Effects Of Z-I Relationship On Radar Measured Areal Rainfall And Run-off Simulations

Rainfall-runoff model named TOPMODEL (TOPgraphy based hydrological MODEL) was used to simulate runoffs of Xianghongdian and Foziling subcatchments in the upper reaches of Pihe River. The input data for the model include evaporation and runoff data collected by the Huaihe River Commission of the Ministry of Water Resources, P. R. C, and rain gauge data and Hefei CINRAD (ChIna New generation RADdar) radar data obtained by the China heavy rainfall experiment under the frame of the 973 Project (China National Key Development Planning Project for Basic Research, Abbreviation: 973 Project) and Project of Huaihe/Huanghe Basins Heavy Rainfall/ Flooding Monitoring System. Simulation results were analyzed. Following are main steps of this work:1) Optimization was used to get subsection optimized Z-I relationship, and subsequently used across study area to get hourly rainfall distribution;2) Comparing the simulation results and accuracies with the different Z-I relationships used in radar precipitation retrievel;3) Comparing the simulation results and accuracies with the different Z-I relationships used in radar precipitation retrievel for 5 and 13 rain gauges calibation aolgrithm in the Foziling catchment.Based upon above investigation, some conclusions were obtained as follows:1) The radar retrived precipitation using optimized Z-I is much closer to observation, and the precision of radar measured areal rainfall is significantly improved;2) Simulation precision for runoff was greatly affected by different Z-I relationship used in radar precipitation arogrithm, and flood peak could be doubled. Therefore suitable Z-I relationships could efficiently improve the runoff simulation.3) As the number of rain gauges increased used in calibration, higher the accuracy of runoff simulation using the data from the radar and rain gauges, especially compared to using rain gauge only. Subsection optimized Z-I relationship still has a higher accuracy than Z=300I1.4 relationship, but not obviously. Therefore, with sparse rain gauge networks in catchments, it's necessary to use optimized Z-I relationship to improve simulation accuracy.