Modeling of flow duration curve deformation in Karkheh Basin

Modeling deformation of flow duration curve, is one of the most important issues in hydrology and it is the suitable tool to hydrological analysis of the catchment. In this research, 22 hydrometric stations with appropriate data and common period (1974-1999) were selected.The study area was determined, using positioning stations on the topographic map with a scale of 1: 50,000 and the initial parameters of the catchments were extracted using geographical information system. Lithological units using digital geological map, with a scale of 1: 250,000, extracted and the area covered by each unit in each catchment were calculated. Flow duration curves plotted using daily flow data and the slope of last inflection of the curve was computed, using coding in MATLAB programming environment. The exceedance value, at the latest inflection point selected as the deformation curve index. Factor analysis was performed using 12 parameters and Homogeneity was conducted based on effective factors. Then, regression models between deformation index of flow duration curve, with hydrological, geological and geometric parameters, at less than 1% significant level were determined. The results of Factor analysis showed that all variables are to be classified in terms of four factors which 74.47% of the variance was included. Parameters of average height, annual precipitation, drainage density and base flow index were identified in the first factor. Geology at the second, the main river length and the area in the third and runoff coefficient were identified as the fourth factor. The results of slope curve analysis showed that exceedance values, at the latest inflection point in the catchments of research area, vary between Q8 and Q60.