Continuous streamflow simulation with the HRCDHM distributed hydrologic model

The objective of the authors' work in the area of distributed modeling is to determine the manner with which rainfall input and model parameter uncertainty shapes the character of the flow simulation and prediction uncertainty of distributed hydrologic models. Toward this end and as a tool for the investigation, a distributed model, HRCDHM, has been formulated and tested as part of the NOAA Distributed Model Intercomparison Project (DMIP). This paper examines hourly flow simulations from HRCDHM applied with operational data obtained for the DMIP study watersheds. HRCDRM is a catchment-based, distributed input, distributed parameter hydrologic model. The hydrologic processes of infiltration/percolation, evapotranspiration, surface and subsurface flow (includes leakage to deep groundwater) are modeled along the vertical direction on a subcatchment basis in a manner similar to the Sacramento Soil Moisture Accounting model, and kinematic channel routing carries the flow through the network of subcatchments to the watershed outlet, providing capability for spatially distributed flow simulations. Subcatchment physical properties are derived from various digital terrain and land-characteristics databases through GIS processing and they are used to derive spatially distributed model parameter values. The NWS operational WSR-88D hourly radar rainfall estimates (Stage III product with pixel scale of approximately 4 km) constitute the rainfall forcing and a combination of model-derived and observed hourly surface meteorological data are used to produce the potential evapotranspiration forcing. HRCDHM was applied to and was calibrated for five watersheds for the period May 1993 through June 2000. Validation was done with data not used during the calibration period. This application shows that: (a) the HRCDHM, when forced with hourly data, is able to reproduce well the observed hourly streamflow at the outlet of each study watershed; and (b) beyond these outlet locations, HRCDHM is able to reproduce adequately the hourly flows at several interior locations. A companion paper [J. Hydrol. (2004)], in this issue details the use of the model for the characterization of simulation uncertainty within a Monte Carlo framework. (C) 2004 Elsevier B.V. All rights reserved.