An-Najah Staff

West Bank, Palestine, is one of the Mediterranean semi-arid areas. The available water resources in the West Bank are limited and insufficient to meet the agricultural and domestic water demand. Rainfall is the main replenishment of surface and groundwater resources in the West Bank. Characterization of rainfall magnitudes and patterns is of great importance in the management and development of scarce water resources in the main cities in the West Bank. This has compelled the motivation for carrying out a statistical analysis of long-term rainfall data for the meteorological station of Nablus City. This city is situated in an intensive agriculture-dominated area and overlaying an important groundwater aquifer. This paper employs the fundamental statistical parameters and concepts to analyze the long-term rainfall data of Nablus Meteorological Station (NMS) in order to evaluate the temporal variation of rainfall in the area. Assessment of daily, monthly, seasonal and annual rainfall was carried out. Results showed that the rainfall for NMS is of high variability where the annual rainfall approximately varies between 280 and 1,400 mm with an average of 658 mm. Drought was observed in 7 years out of the last 30 years. The winter season has the highest amount of rainfall whereas rare rainfall events occurred in summer. The estimated return periods for daily rainfall events of over 70 and 100 mm exceed 3 and 12 years, respectively.