| Abstract: | Subsequent to the selection of design capacity and the construction of a storage reservoir, water demands, valley land-use, and economic constraints may change and the reallocation of storage space in an existing reservoir may become desirable. The benefits of reallocating space to flood mitigation are the equivalent annual flood damages averted, while the costs arise from water shortages which would not have occurred if space had not been reallocated. These benefits and costs can be quantified for a particular region and the optimal airspace provision calculated. In a case study area, reallocation of part of the storage volume was justified, while excessive reallocation would result in significant net costs to the region. The optimum airspace allocation was not sensitive to the value assigned to water. The procedure used here could be applied to other river valleys, where the solution would be dependent on the intensity of land-use, as it influences both potential flood damages and the costs of water shortages. |
