It is the mission of the U.S. Geological Survey to monitor water resources across the country. We talk with Chris Wilkowske, a hydrologist with the USGS at the Utah Water Science Center, about the science and methodology of measuring stream flow. We talk about how stream gauges operate and the process of validating and adjusting data, particularly after events like floods. Local examples from the Moab area and the Colorado River highlight the dual purposes of stream gauges for flood monitoring and groundwater assessments.