Hydrchemical evaluation of groundwater in Khartoum state, Sudan Bicarbonate concentration varies in the range of 122-372, 98-573 and 110-402 mg/l in the eastern, central and Omdurman area respectively (Table 1). High concentration trough zones were appeared outwards of river courses (Figure 5). This is caused by the carbon dioxide (CO2) present in the soil zone formed from the decay of organic matter and the root respiration and may also be derived from the dissolution of silicate and feldspars minerals and the weathering of parent materials (calcretes) due to consecutive dry and wet conditions, characterized the semi-arid area.  Figure 5. Areal distribution of bicarbonates The chloride concentration in the study area, with few exceptions, is relatively low with mean values of 105, 78, and 136 mg/l in the eastern, central and Omdurman area respectively (Table 1). Moreover, the concentration decreases with increasing distance from surface watercourses forming a longitudinal troughs generally trending north-south or northwest-southeast (Figure 6). The analogous distribution of chloride, sodium and total dissolved solids indicates a common source of these ions such as leaching of saline residues in the soil due to climatic conditions and anthropogenic activities.  Figure 6. Areal distribution of chlorides 6. Relationship of groundwater to use The main objectives following the hydrochemical investigations of groundwater is to determine its suitability to different uses. Hence, hydrochemical investigations indicate that water from the upper aquifer ranges from generally acceptable to poor for domestic uses. Whereas, that from lower aquifer is comparatively good for both drinking and household purposes, although very saline and hazards zones were encountered at the eastern central and Omdurman area. |