Water is a limiting resource in most of the western US.  Understanding the volume of water that enters ecosystems, patterns, processes, volumes and timing of water use by plants, and creating water budgets is critical to land and water managers.  We have worked to understand water use patterns of phreatophytes (plants that can use ground water) in the San Luis Valley of southern Colorado, and currently are working with the City of Aurora to understand water application and water use processes as driven by turf grass and trees.