Hydro chemical facies of ground water in the western provinces of Sudan

Abstract

The ground water in the Nubian Sandstone and Umm Ruwaba aquifers in the area under investigation is a good quality calcium-sodium bicarbonate water. It has low total dissolved solids and hardness, and it is slightly basic. In Jabal El Hula and Ghazala Gawazat the total dissolved solids are much higher and the chloride ions are the dominant anions. This high chloride and solid content may be due to the mixing of water of the main ground water body with water of higher chloride and solid derived from (1) mudstone of the Nubian series, (2) deep ground water layers of higher salinity and/or (3) waters which have dissolved solids from evaporite beds in the sedimentary sequence. The basement complex, where it crops out or is covered by a thin layer of Quartinary sediments is only a minor source of ground water. Little is known concerning the shape of the basement complex water table and only one complete chemical analysis from this source is presently available. However, incomplete data indicate that water quality varies over a wide range, and. that nitrates are present and in some places fluorides are high. The nitrate is believed to be of organic origin whereas the fluoride is believed to be from weathering of fluoride-bearing rocks.