Multi-objective Optimization of Reservoir Systems Using HEC-ResPRM

Abstract

HEC-PRM (“Prescriptive Reservoir Model”) is a generalized computer program that performs deterministic network-flow optimization of reservoir system operations. PRM “prescribes” optimal values of flow and storage over time that minimize penalty functions at selected locations in the water resource network. Penalty functions associate a penalty or reward (negative penalty) with levels of flow or storage. For environmental restoration, flow and storage levels that deviate widely from natural levels can be penalized, thus suggesting system operations closer to the natural regime. Optimization with a Network Flow with Gains algorithm enables relatively fast run times for large systems but restricts constraints to capacity limits and flow continuity at nodes. PRM has been applied to several large multi-reservoir systems such as the Columbia River System, the Missouri River System, the Mississippi Headwaters, and the state-wide water resource network of California. HEC-ResPRM is a new software environment for PRM designed to facilitate modeling for data-intensive single or multi-objective reservoir system operation studies. The environment is in large part shared with HEC-ResSim – a reservoir system simulation tool. The integration of PRM into the HEC-Res modeling platform was made to enable the joint development and use of simulation and optimization models. Central to the software’s graphical user interface is a network display of the water system underlain by an optional map or image of the area. Properties of system elements can be edited directly in the network display and time series of results plotted for any network element. The multi-objective nature of water resource problems is addressed by allowing any number of penalty functions (including those with differing units) to be added at any network location. A penalty weights editor facilitates development of trade-off curves between competing objectives by allowing the user to easily change the multiplier on an objective for all locations. Features of the software are demonstrated with an application to the Mississippi Headwaters Reservoir System.