

Streams and Pollutants for Which TMDLs Were Developed

Snake River (Swan Falls to Oregon Line): Nutrients, dissolved oxygen
Castle Creek: Sediment
Jump Creek (Mule Creek to Snake River): Sediment
Sinker Creek: Sediment, temperature
Succor Creek (Headwaters to Oregon Line): Sediment, temperature
Succor Creek (Oregon Line to Snake River): Sediment, bacteria

Revised Addendum: Succor Creek and Castle Creek Temperature TMDLs and S. Fork Castle Creek Analysis

The addendum addresses water quality in Succor, Castle, and North and South Fork Castle Creeks:

South Fork Castle Creek appears on the §303(d) list of impaired water bodies for bacteria. However, bacteria levels have been found to be well below the standard, so DEQ is proposing to remove South Fork Castle Creek from the state's §303(d) list for bacteria and a TMDL for bacteria in South Fork Castle Creek was not developed.
Succor Creek, Castle Creek, and North Fork Castle Creek were placed on the 303(d) list by EPA for temperature. Data collected in 2002-2004 on these creeks verify temperature exceedences of the cold water aquatic life and rainbow trout salmonid spawning criteria. As a result, TMDLs to improve temperature by reaching potential natural vegetation conditions have been developed for these water bodies and several of their tributaries.

Streams and Pollutants for Which TMDLs were Developed (Revised Addendum)

Succor Creek & Tributaries: Temperature
Castle Creek, NF Castle Creek & Alder Creek, SF Castle Creek, Juniper Creek, Clover Creek: Temperature

Department of
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