English

Abstract
Similar to many Palestinian communities, Yatta area located in the southern part of the West Bank receives a limited quantity of water. The area has more than 70,000 inhabitants, more than 37,000 dunums of agricultural land planted with different types of crops in addition to different commercial and industrial activities (Yatta municipality, 2015).
The general objective of this research is to estimate the potential amount of total direct runoff from Yatta watersheds to be used in the agricultural lands and to evaluate its impact on the socio-economic situation in the study area.
In this research, rainfall received on Yatta area including the amount and variation was analyzed using statistical methods. When the standard deviation values of annual rainfall data were examined, their values were found to be far away from the mean. This reflects the variability of annual rainfall data during the long analysis period.
This research focused on estimating the potential amount of rainfall which could be collected from watersheds within the boundary of the area to be used for enhancing the agricultural lands in the area. The water would help improve crop yields, family income, create jobs and stop the deterioration of the green cover of the city. For this reason, a watershed model was developed using the WMS and the HEC-HMS applications. Accordingly, the rainfall distribution, evapo-transpiration, and physical characteristics of the watersheds were defined.
The watershed in Yatta area and the characteristics of this watershed was defined. WMS model was used to define and delineate this watershed and divide it to five sub basins using the Digital Elevation Model (DEM), land use, and soil type for Yatta area. Land use and soil type were created using the Geographical Information System (GIS). The boundary of Yatta watershed and its sub subbasins in addition to their physical properties are saved and exported HEC-HMS. This model was used to simulate the watershed; accordingly, two models were developed based on hourly rainfall data for Yatta area in 2014/2015 rainy season.
As a result, the runoff coefficient was estimated at (1.6 - 2.4) % which is considered very low due to the low intensity of rainfall as well as its annual amount. The analysis concluded that an average of 90,000 m3/yr of storm water could be collected and stored in earth pools and cisterns at different locations within the boundary of the watersheds. This amount can be a supplementary source to irrigate around 300 dunums of olives, almond and grape trees in addition to more than 60 dumuns of vegetables. Therefore, this study proved that storm water can still be considered as a potential source of water which could contribute to solving water problems and improving the socio-economic situation.