Hydrology and Water Resources: Current Research
Development of Optimized Flood Control Rule Curves for the Columbia River Basin in Response to Climate Change and Interannual Climate Variability
- Alan Hamlet, UW Climate Impacts Group
- Se-Yeun Lee, UW Dept of Civil and Environmental Engineering
Flood control operations, which are an important element of many multi-objective water resources systems, must ultimately create a balance between flood risk and other system objectives such as water supply or hydropower production. Water resources operating policies that attempt to preserve this balance are usually predicated on assumptions of stationary climate conditions derived from historic streamflow records. Recent climate research has demonstrated, however, that regional climate varies on interannual and decadal time scales, and that systematic changes in temperature are occurring in response to global warming and other factors. These short- to long-term non-stationary elements of the climate system should be investigated to determine if it is possible to improve dam operations for flood control by explicitly incorporating information about climate variability (e.g. at interannual time scales) or by including the effects of systematic warming as a means to climate change adaptation.
The fundamental design aspects of many of the flood control operating rules in the Western US date to the time of dam construction, and are based on climate conditions that were probably systematically colder than current conditions. Although flood control evacuation schedules at specific reservoirs in the system have been changed on several occasions, none of these changes has been related to changes in climate or flow regime.
In the case of simple, single-reservoir systems, adjustments in flood rule curves could probably be made by hand calculations in a straight-forward manner using conditional or climate change streamflow scenarios and conventional analytical approaches. In complex flood control systems that use multiple reservoirs to meet both local and system wide flood targets (e.g. the Columbia River basin), this adjustment process presents a much more challenging systems engineering problem. Changes in snowpack and streamflow timing, for example, will not be equally distributed throughout the basin, and adjustments in flood evacuation and refill schedules at different dams will not be uniform. Furthermore all of the project-specific adjustments, when combined, must result in effective flood control at a number of local and system wide checkpoints. Therefore, there is a need to develop an objective and well-defined procedure to maintain or improve the current level of system performance in response to climate change scenarios and/or to investigate the possibility of enhancing system operations by incorporating climate as an operational variable at seasonal to interannual time scales.
This research project explores the use of an optimization-simulation approach as an objective and well-defined procedure to improve system operations in response to the effects of global warming (Lee et al. 2008a) and by creating dynamic flood rule curves conditioned by seasonal to interannual climate forecasts (Lee et al. 2008b) at monthly time scales. As a test case, Columbia River Basin is used.
University of Washington Dept. of Civil and Environmental Engineering, U.S. Army Corps of Engineers, Seattle District, Portland District, and Sacramento District, U.S. Bureau of Reclamation, Boise Regional Office
For publications on climate impacts on PNW water resources, please see CIG Publications.
Lee, S.Y., A.F. Hamlet, C.J. Fitzgerald, S.J. Burges, and D.P. Lettenmaier. 2009. Optimized flood control in the Columbia River Basin for a global warming scenario. ASCE Journal of Water Resources Planning and Management 135(6): 440-450, doi:10.1061/(ASCE)0733-9496(2009)135:6(440).