Although water covers most of Earth, less than 3 percent is freshwater. Changes are occurring that strain the supply and demand structure of this vital resource. Warming temperatures are altering the hydrologic cycle and impacting the quality of freshwater resources. Observing and understanding the processes affecting both surface and groundwater systems; identifying and projecting future stressors; and evaluating the capacity of human and ecological systems to adapt, are all necessary to meet the challenge of sustaining freshwater resources. From understanding the physical processes affecting changes in surface water hydrology, to identifying the connections between sea level rise and coastal resilience, to assessing the role of water policy in resilience, CIRES is a world leader in water resources science.