Thesis (M.S., Environmental Science)--University of Idaho, June 2014 | The Yellowstone River and its tributaries are an important case study for water struggles in the highly arid western landscape. In the following chapters I: 1) evaluated seven variables used to characterize the volume and timing of discharge in the Yellowstone River and tributaries for long term (1898-2007) and more recent trends (1970-2007) using 18 USGS Stream gauge stations, 2) quantified all current (2008) water rights in the greater Yellowstone River Basin, evaluated trends in water use, and conducted a physical inventory of all surface water withdrawals from the Yellowstone River and tributaries, 3) I assess, in a general way, water management needs in the Yellowstone River Basin as discerned from the results in the previous chapters and in relation to the needs of native fishes and other biota in the river and provide recommendations for improved Montana water management to benefit water users and native fish species. Declines in volume and magnitude of annual and seasonal discharges are present in the basin, more so in areas where there are no water storage facilities. Timing of flows are occurring earlier in the year throughout the basin, leaving less water in the later summer and fall when water demands are the greatest. Rights to water greatly over allocate the water resources in the basin, though some rights can be considered duplicate and non-consumptive. The estimate of water use and the physical inventory reveal issues of potential resource misuse. There are numerous changes in water policy Montana water managers should consider if water is to remain available in the Yellowstone River Basin.