Hydrologic modeling Of New England river basins using radar rainfall data

Abstract

Quantitative weather radar measurements of rainfall provide the input to a hydrologic forecast model designed to use the full spatial resolution of the radar data. The gridded model, which incorporates a detailed map of the stream network, is based on a simple kinematic representation of the river basin response. Only two parameters control the shape of the hydrograph: the velocity characteristic of subsurface flow to the nearest stream, and the streamflow velocity itself. Comparisons are made between model hydrograph forecasts and observed streamflow records for the Souhegan (440 km2), and the Squannacook (160 km2) river basins. A single Z‐R relation was used for all storms (Z = 230R1.4), except for one case with strong convection (Z = 400R1.3). A linear scaling of the volume of the radar‐derived storm rainfall produces reasonable agreement between the predicted and observed hydrographs. The volume scale factor, which varies from 20% or less in the summer to 100% in the spring, is consistent with the climatological mean monthly rainfall‐runoff ratio. In the two basins studied, for hydrograph peaks of moderate amplitude, overland flow and other quickflow components of the hydrograph are not generally observed. The hillslope response is modeled by a single characteristic subsurface flow velocity (2 × 10−3 m s−1), with a streamflow velocity of 0.6 m s−1 in the Souhegan, (0.3 m s−1 in the Squannacook). The results suggest that models which utilize the basin geometry and rainfall data to a maximum, but which otherwise contain few parameters, can be very successful.