This is particularly true for groundwater management due to the invisible nature of the resource and the associated costs and scarcity of high-quality information. Addressing the lack of detailed understanding of groundwater systems is one of the main challenges for their effective management.
Integrated Assessment, Modelling, and Other IGM Tools
Appropriate modeling takes into account the spatiotemporal detail required in the modelling, the nature of the data (qualitative and/or quantitative), the level of ability to represent uncertainty and feedback (Kelly et al.2013). The system dynamics approach may be appropriate when dynamic processes or system feedback are of interest, while agent-based models are appropriate when interactions between individuals are of interest (Kelly et al. 2013).
Book Overview and Key Messages
13, and are discussed in terms of potential threats resulting from groundwater over-extraction. 21, the assessment of the benefits of the improvement and protection of underground water is treated from the economic point of view of conditional assessment.
Introduction
Understanding the international scope of the groundwater issue requires measurement and analysis on a commensurate scale. Uncertainties surrounding groundwater resources—as opposed to surface water systems—may increase the likelihood of future conflicts.
The Concept of Groundwater Depletion
Despite previous misconceptions of "safe yield". for example, using recharge calculations as a basis for determining an amount of water that can be "safely" withdrawn from an aquifer), has become more widely accepted than discharge to streams, springs, etc., it is often the limiting water. element of balance. First, the specific source of water must be understood to assess whether withdrawals are balanced with resources.
Groundwater Depletion Globally
This storage decline in the HP aquifer accounts for nearly 36% of the total groundwater depleted in the United States during Scanlon et al.2012b). In the northern state of Punjab, 75% of the groundwater is overdrawn; in the western state of Rajasthan, the corresponding proportion is 60% (Rodell et al. 2009; World Bank 2010).
Contamination of Groundwater
Underground release of MTBE (methyl tertiary-butyl ether) can be a source of groundwater contamination. Arsenic contamination of groundwater in Bangladesh has been called the largest poisoning of a human population in history (Smith et al. 2000).
The Water-Energy Nexus
Natural attenuation is generally most effective in the unsaturated zone, particularly in the topsoil, where biological activity is greatest (Morris et al. 2003). Further field and modeling research is needed to understand the depth and breadth of potential groundwater impacts to catch up with the rapid increase in unconventional gas resource development (Jackson et al. 2013).
Transboundary Water Conflict
Some water contaminated by these additions returns as return water and must be disposed of, leading to a potential source of groundwater contamination (Vidic et al. 2013). Using a groundwater footprint-like analysis (Gleeson et al. 2012), Wada and Heinrich (2013) conducted a quantitative assessment of water stress (considering recharge, withdrawal, and environmental flows) for 408 identified transboundary aquifers and found that 8% aquifers are under stress from human nutrition.
Conclusion
Cao G, Zheng C, Scanlon BR, Liu J, Li W (2013) Using flow modeling to assess the sustainability of groundwater resources in the North China Plain. Scanlon BR, Longuevergne L, Long D (2012d) GRACE satellite estimates of groundwater storage changes in California's Central Valley, USA.
Introduction
Groundwater: An Interaction Space of Several Interdependent Dynamics
Water losses occurring in canals and at field level contribute significantly to the recharge of the underlying alluvial aquifer (Mailhol and Merot2008). This example illustrates the complexity of the processes that determine the dynamics of a social-ecological system dependent on groundwater, emphasizing the need to look beyond aquifer boundaries. Declining groundwater levels have led to incidences of reduced groundwater quality, including salt water intrusion in some coastal and estuarine parts of the Gnangara Mound.
Understanding Hydrogeological Complexity
Usually, the water levels in the aquifer are very sensitive to surface water conditions and can vary according to the season (Allen et al.2003). In some cases, water extracted from pump wells may come almost exclusively from surface water sources (e.g. Scibek et al.2007). Longer water residence times in the hyporheic zone usually enhance biogeochemical reactions that favor natural pollution reduction (Gandy et al.2007).
Understanding the Complexity of Groundwater-Society Interactions
Pumping in groundwater increases the vertical gradients and associated velocities from surface water sources (Gilfedder et al.2012). This approach requires accessible surface water, but is even applied in water-scarce areas, such as the southwestern United States (Blomquist et al.2001). In Sri Lanka, deforestation associated with agricultural development has led to an increase in groundwater recharge (Priyantha Ranjan et al. 2006).
Policies for the IGM-Scape
As for the quality aspects of fluxes in the IGM landscape, several ways exist to mitigate poor water quality, such as through pesticide pollution in a drained basin. In practice, different types of these levers exist, such as ditch networks and artificial wetlands (Stehle et al.2011; Tournebize et al.2012). Dealing with externalities often involves payments for ecosystem services, such as flood protection of agricultural areas through compensation to cover losses (Erdlenbruch et al. 2009).
Conclusions
Mailhol J-C, Merot A (2008) SPFC: a tool to improve water management and hay production in the Crau region. Marei A, Khayat S, Weise S, Ghannam S, Sbaih M, Geyer S (2010) Estimating groundwater recharge using the chloride mass balance method in the West Bank, Palestine. The chapter notes that pressures on groundwater resources are likely to increase in the future, with the location, scale, and extent of groundwater use changing in response to other pressures.
Introduction
Implications of Climate Change for Groundwater .1 Direct Impacts from Climate Change
Booming industries, such as biofuels in the United States (US) and unconventional gas production worldwide, have developed ahead of efforts by government regulators to require application of better practices, including the maintenance of groundwater resources (Hussey and Pittock 2012). For example, much of the geothermal 'hot rock' resource in Australia is located in arid areas or in the wet-dry tropics where surface water sources are seasonal or absent (Goldstein et al.2009). These trends in groundwater depletion in the US have been observed and known for many years.
Discussion and Conclusion
Bates BC, Kundzewicz ZW, Wu S, Palutikof JP (eds) (2008) Climate Change and Water, Intergovernmental Panel on Climate Change technical paper. IPCC (2007a) Climate Change 2007: Impacts, Adaptation and Vulnerability, Working Group II contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC (2007b) Climate Change Mitigation: Summary for Policy Makers, Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change.
Introduction and Motivation
Greenhouse gases are assumed to drive much of contemporary climate change, and the global concentration of atmospheric CO2 is the leading indicator of greenhouse gases as well as a major regulator of global climate (Petit et al. 1999). Atmospheric CO2 concentration has been measured in the mid-Pacific Ocean atop Mauna Loa, Hawaii at the National Center for Environmental Prediction since 1958 (Keeling et al. 1976; projections from the Intergovernmental Panel on Climate Change (IPCC) show a warming globally important) changes in rainfall frequency and amount in the twenty-first century (Le Treut et al.2007; Mearns et al.2007).
Climate Projections
Successful simulation and prediction across a wide range of these phenomena increases confidence in the GCMs used for climate predictions of the future (Randall et al. 2007). However, GCMs have been more successful in simulating temperature extremes than precipitation extremes (Randall et al.2007). These include different expected changes in precipitation for the tropics (Neelin et al.2006), subtropics (Wang 2005; Rowell and Jones2006) and high latitudes (Emori and Brown2005).
An Holistic View of Groundwater Hydrology
Climate change and variability are expected to significantly affect soil water and temperature (Jasper et al. 2006; Jungkunst et al. 2008). In many regions of the world, it is not known whether recharge will increase or decrease with projected climate change (Green et al. 2007). Climate change has significant implications for surface water processes (Gosling et al. 2010), including groundwater/surface water interactions.
Methods for Investigating Global Change Beneath the Surface
Gravity measurements have also been used to detect changes in groundwater storage at the site (gravity profiling) and using GRACE satellite data as discussed in the next section. Notable exceptions to this are satellite-based observations of the gravity field associated with changes in groundwater storage. Since its launch in 2002, the GRACE satellites have been used to detect small temporal variations in the Earth's gravity field (Ramillien et al. 2008).
Assessments of Subsurface Hydrology
To address such scale issues, Zaitchik et al. 2008) used an advanced data assimilation approach to incorporate GRACE data into a land surface model, thus fusing it with other datasets and our knowledge of physical processes as represented in the model. This technique may be key to maximizing the value of GRACE data for groundwater resources studies (e.g., Fukuda et al. 2009). Others have used relatively complex, spatially distributed subsurface models and coupled surface-groundwater models (Goderniaux et al.2009; Hunt et al.2013; van Roosmalen et al.2007,2009).
The Role of Groundwater in the Water-Food-Energy- Climate Nexus
Dispersive groundwater models simulate flow in the subsurface, both under saturated and unsaturated conditions, as well as for porous and fractured media. However, challenges remain for coupling GCM projections to hydrologic models (Scibek and Allen2006b; Toews and Allen2009; Xu1999), including issues discussed in the Global Climate Projection section. Studies based on numerical models continue to improve, but for the most part, the approaches are similar to the limited examples given above and the more comprehensive case studies discussed by Green et al.
Adapting to Climate Change: Integrated Groundwater Management
The Netherlands and the rest of the world's coastal delta regions are vulnerable to climate change and sea level rise. Examples of current adaptation to observed and expected climate change in the management of groundwater resources are few, with groundwater typically considered part of an integrated water supply system. The response strategies needed to adapt to climate change highlight the need for water supply-demand adjustments.
Future Directions
Herrera-Pantoja M, Hiscock KM (2008) The effects of climate change on potential groundwater recharge in Britain. Woldeamlak ST, Batelaan O, De Smedt F (2007) Effects of climate change on the groundwater system in the basin of the Grote-Nete, Belgium. Yusoff I, Hiscock KM, Conway D (2002) Simulation of the impacts of climate change on groundwater resources in eastern England.
Governance
