Geothermal prospects in the UK are represented by low enthalpy resources in deep sedimentary basins and 'Hot Dry Rock' (HDR) resources in radiothermal granites, and possibly in deep basement rocks where they are overlain by thick low conductivity sediments. The low enthalpy resources are in Permo-Triassic sandstones at temperatures of more than 40°C. Four deep exploration wells have been drilled to investigate the potential of these sedimentary aquifers. The main HDR resource potential is associated with major granite batholiths in southwest and northern England where temperatures are predicted to be 200°C at about 5.4 and 6 km respectively. The HDR potential is being investigated by the Camborne School of Mines at their test site in Cornwall where three boreholes have been drilled to depths of between 2 and 2.5 km. The Hot Dry Rock Accessible Resource Base at temperatures of more than 100°C and depths of less than 7 km is 36 X 10 21 joules (equivalent to 130 × 10 4 million tons of coal). The low enthalpy Geothermal Resource of the Permo-Triassic sandstones at temperatures of more than 40°C is 200 × 10 l8 joules (equivalent to about 8000 million tons of coal). If only a small fraction of these resources could be developed, it would be significant in terms of the UK’s energy balance.

Following the increase in oil prices in the mid‐1970s, Britain assessed its geothermal resources. Low‐temperature, hot‐water resources, in the range 40°C to 100°C, occur in Permo‐Triassic sandstones in several deep sedimentary basins. In total these resources are estimated at 69.1 × 10 18 joules (J) (2576 million tonnes coal equivalent). Resources also occur in Upper Palaeozoic aquifers but, as the permeability of these aquifers depends upon fissures, exploitation is difficult. The only surface manifestations of hot water at depth are the warm springs at Bath and Bristol and in the Peak District and Taff Valley, which issue from the Carboniferous Limestone. The potential of radiothermal granites for Hot Dry Rock (HDR) development has also been investigated, particularly in the Carnmenellis granite in Cornwall. Three boreholes drilled in the granite to depths of over 2 km have been connected by developing natural fractures. Water circulation between the boreholes and through the fractured rock has been successful.

Summary The instrumentation and techniques developed for the investigation of fissure-flow in consolidated aquifers are described and illustrated by three case histories. The use of closed-circuit underwater television inspection of boreholes is outlined and consideration is given to the implications of flow rates by analyses of the tritium contents of some water samples.

Summary Groundwater derived from the Lower Greensand of the London Basin has been ‘dated’ by the use of tritium and carbon-14 techniques. The data indicate that replenishment from the northern outcrop is feasible but that movement from the southern outcrop is extremely slow and possibly restricted.

Summary Preliminary results are presented of a multi-authority review of the water pollution hazard represented by 2494 landfill sites in England and Wales. Of these, desk studies indicate that only 51 represent a serious pollution risk to major or minor aquifers. River authorities have classified 80 sites as being unacceptable for future use out of 714 locations they have examined. In defining provisional guidelines for the selection of landfill sites, a generalized threefold classification of wastes is proposed. A policy of confinement for hazardous wastes is recommended until and unless further research enables adoption of a less rigorous system. A flow diagram is provided for use in site selection.