Quantifying and Managing Water Withdrawals in the Yellowstone River Basin: Increasing the Scientific Rigor

Abstract

A scientifically-defensible system for accurate and precise quantification of existing water withdrawals and uses within the Yellowstone River Basin is necessary for effective water management. In conjunction with a data inventory of all known consumptive withdrawals from the Yellowstone River and its tributaries during the period 2006-2008, (municipal, industrial, irrigation agriculture and livestock sources), we conducted a physical inventory of surface withdrawals in 2006 to estimate the number of mainstem surface water users. Of the 687 identified water withdrawal sites, 113 were found to have screening devices present, 120 had no screens, and the screening status of 454 sites could not be determined. Ninety-two of the 687 water withdrawal sites identified during the physical inventory were not found to match with locations on the Department of Natural Resources and Conservation (DNRC) points of use or points of diversion. The lack of measured water withdrawals by most water users in the basin forces investigators to rely on indirect estimates of water use, which are inaccurate and propagate error through water use statistics. To improve the scientific credibility of data regarding the water withdrawals and improve conditions for native fish and other aquatic species, several suggestions are forwarded, including the need to screen all diversions, the need for an identification system to enable a withdrawal site to be specifically linked to a water right and the need for an accurate and precise system for measuring and reporting water withdrawals. Other identified needs are to complete the adjudication process in the state, to review the scientific evidence in support of the differential water use hierarchy in the Yellowstone River Basin, and to review terminology to eliminate, to the extent possible, ambiguous or imprecisely defined terms used in water usage. Short term benefits of applying more scientific rigor to the usage of water rights and the water management process will pay long-term dividends of more justifiable quantification of withdrawals, more reliable allocation of water, reduced litigation, and more effective conservation of native aquatic resources in the basin.