Abstract The military aspects of hydrogeology can be categorized into five main fields: the use of groundwater to provide a water supply for combatants and to sustain the infrastructure and defence establishments supporting them; the influence of near-surface water as a hazard affecting mobility, tunnelling and the placing and detection of mines; contamination arising from the testing, use and disposal of munitions and hazardous chemicals; training, research and technology transfer; and groundwater use as a potential source of conflict. In both World Wars, US and German forces were able to deploy trained hydrogeologists to address such problems, but the prevailing attitude to applied geology in Britain led to the use of only a few, talented individuals, who gained relevant experience as their military service progressed. Prior to World War II, existing techniques were generally adapted for military use. Significant advances were made in some fields, notably in the use of Norton tube wells (widely known as Abyssinian wells after their successful use in the Abyssinian War of 1867/1868) and in the development of groundwater prospect maps. Since 1945, the need for advice in specific military sectors, including vehicle mobility, explosive threat detection and hydrological forecasting, has resulted in the growth of a group of individuals who can rightly regard themselves as military hydrogeologists.

Abstract Geomorphological features associated with groundwater discharge zones can affect ground conditions so greatly that they determine the outcomes of battles. Two cases in point are found in Scottish history: (i) despite outnumbering their English foes, the Scots lost the Battle of Flodden Field (9 September 1513), largely due to failing to identify the presence of marshy ground associated with an area of groundwater discharge; (ii) on 21 September 1745, the Jacobites defeated the Hanoverian army at Prestonpans by finding a way around marshland corresponding to a regional groundwater discharge zone, upon which the Hanoverian commander had been relying as a natural defensive feature. Analysis of both battlefields drawing upon present-day understanding of local stratigraphy and hydrogeological conditions allows identification of the specific groundwater discharge patterns that largely determined the outcomes of these two emblematic battles. At Flodden, the proximal source of groundwater discharge is Quaternary outwash gravels, distally fed from sedimentary strata (Cementstones) of lowermost Dinantian age. In the case of Prestonpans, the groundwater emerges from particularly arenaceous coal-bearing strata of Namurian age. Both case studies suggest that military commanders selecting advantageous terrain could benefit from consulting hydrogeologists who are familiar with the intricacies of groundwater geomorphology.

Abstract In the latter part of the 18th century some of Britain's eastern coastal defences, although strategically well-positioned, were vulnerable because of the lack of a secure water supply. The military engineer Captain Thomas Hyde Page was tasked with identifying any water resources within the confines of the forts and garrisons that might be developed. At Sheerness he supervised the sinking of a deep, large-diameter well through the London Clay, which tapped water in underlying sands. The idea of a deep well was possibly influenced by the results of deepening a well at nearby Queenborough Castle some 60 years before. At Landguard Fort he constructed an infiltration gallery that skimmed water from the upper surface of a thin freshwater lens. At Harwich he sank two simple shallow wells to abstract water from beneath the London Clay. At each locality he used a different solution appropriate to local hydrogeological conditions. Although some of his ideas were outdated, he recognized that fresh water appeared to be floating on underlying salt water and speculated that this might be the result of differences in specific gravity. His work was important in publicizing the use of groundwater and foreshadowed the major developments of the following century.

Abstract The first British Army hydrogeologist to be deployed as such on a battlefield was Lieutenant W.B.R. King, in June 1915 on the Western Front. There, the British Expeditionary Force, in Belgium and northern France, expanded at its peak to five armies: 1.5 million men and 0.5 million horses/mules, each man/animal requiring on average 10 gallons (45 l) per day of potable water. A ‘Water Boring Section Royal Engineers’ was eventually raised for each army, equipped with American-made ‘portable’ drilling rigs, and utilizing air-lift pumps. These innovations and King's pioneering ‘water supply’ maps facilitated the development of the British Army's first operational ability to exploit groundwater from deep aquifers, primarily those in Cretaceous Chalk, by drilling >470 boreholes. Additionally, in 1915, a report by three ‘British’ Geological Survey officers helped guide limited boring within Allied amphibious landing areas on the Gallipoli Peninsula, Turkey. A civilian water adviser, Arthur Beeby Thompson, transferred from Gallipoli to the Balkans in January 1916 and thereafter used geology to guide significant groundwater abstraction by siting 125 military boreholes and 211 Norton tube wells. From 1915, the Director of the Geological Survey of Egypt, W.F. Hume, provided similar guidance for campaigns from Egypt into Palestine.

Abstract The success of military mining is inherently controlled by subsurface conditions. Military mining may be offensive (i.e. intended to breach enemy fortifications at the ground surface by explosive detonation), defensive (counter-mining to destroy enemy mine galleries) or passive (to provide troops with underground protection from bombardment). The geology of the British Sector of the Western Front in World War I varied from the Palaeogene–Neogene sediments of the Flanders Plain in Belgium to the late Cretaceous chalks of Picardy and Artois in northern France, all with intermittent Quaternary cover. In Flanders, British mining operations commenced in late 1914. Passive mining created shallow dugouts and isolated shelters, and offensive mines also tended to be shallow, rapidly dug, and of low engineering impact. By 1915, with the war above ground now largely in stalemate, the impetus for more extensive mining grew, leading to the high point of offensive mine warfare with detonations that initiated the Battle of Messines on 7 June 1917. Development of mine warfare required engineering innovations such as ‘tubbing’ to deal with major groundwater problems presented by variation in the permeability of the sediments, as can be illustrated by two examples from the battleground of Ypres (Ieper).

Abstract The German Army developed a military geological organization during World War I largely as a response to near-static battlefield conditions on the Western Front, in Belgium and northern France. In 1916 it was assigned to support military survey, but in late 1918 it was reassigned to the engineer branch of the Army. It contained over 350 geologists and associated technicians by the end of the war. Military geologists contributed advice on engineering geology and hydrogeology (principally on water supply, but also site drainage). They compiled a large number and wide range of groundwater prospect maps to guide military planning, at scales typically from 1:250 000 to 1:25 000. They contributed advice to guide effective use of groundwater by means of dug or bored wells, ‘Abyssinian’ driven tube wells, and protected capturing of springs. Field hygiene was of particular concern, and military geologists helped to avoid contamination of groundwater, for example by appropriate siting of cess-pits and cemeteries. A few officers made use of dowsing in attempts to locate groundwater, including at least one German in support of Ottoman Turk campaigns SW from Palestine towards the British-held Suez Canal, their Austro-Hungarian allies in campaigns south against Italy and in the Balkans, but with relatively insignificant success.

Abstract To drill boreholes for water supply, the Royal Engineers raised ten ‘Boring Sections’ between September 1939 and May 1943, eight in the UK, two in Egypt. While supporting campaigns in World War II, two deployed briefly to France, seven served widely within the Middle East (one of these in Iraq and Iran and later Malta, the others mostly operating from Egypt), one deployed to Algeria/Tunisia, four to Sicily and/or Italy (one of these onward to Greece), two deployed to support the D-Day Allied landings in Normandy and the subsequent advance via Belgium to Germany, and three served long-term in the UK. Greatest use was by Middle East Command, which at its peak had about 35 officers, 750 men and 40 drilling rigs assigned to water supply, and whose boreholes attained a cumulative length of some 40 km. The British Army used geology to help guide emplacement of boreholes in all these regions. Innovations included groundwater prospect maps at scales of 1:50 000 and 1:250 000, to help planning for the Allied invasion of Normandy and the subsequent campaign in NW Europe. Geology also helped guide groundwater abstraction by Indian Engineers in the Far East, and British/South African troops in East Africa.

Abstract In the early years of the Geological Survey, staff built up a considerable understanding of the movement of groundwater, and water supply memoirs were published from 1899. During World War I, one of the tasks of the Survey was to advise on the provision of water supplies. However, this emphasis did not continue when war ended, and it was not until the 1930s that interest in groundwater began to increase. An Inland Water Survey Committee was formed and the groundwater component of its work was entrusted to the Survey. A modest Water Unit was set up in 1937, staffed by members of Field Units on rotation, but limited progress was made. At the outbreak of World War II, attitudes changed and manpower was diverted to the systematic collection of groundwater data, published in a series of Wartime Pamphlets. At the end of the war, the Water Acts imposed significant obligations on the Survey and over the next five years the systematic collection and analysis of information became a professional operation. The Unit became a Department with its own permanent staff. The war acted as a catalyst highlighting problems and initiating action to the benefit of the water industry.

Abstract Problems experienced by armoured fighting vehicles (‘tanks’) crossing soft ground became apparent during World War I. These were avoided early in World War II by the use of ‘going’ maps in North Africa from 1940 to 1943, but when operations moved to NW Europe it was realized that there would be the additional problem of changes in ground conditions due to variations in soil moisture according to the weather. This led to an investigation into factors controlling the movement of tracked vehicles over water-softened ground, beginning in July 1944 with the establishment of the ‘Mud Committee’, tasked to consider problems in light of recent developments in the (then) new science of soil mechanics. Contemporary ideas, as applied to building and road construction, were found to be inapplicable, and attention was therefore focused on empirical trials. The Committee faced the constant problem of balancing the requirement for short-term results with the need for long-term research. As a result, it failed to meet many of its objectives by the end of hostilities, but its work did provide a sound basis for the development of a method of classifying soils for military purposes and for future work on track design.

Abstract A uniformed geological organization was re-created within the German Army by the start of World War II and developed to comprise 40 centres or teams by 1943. Many specialist geotechnical maps and reports prepared by these military geologists have survived the war as part of the Heringen Collection; some remains in the USA, but other parts are in Germany, notably within the archives of the Bundeswehr Geoinformation Office. German armed forces made use of about 400 geologists in total during the conflict, mostly in the Army. Many of their tasks involved groundwater studies, some including the preparation of groundwater prospect maps. Temporary water supplies were set up during mobile campaigns by planning efficient use or enhancement of existing civilian resources, supplemented by driving shallow ‘Abyssinian’ tube wells, for example, in Operation Sea Lion, the invasion of SE England planned for September 1940 but ultimately cancelled. Sustainable long-term supplies in militarily occupied territory were achieved by rigorous data collection and programmes of well drilling, spring capture or percolation gallery construction, one example being on the Channel Islands between 1940 and 1945. Geophysics sometimes aided the geological and borehole studies that guided deployment of well-drilling teams, for example, in 1941/1942, to support German and Italian forces operational in North Africa.

Abstract The islands of Jersey, Guernsey, Alderney and Sark lie close to the Normandy coast of France. They expose a largely Precambrian crystalline basement of metamorphic and igneous rocks – Jersey and Alderney also expose some early Palaeozoic clastic sediments – and all have a thin but widespread Quaternary sedimentary cover. The three largest islands were progressively fortified by the British between the early 13th and mid-19th centuries, and by German forces during occupation in World War II, a legacy illustrated by the castles, forts and numerous German coastal fortifications that still adorn them. A German military geologist based on Jersey from mid-1941 to mid-1944, and a military geological team on Guernsey and Alderney during 1942, generated hydrogeological maps and reports that were then in advance of understanding of crystalline basement aquifers elsewhere in the British Isles. All the major documents have now been found in Germany, the USA and UK, although none survived on the islands themselves. Geological mapping and hydrogeological studies postwar under the auspices of the British Geological Survey were completed without access to German data. However, German and British data together now facilitate an appraisal of the heavily stressed aquifers on these small, hard-rock islands over an unusually long (65 year) timespan.

Abstract Over the past 100 years, hydrogeology has played a role in most military operations undertaken by the USA. The first significant application by US forces took place during World War I, on the Western Front. America's entry into World War II highlighted the need for military hydrogeologists once again, and a combination of civilian and uniformed hydrogeologists provided valuable support to the war effort, notably by terrain analysis. During the Cold War, the United States Geological Survey Military Geology Branch conducted military hydrogeological studies, and in 1985 the US Army Corps of Engineers created the Water Detection Response Team (WDRT) to provide hydrogeological expertise to military well-drilling units. During the Persian Gulf War of 1990–1991, groundwater was important for sustaining troops living in the northern Saudi Arabian desert. Operations in Bosnia and Kosovo later in that decade required the assistance of the WDRT in obtaining adequate groundwater supplies for base camps. Current military operations in Afghanistan rely on groundwater as a significant source for most US bases. In combination, uniformed and civilian geologists serving in a variety of roles to support American troops have located water supplies essential to the success of US military operations around the globe.

Abstract In 2003, three British reserve army geologists contributed hydrogeological advice to assist planning for the Coalition invasion of Iraq by predicting likely groundwater and drilling conditions. In consequence, 521 Specialist Team Royal Engineers (Water Development) was deployed in theatre soon after hostilities began, to provide a water supply infrastructure for British troops. However, a speedy end to combat, and concentration of British troops in southern Iraq where surface waters were the primary source of supply, necessitated only four new boreholes. Elements of 521 STRE deployed to Afghanistan in 2006, again with hydrogeological guidance, to enhance water supplies for a Provincial Reconstruction Team and Forward Operating Base (FOB), and to develop a water supply infrastructure for the main British operational base at Camp Bastion. Local contractors were used to drill 11 wells, each to over 100 m depth, in Quaternary alluvium. Subsequently, hydrogeology was used to guide successful groundwater development at four out of five FOBs, involving 28 new boreholes, minimizing risks associated with water supply by road or helicopter, and to facilitate expansion of Camp Bastion to accommodate a surge of Coalition troops. Tasks in Afghanistan have generated the most significant British military use of hydrogeology in recent years.

Abstract An army, the Bundeswehr , was created in the Federal Republic of Germany in 1956, from the 1960s supported by full-time geologists employed as civilians but with reserve army military ranks. A peak geologist strength (about 20) was achieved in the 1980s, to provide expertise that included hydrogeology. Roles in these Cold War years were confined to Germany, but included guidance to ensure that potable water would be available both to the civilian population and armed forces during a state of emergency, and the optimum siting of boreholes to supply water to military installations. In 1993, Bundeswehr troops deployed overseas, to support United Nations (UN) peace-keeping operations in Somalia. Military geological expertise was used to site wells that enhanced secure water supplies for German and other UN personnel, and the civilian population. In 1999, Bundeswehr troops were among those of the North Atlantic Treaty Organisation (NATO) deployed to Kosovo. Wells to supply water to German troops in Albania and Yugoslavian Macedonia prior to deployment, and in Kosovo itself, were drilled under civilian contract but military geologist guidance. From 2002, Bundeswehr troops joined coalition forces in Afghanistan. Well drilling was again guided by military geologist expertise, but contract drilling proved inadequate, so was supplemented by rigs operated by military engineers. These operations have proved the value to the Bundeswehr of retaining military expertise in both hydrogeology and well drilling.

Abstract The US Army has compelling needs for making hydrological forecasts. These range from tactical predictions of water levels and soil moisture, to strategic protection of both Army and civilian assets and environmental resources. This paper discusses the history of hydrological model development by the US Army Corps of Engineers (USACE) as influenced by changes in needs and technologies. It concludes with a description of the Gridded Surface/Subsurface Hydrologic Analysis ( GSSHA ™) model, a two-dimensional, structured-grid, physics-based hydrological, hydrodynamic, sediment and nutrient/contaminant transport model, developed over the past two decades, that is currently used by the USACE. The surface hydrology of the USA has been divided by the US Geological Survey into 21 major geographic domains that contain either the drainage area of a major river or the combined drainage areas of a series of rivers of similar character developed in one geographic province. Eighteen of the regions occupy the land area of the conterminous USA. Alaska, the Hawaiian Islands and Puerto Rico are separate domains. This approach provides a framework for the hydrological modelling discussed in this paper for sites within six of these regions. That the physics-based GSSHA modelling capability has so far been applied with success gives confidence in its more widespread application.

Abstract Finding explosive threats in complex environments is a challenge. Benign objects (e.g. rocks, plants and rubbish), ground surface variation, heterogeneous soil properties and even shadows can create anomalies in remotely sensed imagery, often triggering false alarms. The overarching goal is to dissect these complex sensor images to extract clues for reducing false alarms and improve threat detection. Of particular interest is the effect of soil properties, particularly hydrogeological properties, on physical temperatures at the ground surface and the signatures they produce in infrared imagery. Hydrogeological variability must be considered at the scale of the sensor's image pixels, which may be only a few centimetres. To facilitate a deeper understanding of the components of the energy distribution, a computational testbed was developed to produce realistic, process-correct, synthetic imagery from remote sensors operating in the visible and infrared portions of the electromagnetic spectrum. This tool is being used to explore near-surface process interaction at a fine scale to isolate and quantify the phenomena behind the detection physics. The computational tools have confirmed the importance of hydrogeology in the exploitation of sensor imagery for threat detection. However, before this tool's potential becomes a reality, several technical and organizational problems must be overcome.

Abstract History has repeatedly demonstrated the potentially negative influence of near-surface hydrology on military mobility. Increased moisture and saturation in soil results in a transition from solid to somewhat liquid states. As soil approaches the liquid state, the shear strength available for supporting traffic of ground vehicles or aircraft diminishes. Historical engagements elucidate the importance for armies to recognize soil conditions that could compromise manoeuvre. Since World War II, the US Army has pursued research aimed at equipping soldiers with the tools and knowledge needed to account for the impact of near-surface hydrology on mobility. Significant portions of the research have been focused on characterizing soil trafficability as a controlling factor in ground vehicle mobility and on developing methods for rapidly assessing soil conditions to ensure adequate bearing capacity for expediently constructed roads and airfields. In contrast, hydrological conditions can also produce extremely dry soil with potential for surface layers to break down under ground vehicle and aircraft traffic loadings, resulting in a propensity for extreme dust generation, an entirely different problem for military mobility that the research has also been addressing. Mobility problems associated with these adverse soil conditions have not been eliminated, but the research has produced significant advancements.

Abstract In 1989 the environmental restoration programmes conducted independently by the US Army, Navy and Air Force were rationalized to jointly support research and technology transfer in this important field. By 1994 cleanup efforts were concentrated in four main areas: site investigation, groundwater modelling, treatment technologies and the fate/impact of potential contaminants. Since 1994, technology development has moved forward rapidly. Groundwater monitoring wells have served as the conventional method of collecting groundwater samples, although direct pushed technologies are now providing a faster and cheaper alternative. A range of groundwater models has been supported and a model is being developed for the Army to forecast the fate and risk of constituents derived from munitions. Cleanup technologies are increasingly moving away from processes that remove sediment or groundwater to in situ solutions. These include range management using lime, the establishment of biologically active zones for indigenous microbes, and phytoremediation. The environmental fate of contaminants has been predicted using flexible models. Examples are given from a number of sites including the US Military Academy at West Point and Langley Air Force Base. Investment continues to support studies to provide safer, faster and better remediation of contaminants related to past military use.