Ecology, Environment and Conservation Paper

Vol.18, Issue 04, 2012; Page No.(805-812)

CALIBRATION, VERIFICATION AND SENSITIVITY ANALYSIS OF THE HEC-HMS HYDROLOGIC MODEL (STUDY AREA: KABKIAN BASIN AND DELIBAJAK SUBBASIN), IRAN

Arash Asadi, Hossein Sedghi, Jahangir Porhemat and Hossein Babazadeh

Abstract

Rainfall-runoff processes in small subbasin Delibajak(16.3 km2) and Kabkian basin(846.5 km2) in kohgilouye and boyerahmad, iran were examined. in fact, Delibajak is one of the subbasins of Kabkian basin. In this study, the basins were considered as Lumped. The hydrologic model HEC-HMS (Hydrologic Engineering Center, Hydrologic Modeling System), used in combination with the Geospatial Hydrologic Modeling Extension, HEC-GeoHMS. The SCS curve number method (Soil conservation Service, 1972) was considered for the Rainfall-runoff modelling and the model was carefully calibrated and verified in basins using simultaneous historical observed data. The determination coefficients and coefficients of agreement for all the flood events were above 0.9, and the percent errors in peak flow and volume were all within the acceptable range. Then a local sensitivity analysis was adopted for evaluating the event model. There are three parameters(curve number, initial abstraction and lag time) of the event model that were subject to the sensitivity analysis.In the Delibajak and kabkian basin the highest differences between the generated peak hydrographs and the baseline peak hydrograph were caused by initial abstraction and curve number, respectively. Also, the optimmized hydrologic parameters, curve number and initial abstraction were compared in this two basin. In the Kabkian basin, curve number, initial abstraction and Lag Time Were 62 , 34mm, and 347 min, respectively. In the Delibajak subbasin, this parameteres Were 53,49 mm and 92 min. This variationes is due to differences in basin slope, geologic formations,vegetation cover and land use in basins.

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