Tenkiller Ferry Lake WQ Study (OK/IL, USA)


Oklahoma Department of Environmental Quality


From 2004 – To 2005

The final report was submitted to USEPA to support TMDL development.


  • TMDL Water Quality Assessment
  • Watershed Modeling
  • Hydrodynamic Modeling
  • Water Quality Modeling
  • Waste Load Allocation

Key Staff

Paul Craig, P.E.

President and Senior Consultant



Senior consultants at DSI, LLC. have a legacy of bringing water quality expertise to hydrodynamic modeling. The Oklahoma Department of Environmental Quality ben- efited from our personnel’s contribution to a TMDL which was created through a linked watershed, hydrodynamic and water quality model for Tenkiller Ferry Lake. As part of the Illinois Basin, Tenkiller Ferry Lake is located in the Illinois River wa-tershed, which straddles the Oklahoma-Arkansas boundary and covers 1 million acres. Elevated nutrients made Tenkiller Ferry Lake a high-priority target for TMDL on Oklahoma’s 1998 303(d) list; our team members continued to collaborate on this project even after its completion in 2005.

Project Goal

The first modeling efforts of Tenkiller Ferry Lake were conducted by Tetra Tech in 1999 and had the goal of reassessing the prior water quality model, recalibration, and provide recommendations for enhancement. Additionally, a water quality model for runoff from the upstream watershed also needed to be developed and linked to the lake model to create an integrated modeling system

The lake model simulates 1, 2 & 3D hydrodynamics with densities dependent on variable temperatures and salinities. For this application, our leaders used the in- ternal water quality capabilities of EFDC to recalibrate the model. The water quality boundary conditions were determined from the HSPF model that was developed and calibrated for the current (i.e. historic) land use conditions, as well as provided to- tal nitrogen, total phosphorus and BOD (taken as 5day) concentrations. The EFDC model required these totals to be split into the various labile, refractory, particulate and dissolved components. A simple constant fractionation approach was used based on some site-specific data and literature by our current leaders to offer a cohesive response.


The HSPF model generated four separate boundary conditions, one for the Illinois River, the Baron Fork River, the Caney Fork and the “ungaged” area. Flow weighted average concentrations for the totals and BOD were generated for the combined Illinois and Baron Fork rivers. The EFDC model was calibrated to the water quality data of 1992 and 1993. Deeper regions of the lake that were experiencing thermal stratification had significant DO depletion in the hypolimnion and the model gen- erally reproduced the general seasonal and event driven trends. The trends in the model results track well with the data at the end of the 2 year simulation, without significant divergence. Tenkiller Ferry Lake was shown to be significantly impacted by mass transfer processes, both at the surface and the lake bottom, the interaction of nutrients and oxygen between the overlying water and the sediment surface was a critical element of the modeling effort.

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