Simulation of streamflow of Rock River at Lake Koshkonong, Wisconsin, to determine effects of withdrawal of powerplant-cooling water

A flow-routing model was used to simulate 44 years of stage data from Lake Koshkonong, Wis., and streamflow data from the Rock River downstream from the lake. The simulation was repeated for five possible degrees of consumptive use, ranging from zero to an annual average of 40 cubic feet per second. A minimum release rule was applied to the simulated operation of the dam at Indianford to guarantee at least the 7-day, 10-year low-flow discharge in the Rock River downstream from Lake Koshkonong.

The simulated stage of Lake Koshkonong with consumptive use at 40 cubic feet per second was as much as 0.42 feet lower than the simulated stage with zero consumptive use for the same period. Duration of drawdown below the regulatory minimum stage of 11.8 feet, occurring once in 10 years, increased from 83 to 132 days as consumptive use increased from 0 to 40 cubic feet per second.