The process whereby hydrogeologists interpret the available information to produce a justifiable set of simplifying assumptions to describe a groundwater system is called conceptual modelling. Although this process is inherent in all hydrogeological assessments and can therefore be regarded as synonymous with hydrogeological practice there are no standard specifications for it. A framework for conceptual modelling has been designed to both assist in the planning and process of the work and to provide an audit trail to facilitate independent scrutiny. The application of this framework is illustrated by two case histories, one of a small-scale investigation for a proposed cemetery and the other of an investigation of the migration of a large-scale sulphate plume in a public supply aquifer. This framework is applicable across the full range of scales of hydrogeological systems, and indeed is readily extendable to other analogous areas of endeavour in the management of natural resources.

Summary As part of a hydrogeological investigation in a Permo-Triassic Sandstone aquifer in northwest England, various methods of field permeability testing have been developed and evaluated. These techniques involve the use of borehole packers to isolate specific test sections and permeability measurements made by either injection or pumping tests. Field results have been compared with both laboratory permeability measurements and conventional pumping tests. The test procedures were found to have a significant effect on the results obtained. Packers have also been employed to examine the vertical distribution of piezometric heads within an aquifer, both in pumping and non-pumping conditions, and to obtain groundwater samples from selected horizons. Some of the test results are presented to illustrate the value of packer techniques in hydrogeological investigations.

Ten thermal springs occur in seven centres in Derbyshire, England, with temperatures up to 27.5 °C compared with an ambient groundwater temperature of about 9 °C. The springs discharge from a karstic Dinantian limestone aquifer along the boundary with the overlying Namurian strata around the edge of a regional dome structure. The water is heated by deep circulation to as much as 1 km, with the hottest spring being at Buxton spring, where the water is 5000 years old. A comparison of flow data from the Buxton spring with groundwater hydrographs shows seasonality in the thermal flows, suggesting that the loading effects produced by recharge are transmitted through this deep aquifer system. From a review of the geological history and the hydrogeology and the use of measurements on the Buxton spring it is suggested that the thermal flow system may have its roots in ancient convection cells possibly established in the deeply buried aquifer in late Carboniferous–Early Permian times. Subaerial erosion during the Pliocene removed the impermeable cap rocks and allowed both the thermally heated water to form warm springs and this deep groundwater circulation to be recharged by meteoric waters. The location of the individual springs is likely to date from the downcutting during the Late Pleistocene that formed the modern river valley topography.

As part of several groundwater investigations of the Permo‐Triassic Sandstone aquifers in north west England, a detailed measurement of piezometric heads and groundwater flow within observation boreholes was made which showed that vertical differences of groundwater heads persist within aquifers. A number of case histories of these studies are presented, which are used to consider the impact of head variations on typical groundwater level and groundwater quality measurements taken in observation boreholes, with a view to recommending design criteria for observation boreholes and groundwater monitoring programmes.

Over the past few years, new abstractions from the Sherwood Sandstone aquifer in North West England have only been permitted in areas with known saline intrusion subject to the abstractor demonstrating that the new pumping will not cause deep-seated saline groundwater to up-cone. This requirement has necessitated drilling deep boreholes to prove the depth to the fresh–saline groundwater boundary and also to facilitate long-term monitoring. Vertical salinity profiles were defined during borehole construction in two such investigations by monitoring the conductivity of water samples obtained from drilling returns during air-flush drilling and later by the geophysical logging of the completed boreholes. Deep piezometers were constructed allowing samples to be taken from specific depths for chemical analysis, and the results have been compared with the earlier data. These methods successfully defined the broad features of vertical salinity profiles within the aquifer and showed that measurements during drilling provide a practical and economic indication of the position of the interface so that the borehole final depth can be determined.