A multi-institutional effort is proposed to obtain space-time series of regional hydrological quantities reflecting climatic change scenarios. The geographical areas to be investigated cover central Arizona and the lower Platte river basin of Nebraska. The approach is based on an analysis of the occurrence, persistence and transition probabilities of atmospheric circulation patterns. These patterns are defined daily as pressure surfaces using available and reliable data. The proposed research consists of three phases. In the first phase, a classification of circulation patterns will be sought; each type of pattern is then related in a conditional framework to local space-time precipitation, runoff, temperature, and wind. Temperature and wind are used to define regional drought indices. Precipitation will be transformed into runoff using relatively simple watershed models. In the second phase of the research, available GCM outputs are used to define scenarios of possible daily time series of circulation precipitation, runoff, temperature, and regional droughts. Finally, the historical series of regional hydrologic events can be compared to the various scenario predictions. In the third phase of the research, the consequence of climatic change will be analyzed by taking the example of the Great Salt Lake in Utah.
