by Yakubu Mohammed, Ibrahim B. Wulo, A. K. Yusuf and Ashe K. Gazali
Original Research
The study was conducted in the Biu plateau with a major objective of elucidating the geomorphic and geologic mechanisms influencing the occurrences and hydrochemistry of surface and ground waters of the area. This was achieved by analyzing surface and groundwater from rivers, lakes, wells and boreholes from different landforms of the plateau. Also, lithologic logs of boreholes and wells from different parts of the plateau were analyzed to give insight to the near surface characteristics of the area. Data on the geology and geomorphology were obtained from field mapping and complimented by secondary sources from journal articles, unpublished thesis and reports on these aspects of the plateau. The plateau with a land mass of 2635.12 Km2 is traversed by a total of 14671 streams, with 9814 1st and 3783 2nd order streams totaling a length of 6879.5 Km. The drainage pattern of the plateau is dendritic in nature reflecting the uniform nature of the geology and absence of major geologic structures such as faults. The predominant major cation trends in the surface and groundwater samples is in the order of Na+ > Ca 2+ > Mg2+ > K2+ and Ca 2+ > Mg2+ > Na+ > K2. This reflects the chemical composition of rocks in the plateau which also has a relatively high Mg2+, K2+, Na+ and Ca 2+ ionic concentrations. Analysis of lithologic logs of boreholes and hand dug wells from different parts of the plateau indicated that three sources with high groundwater potentials exist in the plateau. The study also found out that the spatial variation in the surface and groundwater hydrochemistry is a reflection of water-rock interaction over space and time.
American Journal of Water Resources. 2020, 8(6), 256-263. DOI: 10.12691/ajwr-8-6-2
Pub. Date: December 20, 2020
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by Alassane Thiam, Ousmane Coly Diouf, Abdou Aziz Gning and Issa Ndoye
Original Research
The “Niayes” area plays a major role in the Senegalese economy due to a very high market garden production. This “Niayes” area produces almost all of Senegal's vegetables (onions, potatoes, carrots, green cabbage, tomatoes, cherries, eggplants, lettuce and chili). Water supply to meet irrigation needs in this area comes mainly from groundwater resources. This Groundwater pumping has harmful consequences on the behavior on the groundwater piezometric level drop. Since 1987, the piezometric dome observed in this aquifer experienced a water level drop of 2.5 m at Taїba and Tawa Fall areas. The electrical resistivity tomography (ERT) shows the presence of a saturated and an unsaturated zones in the presence of dry sandy dunes with a thickness of about 12 m resting on a saturated zone corresponding to the aquifer captured by the 2 boreholes and the piezometer. Chemical analyzes showed an Electrical Conductivity values equal respectively to 269, 470 and 1110 µS/cm at Fass Boye piezometry, Darou Thiam and Ségoul Thioune wells. Electrical Conductivity value of 1110 µS/cm indicates a strong groundwater mineralization. This mineralization is correlated with Na+ concentration of (145 mg/L) close to pollution by salt resulting in salinization of water making them unsuitable for consumption and irrigation. Water samples at Fass Boye piezometer and Ségoul Thioune well show low to medium mineralization because the electrical conductivities are respectively in the order of 269 and 470 µS/cm. Majors ions concentration (Cl-, Ca2+, Mg2+, K+, SO42-, HCO3-) with respective maximum concentrations of 140.84; 48; 21.32; 8.81; 78 and 122 mg/L, meet all World Health Organization standards for drinking water. Applying the Piper diagram to these groundwater samples shows a sodium and potassium chloride facies associated with proximity to the sea.
American Journal of Water Resources. 2020, 8(6), 246-255. DOI: 10.12691/ajwr-8-6-1
Pub. Date: November 29, 2020
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