Operation of water supply reservoirs for flood mitigation : hydrologic and institutional considerations

Abstract

Additional demands are being placed upon reservoirs to meet a variety of diverse needs. These demands require efficient management of the limited storage through reservoir operations. This efficiency is most critical with water supply reservoirs. Reservoirs operated strictly for conservation purposes typically provide only incidental flood control. As the construction age of water resources declines, innovative strategies to utilize the finite water supplies Must be developed. Significant numbers of reallocations in reservoir storage between flood control and water supply pools have occurred in the past. Historically, storage transfer has increased the conservation pool at the cost of flood control storage due to the greater direct economic benefits associated with municipal and industrial water supply. This transfer can only occur in multipurpose reservoirs; however, the majority of reservoirs contain no flood control storage. This characteristic is fostered by the high (and generally rising) cost of including the flood control purpose in the reservoir scope. This investigation presents findings specific to operating strategies of reservoirs lacking flood control storage. The non-structural strategies applied include seasonal and permanent reallocations of water supply storage for flood control purposes. Lake Limestone in Central Texas serves as the case study. The highly variable conditions of the watershed commonly exhibit both hydrologic extremes, floods and droughts. The agency responsible for this reservoir, the Brazos River Authority (BRA), is intensifying their efforts in the management of the water resources under their jurisdiction. This active role highlights the legal aspects involving water resources management; and, in particular, reservoir operations. Thus, the related matter of institutional liabilities of reservoir operations are discussed herein to give a comprehensive view of the affiliated concerns in the complex world of reservoir operations.