It has become apparent that the effects of climate change will be especially important for Southwestern US water users. The NSF-funded EPSCoR project “Climate Change Impacts on New Mexico’s Mountain Sources of Water” focuses on improving hydrometeorological measurements, developing basin-wide and sub-basin snow cover mapping methods, generating snowmelt runoff simulations and long-term climate change assessments, and informing the public of the results through outreach and educational activities. Five new and 12 upgraded SNOTEL sites, four SCAN stations and about 30 new automated weather stations are being added to New Mexico measurement networks. 25 sub-basins of the Rio Grande have been identified as important snowmelt basins where development and testing of snow cover mapping methods will be conducted. High spatial resolution Landsat TM data (30 m) are being used to evaluate estimates of snow cover from Terra MODIS moderate spatial resolution data (250m and 500 m). We aim to identify the best snow-mapping algorithm for the Rio Grande basin using Snowmelt Runoff Model (SRM) simulations. For the snowmelt modeling, we are using an updated revision of SRM which can automatically assess the climate change effects on water supplies of future climate scenarios.