Which country extracts the most groundwater

It is estimated that out of the total Detail beyond the following overview of land and aquifer salinization process is given in Chap. Salinization is a characteristic of soil and water which relates to their water-soluble salt content. Such salts predominantly include sodium chloride, but sulfates, carbonates, and magnesium may also be present. A saline soil is one which contains sufficient soluble salts to adversely affect plant growth and crop production. Waterlogging and salinity have been persistent problems in many irrigation regions of the world.

Rainwater, which is considered a source of pure water, can also become a source of salt addition to aquifers and land. Raindrops, during their brief residence in the atmosphere, dissolve carbon dioxide to form a weak carbonic acid. During infiltration, the weak carbonic acid reacts with minerals and rocks in the soil to dissolve them more readily to become a source of salt in aquifers Hillel Changes in properties of soil and water lead to the development of an environment which deteriorates soil and water quality.

Waterlogging, another major problem in irrigated land, is the saturation of soil particles with water that results from the rising of the water table due to overirrigation, seepage, or inadequate drainage. The processes of waterlogging and salinization, although different in their characteristics, usually occur together and adversely affect water quality and crop yield. Mixing of saline water with freshwater is a frequent cause of aquifer salinization in many coastal regions Werner et al.

Coastal aquifers are more vulnerable to groundwater extraction because of high population densities and predicted sea-level rise Ferguson and Gleeson Coastal areas are the most densely populated areas in the world, with 8 of the 10 largest cities of the world located at coastlines.

In most cases, coastal aquifers are hydraulically connected to seawater. Under natural conditions, the hydraulic gradient in part, a function of the density variation of the seawater and freshwater systems maintains net water flow from the freshwater aquifer toward the sea. However, the gradient is usually small, and any excessive groundwater pumping can alter the hydraulic balance and allow seawater to enter and replace the freshwater pumped out from the aquifer Werner et al.

The quality of groundwater aquifers can also be adversely affected by pumping if interlink connections exist between brackish or saline water. Additionally, a low rate of natural groundwater recharge in combination with sea-level rise can introduce and accelerate movement of saltwater into freshwater aquifers, although Ferguson and Gleeson found that the impact of groundwater extraction on coastal aquifers was more significant than the impact of sea-level rise or changes in groundwater recharge.

The overall impact of saline water intrusion highly depends on the amount of extraction and natural groundwater recharge. Incorrect positioning of well fields can accelerate the problem. Climate change is expected to exacerbate many water resource problems, but the impact of seawater intrusion may be much more serious and widespread because many areas with moderate population densities and water demand are expected to experience saltwater intrusion. Seawater intrusion has affected groundwater quality in major coastal irrigation regions around the globe where pumping has destabilized the hydraulic equilibrium of the aquifers.

Coastal regions such as Queensland in Australia, Florida in the United States, the southern Atlantic coastline of Spain, and Lebanon are among the most highly visible and notable cases where saltwater has intruded into coastal aquifers. Similarly, in the western State of Sonora in Mexico, seawater has intruded approximately 20—25 km inland, forcing the closure of irrigation wells.

In the Burdekin coastal region of Queensland, Australia, more than wells are currently used for irrigation. The large volumes of groundwater extracted have at times lowered the regional water surfaces and made it challenging to control seawater intrusion Narayan et al. To confront long droughts, future use of groundwater is likely to increase in Australia. This growing use of groundwater will stress the aquifers already in deficit.

Thus, saltwater intrusion will likely become more challenging because of the extensive coastlines where the majority of the population resides. Fertilizers, pesticides, and salts contained in irrigation water can be major agricultural contaminants.

Excessive irrigation drives water from the root zone of crops to the groundwater below Chowdary et al. Industrial wastes contain a wide variety of heavy metals and solvents. A recent study by Dwivedi and Vankar reported contamination of groundwater potentially from industrial sources tanning, textile, and several others in the Kanpur-Unnao district of India.

Concentrations of cadmium, cobalt, chromium, copper, mercury, nickel, lead, tin, and zinc were found to exceed the maximum permissible limit. The accidental spillage and leakage of industrial chemicals can also cause serious groundwater contamination Foster and Chilton a.

Subsurface releases of MTBE methyl tertiary-butyl ether can be a source of groundwater contamination. MTBE is a gasoline fuel additive that can leak from gasoline underground storage tanks and contaminate aquifers and wells. In the United States alone, releases of gasoline fuels has been reported at more than , sites, putting over municipal water supply wells at risk of contamination with MTBE Einarson and Mackay Synthetic microorganic compounds also known as emerging organic contaminants EOCs are another and new source of groundwater contamination reported across Europe and many other parts of the world Lapworth et al.

EOCs are used for a range of industrial purposes including food preservation, pharmaceuticals, and healthcare products Lapworth et al. Public health and environmental impacts of EOCs in groundwater are currently under-researched areas. Arsenic and nitrate are two major contaminants with serious public health impacts. High concentrations of arsenic in groundwater have been recognized as a major public health concern in several countries and often are the result of natural conditions rather than human activity.

The contamination of groundwater by arsenic in Bangladesh has been called the largest poisoning of a human population in history Smith et al.

An estimated 36 million people in the Bengal Delta alone Bangladesh and India are at risk of drinking arsenic-contaminated water Nordstrom Long term exposure of arsenic in drinking water and its impacts on human health are documented in Ng et al. Geochemical processes in the presence of oxygen dissolve arsenopyrite [FeAsS], leading to increased concentrations of dissolved arsenic in groundwater. Oxidation can be a major driver to mobilize arsenic already present in aquifer rocks and can be promoted as a result of recharge by oxygenated waters or through lowering of the groundwater surface by excessive pumping Nordstrom The incidence of high concentrations of arsenic in drinking water is significant in Asian countries.

The problem was initially detected in Bangladesh, India, and China. A global summary of arsenic contamination of groundwater is available in Ravenscroft et al. Nitrate contamination of groundwater is a widespread and global problem both in developed and developing nations. Excessive application of commercial fertilizers or animal waste and inadequate waste disposal of municipal and animal waste are associated with this problem.

Nitrate contamination of groundwater due to agrochemicals has become a serious problem in China and India Foster and Chilton b. A detailed review of nitrate contamination of groundwater and its health impact is available in Spalding and Exner and Canter Microbial contamination of groundwater can be caused by inadequate protection of aquifers against release of sewage effluent into groundwater. Contamination of groundwater can occur via many pathways, such as from urban landfills in proximity to natural groundwater recharge sites, rural on-site sanitation facilities, leaking septic tanks and sewers, and waste from farm animals.

The concentration of many harmful microorganisms attenuates naturally reduces when water passes through the unsaturated zone; however, the degree of pathogen removal depends on the type of soil, level of contamination, and type of contaminant. Natural attenuation generally is most effective in the unsaturated zone, especially in the top soil layers where biological activity is greatest Morris et al. Several viral and bacterial pathogens present in human and animal waste contaminate groundwater and cause human health problems.

Baldursson and Karanis give a comprehensive review of worldwide waterborne disease outbreaks that occurred and were documented between and Similarly, a recent study based on a systematic review by Ngure et al. All incidence of waterborne diseases cannot be attributed to groundwater, because microbial contamination of water can occur in surface water bodies and in distribution pipes. Water and energy are inextricably linked in many important ways and this issue is covered in more detail in Chap.

Water is used in the generation of energy, and energy is required for the movement and treatment of water. This linkage results in multiple management challenges. The movement of water requires a significant portion of all energy generated worldwide. Such energy requirements account also for significant contributions to greenhouse gas emissions, estimated as 0.

These energy requirements increase with the distance the water must be lifted depth to water and decrease with pump efficiency. Hence, declining water levels will increase energy requirements for groundwater pumping unless offset by increased pump efficiency.

This increased energy demand for pumping is exacerbated in India by government subsidies for electrical power for the purpose of groundwater extraction Badiani et al. In addition to energy use for water movement and treatment, groundwater plays an important role in the generation of energy—particularly the production of alternative energy such as biofuels Gerbens-Leenes and Hoekstra ; Dominguez-Faus et al.

Significant water is used both in the growing of feedstock to create ethanol and in the distillation of the feedstock into fuel. In the United States, governmental mandates require that ethanol from corn maize will continue into the future Dominguez-Faus et al. Other alternative energy technologies can have surprising energy implications. Concentrated solar power generation on a large scale in desert environments can require large amounts of water for cooling and washing Woody ; McKinnon In the United States, the National Research Council has also studied production of biofuel from algae, raising questions about sustainability.

In recent years, unconventional drilling for shale gas and coal bed methane—particularly in the United States, China, and Australia—has increased dramatically Vidic et al. Improvements in the accuracy of horizontal well drilling, coupled with hydraulic fracturing, have made it practical to extract methane from thin, deep and tight strata. These advantages, coupled with increasing energy demand, have resulted in massive expansion of exploitation of these unconventional gas reserves.

Hydraulic fracturing uses a focused large amount of water for short periods of time, resulting in competition with other water users—particularly in arid regions like the Eagle Ford Formation in Texas United States. Hydraulic fracturing also uses a variety of chemical additives in the process. Some water contaminated with these additives returns as flowback water and must be disposed of, leading to a potential groundwater contamination source Vidic et al. One concern is that methane liberated by the hydraulic fracturing process and additive chemicals could migrate to shallow aquifers or the surface.

A recent study Myers attempted to address this issue and prompted discussion and criticism Saiers and Barth ; Myers ; Cohen et al. Further research in the field and through modeling is necessary for understanding of the depth and breadth of potential groundwater impacts to catch up with the rapid increase in development of unconventional gas resources Jackson et al.

Most of the literature discussing transboundary water conflict has focused on surface water. Groundwater conflict has received less attention. This condition is exacerbated by a lack of regulation and management of groundwater, which is often blamed on the same uncertainties surrounding the quantity and dynamics of groundwater at the regional scale Llamas and Martinez-Santos ; Jarvis et al.

Several conceptual models can apply to transboundary aquifers, including cases where the source of water to the aquifer is in one country but the main demand is in another for example, Eckstein and Eckstein Using analysis similar to the groundwater footprint Gleeson et al.

They point out, however, that many of these transboundary aquifers are found in geopolitically charged areas such as the Arabian Peninsula, the United States—Mexico border, and India and Pakistan.

In one example of this type, the Ceylanpinar aquifer spans the border between Turkey and Syria, with recharge in the Turkish headwaters and the majority of discharge in the Ras al-Ain Springs in Syria Oeztan and Axelrod Data availability is asymmetric, with much more information available about conditions in the aquifer in Turkey than in Syria. Nonetheless, Oeztan and Axelrod modeled the aquifer to try to calculate sustainable extraction rates based on discharge from the springs. Mutually beneficial organic agriculture along the border that previously was unfarmable due to extensive placement of landmines is proposed but would first depend on cooperation with respect to hydrogeologic and water use information.

Joint management to prevent overdepletion requires collaboration, which may be at odds with other priorities of neighboring countries, but this example shows it can have positive outcomes. Beyond water quantity, water quality concerns can arise when contaminants enter an aquifer under a different governance than that of the users of the aquifer; for example, such as bordering northeastern Greece Vryzas et al.

Similar challenges as facing depletion problems are encountered in managing water quality. The parallel challenges of establishing responsibility for contamination and finding the motivation to remediate it can present opportunities for constructive collaboration but also may heighten tension in some areas. In modern times —present , no full-scale declarations or acts of war have been attributed to the tension related to the use of transboundary water De Stefano et al.

This is contrary to predictions stemming from at least the s onward that major wars—particularly in the Middle East—would be fought over water because of stress over increasing demand for water resources due to increasing population, climate change, and depletion of water sources see Cooley and Starr , for example. It is still possible for this to happen, and indeed tensions and local violence have been attributed to water conflict, but thus far full-scale war has not resulted with the exception of the war between Sumerian city-states Lagash and Umma in BCE Wolf Although a somewhat controversial notion, it has been argued that interactions among states involving water more often, of necessity, lead to cooperation than conflict De Stefano et al.

In summary, transboundary aquifers present many challenges in integrated management. Data sharing and integration are more challenging across national borders but are extremely important to reduce the uncertainties surrounding integrated management.

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Related latest. Press Release. It uses an estimated cubic kilometers of groundwater per year - over a quarter of the global total. Urban residents increasingly rely on groundwater due to unreliable and inadequate municipal water supplies. Groundwater acts a critical buffer against the variability of monsoon rains.

Farms irrigated with groundwater have twice the crop water productivity of those that rely on surface-water alone. This is largely because the resource allows farmers greater control over when to irrigate their fields and how much water to use each time.

Moreover, aquifers are depleting in the most populated and economically productive areas. Climate change will further strain groundwater resources. India has both hard-rock and alluvial aquifers which differ considerably in their physical and socioeconomic profiles and require very different sets of solutions at both the macro and micro levels.

As global experience offers few comparable models, home grown solutions are needed. The World Bank report provides a menu of practical and non-controversial interventions which can be implemented in the current environment. Amongst its several suggestions, the report calls for community management of ground water wherein the user community is the primary custodian of the resource and is charged with implementing management measures.

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