Simplified agricultural water use accounting in the Colorado River Basin using OpenET

Abstract Colorado River agricultural producers are facing the prospect of substantial water use reductions over the coming years in the face of overuse, drought, and the impacts of climate change. To inform management decisions and to ensure that water can be allocated efficiently and equitably, decisionmakers and stakeholders will require new methods of agricultural water use accounting (WUA) that are consistent, transparent, and fast. Here we provide estimates of agricultural water use across the entire Colorado River Basin using publicly available data from OpenET, and we demonstrate strong agreement with available WUA from the US Bureau of Reclamation. Crucially, the methods employed here allow basin-wide agricultural water accounting to be completed in a matter of hours—a process that currently takes months or even years. We demonstrate how these same data can also be used to inform water conservation strategies at the field scale, thereby synchronizing basin-scale water accounting with project-scale conservation planning. We discuss key sources of uncertainty inherent in the methodology, along with strategies for managing those uncertainties to improve agricultural water conservation planning.