Classifying zones of suitability for manual drilling using textural and hydraulic parameters of shallow aquifers: a case study in northwestern Senegal

Abstract

A method is proposed that uses analysis of borehole stratigraphic logs for the characterization of shallow aquifers and for the assessment of areas suitable for manual drilling. The model is based on available borehole-log parameters: depth to hard rock, depth to water, thickness of laterite and hydraulic transmissivity of the shallow aquifer. The model is applied to a study area in northwestern Senegal. A dataset of boreholes logs has been processed using a software package (TANGAFRIC) developed during the research. After a manual procedure to assign a standard category describing the lithological characteristics, the next step is the automated extraction of different textural parameters and the estimation of hydraulic conductivity using reference values available in the literature. The hydraulic conductivity values estimated from stratigraphic data have been partially validated, by comparing them with measured values from a series of pumping tests carried out in large-diameter wells. The results show that this method is able to produce a reliable interpretation of the shallow hydrogeological context using information generally available in the region. The research contributes to improving the identification of areas where conditions are suitable for manual drilling. This is achieved by applying the described method, based on a structured and semi-quantitative approach, to classify the zones of suitability for given manual drilling techniques using data available in most African countries. Ultimately, this work will support proposed international programs aimed at promoting low-cost water supply in Africa and enhancing access to safe drinking water for the population.

Manual Borehole Drilling as a Cost-Effective Solution for Drinking Water Access in Low-Income Contexts

“…As a rule of thumb, flow rates in excess of 3-4 m 3 /h may be enough to underpin small-scale community orchards, while yields below 2-3 m 3 /h are often insufficient. The aquifer's hydrodynamic parameters thus play an important role, regardless of the technique of choice [47,48].…”

Quantifying Focused Groundwater Recharge Induced by Irrigation Surface Water Reservoirs in Crystalline Basement Areas for Complementary Irrigation

“…With regard to the magnitude of the values of the hydraulic conductivity, these aquifers are rather poor and semi-permeable according to the classification of Bear [92]. However, even if these aquifers could be considered as aquitards, in basement areas where water resources are scarce, they can be exploited through large-diameter wells [93].…”