ABSTRACT
The work articulates borehole systems definition and project criteria, as systems evaluation principles. These serve as background knowledge for the assessment of availability of handpump-equipped boreholes in the Crystalline Groundwater Province of Northern Nigeria. The study which is mainly based on project files and performance records, draws samples of a hundred boreholes from each of four states (Kaduna, Kano, Kwara and Niger States) within the area of interest. Also assessed are such related measures of systems effectiveness as: reliability, maintainability, failure patterns and frequencies, times to first failure, up-times and down-times of the boreholes. The study shows that there are no significant differences in the respective values of these parameters, in the four states. Availability as a measure of the up-times of the boreholes over the initial five-year period of their operation is found satisfactory. However, as a measure of the probability for adequate performance over the designed life of the boreholes, with no down-times in excess of one week; availability is found problematic as from the fourth year of operation of the boreholes. The handpump sub-system shows a much higher failure frequency - 88% approx.of the system failure - than the well. This in turn is accounted for mainly by the cylinder assembly, riser pipe and head assembly components; with 41%, 22%, 12% approx. of the system failure respectively. Suggestions made for improving the availability include: improving the inherent reliablity of the handpump, closer monitoring of the borehole systems in operation to ensure timely failure identification and reporting, keeping adequate stock of spares and swift mobilisation of resources for repair work.