Estimating Watershed-Scale Precipitation by Combining Gauge

4 Watershed modeling requires accurate estimates of precipitation, however in some cases 5 it is necessary to simulate streamflow in a watershed for which there is no precipitation gauge 6 records within close proximity to the watershed. For such cases, we propose an approach for 7 estimating watershed-scale precipitation by combining (or fusing) gauge-based precipitation 8 time series with radar-based precipitation time series in a way that seeks to match input 9 precipitation for the watershed model with observed streamflow at the watershed outlet. 10 We test the proposed data fusion approach through a case study where the Soil and Water 11 Assessment Tool (SWAT) model is used to simulate streamflow for a portion of the Eno 12 River Watershed located in Orange County, North Carolina. Results of this case study show 13 that the proposed approach improved model accuracy (E = 0.60; R = 0.74; PB = -10.2) 14 when compared to a model driven by gauge data only (E = 0.50; R = 0.54; PB = -25.5) 15 or radar data only (E = 0.33; R = 0.61; PB = -13.7). While this result is limited to a 16 single watershed case study, it suggests that the proposed approach could be a useful tool 17 for hydrologic engineers in need of retrospective precipitation estimates for watersheds that 18 suffer from inadequate gauge coverage. 19