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This chapter examines how geology and climate create vastly different groundwater situations. Effective management of groundwater depends upon full consideration of these differences. The chapter begins with a distinction between confined and unconfined aquifers and a look at artesian wells, with a focus on Australia’s Great Artesian Basin. The characteristics of different rock types are illustrated by four basic aquifer rock types in sub-Saharan Africa. The chapter then turns to non-renewable aquifers in North Africa and Saudi Arabia. The fast-recharging Edwards Aquifer in Texas then provides a quite different story with its sensitivity to short-term climate variability and concerns about endangered species. The chapter concludes with a discussion of saltwater intrusion in coastal aquifers and the potential of brackish groundwater for water supply.

There is a common myth that deserts are extremely sensitive to perturbation. While it is true that tracks made decades ago can still be seen in certain desert areas, there are also large regions of deserts that show little negative impact of heavy use by humans. This paradox can be explained by considering the interactions between the high spatial and temporal variability in rainfall, and patterns of human disturbance. Desertification is of great concern in many parts of the world, yet people struggle to define it. Losses of agricultural productivity are associated with the process of desertification, although these can have other causes such as declining returns from certain agricultural products. Indeed, it is the long-term declines in productivity and ecosystem function that are most closely tied to desertification. These are usually caused by direct human intervention.

Among shallow subterranean habitats, representative communities of hypotelminorheic (Lower Potomac seeps, Washington, DC), epikarst (Postojna–Planina Cave System, Slovenia), milieu souterrain superficiel (MSS) (central Pyrenees, France), soil (central Pyrenees, France), calcrete aquifers (Pilbara, Western Australia), lava tubes (Tenerife, Spain and Lava Beds National Monument, California), fluvial aquifers (Lobau wetlands, Austria), and iron-ore caves (Brazil) are described. Among non-cave deeper habitats, communities of phreatic aquifers (Edwards Aquifer, Texas), and deep phreatic aquifers (basalt aquifers, Washington) are described. Among cave habitats, representative tropical terrestrial (Gua Salukkan Kallang, Sulawesi, Indonesia), temperate terrestrial (Mammoth Cave, Kentucky), chemoautotrophic (Peştera Movile, Romania), hygropetric (Vjetrenica, Bosnia & Herzegovina), anchialine (Šipun, Croatia), cave streams (West Virginia and U.K.) and springs (Las Hountas, Baget basin, France) communities are discussed.

This chapter describes the extent and formation of karst in Kentucky: how the dissolution of limestone by water shapes the underground and surface of over half of Kentucky; the ways that hydro geologists map karst aquifers, including illustrative examples. The beauty of caving in the Mammoth Cave area and throughout Kentucky karst is illustrated. The special challenges of construction and development on karst are discussed: karst flooding, cover-collapse sinkholes, maintaining water quality in karst.

Kentucky’s waterways carry a history of the landscape as well as life-sustaining water. Watersheds are any area of land draining water to a common water body, and the quality of the water body reflects human activity and natural processes. The Cane Run watershed is a polluted watershed in central Kentucky. A watershed-based plan was created by investigating the current status of the watershed and making plans to improve its conditions. Some progress has been made to improve the Cane Run watershed. Effective watershed-based plans require scientific inquiry as well as social considerations of the citizens in the watershed.

Much natural capital is common property – owned by no one. Important examples are water and fish. Such property is generally greatly overused – the lamentable histories of the American bison and the passenger pigeon illustrate the power of this tendency. Commercially valuable fish are today going through the same process. But there are ways of avoiding this, by establishing property rights or in other ways limiting access and usage. Such mechanisms have worked well for some fisheries and some aquifers, but fishing on the high seas is still out of control.

The chapter begins with looking at ways humans have dealt with drought—praying for rain, hiring a rainmaker, or hoping for the best. After World War II, the widespread availability of rural electrification, the deep turbine pump, and center pivot irrigation gave people the option of large-scale use of groundwater. This chapter provides an overview of how groundwater development has radically improved water and food security. The discussion then moves to the growing problems that have resulted from groundwater overuse in places such as the High Plains (Ogallala) Aquifer and the North China Plain. Recently, the GRACE (Gravity Recovery and Climate Experiment) satellites, which can provide precise estimates of changes in groundwater storage over very large areas, have helped draw attention to groundwater depletion around the world.

Managed aquifer recharge is a widespread and growing practice. In addition, using recycled water for groundwater recharge and water supply continues to grow as water resources are increasingly strained by population growth and climate change. Through a series of examples from around the world, the chapter illustrates the value as well as limitations of managed aquifer recharge and recycled water.

Virtually all chemicals that humans use can find their way into groundwater. The cost of aquifer protection through proper handling and disposal of hazardous chemicals is miniscule compared to the ongoing costs of trying to clean up a contaminated aquifer—if it’s even possible. This chapter provides historical background on major chemical pollutants and examines key difficulties surrounding chemical contamination and remediation of groundwater with examples from throughout North America.

The difficulties of determining who has the right to use groundwater and how much they can pump becomes even more complicated for aquifers that cross international boundaries. The chapter discusses the few countries that have made progress in addressing transboundary aquifer issues. The chapter also provides a brief history of the Transboundary Aquifer Assessment Program along the U.S.-Mexico border to illustrate key concepts and challenges.

Terrestrial, wetland, and underwater sediment types are the focus of chapter 2, and no consideration of stratigraphy would be complete without their examination. Archaeological research has reached the point now that inundated sites are as much a part of the archaeological vocabulary as land sites have been. It is important to realize, for example, that the territorial extent of the Floridan Aquifer in the Southeast Coastal Plain also encompasses one of the major concentrations of Paleoindian sites in the Southeast. This aquifer, an important potable water source, is held in Tertiary limestones that are also chert bearing, making them an important toolmaking resource. Unlike land sites in the Southeast, which typically do not present preserved organic materials, wetland and submerged sites frequently offer preserved bone and organic materials, including plant seeds and wood. Sedimentation in karst rivers is most often neutral to slightly alkaline, whereas most upland sites lie buried in acidic sand. Lake and channel-fill deposits are important receptacles of preservation and will be the focus of future investigations. The rivers and lakes in Florida and the extreme Southeast are of great significance because they do not have their headwaters emanating from mountains and therefore provide us with an excellent record of late Pleistocene environments.

This chapter reviews the geological context of Florida’s springs and the St. Johns River valley. This provides a basis for understanding the abundance of springs in Florida and the forces that drive their geographic distribution and hydrology. The chapter begins with a sketch of the geologic history of the Florida Platform and the formation of the karst Floridan Aquifer system, with emphasis on those events and processes relevant to springs. This is followed by a discussion of the environmental factors affecting spring flow and how these were impacted by global and regional climatic changes during the late Pleistocene and Holocene. Finally, it discusses the geomorphology of the St. Johns River valley and the springs that feed into it.

This chapter addresses Miller’s hypothesis that the onset of spring flow led to the inception of shell mounding during the Mount Taylor period (7400–4600 cal BP) in the St. Johns River valley. It argues that spring flow has been treated as an ecological founding event by archaeologists. After discussing the concepts of “event” and “non-event” as they are used here, it discusses Geographic Information Systems (GIS) based modelling of pressure within the Floridan Aquifer that approximate pre-modern conditions. Following this, the archaeological and paleohydrological records of two springs—Salt and Silver Glen—are presented. This work indicates that springs began flowing far earlier than previously thought and that the onset of spring flow was likely discontinuous and time-transgressive across the valley. It is therefore argued that the onset of spring flow was not, in itself, a significant event that precipitated rapid changes in human lifeways in the region.

The story of the Desagüe encapsulates the essence of uneven and combined development that characterized the Spanish legacy in those American regions that had once supported populous and complex indigenous societies. That legacy left behind both the survival of a battered but by no means defeated peasantry and a weak, fractured, and fearful elite that was perpetually desirous of a different reality yet unable to impose it. As Spanish rule collapsed, in the Desagüe district this tension could be observed in the silted trench, the rotting wood of the sluicegates, and the slack enforcement of the measures and obligations the colonial superintendants had labored to put in place. The drainage project resumed under Porfirio Díaz. Although the lakes were eventually dried out, flooding did not end. Instead, it became compounded by sinking resulting from overpumping the aquifer.

The idea that there are many subterranean habitats close to the surface that are little known and do not fit comfortably into any habitat classification scheme is introduced. Four of these shallow subterranean habitats (SSHs) are unique (strict sense shallow subterranean habitats)—hypotelminorheic and seepage springs, milieu souterrain superficiel (including talus and scree), epikarst, and calcrete aquifers—and have intermediate sized habitat spaces, no light, and close connections to the surface. Broad sense shallow subterranean habitats include habitats with large (lava tubes) or small (aquatic interstitial and soil) spaces. SSHs are generally broadly but patchily distributed across the landscape although some have restricted physical requirements, such as the presence of a shallow clay layer for hypotelminorheic habitats. Close surface connections have impacts on environmental conditions, nutrient fluxes, and movement of animals through SSHs. While SSHs can be ecotones, they are habitats in their own right, and not necessarily connected with deeper subterranean habitats. They are of general biological interest because of the presence of eyeless, depigmented species, their possible role as stepping stones to adaptation to deeper subterranean environments, their geographic pattern, and conservation issues raised by them. Brief examples of each type of SSH are discussed.

Wetlands, rivers, riparian zones, alluvial floodplains, and estuaries have various dependencies on groundwater, and on water derived from the unsaturated zone and surface runoff from land. Humans have accessed groundwater for domestic and agricultural use for over eight thousand years, and at least one third of the world's population draws its water from aquifers. In extreme cases, declines in the groundwater table completely sever the river baseflow system from its underlying aquifer. Extended low flow periods or changes in the timing of dry periods because of groundwater extraction can disrupt ecosystems processes and food-web structure in fragmented habitats, potentially leading to localised species extinctions. Salmonids appear to be particularly sensitive to the groundwater dependencies of their spawning habitats.

The main subterranean habitats are: small cavities—interstitial spaces beneath surface waters; large cavities—caves; and shallow subterranean habitats—voids of various sizes close to the surface. The defining feature of all these habitats is the absence of light. Environmental variation is also reduced and most subterranean habitats rely on nutrients transported from the surface. The aquatic component of caves includes water percolating from the surface (including epikarst), streams, and resurgences. Terrestrial habitats include epikarst, and the vadose zone. The aquatic interstitial habitat is comprised of the water-filled spaces between grains of unconsolidated sediments. Shallow subterranean habitats are ones close to the surface. They include the hypotelminorheic, interstitial, epikarst, MSS, soil, lava tubes, calcrete aquifers, and iron-ore caves. They share an absence of light, close surface connections, relatively high nutrient levels relative to other subterranean habitats, and the presence of species highly modified for subterranean life.

Researches on water resources focused on assessing the availability and increasing efficiency of uses of water resources. Issues related to irrigation, interlinking of rivers, conflict of interests, large scale displacement, depletion of groundwater, and impact of climate change are discussed. Such themes as quality of portable water, status of water supply and sanitation, impact of energy-irrigation nexus, people-oriented and demand driven groundwater water management and aquifer management framework also are elaborated. Problems of flood and drought management are also examined. Scholar reviewed institutions and structure of water resource management, food security and sustainable agriculture, adaptive water resource management, rainwater harvesting, and feasibility of integrated water resources management and plan for groundwater recharge.

Tunnel-digging, or tunneling, hardly features in international legal instruments. Unlike land, space, and sea, the underground remains largely unregulated. In trying to decipher international law’s take on the underground, this chapter searches for answers in general international law. Does international law recognize state sovereignty over the underground as it does for air, land, and space, or does sovereignty over the underground fall into an unregulated loophole? A close analysis reveals that states have sovereignty over underground resources located in areas under their control or jurisdiction, provided these rights have not been transferred to private entities. This chapter argues that the same principles governing sovereignty over land, air, and water—sovereignty, development, shared resources, cooperation, and peace and security—should apply to state sovereignty over the underground. The implications for the legality of tunnel-digging under international law are far-reaching.