Take a little water with it: a century of hydrogeology

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From: Wilson, H.E. Down to earth - one hundred and fifty years of the British Geological Survey. Edinburgh:Scottish Academic Press, 1985.
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XI Take a little water with it: a century of hydrogeology. Chapter-head sketch by Robery Geary.

XI Take a little water with it: a century of hydrogeology[edit]

Perhaps the most significant contributions to human welfare from the science of geology have been in the study of underground water supplies, a field pioneered by the Geological Survey more than a century ago. As with all innovation, the initial impetus came from a few people and though Flett and Bailey gave the credit to William Whitaker, two of his colleagues, Joseph Lucas and Charles de Rance, seem to have been given less recognition than they deserve.

Lucas was ten years younger than Whitaker and spent most of his nine years on the Survey working in Yorkshire. He retired in 1876 and practiced as a water engineer for a further forty years in the south of England. His obituarist describes him as the first to emphasise the need for systematic surveying of all sources of underground water and he first used the term 'hydrogeological' in 1874. A year after his retirement he published a paper on 'The artesian system of the Thames Valley' which contained a map showing the underground contours of the water level in the Chalk, south of the Thames. A year later he published a second map extending these contours north of the river. These were the first-ever hydrogeological maps and Lucas must take credit for them.

De Rance was a year younger than Lucas and was Whitaker's colleague for twenty eight years, though for much of this time he was working in the north-west and north Wales. In 1874 he was appointed Secretary to a Committee of Enquiry into the 'Underground Circulation of Water', set up by the British Association to consider, initially, the New Red Sandstone and Permian, hut later to consider all the aquifers in the country. This Committee carried on for twenty years, chaired by Hull, Director in Ireland, and including Whitaker among its members. De Rance who, like so many of his contemporaries, was caught in the Geikie non-promotion trap and never reached the rank of Geologist, served on this committee with the Director-General's permission, for all of those twenty years.

In 1882 he produced a remarkable volume of six hundred pages, The Water Supply of England and Wales. It was published by an outside firm, Stanfords, and was not strictly a Survey publication. In his introduction he claims that it is based on his notes for contributions to two conferences on water supply, organized by the Society of Arts, and acknowledges the help of his Survey colleagues.

The volume is a comprehensive account of the water supply to every sizable town in the countries, arranged by river catchments, with notes on the geology as well as the actual mode of supply reservoirs, wells, etc — and must have involved a great deal of work in its compilation. It includes six hand-coloured maps which divided the country into 'Impermeable', 'Partially Porous', 'Super-pervious' (pervious rock overlain by impermeable beds) and 'Permeable' areas.

De Rance was the son of a Colonel in the French National Guard who fled to England on the establishment of the Second Republic in 1848 when the boy was one year old. He was appointed Assistant Geologist at the age of twenty-one and after thirty years without promotion he resigned — or, more accurately, was sacked for inefficiency and addiction to drink — and retired to Blackpool where he set up as a consultant in mining and water engineering. His obituaries described him as 'having lost his enthusiasm for science' and 'failing to fulfil his early promise', but it seems clear that he was, at least in part, a victim of Geikie's insensitive management. Part of his trouble was said to be a propensity for undertaking too much consulting work — but for a man who had to live, after thirty years' service, on 14 shillings (70p) a day, it would be hard to blame him.

There is no doubt, however, that Whitaker was the father of English hydrogeology. Appointed an Assistant Geologist in 1857, his work in the South-east of England was regarded highly by Murchison, who offered him a chance to work on some harder rocks which were then looked on — as they were for another hundred years — as 'real' geology. Ramsey, Director tor England and Wales, is recorded as saying that Whitaker was happier in the Mesozoic and Tertiary country and he was left in the South-east.

In 1875 he and Ramsey, then Director-General, went to Gibraltar to report on water supply for The Rock, but could only recommend exploration in the area beyond the North Front.

It is clear that Whitaker was Ramsey's man, for the annual report on staff compiled by Bristow in 1880 was less than complimentary 'Inadequate amount of work, difficult to move, obstructive and needlessly controversial, a kind of mutineer. Does not obey instructions. Makes absurd excuses for staying far too long in one place'.

Nonetheless Whitaker was made a District Surveyor in 1882 at the age of forty-six and it was doubtless expected that the mutineer would calm down when he reached the quarter-deck. Far from it!

This picture is very different from that painted of Whitaker by later chroniclers — 'the friend of all and enemy of none' — but it shows us a strong-minded and determined man who saw the value of his work and refused to have it compromised. Certainly his heritage is worthy. His interest in water supply from wells must have started early in his career and his collection of well records from water companies, well-sinkers and local borough surveyors must have begun soon after his appointment. In 1872, fifteen years after he started work, Whitaker was the sole author of the fourth and last of the first series of Geological Survey Memoirs, The Chalk and Tertiaries of the London Basin, which included 150 pages of well records. Thereafter all the Memoirs produced in the South-east had sections on water supply and well records — the latter to the extent that the conventional geological hierarchy began to regard them as overloaded with non-geological minutae. The 'second edition' of the 1872 Memoir — now titled The Geology of London — in 1889 had 352 pages of well records, which necessitated its publication in two volumes!

What discussions and dissension there may have been about this we do not know but suffice it to say that in 1899 there appeared the first Water Supply Memoir — The Water Supply of Sussex from Underground Sources — compiled by Whitaker (who had retired in 1896) and Reid.

Whitaker had a considerable private practice as a water engineer after his retirement and continued to provide information to the Survey. He was sole or joint author of twelve Memoirs, and contributed to three others, in the period between his sixty sixth and eighty ninth years. He lived in Croydon and was an early conservationist, leading a battle against the Croydon Corporation's attempt to demolish the Whitgift's Hospital. Bailey quotes the apocryphal tale that the elderly, white-bearded, Whitaker would accept the presidency of any local society which would promise to publish his well records. His prolific publication in official journals makes this seem unlikely but his obituary records his generous assistance to amateur geological societies and his 'unusually free and unconventional contributions' to the discussions of the Institute of Water Engineers. Clearly he was a notable character!

The Water Supply of Sussex inaugurated a series of Water Supply Memoirs which continued for thirty nine years, during which twenty eight were published, some under the title 'Wells and Springs of ....'. This series was based on the records collected on a County basis and was the responsibility of the field units concerned. One interesting point is that in The Water Supply of Essex, published in 1916, Dr J C Thresh, joint author with Whitaker and Medical Officer of Health for Essex, proposed that the softening of groundwater in the Chalk and Thanet Beds below the London Clay is due to what is now referred to as ion exchange, a chemical process now accepted as the explanation of this change typical of groundwater in sedimentary aquifers.

In 1932 the British Association appointed a committee, including Bernard Smith, Assistant Director, England and Wales, to inquire into the position and prospects of an inland water survey. It decided that such a survey was desirable and, with the impetus given by the severe drought of 1933 and 1934, a joint approach by the Institute of Civil Engineers and the British Association to the Minister of Health produced an 'Inland Water Survey Committee' in 1935. The first report of this Committee in 1936 recommended that work on underground water could best be done by the Geological Survey and that DSIR had agreed that the Survey would assist in this work.

As a result of this agreement the Water Department was established in 1936, the first new and dedicated unit in the Survey, save for the old-established Petrography and Palaeontology departments. This new department comprised two members; F H Edmunds and T R M Lawrie. In response to the Ministry of Health's representation, the County system of data collection was abandoned and replaced with one based on the one-inch geological maps. Good progress in collecting and correlating records led to the recruitment of two more staff for the new department, but war broke out in 1939 before it could publish any of its results.

The only publication on groundwater between 1936 and 1939 was the last revision of The Water Supply of the County of London by S. Buchan of the South of England Field Unit. In this, for the first time, location diagrams gave the sites of all recorded wells. After its publication in 1938 Buchan used this memoir as the basis for a plan for the emergency water supply of the city from private wells.

The outbreak of hostilities in 1939 led to the construction of enormous numbers of army camps and airfields, in the South and East of England in particular, and brought a remarkable increase in official interest in groundwater supplies.

From the first winter of the war a large proportion of the Survey staff — 27 out of a total of about 50 in all — were engaged in ground-water work, under a plan devised by Eastwood, Assistant Director for England and Wales, who foresaw theneed. A systematic collection from water companies, well drillers and consultants of all available information, freely given, was followed by field investigation to locate accurately all well sites and details of water levels, yields and other relevant facts. Virtually all London-based members of the geologist staff spent the first winter of the war 'commercial travelling' the roads of England, all leave forgotten in the emergency. A H Noble, who had been a member of staff before the 1914-18 war, volunteered to help and came out of retirement to site and record wells over an area of several hundred square miles in the South-west. During the war fifty six parts of sixteen Wartime Pamphlets dealing with water supply were published, 13,630 well records filed and reports produced on 735 sites for the Army, Air Ministry and the Ministry of Works.

There is no doubt that the foresight of Bailey and Eastwood in arranging the collection of the basic data, before the information was urgently needed, allowed the rapid response to the national need when it became apparent, and was probably the Survey's most important contribution to the war effort.

During the build-up to D-day, when the south of England was the base for many hundreds of thousands of troops, the field units were heavily involved in dealing with water supply problems for military camps. Buchan was also involved with W B R King, an ex-member of the Survey, who was Chief Geological Advisor to Supreme Headquarters, Allied Expeditionary Force, in the preparations for the Normandy invasion and its aftermath.

By the end of 1945 McClintock, who had succeeded Bailey as Director, was able to report that as a result of war-time efforts, eight of the old series of County Water Supply Memoirs had been completely replaced and thirteen had been updated, apart from new information in areas which had never been recorded before.

The reforming ideals of the post-war Parliamentary legislation included the Water Act of 1945. In retrospect, this piece of legislation may be regarded as a watershed for hydrogeology in the UK, for it marked a change of emphasis to a more quantitative approach to the subject — a necessary step as the demand for water steadily increased in the post-war years during which mains supplies were extended to rural areas and the use of groundwater for irrigation became more widespread as its benefits were appreciated.

In detail the requirements of the Act influenced the work of the Water Department in several ways. As a result of Section 7 details of new wells and boreholes more than 50 ft deep had to be sent to the Survey and, following regulations issued in 1947 by the Ministry of Health under Section 6 of the Act, returns of annual abstraction from major wells had to be made at the end of October each year, together with rest and pumping water levels and the yields of the wells. The first returns were received in October 1948 and continued each October until this section of the Water Act was repealed by the Water Resources Act of 1963. Analysis of the data provided the first reliable indication on a national basis of the use of groundwater and the consequences of its abstraction.

The Water Department was deeply involved in providing the basic information required by government departments to implement the provisions of the Water Act so far as these concerned groundwater. The collection of data about wells and aquifers, accelerated during the War, received a new impetus and the data for many areas were published in a Well Catalogue Series of the Water Supply Papers of the Geological Survey. The conservation and protection of groundwater resources became increasingly important. Under Section 14 of the Act, areas where resources were over-developed, or where this was anticipated, were defined and abstractions were controlled by licences issued by the Ministry of Health and subsequently the Ministry of Housing and Local Government. The advice of Water Department geologists was sought and given when the areas and their boundaries were being defined. In fact the Department's Head was adviser on groundwater to both Ministries.

The successful operation of a groundwater licensing system required reliable information about the nature and extent of major aquifers and the amount of natural recharge, as well as abstraction from wells. As a consequence considerable efforts in the 1950s were directed towards assessing the groundwater resources of the main aquifers and many reports were prepared which were subsequently placed on open-file.

The Water Department was concerned with testing all major new public supply and industrial wells before licences were granted by the Ministry of Housing and Local Government. Following these tests the Ministry was advised as to the most appropriate long-term yield and the considerations that should be attached to the licence.

This involvement in the administration of the Water Act led to research in a number of fields. Jack Ineson began applying to British aquifers the methods proposed by Theis and Jacob in the USA for the analysis of groundwater flow to wells. The work had a direct bearing on the well-testing programme referred to above. It was concerned with evaluating the properties of aquifers, suggesting suitable well-spacing as well as defining 'safe-yields' from wells of appropriate diameters. It also led to an understanding of the basis for the regional variation of the transmissivity of the Chalk.

The studies of well hydraulics led to a need for more sophisticated instrumentation to assist in understanding the finer points of groundwater flow. Automatic water level recorders were increasingly used and, in co-operation with local authorities and industrial companies, the Water Department eventually established an observation-well network of some 80 wells, principally in the Chalk but also in the Triassic sandstones and other important aquifers.

David Gray began applying geophysical techniques to groundwater problems. Downhole electrical resistivity logging enabled him to recognise a number of 'marker bands' in the Chalk with apparent stratigraphical significance, initially in Hertfordshire and ultimately throughout the Chalk outcrop and subcrop. The stratigraphical significance was confirmed when the Survey drilled the Fetcham Mill Borehole, near Leatherhead, in 1960-61. Continued development of instrumentation led to downhole temperature, conductivity and flow metering systems that were particularly appropriate for groundwater studies. These instruments provided a much greater understanding of the nature of flow in the fissured aquifers that provide the principal resources in the UK.

The chemical quality of groundwater was investigated during the course of the surveys of groundwater resources and the regional variation of the principal constituents was described for the major aquifers, extending the work of Thresh referred to earlier. The problem of saline intrusion in coastal areas was recognised and the extent of the intrusion was defined in Lincolnshire, the north bank of the Humber, the north Kent coast and in other areas.

In 1959 the Ministry of Housing and Local Government began a series of hydrological surveys of the major catchments in England and Wales and the Water Department was responsible for the groundwater content of these reports. The studies required reliable estimates of groundwater resources. Much effort was applied in the 1950s and early 1960s, in co-operation with the Meteorological Office, to the problem of estimating natural recharge to aquifers. As the development of groundwater increased, the need for more reliable figures assumed greater importance. Another factor of increasing significance was the relationship between surface and groundwater. The abstraction of groundwater began to have a noticeable impact on river flows, especially during dry periods such as occurred in 1959. The relationship between groundwater and river flows may be perfectly obvious now, but at that time it was a subject of heated debate and was far from obvious to many engaged in the water industry and its administration.

The post-war build up of the Water Department was led by Steve Buchan from 1945 until 1960 and then by Jack Ineson when Buchan was promoted to Head, Special Services Division. The scientific staff had increased to about ten in 1965. There were also a number of attractive young ladies who looked after the records, assisted with pumping tests and maintained water level recorders in the field. The staff of the Department were immured on 'The Bridge' — the two-storey link with the Science Museum — and eventually also in a glass penthouse on the roof of the office block behind the Museum.

The extent of the contribution that the Department made to the administration of the Water Act can be judged by the fact that eight of the staff were on the complement of the Ministry of Housing and Local Government which bore their costs. During this period an important aspect of the work was answering enquiries — both major and minor — from water companies, industrial concerns and the general public, particularly farmers. The advice to farmers was provided as a service to the Ministry of Agriculture, Fisheries and Food. In the early 1960s some 1200 enquiries were dealt with each year.

It is amusing to recall that Bailey records the difficulty he had in 1938 in getting the field staff to agree that the new Water Unit should deal with routine groundwater enquiries. By the end of the 1950s they were glad to leave most of them to the 'Water Cart'!

The Water Resources Act of 1963 marked a turning point in the history of the Water Department, though not immediately. This Act transferred the bulk of the routine assessment of groundwater activity to the new Water Resources Board and the River Authorities, and these new bodies — as the National Coal Board had done a decade earlier — wooed away several of the Survey staff, including the head of the unit, Jack Ineson, who went to the Water Resources Board in 1965.

Full implementation of the Act did not take effect until 1966, when the transfer of staff, and of enquiries relating to water resources and management, to the Water Resources Board changed the emphasis of the work of the group. Now under David Gray, it was directed towards groundwater and the rocks through which it flowed rather than towards water-supply problems. The curation of well records continued but the main effort was directed towards a comprehensive research programme involving the creation of hydrochemical and aquifer-property laboratories and the introduction of mathematical modelling techniques.

These developments enabled the unit to tackle fundamental as well as applied research and occurred at the same time as the merger of the Overseas Geological Surveys and the home Survey.

Since the thirties the work of geological surveys in the colonies and since 1947, of Overseas Geological Surveys and the surveys in the countries of the new Commonwealth, had been much concerned with groundwater. In its new role the Water Department, to be renamed the Hydrogeology Department in 1967, was comprehensively equipped in hydrogeological terms and was able to offer a service to the new Overseas Division which was soon taken up. Overseas projects developed from advisory visits to territories such as Cyprus and Bahrain on behalf of British Technical Aid programmes to an investigation of groundwater in Libya, financed by British Petroleum and Hunt International Petroleum. This project continued for three years and was followed by further contracts with oil companies and the Libyan Government.

Applied hydrogeological studies on behalf of Overseas Development Administration (ODA) grew to such an extent that a special Hydrological Adviser, Dr E P Wright, was appointed. The work for which he is responsible now forms a major part of the Unit's activity and occupies not only staff in the field but also their colleagues in the hydrochemical, physical properties and groundwater modelling laboratory.

In 1968 a successful pilot study at the Atlas Computer Laboratory of the Science Research Council was carried out on the computerization of well-records and for several years thereafter parties of 'vacation students' laboured to convert the archive to metricated and machine-readable form — a programme not yet complete.

This involvement with the new science of computing led to the first stages of the formation of a Computer Unit being trusted to the Head of the Water Department.

The mid-sixties saw the rapid development of more sophisticated methods of research. The use of isotopes for determining relative ages of groundwater by '4C and rates of increment by the analysis of thermonuclear tritium was paralleled by the study of trace-element hydrogeochemistry and more sophisticated logging of boreholes by electrical methods. Experimental work on infiltration and recharge of aquifers included the construction of large lysimeters in England and in Cyprus. In 1970 the first work on core analysis of specimens from North Sea hydrocarbon wells was undertaken for the Department of Trade and Industry in the Aquifer Properties Laboratories; and work now continues under the auspices of the Department of Energy.

Work overseas continued to increase and far-flung territories such as Chile, Nepal and the Gilbert and Ellice Islands appear in the Annual Reports.

At home one interesting study was on the effect of the proposed Thames flood barrage on ground water in the flood plain and, for example, the effects of changed levels on the shallow tunnels of the District and Circle lines of the Underground Railways. A considerable amount of work was carried out on groundwater supplies in Northern Ireland at a time when 'The Troubles' reached their peak, and Hydrogeological Department staff were among the few visitors to the Belfast office.

In 1972 the Department of the Environment commissioned a study of the risk of pollution of water supplies by leachate from waste disposal tips — an activity which was to assume considerable significance in the following decade.

The introduction of the Rothschild recommendations in 1973, therefore, found the Hydrogeological Department already well acquainted with the problems of commissioned research and even in the first year of the new dispensation about half of its work was commissioned by DOE and the Overseas Development Administration.

The DOE work was increased by a new commission to continue and expand the study of waste disposal hazards, in association with the Atomic Energy Research Establishment at Harwell. In 1974 a group of IGS staff were transferred to an office established in the Harwell Complex to facilitate liaison on this work with the Hazardous Materials Service of the UK Atomic Energy Authority.

A new Water Act was implemented in the same year combining the River Authorities, most statutary water undertakings and sewage disposal authorities into nine Regional Water Authorities and a Welsh National Water Development Authority, a reorganisation which involved the Department in a lot of liaison work with the new organisations.

As in the rest of the Institute, the first years of commissioned research produced an expansion of staff and activities, and 1975 was the start of work on nitrates in groundwater and, in St Lucia, on the study of geothermal energy. The staff, now over fifty strong under John Day, were accommodated in prefabricated buildings on the roof of the museum building and the transfer of some activities to the Institute of Hydrology building at Wallingford was suggested. In the Director's Report for that year there was a statement of the role of the Unit which merits repetition:

The overall objectives of the work of the Hydrogeological Department are to investigate in theory and in practice, all aspects of fundamental research (and many applied aspects) into the behaviour of groundwater, the occurrence of aquifers, ,ind the physiochemical interactions between the two in both unsaturated and saturated zones; and following interpretation, to publish the results.

The location of the Environmental Pollution Section at Harwell two years earlier as a working convenience proved valuable, when as part of an EEC project in 1976, it was asked to undertake research on the suitability of geological formations as the sites of repositories for the disposal of radioactive wastes. The British part in this EEC programme was to examine the feasibility of disposing of high-level radioactive material in crystalline rocks and work was proposed in three areas underlain by granite complexes — Strath Halladale in Caithness, Loch Doon in Galloway and Cheviot. Only in Caithness was work able to proceed — in the others local planning authorities refused permission for trial boreholes and expensive and protracted public enquiries had to be held.

The situation was compounded in 1980 when a further stage of radioactive waste disposal investigation was commissioned by DOE, this time into possible repositories in argillaceous rocks. The areas designated for this work were in rock of both Paleozoic and Mesozoic ages — Somerset, Worcester and Leicestershire for the latter, and an area in mid-Wales for the former.

By this time the anti-nuclear lobby was well organised and protests were immediate and vociferous. Public enquiries in Ayr and Newcastle in 1980 and at Loughborough in 1981 were prolonged affairs, and a severe ordeal to John Mather, head of what had become, in 1979, the Environmental Protection Unit. Though IGS and DOE witnesses repeatedly made the point that the proposed study was only of the feasibility and safety of using deep repositories for high-level waste the opposition insisted on using the term nuclear 'dumping' and highly emotive appeals were made to the public about hidden poison. The facts that the waste existed in vulnerable surface tanks in Cumberland and that the proposed work was to make certain that it could be contained in complete safety, were dismissed as irrelevant.

The degree of political pressure became so high that in 1982 the government capitulated and announced that, as the feasibility had been established by work in other countries, the geological programme would be reorientated to confirm the applicability to the UK of the findings of research from other countries', and would be confined to desk studies and laboratory work. Though the public enquiries had recommended that the planning applications should be allowed these results were overruled by the Secretaries of State and appeals against planning refusals in Somerset and Worcester were abandoned.

In Wales, where no planning application had been made, though the area concerned had been delineated (in a published article designed to allay public concern!), the pressure generated by the environmental and nationalist lobbies was such that it required yet another public enquiry in Dolgellau (Gwynedd) to get permission to put down a few shallow boreholes for mineral reconnaissance purposes. At this enquiry allegations were made that this was an underhand way of getting information for the Atomic Waste programme, and though many of the protesters admitted, outside the enquiry, that they believed the IGS witness, they could not forbear using the enquiry as a forum for anti-nuclear protest!

This use — or manipulation — of public opinion was probably the first time that the Survey has been deflected from a research programme since Whitaker's public relations exercise in Hampshire almost a century ago.

Since the abandonment of the active UK programme in the field, the Environment Protection Unit has been continuing laboratory studies for the EEC, related to heat-generating wastes, particularly in the fields of high pressure/temperature radiochemistry. Work also continued on the result obtained by studies on the boreholes atAltnabrec in Caithness — the only site on which drilling took place and, of course, the original remit to study the hydrogeology of land-fill sites has continued. The unit was renamed the Fluid Processes Research Unit in 1983.

To return to the Hydrogeology Unit, as it was renamed in 1977: the Hydrogeochemical Section, which had occupied inconvenient converted office accommodation on the top floor of the Exhibition Road building, was moved in 1977 to the Maclean Building on the Institute of Hydrology site at Wallingford, in Oxfordshire, where a new air-conditioned laboratory suite was provided. In 1978 the Aquifer Properties Section followed, at which stage the large unit, over sixty strong, was in three near-equal sections in three locations.

The separation of the Environment Protection Unit in 1979 was followed by the move of most of the rest of Hydrogeology to Wallingford in 1980, leaving only a small group in London mainly concerned with the National Well Record Collection.

The location of the whole scientific effort on the Institute of Hydrology campus at Crowmarsh was initially for the sake of convenience and available accommodation. In 1983 however, the position of this unit was described as under NERC review and it seemed possible that after 111 years of work on ground water, responsibility for research in hydrogeology could be transferred to another Institute.

The proposal was finally rejected in 1984 and hydrogeology remains with the Survey. The geology of ground water cannot be divorced from the study of rocks and no doubt, when NERC is long forgotten, the successors of the Geological Survey will continue to be concerned with it.

It is interesting to note that hydrogeological enquiries, originally an IGS task since the days of Whitaker, were transferred to the short-lived Water Resources Board in 1966, thence to the Central Water Planning Unit of the Department of the Environment and finally back to Hydrogeology Unit in 1980.

Geothermal energy[edit]

The exploitation of the enormous reserves of heat energy in areas of recent vulcanism goes back for many hundreds of years — the Maoris in New Zealand using hot springs for cooking, the Icelanders using hot water for heating — but the possibility of using geothermal energy on an industrial scale dates from the 1950s when, in New Zealand, Italy and the USA the idea of generating electricity from geothermal steam was considered, developed and brought into production. Following the Arab oil embargo in 1973, the realisation that the world's energy resources were finite directed attention to alternative sources of energy — the so-called 'renewables' with which geothermal energy is generally included.

The then Director, Sir Kingsley Dunham, prepared a paper in 1974 for the government reviewing the prospects for geothermal energy in the UK, and in 1977 the Institute was invited by the Department of Energy, with support from the Commission of the European Economic Community, 'to investigate the geothermal potential of the UK'. A multi-disciplinary group was formed, comprising geologists, geophysicists and hydrogeologists, with support from chemists and mathematicians, to undertake this task which extended over the next seven years.

The potential for hot water (low enthalpy) resources was examined in deep on-shore Mesozoic and Upper Palaeozoic basins and the Permo-Triassic sandstones were identified as the aquifers with the best prospect. Deep exploration wells were drilled to test the sandstones at Marchwood near Southampton and at Larne in Northern Ireland. Although the Survey had been involved with deep drilling projects in connection with exploration for oil and coal, the geothermal work marked a new departure, as it was the first time that the Survey had been responsible for drilling, completing and testing deep production wells. To carry out this task, which was on behalf of the Department of Energy and the EEC, staff mainly from the new Deep Geology Unit, with some outside consultant advice, had to learn the techniques of well-site geologists with a very short apprenticeship.

The Marchwood Well was 2615 metres deep and the Lame Well 2880 metres. Hot water was not proved in economic quantities at Larne but the Marchwood Well yielded 30 litres per second at a temperature of 73C. A second well was drilled in the centre of Southampton, again for the Department of Energy and the EEC. Its long-term yield is predicted as over 10 litres of water per second at 75C and is expected to be used to heat civic offices and a swimming pool in Southampton.

Hot impermeable rocks at depths of more than three or four kilometres are also potential sources of geothermal energy if suitable heat exchange areas can be created at depth between two or more wells by hydraulic fracturing.

The technology for developing 'hot dry rock' resources is being investigated by the Cambourne School of Mines at their test site in the Carnmenellis Granite in Cornwall. Apart from technical advice, including secondment of a member of the Engineering Geology Unit, the Survey's role in this field was to identify other areas suitable for development and to quantify the potential. Initially studies were concentrated in northern England and the eastern Highlands of Scotland but these were extended to assess the prospects under some major urban areas. By 1984 a first assessment of the geothermal resources of the UK had been published, representing the end-product of a major programme of work.

Although the marked increase in energy prices in 1973 gave the impetus for these studies of the hot water (low enthalpy) and hot dry rock geothermal potential of the UK, natural geothermal steam fields (high enthalpy geothermal resources) had been explored and developed for many years in areas of recent or active volcanic activity. While in the years before the early 1970s the Survey had not been involved in high enthalpy geothermal exploration, much of the scientific wherewithall existed. A request from the Overseas Development Administration in 1973 to assist in borehole location and steam production tests on St Lucia in the Caribbean resulted in the mobilisation of staff from a number of units and the development of interest in a subject which requires application of a wide spectrum of geological sciences — vulcanology, hydrothermal geochemistry, exploration geophysics, and not least hydrogeology. Because of the paramount practical importance of assessing the geothermal reservoir, involving concepts similar to those used in the assessment of groundwater aquifers, co-ordination of the Survey's high enthalpy geothermal projects became vested in the Hydrogeology Unit. Following St Lucia, studies continued with a major exploration project in Panama (1976-1981) and preliminary assessments elsewhere, notably Montserrat (1976) and Vanuatu (1982). Staff from several units applied their skills in these new geothermal ventures, but perhaps the first project in St Lucia was the biggest step for the Hydrogeology Unit and the Survey for, while conceptually related, production of superheated steam at mass flow-rates of 5 kg/s from boreholes sited near an active volcanic centre is a far cry from testing water boreholes in the comfort of rural England.