Attribute Strength for the Site Selection of Satellite-Based Stream Gaging in the Continental United States

Abstract:

Satellite-based stream gaging has emerged as a potential solution to close gaps at ungagged locations in the US national stream monitoring record caused by logistical inaccessibility or resource constraints that limit continuous study and discrete field visits. In the ongoing effort to reduce error and uncertainty in satellite-based discharge (flow) estimates, ground-truth data archived by the United States Geological Survey provide opportunities to assess and improve the accuracy of remotely sensed flow algorithms. This presentation will describe how a nationwide analysis of geomorphic, topographic and hydraulic effects on flow can be used to inform where satellite-based flow estimation measurements can be readily employed. We utilized a database of multiple attributes collected at 958 stream monitoring sites within 46 states between 2007 and 2014. Width, depth, and velocity collected at each site were compared against no less than 10 flow measurements to determine their relation to discharge. A separate database consisting of slope-discharge relationships was developed for pairs of continuous stream gages separated by no more than 15 kilometers (km). The differences in a pair’s stage values were used in conjunction with their 15-minute counterpart instantaneous flow measurements to examine relations between hydraulic slope and discharge to compare the strength of a dynamic Manning’s coefficient against that of a traditional stage-discharge model. Our results confirm similar discharge observations that velocity and depth*width are strong explanatory factors for flow, however slope’s (the continuous difference between paired sites’ stage values over their reach distance) usability is diminished when flow approaches peak events. Our findings suggest that slope is a less reliable explanatory variable for flow, although there are few river reaches available for testing slope-discharge relations containing the necessary parameters required for such a robust exploration (no dam/tidal influence, paired sites of 15 km or less thalweg length, and available continuous stage and discharge data for each pair site). These results provide new insights into conditional attributes that may affect the accuracy of satellite-based streamflow estimations at ungagged single and paired site locations.