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Key Rulemaking Dates

Jan 7, 2021
Public Hearing
Staff Presentation

Feb 15, 2021
End of Public Comment


Sep 8, 2020 at 7:00 pm Sep 22, 2020 at 7:00 pm Oct 6, 2020 at 7:00 pm

Supporting Documents

10-6-20 Stakeholder Webinar Recording 9-22-20 Stakeholder Webinar Recording 9-22-20 Stakeholder Webinar Presentation 9-8-20 Stakeholder Webinar Recording 9-8-20 Stakeholder Webinar Presentation 9-10-20 Technical Memo - Critical Condition: Hydrograph Separation Analysis


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Program Contacts

Monty Porter, Assistant Chief Becky Veiga Nascimento, Environmental Programs Manager Jade Jones, Environmental Specialist III

Water Quality Division
Oklahoma Water Resources Board
3800 North Classen Blvd.
Oklahoma City, OK 73118
Phone 405-530-8800
Fax 405-530-8900

Stay Informed

The best way to stay informed on water quality standards actions in the Illinois River Watershed, as well as any other water quality standards actions, is to sign up to receive updates from OWRB staff through the gov delivery system.

2020-2021 Illinois River Watershed Total Phosphorous Criterion Revision

This web page is intended to provide stakeholders with current information on the 2020-2021 total phosphorus criterion revision for the Illinois River, Flint Creek, and Barren Fork Creek.

The Illinois River watershed (HUC 11110103) is located in northeastern Oklahoma and northwestern Arkansas and spans the political boundary between the two states. The watershed area is about 1,654 square miles. The mainstem of the Illinois River originates in the Boston Mountains in Washington County Arkansas. The river flows north for approximately 36 miles and turns westward at the confluence with Osage Creek; from here it flows west into Oklahoma. Flint creek is a major tributary to the Illinois River. Flint Creek drains 127 square miles in the northwest portion of the watershed and has its confluence with the Illinois River just south of the Oklahoma state highway 59. Below this confluence the Illinois River flows southwest past the city of Tahlequah to Tenkiller Ferry Reservoir (Lake Tenkiller). Barren Fork Creek is another major tributary that has a confluence with the Illinois River just before it enters Lake Tenkiller. Barren Fork Creek drains 346 square miles in the central area of the watershed. Below the Lake Tenkiller dam the Illinois River flows 9.5 miles to its confluence with the Arkansas River.

Barren Fork
Barren Fork

The Illinois River watershed and Lake Tenkiller are among Oklahoma's most beautiful and popular waters. The Oklahoma Water Quality Standards (WQS) designated beneficial uses for these waters are public water supply, aquatic life, aesthetics, body contact recreation, and agriculture. There are millions of visitors to these waterbodies annually who enjoy activities like swimming, boating, fishing, and scenic vistas. These visitors contribute substantially to the local economic activity; for example in 2019 visitor spending within 30 miles of Lake Tenkiller was just under $70 million dollars. In addition to direct measures of economic activity, the experiences people enjoy on the Illinois River are equally valuable.

The Oklahoma legislature recognized the intrinsic value of the Illinois River, Flint Creek, and Barren Fork Creek with the 1970 Scenic Rivers Act (82 O.S. 1451-1471). This act states that these waters:

"...possess such unique natural scenic beauty, water conservation, fish, wildlife and outdoor recreational values of present and future benefit to the people of the state that it is the policy of the Legislature to preserve these areas for the benefit of the people of Oklahoma."

The Illinois River, Flint Creek and Barren Fork Creek are protected as Scenic Rivers and as outstanding resource waters under the WQS Antidegradation Policy.

Total Phosphorus Water Quality Criterion

In 2001 it was recognized that Oklahoma's Scenic Rivers were being negatively impacted by phosphorus pollution and in response the OWRB adopted a total phosphorus criterion to protect the aesthetic beneficial use of these waters. Since the adoption of this criterion, the Illinois River watershed has been the focus of numerous projects to improve water quality and special studies to evaluate the total phosphorus criterion.

Cladophora in the Illinois River

The Second Statement of Joint Principles and Actions between Arkansas and Oklahoma Environmental Agencies was signed in February 2013. Under this agreement the states completed the Joint Phosphorus Criteria Study (Joint Study) managed by the Joint Study Committee. The committee was composed of six members, three from each state. The Joint Study was conducted from 2014 through 2016 and culminated in a Final Report submitted to both state governors on December 19, 2016. The Joint Study Committee made a recommendation regarding Oklahoma's total phosphorus water quality criterion. OWRB is conducting this criterion revision as an outgrowth of recommendations from the Arkansas-Oklahoma Joint Study Committee.

Water quality criteria protect beneficial uses by setting limits on pollutants or describing waterbody condition that supports a particular beneficial use. Water quality criteria are based on data and scientific judgements about the relationship between pollutant concentrations and water quality effects. In this case the total phosphorus criterion was developed to protect the aesthetic beneficial by guarding against excessive algae growth in the rivers. The draft criterion language is:

"The total phosphorus six month rolling average of 0.037 mg/L shall not be exceeded more than once in a one-year period and not more than three times in a five-year period."

Critical Condition Recommendation

The Joint Study Committee's 2016 Final Report and recommendation included the term "critical condition." This term introduced in the Final Report is defined as "conditions where surface runoff is not the dominant influence of total flow and stream ecosystem processes" and is a new term for Oklahoma WQS. Implementing this new term would limit the data used for assessment of the aesthetics beneficial use to those data values collected when the critical condition was satisfied. This is a transition away from the present inclusive use of data for beneficial use assessment.

The committee critical condition terminology was translated into an operational definition that could be feasibly and consistently implemented by water quality management programs across multiple agencies in both Oklahoma and Arkansas. Please see the Critical Condition Technical Memos for details on the technical analyses. The draft operational definition for the critical condition term is:

"The critical condition is when baseflow is fifty-five percent (55%) or greater of the total daily average flow calculated by the USGS hydrograph separation method sliding-interval. Measurements of total daily average flow must be obtained from a permanent continuous streamflow gage."

The application of a baseflow percentage threshold as a means to implement the Joint Study Committee recommended critical condition language will limit the total phosphorus data that can be used for water quality assessment. In identifying a baseflow percentage threshold, OWRB staff had the objective of maintaining a WQS that is evenhanded and functional for diverse programs and to minimize artificially influencing the evaluation of ambient total phosphorus water chemistry. Therefore, based on the considerations of 1) longstanding water quality monitoring practice, 2) influence that flow restrictions has on evaluation of ambient TP concentrations and loads, and 3) the need for evenhandedness across water quality programs, OWRB staff finds that a 55% baseflow threshold would reasonably address the critical condition recommendation from Joint Study Committee.

Stakeholder Participation

OWRB Water Quality Standards staff truly values stakeholders and we want to hear from you! We are committed to a transparent and interactive rulemaking process. We strongly encourage participation in both the informal and formal stakeholder participation processes by our fellow Oklahomans!

Informal Stakeholder Participation

Water Quality Standards staff will be hosting webinars to provide information on intended revisions to the total phosphorus criterion. The webinars will be live events with a staff presentation and a moderated question and answer session.

Scheduled Webinars
Sep 8, 2020 at 7:00 pm
Sep 22, 2020 at 7:00 pm
Oct 6, 2020 at 7:00 pm

A link to join the webinar will be posted on this web page a few days in advance of the scheduled webinar. Recordings of past webinars will also be posted on this web page.

Formal Stakeholder Participation

The formal stakeholder participation process is the public's opportunity to communicate directly in written or verbal format to the Oklahoma Water Resources Board Members regarding water quality standards rulemaking. The formal stakeholder participation process is required by the Oklahoma Administrative Procedures Act and includes a 45-day public comment period; all comments must be received within the 45-day period. The formal public participation process is expected to begin in December 2020 when the proposed rules are published in the Oklahoma Register. The proposed rules will be presented at a public hearing of the Oklahoma Water Resources Board in January 2021. At the public hearing, stakeholders have the opportunity to give verbal comments directly to the Board Members. The OWRB typically takes formal action on proposed rules at the next monthly board meeting, February 2021. The table below provides general timeline of key water quality standards rulemaking actions.

2020-2021 Water Quality Standards Rulemaking Key Dates*
Proposed rules published in OK Register December 2020
Public Hearing (Opportunity for Public Comment) January 7, 2021 at 2:00 p.m.
End of Public Comment Period February 15, 2021 at 5:00 p.m.
Staff Presentation to the Board (No Public Comment) February 16, 2021 at 9:30 a.m.
Board action on proposed rule March 16, 2021
Legislative & Gubernatorial Review Spring 2021
Rules become state law September 2021
Submit to EPA for review & approval Fall 2021
*Timeline subject to revision as necessary

Submittal of Written Public Comments

During the 45-day public comment period, written comments should be submitted electronically to IRTPcriteria@owrb.ok.gov. Where electronic comment submittal is not feasible, written comments should be submitted by mail to the following address:

Oklahoma Water Resources Board
3800 North Classen Blvd.
Oklahoma City, OK 73118
ATTN: Rebecca Veiga Nascimento

Stay Informed

The best way to stay informed on water quality standards actions in the Illinois River Watershed, as well as any other water quality standards actions, is to sign up to receive updates from OWRB staff through the gov delivery system.

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