Article and photo by Dan Morrissey
Warner River flow is measured at a gaging station near the Route 127 bridge in Davisville, New Hampshire. The station has been operated continuously from 1939 to the present by the local office of the U.S. Geological Survey. This gage, and many others in New Hampshire, were installed after major floods in 1927, 1936 and 1938 highlighted the need for information on river flows. The Warner River gage has been designated as a Federal Priority Stream gage because it meets strategic, long-term Federal information needs.
At present the Warner River gage is funded cooperatively by the U.S. Geological Survey and the U.S. Army Corps of Engineers. The local office of the Geological Survey in Pembroke, NH operates and maintains the Warner gage and a network of 46 continuous gaging stations across New Hampshire. In 2022, the annual operating cost of a full-time, continuously recording stream-gaging station with satellite telemetry is approximately $15,500. Data from the Warner River station is sent by satellite to U.S. Geological Survey computers once every 4 hours, and more frequently at times of flooding.
Streamflow data from the Warner gage are used by the National Weather Service Northeast River Forecast Center (NERFC) for issuing river forecasts and warnings in New Hampshire. The U.S. Army Corps of Engineers Reservoir Regulation Team uses data from the Warner River gage for managing their flood control reservoirs in the Merrimack, and Contoocook River Basins. Flow data can also be used for water allocation, monitoring of streamflow withdrawals, and water-quality management, including the maintenance of instream flows. Recreational users of flow data from the Warner gage include kayakers and anglers.
Because of the long record of flow on the Warner River, and the fact that flow is unregulated by dams or reservoirs, data from the gage are particularly useful to scientists for detailed assessment of water resources, evaluation of flow-frequency characteristics, trends in basin yield and for predicting flows at ungaged sites.
The Warner River gaging station measures the stage or water-surface elevation of the river. Equipment at the stream-gaging station automatically measures and records the stage every 15 minutes. The stage then is converted to streamflow (defined here as the volume of the water in cubic feet passing the site every second) based on the relation between stage and streamflow. This relation is developed and maintained for accuracy by measuring the flow of a river directly at each station with a flow meter at various stages throughout the year. Because of ice cover and changes in riverbed form, roughness, and vegetation, the relation between stage and streamflow is changing continually and direct measurements are made frequently.