89th American Meteorological Society Annual Meeting

Tuesday, 13 January 2009: 2:30 PM
Effects of biases in NEXRAD precipitation estimates and sub-basin resolution in the hydrologic modeling of Blue River Basin using a semi-distributed hydrologic model
Room 127BC (Phoenix Convention Center)
Md. Zahidul Islam, University of Alberta, Edmonton, AB, Canada; and T. Y. Gan
Semi-distributed, Physically based Hydrologic Model using Remote Sensing and GIS, DPHM-RS (Biftu and Gan, 2001, 2004) was applied to the Blue River Basin (BRB), Oklahoma having a basin area of 1235 km2 in a multi-year mode using NEXRAD (Next-Generation Radar) precipitation and other data of Distributed Model Intercomparison Project Phase 2 (DMIP 2) of NOAA. The overall model performance at both calibration and validation stages are comparable to other previous DMIP studies on BRB. DPHM-RS generally over simulated low flows during the validation stage partly because rainfall events based on radar precipitation data are likely larger than what actually occurred, which became a major source of bias, even though NEXRAD data has already being merged with rain gauge data. However, by adjusting the NEXRAD data based on 3 gauge measurements of the Mesonet stations near the BRB, the validation results improved significantly, which demonstrate that the former still contain biases. Therefore whenever possible, NEXRAD data should first be compared and adjusted to local conditions (e.g., rain gauge data) before applying the data to simulate basin hydrology. With respect to the Oklahoma Mesonet estimates, it seems that DPHM-RS simulated realistic soil moisture, which together with realistic simulated runoff hydrograph, demonstrate the physical basis of DPHM-RS. However, the model performance also depends on the sub-basin resolution, and we found that BRB can be optimally modeled with 7 sub-basins.

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