Methods for evaluating the regional hydrologic impacts of global climatic changes

Abstract

Concern over changes in global climate caused by rising atmospheric concentrations of carbon dioxide and other trace gases has increased in recent years as our understanding of atmospheric dynamics and global climate systems has improved. Yet despite a better understanding of climatic processes, many of the effects of human-induced climatic changes are still poorly understood. The most profound effect of such climatic changes may be major alterations in regional hydrologic cycles and changes in regional water availability. Unfortunately, these are among the least well-understood impacts. This paper reviews approaches for evaluating the regional hydrologic impacts of global climatic changes and presents a series of criteria for choosing among the different methods. One approach — the use of modified water-balance models — appears to offer significant advantages over other methods in accuracy, flexibility, and ease of use. Water-balance models are especially useful for identifying the regional hydrologic consequences of changes in temeprature, precipitation, and other climatic variables. The ability of water-balance models to incorporate month-to-month or seasonal variations in climate, snowfall and snowmelt algorithms, groundwater fluctuations, soil moisture characteristics, and natural climatic variability makes them especially attractive for water-resource studies of climatic changes. Furthermore, such methods can be combined with state-of-the-art information from general circulation models of the climate and with plausible hypothetical climate-change scenarios to generate information on the water-resource implications of future climatic changes.