regional flow duration curve in arid regions for ungauged basins (case study: central iran)

a flow-duration curve (fdc) illustrates the relationship between the frequency and magnitude of streamflow. applications of fdc are of interest for many hydrological problems related to hydropower generation, river and reservoir sedimentation, water quality assessment, water-use assessment, water allocation and habitat suitability. this study was carried out in 11 selected watersheds with common characteristics such as the 20 years period, the minimum land use change and similar annual water volume through all watersheds in 3 province of: yazd, semnan and markazi which are located in central zone of iran to regional flow duration curve. it was extracted q5, q10, q20, q30, q40, q50, q60, q70, q80 and q90 from 11 hygrometric stations as a dependent variable were derived from flow duration curve. the flow duration curve is regionalized by using morphoclimatic characteristics of the drainage basin. using multiple regression techniques, the geographic variation of each parameter of the best fitted flow duration model is explained in terms of the drainage area, length of longest flow, stream slope, mean annual areal precipitation, course from the divide of the basin to the site of interest. the regionalized nonlinear regression equations are successfully used to flow duration curves at other locations within the hydrologically homogeneous regions of center of iran. a cross-validation nash–sutcliffe efficiency procedure was used to evaluate best fitting of the regional model in ungauged watershed.