Hydrological modelling of a heterogeneous catchment using an integrated approach of remote sensing, a geographic information system and hydrologic response units: the case study of Wadi Zerka Ma'in catchment area, north east of the Dead Sea

Wadi Zerka Ma'in is the smallest catchment area at the eastern side of the Dead Sea basin and has the largest city in that region. It receives direct groundwater recharge from an area of about 611.25 km(2). Climatically and geomorphologically the region is heterogeneous. These heterogeneities have a major impact on the spatial distributions of the groundwater recharge. We used a Hydrological Response Unit method to investigate the spatial distributions and estimate the amount of groundwater recharge. An integrated approach of remote sensing and a geographic information system was used to feed the hydrological model with the land surface and climatic data. According to our model, it was found that during the last 30 years the average amount of rainfall in the studied area decreased from 275 mm/year to 100 mm/year and the temperature increased from 24.8 to 26.8 A degrees C. These climatic changes had a major impact on the hydrological cycle of the study area by decreasing the runoff of the Zerka Ma'in River and increasing the evapotranspiration. As a result, the groundwater recharge of that catchment decreased during the same time period. It was found that recharge reached a maximum value of 94 million cubic metre (m(3)) in 1983, and since 1991 was not exceeding 50 million m(3) per year any more.