科研之友
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摘要
The hydraulic characteristics of the Quaternary aquifer in N＊Djam谷na town and environs were estimated in order to highlight the groundwater potential and vulnerability of the aquifer to heavy abstraction. Pumping test data from 26 boreholes were analysed to determine the hydraulic conductivity, transmissivity and the specific yield of the aquifer. The hydraulic conductivity was calculated based on changes in elevation head of water in the borehole being pumped, the transmissivity was derived in relation to the hydraulic conductivity and the specific yield was estimated using an empirical formula. Results show that hydraulic conductivity varies from 1.20x10-1 m day-1 (1.41x10-6 m sec-1) to 5.46x10-3 m day-1 (6.32x10-2m sec-1), transmissivity ranges from 5.99x10-1 m day-1 (6.95 x10-5 m2sec-1 ) to 2.69 x10-4 m day-1 (3.12 x10-1 m day-1) while the specific yield is between 0.006 and 0.052. These results indicate that the aquifer is heterogeneous, has high permeability, but with low storage. On account of the specific yield, it can be deduced that groundwater supply for domestic use is reliable, but withdrawals for industrial and irrigational uses must be limited.
