Ups and Downs in Negotiating Stream Flow Management at the Taum Sauk Pumped Storage Project

State agencies and Ameren Missouri collaborated over several years to negotiate a water management plan for the Taum Sauk Pumped Storage Project, a hydroelectric facility located in southeastern Missouri. Early in the negotiations, the parties agreed that outflow from the project’s lower reservoir on the East Fork Black River should closely approximate the timing, magnitude, and rate of change of inflow to the reservoir. That approach required accurate measurement of reservoir inflow and outflow. Initial efforts to measure inflow via changes in reservoir volume proved inaccurate due to reservoir elevation fluctuations caused by the daily generation-pump back cycle between the upper and lower reservoirs. Accurate outflow measurements were precluded by insufficient precision in the control of gates used to release water through the lower reservoir dam. The water management plan outlines how the project uses gaging stations on the East Fork Black River, in concert with a watershed area adjustment factor and reservoir volume estimates, to approximate inflow and adjust outflow accordingly every 15 minutes. Frequent meetings and collaborative postures between the parties were essential in developing needed understanding of the structural and operational constraints of the project and gaging stations, and establishing the plan’s operational guidelines and evaluation criteria.