Geochemical Signatures of Bara Basin Aquifers, Kordofan State, Sudan

Abstract

Purpose: In this paper, geochemical investigation has been carried out to study the concentrations of major cations; Sodium (Na⁺), Potassium (K⁺), Magnesium (Mg²⁺), and Calcium (Ca²⁺), and major anions; Chloride (Cl^-), Bicarbonate (HCO₃^-), Nitrate (NO₃^-) and Sulphate (SO₄^2-), other parameters such as (pH), Electric conductivity and T.D.S were also studied in all water samples taken from wells in Bara basin.

Methodology: Forty five (45) water samples have been collected from wells. Lab works were done at Groundwater and Wadis Directorate (GWD), Khartoum State according to Sudanese Standards and Metrology Organization, (2002), to study the major cations and major anions.

Findings: The results revealed that the average value of pH was (7.9) E.C values were (843.4 μS/cm) and T.D.S values were (59 mg/l). The average concentrations of the major cations obtained were; Na⁺ (126.3), K⁺ (5.22), Mg²⁺ (28.30), Ca²⁺(66.41) and the major anions (mg/l) were; Cl^- (159.00), HCO₃^- (165.30), NO₃^- (156.70) and SO₄^2- (164.70). The (Na/Cl) ratio is (2.47) is also high which reflects the abundance of (Na⁺) ions relative to the Chloride (Cl^-) ions which confirmed the light-salty nature of groundwater. Geochemical mass balance calculations indicate that upper aquifer is mainly affected by the dissolution and dolomitization processes of major anions.

Unique Contribution to Theory, Policy and Practice: This process is highly developed in the central west part of the basin due to the abundance of Sulphate (SO₄^2-), Bicarbonate (HCO₃^-), Magnesium (Mg²⁺⁾, and Calcium (Ca²⁺) ions. High values of E.C, T.D.S, Ca²⁺, and SO₄^2- are mainly presents as a saline water resource  in some villages. Two types of water are  classified  here these are : i). Na-HCO₃ type  and ii). Ca- Cl -SO₄ type. The study concluded that water samples from Almakser, Hamdan-2, Um-Zeeraga-2, and Al-Zareeba-2 villages have very high concentrations of  E.C, T.D.S Ca^2-, Cl^-, NO₃^- and SO₄^2-, which may suggest that water samples are not fit for human consumption, according to guidelins by W.H.O (1984). This paper recommends further study on  water quality.