Productivity of Some Water Wells in the Alluvial Sediments of Lake Chad

Abstract

The performance of ten (10) water supply boreholes drilled in the quaternary sediments of the Chad Formation at Nguru, Yobe state have been evaluated using the Step draw down test (SDDT). Pertinent hydraulic characteristics such as aquifer and well loss coefficients, specific capacity and transmissivity of the wells and aquifer tapped were also determined using regression techniques. Results show that the specific capacity of the wells range between 9.3 and 261 m²/day, aquifer loss range from 1.61 – 19.57m, well loss range from 0.25 – 4.49m and  Transmissivity of the tapped aquifer range from 13m²/day – 356m²/day.  The efficiency of the wells used as the performance criteria range from 51.1% - 89.1%, indicating satisfactory performance. The highest draw down of 24.56 m was observed in well NG27, this well was also found to have the least transmissivity of 13m²/day, it is suspected that this well was badly developed after construction. The result obtained shows that most of the boreholes are still productive. The performance should be updated annually in order to guarantee future supply of water. The result of the study is expected to be a reference for future well testing program in the area.