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Impaired Waters and TMDLs

Impaired Waters and TMDLs in Region 6

Map of Region 6Region 6 serves Arkansas, Louisiana, New Mexico, Oklahoma, Texas and 66 tribes

Public Notices in Region 6

There are no public notices at this time

Recent Actions


2014 § 303(d) List: Responsiveness Summary and Record of Decision

Arkansas and Oklahoma

Illinois River Watershed

The Illinois River is a multi-jurisdictional tributary of the Arkansas River, approximately 100 miles (160) km long, between the states of Arkansas and Oklahoma. The Illinois River begins in the Ozark Mountains in the northwest corner of Arkansas (Washington County) and flows west into northeast Oklahoma. Once the Illinois River enters Oklahoma, it then flows southwest and south through the mountains of eastern Oklahoma into Tenkiller Ferry Lake. The Illinois River in Oklahoma is currently on the 303(d) list for total phosphorus, while tributaries to the Illinois River (e.g. Osage Creek, Muddy Fork and Spring Creek) in Arkansas are also on the 303(d) list for total phosphorus.

Project Updates

Current Phase – Watershed and Lake Calibration/Validation Modeling

The calibration/validation modeling is currently being conducted for both Illinois River and Lake Tenkiller. The purpose of the calibration/validation modeling is to ensure a scientifically sound modeling system is developed to represent the entire Illinois River Watershed. Calibration modeling will be performed using data obtained from the time period of 2001 to 2009, whereas data obtained from the 1992 to 2000 period of record will be used for validation modeling. Calibration and validation of the Illinois River Watershed models will be achieved by considering qualitative and quantitative measures, involving both graphical comparisons and statistical tests.

Modeling is still underway. Preliminary information is anticipated late October 2014.

New Mexico

There are no recent actions at this time.


There are no recent actions at this time.

State 303(d) Listing (Impaired Waters) Programs in Region 6

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State TMDL Programs in Region 6 (if different from listing)

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Region 6 Staff Contacts

Region 6 Staff Contacts