Evaluation of Surface Water Resources Using WEAP Model (Case Study: Qaraso Basin)

Abstract

This paper provides a method that by using hydrologic models determines risk and flood prone zones into the basin and also determines fl ooding intensity at each sub-basin. First, the basin in the geographic information system (GIS) using Arc Hydro amendment were divided into 14 sub-basins and then the physical characteristics of the basin and sub-basin using ArcHydro entirely were determined by climate and land use and using WEAP model which required simulation of hydrological catchments and the total for each sub-basin have been done. Resulted calculations from model run indicate that the contribution level of the small and large sub-basins in the flood basin outlet does not depend on sub-basin discharge quantity and sub-basins with more di charge do not necessarily have more contribution in the outlet discharge. In other words, sub-basins have shown a kind of non-linear behavior. Also, this paper also examines quantitative comparison of peak discharge changes of the basin outlet per watershed, average slope changes, stream, Runoff Resistance Factor (R.R.F) in each of sub-basins, take action to identify most important effective factors on watershed flooding and also critical sub-basin. For this purpose, each of desired factors in specific range separately changed at each of sub-basins and amount of this change obtained in the whole basin outlet discharge. In this regard, amon g sub-basins the sub-basin A9 has the most critical condition regarding effect on the basin outlet flood . On the other hand, among other effective factors on outlet discharge of the basin and sub-basins the R.F.F was detected as the most important factor in terms of its impact on the basin outlet flood an d control. For example, if using flood control operation in the stream path of the critical subbasin its slope decreases to 30% of initial slope only about 8% of the outlet peak discharge decreases and it requires a lot of spending. But in these sub-basins if the value of Kcreduced to 10% of initial value about 24% of peak output will be reduced.