Marketing Western water: Can a process based geographic information systemimprove reallocation decisions?

Reallocating water is a politically sensitive issue in the western United S tates. Changes from agricultural uses to urban or environmental uses are oc curring, but the process tends to polarize competing water users, thus crea ting barriers to reallocation. Other barriers are inherent in the appropria tion doctrine, and some barriers exist because of poor data or inadequate s cience. These barriers could be more easily overcome and the process made l ess political if the impacts of change were better known. Water users frequ ently resist change because of the uncertainty change brings. The biophysic al and behavioral models currently used to predict the impacts of change do not account for spatial complexity or information uncertainty in ways that overcome legal and other barriers to reallocation. An integrated approach that couples a spatial and temporal framework to biophysical, institutional , and behavioral science can reduce uncertainty. Process based geographic i nformation systems can fill that role by allowing impacts to be assessed mo re accurately. A better understanding of impacts will potentially facilitat e reallocation decisions in a water market setting.