Groundwater balance in the Khor Arbaat basin, Red Sea State, eastern Sudan

The Khor Arbaat basin is the main source of potable water supply for the more than 750,000 inhabitants of Port Sudan, eastern Sudan. The variation in hydraulic conductivity and storage capacity is due to the heterogeneity of the sediments, which range from clay and silt to gravely sand and boulders. The water table rises during the summer and winter rainy seasons; it reaches its lowest level in the dry season. The storage capacity of the Khor Arbaat aquifer is estimated to be 21.75 × 10⁶ m³. The annual recharge through the infiltration of flood water is about 1.93 × 10⁶ m³. The groundwater recharge, calculated as underground inflow at the ‘upper gate’, is 1.33 × 10⁵ m³/year. The total annual groundwater recharge is 2.06 × 10⁶ m³. The annual discharge through underground outflow at the ‘lower gate’ (through which groundwater flows onto the coastal plain) is 3.29 × 10⁵ m³/year. Groundwater discharge due to pumping from Khor Arbaat basin is 4.38 × 10⁶ m³/year on average. The total annual groundwater discharge is about 4.7 × 10⁶ m³. A deficit of 2.6 × 10⁶ m³/year is calculated. Although the total annual discharge is twice the estimated annual recharge, additional groundwater flow from the fractured basement probably balances the annual groundwater budget since no decline is observed in the piezometric levels.