How does the USGS collect streamflow data?
USGS has used consistent procedures for over 100 years to collect streamflow data, and currently operates over 7000 stream-gaging stations across the United States. All regular stream-gaging stations record stage, or water depth, at a fixed time interval, usually every 15, 30, or 60 minutes. Most stations in Maryland, Delaware, and the District of Columbia record at a 15-minute interval. Stage is most often measured using either a float and pulley device or a pressure transducer. A relationship is developed by USGS hydrographers between stage (usually expressed as feet) and discharge (usually expressed as cubic feet per second). This relationship is developed by making frequent direct discharge measurements at stream-gaging stations. Discharge is the primary streamflow data product of USGS, and operations have been specifically designed to provide accurate determinations of average daily streamflow, flood peaks, minimum flows, and flows associated with water-quality samples. In most ca
