Water resources implications of global warming: a U.S. regional perspective

摘要

The implications of global warming for the performance of six water resource systems in the USA were evaluated. The six case study sites represent a range of geographic and hydrologic, as well as institutional and social settings. Large, multi-reservoir systems (Columbia River, Missouri River, Apalachicola-Chatahoochee-Flint (ACF) Rivers), small, one or two reservoir systems (Tacoma and Boston) and medium size systems (Savannah River) are represented. The river basins ranged from mountainous to lowrelief and semi-humid to semi-arid, and the system operational purposes ranged from predominantly municipal to broadly multi-purpose. The studies inferred, using a chain of climate downscaling, hydrologic and water resources systems models, the sensitivity of six water resources systems to changes in precipitation, temperature and solar radiation. The climate change scenarios used were based on results from transient climate change experiments performed with coupled ocean-atmosphere General CirculationModels (GCMs) for the 1995 Intergovernmental Panel on Climate Change (IPCC) assessment. For the river basins where snow was important important in the current climate hydrology (Tacoma, Columbia, Missouri and, to a lesser extent, Boston) changes in temperature, important changes in seasonal streamflow hydrographs were shown. In these systems, spring snowmelt peaks were reduced and winter flows increased. Changes in precipitation were reflected in the annual total runoff volumes more than in the seasonal shape of the hydrographs. In the Savannah and ACF systems changes in hydrological response were linked directly to temperature and precipitation changes. Effects on system performance varied from system to system, from GCM to GCM, and for each system operating objective (such as hydropower production, municipal and industrial supply, flood control, recreation, navigation and instream flow protection). Effects were smaller for the transient scenarios than for the doubled CO2 scenario. The water resource system performance effects were determined by the hydrologic changes and the amount of buffering provided by the system's storage capacity. The effects of demand growth and other plausible future operational considerations were evaluated. For most sites, the effects of these non-climatic effects on future system performance would equal or exceed the effects of climate change over system planning horizons.