A new simple and quick geophysical method for the siting of boreholes for hand‐pump supply in the crystalline rocks of Kano State, Nigeria has been developed. A single electromagnetic traverse with at least two depths of investigation is used to locate a potential subsurface feature which is then assessed by a vertical electrical sounding. Ground‐water quality has a significant influence on the data. The method and criteria for selecting a site are described in detail because careful site selection is important in reducing the time and money spent on unproductive drilling. In spite of generally unfavorable hydrogeological conditions in the crystalline rocks, 364 boreholes had acceptable rates of ground‐water production out of 429 sited using this method.

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More than 100 groundwater sources operated by Anglian Water Services are vulnerable to diffuse and point pollution, and 33 of these sources have nitrate concentrations in excess of 50 mg l −1 as NO 3 . Most time series nitrate data ‘recess’ to a long-term rising baseline, upon which seasonal variations and/or data scatter are superimposed. Investigations at boreholes abstracting from the Chalk aquifer show that concentrations decrease with depth below the water table and with time after pump start-up. Abstraction rates do not affect concentrations but the combination of boreholes in use does. A reliable and robust semi-quantitative method for predicting future nitrate concentrations has been developed. Use of this method has allowed a rigorous definition of capital investment requirements under the AMP4 process to maintain compliance with drinking water standards. The method has been used to predict short-term nitrate concentrations for a variety of recharge scenarios.

The described methodology for the assessment of the reliable outputs of groundwater sources was developed during a recent contract for UK Water Industry Research. It is relatively simple and flexible so that it can be applied to the wide range of groundwater source types and aquifers encountered in the UK. It can be used for all water level conditions, including that of drought, and for various demand conditions. There are two approaches, one based upon operational data and the second upon the analysis and extrapolation of pumping test data. The operational approach has several options of increasing refinement – the choice of option depending on data availability and user requirements. The application of the methodology to real groundwater sources is described using three examples.