Improving Hydrologic Observing Capabilities with Stream Radars

Conventional stream gauges often measure stage with instruments that are in contact with the stream or river. These instruments can be damaged or even lost during extreme flooding conditions. The United States Geological Survey (USGS) operates and maintains over 7000 of these conventional gauges in the United States. The annual maintenance costs make gaging smaller basins uneconomical, while manual updating of stage-discharge rating curves is inefficient and can be hazardous to operators. This contribution presents results from the installation of a suite of new, non-contact stream sensors and an evaluation of their utility in providing measurements of stream height and velocity, ultimately enabling estimation of discharge without the need to update and maintain an empirical rating curve. Results from evaluating the observations obtained with the sensors illustrate the importance of measuring velocity to estimate stream discharge, which is not possible with conventional stream gauges that rely on water level alone. Likewise, the sensors have proved useful to some of the sites’ local stakeholders in providing them with early alerts of flash floods. More importantly, the evaluation demonstrates the complimentary value of the non-contact sensors to the existing USGS stream gauge network in supporting the operations of the National Water Model.