In a continuing effort to share research, case studies and water management techniques that impact our watershed,  this edition of Water Proof will provide an overview of a major water quality study currently being done within the Illinois River Watershed in Northwest Arkansas and Northeast Oklahoma —  “The Stressor Response Study for the Second Statement of Joint Principals and Actions between Arkansas and Oklahoma”.

Illinois River


The Stressor Response Study for the Second Statement of Joint Principals and Actions between Arkansas and Oklahoma: 

If you live in the Illinois River Watershed, having information that is current and based on sound science is important to you in understanding the condition of the Watershed and how our actions can improve or hurt our land and water resources.  The 2013 Second Statement of Joint Principals and Actions between Arkansas and Oklahoma calls for the joint study to assess how the water quality of our streams and all that lives in our streams respond to particular “stressors”.   This study, following EPA’s “Using Stressor-response Relationships to Derive Numeric Nutrient Criteria” (EPA 820-S-10-001, November 2010) is one of three methods approved by EPA to determine water quality standards.

Clear Rive

Illinois River between Fisher Ford Bridge and Hwy 59

What this new study will seek to determine that previous studies have not definitively answered is the frequency and duration component of the numeric water quality criterion, which has always been a source of disagreement between the States. Also unique to this study, reference streams or sites included in the study should be limited to streams and rivers that are comparable to the streams in the Illinois River watershed.


Illinois River Headwaters

Headwaters of the Illinois River near Hogeye, Arkansas 

The final report to be completed in 2016 by newly selected researchers from Baylor University led by Ryan S. King, will analyze water quality data and identify relationships and response levels that produce undesirable aesthetic water quality conditions. The study will recommend phosphorus thresholds and identify the frequency and duration components of water quality measures, which can suggest an “undesirable shift in algal species composition and or biomass”.   The phosphorus thresholds identified will be based on sound science for water quality in the Illinois River Watershed.

Caddis flies equal excellent water quality

Caddis flies visible at the headwaters of the Illinois River,

an indication of excellent water quality



  • Arkansas agreed in 2003 to one of the most strict standards in Region 6 reducing WWTP phosphorous to 1 mg/L or less. NWA spent close to $300 million with 5 cities achieving new strict standard.
  • Arkansas passed laws in 2007 related to farming, creating a Phosphorous Index and requiring Nutrient Management Plans use AR  P-Index, one of most strict in EPA Region 6.  Over 75% of poultry litter is trucked out of the watershed.
  • 2013 Second Statement of Joint Principles signed by Arkansas and Oklahoma.
  • A six-person team with 3 persons appointed by respective Governors from each state have selected Ryan King, Center for Reservoir and Aquatic Systems Research at Baylor University to conduct Stressor Response Study.  
  • Stressor response study will be completed by February 2016.
  • Water quality standard to be revised unless the findings are between 0.027 and 0.047, in which case the standard would remain at 0.037.
  • January – June 2013 0.045 mg/L was the average total phosphorus during base flow (January to June)


We know from 2013 water quality monitoring that the water quality of streams in this watershed is improving, and that is tied to wastewater treatment plant upgrades, stream bank restorations, urban storm water treatment, farmers’ adherence to nutrient management plans and regional watershed protection efforts such as those by the IRWP and others.


How can you learn more?

Click here to find out more about this bi-state study on the Illinois River Watershed.  The next public meeting on this study will be held March 6 from 10:00 am to 3:00 pm in Tulsa, OK, location TBD by Oklahoma Conservation Commission.   We encourage you to attend to hear the diverse perspectives on this very important issue within our watershed.


Additional Resources:

Oklahoma State University Poultry Waste Management Publications

Phosphorus Concentrations Have Been Declining In The Illinois River: Was It Point Sources, Farm-Level Nutrient Management, Or What?


Related Posts:

What’s in a Name?  Watershed Learning Center

Water Proof:  Watershed Management for the Future

Water Proof:  Tackling Wicked Problems