TEMPERATURE IMPROVEMENT IN THE LMFR TROUT FISHERY
The lower Mountain Fork River (LMFR) is home to the most successful trout fishery in Oklahoma. Even so, this fishery is limited from reaching its full potential by seasonally high water temperatures.
This is due, in part, to warm water being released during summer hydropower generation at Broken Bow Reservoir (BBR). ODWC seeks to improve thermal characteristics in the LMFR and subsequently enhance trout fishing opportunities in this scenic stream for Oklahoma anglers.
A model designed to determine potential temperature improvement options in the LMFR was recently completed. Results from the model indicated that improved access to and subsequent release of cold water in the Broken Bow Reservoir (BBR) is the most tractable solution for enhancing stream temperature. Studies show that a considerable volume of cold water exists below the intake structures at BBR. The problem is that this cold water, which is the lifeblood of the LMFR trout fishery, is inaccessible during turbine or sluice operation in the present state of these intake structures.
Selective withdrawal techniques can be used to gain access to cooler water in reservoirs with cold water access problems. Solutions being considered to achieve releases of cooler water in the BBR include:
- Flexible curtains in the forebay to force withdrawal of deeper water by the turbines;
- Deploying air diffusers in the forebay to entrain and bring cold water up to the intake levels and;
- Attaching extensions to intake structures that penetrate the cold water layer.
Before these solutions can be implemented, a detailed evaluation of the water quality issues in BBR is required. A reservoir water quality model is the most dependable and defensible method of accomplishing these endeavors.
A preemptive reservoir water quality model of the BBR is ongoing. The study includes evaluation of seasonal and long-term effects of the selective withdrawal on temperature and water quality in the reservoir and the tailwater. For example, dissolved oxygen (DO) levels are currently quite good at lower elevations in the Broken Bow Reservoir. However, deep warming due to cold water withdrawal ma impact DO at these depths. Laminar hypolimnetic movement may also pull undesirable constituents from the upper reaches of Broken Bow Reservoir downstream towards the dam. The ability of the reservoir to sustain a cold water supply throughout each year’s access period will also be assessed. If the reservoir and tailwater impacts are acceptable and the options appear to have potential, a subsequent engineering feasibility evaluation of options for providing cold-water access will follow. The feasibility evaluation is necessary to determine engineering of and operation and maintenance protocols necessary to facilitate the most tractable solution identified during reservoir modeling. Finally, an implementation phase will complete the project and benchmark the final step in water temperature improvement and that is paramount to enhanced fishing opportunities.
Cold Water Project (UPDATE)
The ODWC is preparing to do $10,000 of further computer modeling of the bubble diffusers. They will be using data from last year and extrapolating it out to check the feasibility of further testing this summer. The funds for this were not from the LMFRF. The ODWC worked on a warm water stream restoration project in NE Oklahoma which actually made money. Some of this excess money went to fund this new modeling. LMFRF funds were earmarked for the Cold Water Project several years ago and last year we funded the initial phase involving the bubble diffusers. Once we get conclusive reports from the ODWC that the diffusers have worked, then we will be vote to approve the next step
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