ABSTRACT
An attempt was made to derive the mean annual ground water recharge from the vertical distribution of tritium, deuterium 180 and of Cl− in the soil moisture of the 40 to 90 meters thick unsaturated zone of the Umm Kedada Basin in NW-Sudan. The soil samples were collected by roping down into dug wells and horizontal drilling into the walls at various depth positions down to 45 meters below ground surface. Since the drilling depths were less than 40cm only, the soil moisture samples were affected by evaporative isotope exchange with the atmosphere in the well. From the soil moisture quantity in the sediments and the depth position of the bomb tritium peak due to infiltration water from 1963/64, ground water recharge rates of 25mm/y and 1.5mm/y were calculated as local long time average values since 1963/64.
