Editing Hydrogeology of Chad

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||Outcrops of Quaternary alluvium in major river valleys are likely to be permeable and to have high groundwater storage potential, and shallow water tables. Where they are hydraulic connection with groundwater in underlying bedrock, such as weathered Precambrian basement, they can contribute significantly to local groundwater potential.
 
||Outcrops of Quaternary alluvium in major river valleys are likely to be permeable and to have high groundwater storage potential, and shallow water tables. Where they are hydraulic connection with groundwater in underlying bedrock, such as weathered Precambrian basement, they can contribute significantly to local groundwater potential.
 
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====Sedimentary - Intergranular Flow====
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{| class = "wikitable"
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|Named Aquifers||Aquifer Productivity||General Description||Water quality
 
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|Chad Formation: Quaternary (to Pliocene) - upper part of the '''Lake Chad Basin Aquifer'''
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|Chad Formation: upper part of the '''Lake Chad Basin Aquifer'''
 
||High  
 
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||The Pliocene-Quaternary Chad Formation aquifer within the Lake Chad Basin is dominated by permeable sands that are present at depths of up to 500 m; the top surface of the aquifer varies from 250 to 350 m. Clays are most extensive near to the present day lake shore (Goni 2008). The upper part of the aquifer is often unconfined but in some places semi-confined to confined by clay layers (Goni 2008), and in its shallowest zones is in direct hydraulic contact with the Logone-Chari river system and with Lake Chad. Parts of the lower aquifer are confined by clay layers, and under artesian pressure. Sub-aquifers are identified within the overall basin, including the Kanem, Koros and Chari-Baguirmi areas. Borehole yields of 2.5 litres/second (l/s) have been recorded (United Nations 1988), but it is likely that much higher potential yields are possible.  
 
||The Pliocene-Quaternary Chad Formation aquifer within the Lake Chad Basin is dominated by permeable sands that are present at depths of up to 500 m; the top surface of the aquifer varies from 250 to 350 m. Clays are most extensive near to the present day lake shore (Goni 2008). The upper part of the aquifer is often unconfined but in some places semi-confined to confined by clay layers (Goni 2008), and in its shallowest zones is in direct hydraulic contact with the Logone-Chari river system and with Lake Chad. Parts of the lower aquifer are confined by clay layers, and under artesian pressure. Sub-aquifers are identified within the overall basin, including the Kanem, Koros and Chari-Baguirmi areas. Borehole yields of 2.5 litres/second (l/s) have been recorded (United Nations 1988), but it is likely that much higher potential yields are possible.  
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||In the Chad Formation aquifer there are areas of high nitrate concentrations linked to agriculture discharges and faecal contamination. High fluoride concentrations are also seen. Groundwater in parts of the northern Kanem region contains high concentrations of sodium carbonates and sodium sulphates.
 
||In the Chad Formation aquifer there are areas of high nitrate concentrations linked to agriculture discharges and faecal contamination. High fluoride concentrations are also seen. Groundwater in parts of the northern Kanem region contains high concentrations of sodium carbonates and sodium sulphates.
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====Sedimentary - Intergranular Flow====
 
{| class = "wikitable"
 
|Named Aquifers||Aquifer Productivity||General Description||Water quality
 
 
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|Continental Terminal: Tertiary - lower part of the '''Lake Chad Basin Aquifer'''
 
|Continental Terminal: Tertiary - lower part of the '''Lake Chad Basin Aquifer'''

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