DEQ works with the United States Geological Survey (USGS) to collect hydrologic data in Virginia. Together the two agencies cooperatively provide a comprehensive picture of real-time and historical hydrologic conditions in the Commonwealth.  

DEQ’s Surface Water Investigations Program (SWI) is managed under the Office of Water Supply and is located in Charlottesville. Reliable hydrologic data including the quantity of surface water and elevation of ground is collected through a network of real-time satellite telemetry gage stations and is essential for the successful planning and management of the Commonwealth’s water resources. 

SWI field personnel monitor 79 surface water gages on an eight-week schedule, servicing the real-time satellite equipment and measuring streamflow (“discharge”) to ensure data accuracy. Stream depth, width, and velocity are measured in the channel to determine total discharge. From these measurements, a rating curve is developed by correlating discharge with water level in the stream (“gage/gauge height”). The gage height is recorded every 15 minutes by a data logger located in a permanent gage house, which is transmitted to the USGS database hourly via satellite. The data is then converted into computed discharge through established rating curves and published to the USGS website.