Systems analysis and hydrologic modeling can be expected to play an even greater role in the future in providing a quantitative basis for reservoir operation decisions. In addition to examining reservoir operation in Texas in general and capabilities for analyzing reservoir operations in general, the present investigation focused on the particular management strategy of reallocating storage capacity between flood control and conservation purposes in response to changing conditions. Converting a portion of the storage capacity of a reservoir from one purpose to another is concluded to be a viable management strategy for optimizing the beneficial use of existing reservoirs under changing conditions. Although given relatively little consideration in the past, storage reallocations will likely be proposed more and more frequently in the future as demands on limited resources increase. Seasonal rule curve operation may be a viable alternative to a permanent storage reallocation under certain circumstances.
Many factors affecting reservoir operation are seasonal in nature.
In the case study, firm yield was found to be significantly increased, relative to a permanent reallocation, by raising the top of conservation pool for only a portion of the year. However, the seasonal nature of flood threat and damage susceptibility results in a significant overlap between the time periods when flood control and water supply capacity are most needed. Consequently, seasonal rule curve operation still requires tradeoffs between water supply and flood control benefits. A hydrologic and economic evaluation procedure was developed for analyzing proposed reallocations of storage capacity between flood control and municipal and industrial water supply. The generalized procedure consists of evaluating the risks and consequences of failing to prevent flooding and failing to meet water demands, associated with alternative allocations of storage capacity between flood control and water supply.