The influence of the Nile water system on groundwater recharge and discharge at Khartoum City- Central Sudan

Abstract

The study area lies at the confluence of the Blue and White Niles in Khartoum, the capital of Sudan. The main objective of the current study is to assess the influence of the Niles water system on groundwater recharge and discharge. Three methods of investigations were applied; base-flow Recession Method, Water Levels Fluctuations (WLF) and the Darcy Method. The amount of water discharge of the Niles varies seasonally; the highest flows were registered in the autumn seasons. The amount of 816 × 10⁶m³/day was registered in 1988 as maximum discharge and 49 × 10⁶m³/day in 1984 as minimum one in Soba Station on the Blue Nile. Groundwater is mainly stored in two aquifers, Gezira and Sandstone formations, both aquifers are hydraulically interconnected to form one aquifer system. Gezira formation represents the saturated upper zone that let it in direct contact with Niles waters. The hydraulic gradients range from ≥0.005 to ≤0.002 from west to the east direction; indicating that, the White Nile is the main source of recharge for groundwater rather than the Blue Nile. Using the Darcy method, the groundwater recharge from the While Nile is more than twice the recharge from the Blue Nile. In general the groundwater recharge from the River Niles using the three methods is estimated at about 130 × 10⁶ m³ annually. The strong interface between the Niles surface water and groundwater in the Khartoum area will raises concerns on Niles waters contamination with already polluted shallow groundwater aquifers.