Shahram Bahrami - Assistant Prof, Department of Geography, Sabzevar Tarbiat Moalem University

The Kangir catchment in Ilam province, Iran, has a drainage area 122.71 km2 and is located in the latitude range of 33o 41’ to 33o 51’ and longitude range of 46o 17’ to 46o 27’. The altitude in the study watershed varies between 1175 m in northwest and 2650 m in southeast. The study area is upstream part of Kangir basin and drained by permanent Kangir river that flows from southeast to northwest. Geologically, Kangir catchment is part of the Zagros Fold Belt of the Zagros Mountains. The structures are composed of anticlines and synclines and trend in NW-SE direction. The linking of the geomorphological and climatic parameters with the hydrological characteristics of the basin can provide a simple way to understand the hydrologic behavior of different catchments, particularly the ungauged ones. In this study, geomorphological instantaneous unit hydrograph (GIUH) geomorphoclimatic instantaneous unit hydrograph (GCIUH) and Nash models were evaluated based on geomorphological characteristics, velocity, rainfall data and geometrical parameters of stream channel, in Kangir catchment. Results of this study shows that GIUH and GCIUH methods approximately estimated the observed peak discharges but underestimate the time to peak discharges. in Nash model, the calculated QP and TP values effectively differ from observed QP and TP values. also, in spite of relatively better performance of GIUH and GCIUH methods, error function (ERR)results represent that three mentioned methods failed to predict the complete shape of observed hydrographs. This study reveals that karstic landforms such as karren and doline and tectonic joints perpendicular to topographic slope reduce the velocity of runoff and increase the travel time and, hence, affect the QPs and TPs of GIUH, GCIUH and Nash models.

GIUH, GCIUH, Nash, Kangir, geomorphologic characteristics, karstic landforms