The Future of Municipal Water Resources in the Williamette River Basin: A Basin-Level Analysis

Under current trends, municipal demand for water in Oregon's Willamette River Basin will double by 2050. Municipalities will have to develop new sources of water, in competition with agricultural and other established uses, as well as increased demand for water to support ecological values. Municipalities can, to a limited extent, turn to their currently dormant water rights, but executing these rights will displace other currently established uses of water or diminish flows for fish and wildlife. Recent listings of salmon and other fish under the Endangered Species Act greatly diminish the acceptability of making water-use decisions without accounting for their potential impacts on water quantity and quality throughout the basin. This paper adopts a basin-wide perspective to analyze the need for new development of new sources of municipal water in the basin, and the impact of increased municipal water demand on water resource management in the basin as a whole. The analysis employs a computer model that simulates the regulation of water rights across the basin. We develop scenarios for future demand and supply of water, and use the computer model to determine the resulting allocation of water across water rights in the basin. Results indicate that the state's three largest urban areas have adequate water resources, but many smaller municipalities will have to develop new sources. The analysis here indicates that eliminating summer releases from storage in the basin's federal reservoirs would not affect water availability at current municipal points of diversion.