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The Lower Greensand (LGS) forms the second most important aquifer in the London Basin but, being largely absent beneath the city itself, has received much less attention than the ubiquitous overlying Chalk aquifer. While the general directions of groundwater flow in the Chalk are well established, there has been much less certainty about flow in the LGS owing to regionally sparse borehole information. This study focuses on two hitherto uncertain aspects of the confined aquifer: the sources of recharge to the west-central London Basin around Slough, and the fate of LGS water where the aquifer thins out on the flank of the London Platform in the Gravesend–Medway–Sheppey area on the southern side of the basin. The application of hydrogeochemical techniques including environmental isotopes indicates that recharge to the Slough area is derived from the northern LGS outcrop, probably supplemented by downward leakage from the Chalk, while upward leakage from the LGS in North Kent is mixing with Chalk water to the extent that some Chalk boreholes on the Isle of Sheppey are abstracting high proportions of water with an LGS fingerprint. In doing so, this study demonstrates the value of re-examining previously published data from a fresh perspective.

Three types of thermal groundwater are known from the UK: warm springs (≤45°C), mine inflows (≤50°C) and deep basin waters (≤80°C). The warm springs depend on Carboniferous Limestone conveying water to sufficient depth (600–3000 m) to acquire a significantly higher temperature. The springs have residence times of a few thousand years, but also contain ≤5% modern groundwater. Their water quality is little threat to the environment; the main danger to the springs is construction activity near the emergences. Mine inflows significantly >20°C are known only from Cornish granite. High dissolved 4He has been interpreted as indicating long residence of the thermal component, but there is also modern water in the system, leading to uncertainty in the mean age. Unpredictable fracturing could hinder development of this resource, while the seawater-like salinity, combined with the presence of toxic metals, would require treatment or re-injection of the spent water to protect the near-surface environment. Mesozoic sedimentary basin brines reach temperatures >60°C, suitable for district heating. This resource is large and effectively invulnerable. However, these waters are generally more saline than seawater and, while disposal of spent brine could take place into the sea under favourable conditions, re-injection would be necessary for inland sites.

Groundwater plays a significant role in glacial hydrology and can buffer changes to the timing and magnitude of meltwater flows. However, proglacial aquifer characteristics or groundwater dynamics in glacial catchments are rarely studied directly. We provide direct evidence of proglacial groundwater storage, and quantify multi-year groundwater-meltwater dynamics, through intensive and high resolution monitoring of the proglacial system of a rapidly retreating glacier, Virkisjökull, in SE Iceland. Proglacial unconsolidated glaciofluvial sediments comprise a highly permeable aquifer in which groundwater flow in the shallowest 20–40 m of the aquifer is equivalent to 4.5 % (2.6–5.8 %) of mean annual meltwater river flow, and 9.7 % (5.8–12.3 %) of winter flow. Groundwater flow through the entire aquifer thickness represents 9.8 % (3.6–21 %) of annual meltwater flow. Groundwater in the aquifer is actively recharged by local precipitation, both rainfall and snowmelt, and strongly influenced by individual precipitation events. Significant glacial meltwater influence on groundwater within the aquifer occurs in a 50–500 m river zone within which there are complex groundwater / meltwater exchanges. Stable isotopes, groundwater dynamics and temperature data demonstrate active recharge from river losses, especially in the summer melt season, with more than 25 % of groundwater in this part of the aquifer sourced from meltwater. Such proglacial aquifers are common globally, and future changes in glacier coverage and precipitation are likely to increase the significance of groundwater storage within them. The scale of proglacial groundwater flow and storage has important implications for measuring meltwater flux, for predicting future river flows, and for providing strategic water supplies in de-glaciating catchments.

Mike Edmunds was a pioneer in modern applied hydrogeochemistry, helping to develop geochemical tools and their application to managing water resources. In a career span- ning almost 50 years, Mike made major contributions to water resource science as well as pro moting the role of chemistry in solving groundwater problems and championing the need to incorporate science into policy. There can be few hydrogeologists who travelled so extensively in order to study the vast range of groundwater environments of the world. Mike ’ s contribution to water scie nce was recognised through the many accolades he received including the Whitaker Medal in 1999, the O.E. Meinzer Award in 2009, and the Vernadsky Medal in 2010.