Spatial and temporal patterns of soil water are major determinants of net primary production and plant functional composition in arid and semiarid ecosystems which cover approximately 30% of global land area. The ‘ecohydrological niche’ defines the components of species' niche that are described by the relationship between ecohydrological conditions and species occurrence. We modelled the ecohydrological niche of different sagebrush ecosystems types, which are widespread in the semiarid western United States, and identified characteristics, which, if altered, will potentially lead to changes in their geographic distribution. We ran a daily soil water simulation model, SOILWAT, to simulate the water balance in space and time for sites from across the geographic range of sagebrush ecosystems. Additionally, to evaluate the relative importance of weather type, soil texture, soil depth, vegetation biomass, and phenology, we performed a sensitivity analysis using output from SOILWAT. Our results demonstrated that soil water dynamics in sagebrush ecosystems are characterized by spring recharge followed by a dry period (timing dependent on ecosystem type), where top soil layers dry earlier and more completely than the bottom layers. Most response variables were strongly influenced by weather type, followed by phenology of biomass, and soil depth. Reducing the availability of deep soil water during summer dry periods by increasing evaporative demand or reducing spring recharge will potentially lead to shifts in the range of sagebrush ecosystems. Characterizing the ecohydrological niche will be essential for improving our understanding of how semiarid ecosystems will be affected by future climate and biological invasions. Published in 2011. This article is a US Government work and is in the publish domain in the USA.