Tuesday, 11 February 2003
Use of small basin networks for monitoring continental scale changes in the water cycle
Detection of continental scale changes in the water cycle involves monitoring a range of variables over large space and time scales. Because monitoring water cycle variables for entire continents is not feasible at this time, the use of large-scale basins, such as those under the GEWEX umbrella, for detection of change is attractive because they cover a significant part of their respective continents. To do so, however, we must assume that changes occurring in the GEWEX basin are representative of those occurring on the continent as a whole. Numerous GCM studies of global warming suggest, however, that the ensuing hydrological cycle changes will vary from region to region, with some areas showing various degrees of increases and decreases. Thus, the changes occurring in any one region (up to some threshold spatial scale) could differ substantially from that occurring for the continent as a whole. We investigate the use of existing small scale, but long-term, monitoring basins within the USA as indicators of change in the continental hydrologic cycle. Using a genetic algorithm we select a small number of "indicator basins" that are statistically representative of the USA as a whole using precipitation and streamflow records from the 1947-1987 U.S. Hydrology and Climatology dataset of Wallis, Lettenmaier, and Wood. Results indicate that a small number of representative basins scattered over a range a climate zones can be used to collectively mimic the behaviour of the USA as a whole and could provide a network of existing monitoring stations for rapid detection of future changes in the continental water cycle.