Services Rendered:

TMDL Water Quality Assessment

Watershed Modeling (HSPF)

Hydrodynamic Modeling (EFDC)

Water Quality Modeling (EFDC)

Waste Load Allocation


Oklahoma Department of Environmental Quality
Water Quality Division


Mr. Bob Bednar
(405) 702-8197

Dates of Performance:


Status of Project:


DSI developed a linked watershed, hydrodynamic and water quality model of a portion of the Illinois Basin as part of development of a TMDL for Tenkiller Ferry Lake, OK. Tenkiller Ferry Lake is located in the Illinois River watershed, which straddles the Oklahoma-Arkansas boundary and covers 1,053,032 acres. Tenkiller Ferry Lake is identified on Oklahoma’s 1998 303(d) list as impaired because of elevated nutrients, and it is a high-priority target for TMDL development. The HSPF watershed model was used to simulate watershed runoff and point and nonpoint source loads from the watershed. The HSPF model was recalibrated to a 20 year simulation period. The HSPF provided flow, Total Phosphorus, Total Nitrogen and BOD loads. These HSPF results were then linked to the Environmental Fluid Dynamics Code (EFDC) 3-dimensional water quality model flow boundaries. A two year simulation period was used for calibration of the EFDC water quality model (HEM3D). The calibrated model was then used to conduct load reduction scenarios as part of the TMDL process.