An Initial Framework for Understanding the Resilience of Aquifers to Groundwater Pumping

<p>    Groundwater is the largest freshwater resource available on Earth, and many coastal regions are depending on groundwater as a primary freshwater source. For example, in Busan and Incheon, two of the largest coastal cities in South Korea, 5.7% and 7.0% of freshwater uses are from groundwater while only 1.8% is from groundwater in Seoul, the capital of the country. Globally, groundwater availability is diminishing primarily by population increase, and especially in coastal regions, this problem is exacerbated by overexploitation and seawater intrusion, which causes groundwater contamination and further reduces its availability. Here, we view the groundwater system and its management for sustainability as a complex problem that is associated with various social, economic, and environmental factors. By adopting the City Blueprint Approach (CBA), which has been used extensively for assessing the sustainability of integrated water management of numerous cities on the globe, we identify water management factors that potentially have direct and indirect links and feedbacks with groundwater variables. We selected Busan and Incheon as case studies for coastal cities that are facing the risk of groundwater salinization by seawater intrusion. This study aims to 1) assess City Blueprint (CB) of selected coastal cities, 2) identify major factors for coastal groundwater management through correlation analysis, and 3) suggest management options regarding identified factors for sustainable groundwater management of the study areas. Our results on CB indicate that the groundwater quality and quantity of the selected cities are currently in ‘good’ status. Also, from the correlation analysis, we identified heat risk and freshwater scarcity as the major factors that potentially can affect groundwater quantity. For groundwater quality, the factors of voice and accountability, regulatory quality, and rule of law and control of corruption, most of which had not been explicitly considered for groundwater management, were identified as the major factors. Some of these factors were assessed from ‘little concern’ to ‘very concern’ for both cities. These results indicate that, regarding the linkages between groundwater variables and other factors in concern, more actions beyond environmental factors should be taken for sustainable groundwater management. This study helps to understand how non-conventional factors could contribute to coastal groundwater, and can provide extensive options for sustainable groundwater management.</p><p> </p><p><strong>Acknowledgement</strong>: This research was supported by the Development program of Minimizing of Climate Change Impact Technology through the National Research Foundation of Korea (NRF), funded by the Korean government (Ministry of Science and ICT) (NRF-2020M3H5A1080775).</p>

Coastal ecosystems occupy an interface between land and ocean, making them vulnerable to a variety of natural and anthropogenic disturbances. Large, episodic disturbances (mega-disturbances) cause immediate and long-lasting changes to coastal wetland plant communities and soils by changing the environmental conditions in which they exist. Here I examined the impacts of storm-induced saltwater intrusion and post-intrusion conditions on the structure and growth of an oligohaline wetland plant community, and on wetland soil biogeochemistry and conditions during and after saltwater intrusion. In the greenhouse, a six-week saltwater intrusion reduced canopy cover and species richness. Once intrusion stress was alleviated, plant community structure and growth were heavily influenced by water level during the 20-month recovery period. Plant resilience after subsequent but non-lethal disturbance (clipping) was dependent on the interaction of flooding and salinity, such that canopy cover recovered to pre-clipping condition more slowly under salty, drained conditions. I also found that sustained high water level favored belowground biomass accumulation, high shear strength, and a relatively low decomposition rate in oligohaline wetland soils in the greenhouse. In the field, plant community structure and growth following saltwater intrusion were heavily influenced by the degree of flooding during the recovery period. High flooding depressed canopy cover and species richness, and influenced species dominance. High flooding also resulted in reduced soil conditions in which sulfide accumulated, and in depressed belowground biomass accumulation. Conversely, sediment inputs enhanced wetland recovery from saltwater intrusion by increasing end-of-season aboveground biomass, providing nutrients, and lowering sulfide concentration when flooding was high. Post-intrusion grazing intensity had few impacts on wetland plants and soils during the recovery phase. Soil response variables measured in intrusion-impacted and reference soils before, during, and after a 6-week saltwater intrusion event indicated that although some significant changes in microbial activity, abundance, and nutrient availability occurred due to saltwater intrusion, these impacts were generally transient, with post-intrusion conditions resembling pre-intrusion conditions. In conclusion, storm-induced saltwater intrusion has some long-lasting impacts on oligohaline wetland plant communities, but mostly transient impacts on oligohaline wetland soils. Possibly more importantly, I found that the oligohaline wetland plant community and soil structure and function was determined by post-intrusion environmental conditions. Because oligohaline wetlands provide vital ecological services in many coastal regions, great effort should be put forth to understand both natural and human impacts to these systems. Information gained through research should be applied in a way that encourages the maintenance of healthy, productive,

Groundwater is valuable to supply fresh water to the public, industries, agriculture, etc. However, excessive pumping has caused groundwater storage degradation, water quality deterioration and saltwater intrusion problems. Reliable groundwater flow and solute transport modeling is needed for sustainable groundwater management and aquifer remediation design. However, challenges exist because of highly complex subsurface environments, computationally intensive groundwater models as well as inevitable uncertainties. The first research goal is to explore conjunctive use of feasible hydraulic control approaches for groundwater management and aquifer remediation. Water budget analysis is conducted to understand how groundwater withdrawals affect water levels. A mixed integer multi-objective optimization model is constructed to derive optimal freshwater pumping strategies and investigate how to promote the optimality through regulating pumping locations. A solute transport model for the Baton Rouge multi-aquifer system is developed to assess saltwater encroachment under current condition. Potential saltwater scavenging approach is proposed to mitigate the salinization issue in the Baton Rouge area. The second research goal aims to develop robust surrogate-assisted simulation-optimization modeling methods for saltwater intrusion mitigation. Machine learning based surrogate models (response surface regression model, artificial neural network and support vector machine) were developed to replace a complex high-fidelity solute transport model for predicting saltwater intrusion. Two different methods including Bayesian model averaging and Bayesian set pair analysis are used to construct ensemble surrogates and quantify model prediction uncertainties. Besides. different optimization models that incorporate multiple ensemble surrogates are formulated to obtain optimal saltwater scavenging strategies. Chance-constrained programming is used to account for model selection uncertainty in probabilistic nonlinear concentration constraints. The results show that conjunctive use of hydraulic control approaches would be effective to mitigate saltwater intrusion but needs decades. Machine learning based ensemble surrogates can build accurate models with high computing efficiency, and hence save great efforts in groundwater remediation design. Including model selection uncertainty through multimodel inference and model averaging provides more reliable remediation strategies compared with the single-surrogate assisted approach.

Sea-level rise from a warming climate threatens to inundate coastlines around the world.1 But some of the world’s most vulnerable coasts—those fringing flat delta plains, mainly in Southeast Asia—face the far more immediate threat of sinking land.2 Induced mainly by human activities on a local rather than global scale, this phenomenon, known as land subsidence, can outpace sea-level rise substantially. Indonesia’s biggest city, Jakarta, is sinking at an average rate of 5–10 cm per year,3 much faster than the global rate of sea-level rise, which clocks in at 3.2 mm per year, according to the recent estimates.1 Should subsidence in Jakarta continue unabated, the city could sink up to 6 m by the end of the century, according to JanJaap Brinkman, a water management specialist with Deltares Research Institute in Delft, the Netherlands.

ContextAnthropogenic and natural disturbances may interact synergistically, magnifying their individual effects on biodiversity. However, few studies have measured responses of ecological communities to multiple stressors at landscape scales.ObjectivesWe use a long-term dataset to test for synergistic effects of anthropogenic and natural disturbance on plant community diversity and composition in a large protected area.MethodsWe quantified changes in plant communities over two decades in 98 plots in Waterton Lakes National Park, Canada. Fifty-three plots burned in a wildfire in the interim. We modeled the effects of wildfire, proximity to trails or roads, and their interaction on changes in species richness, community composition, relative abundance of disturbance-associated species, and colonization by exotic species.ResultsInteractions between wildfire and proximity to roads and trails affected all metrics except species richness. Only one interaction was synergistic: the relative abundance of disturbance-associated species following wildfire was magnified closer to recreational corridors. The other community metrics showed unexpected patterns. For example, plots with no exotic species in the baseline survey that burned in the wildfire were more likely to gain exotic species than unburned plots only when they were distant from recreational corridors.ConclusionsOur study demonstrates interactive effects of natural and anthropogenic disturbance at landscape scales within a protected area. Plant community response to wildfire was influenced by proximity to recreational corridors, sometimes in surprising ways. As the frequency and severity of anthropogenic and natural disturbances both continue to rise, documenting the prevalence and magnitude of interactions between them is key to predicting long-term effects and designing mitigation strategies.

The fulfillment of water needs for living things is the responsibility of the State. State control of dealing with water is done through the arrangement and management of licenses ensuring the right of everyone to get water as a primary need. Groundwater extraction and management will be a separate issue when the legal norms do not guarantee certainty and justice for society. The Constitutional Court decision No. 85/PUU-XI/2013 dated February 18th, 2015, states that Law No. 7 of 2004 on Water Resources has no legal force. Therefore, the re-enactment of Law No. 11 of 1974 on watering gives impact to the regulation of groundwater extraction. This should meet the principles of the decision of the Constitutional Court. Governments, including local governments, have an important duty regarding groundwater management, so that the water needs can be fulfilled for all people.

Groundwater is essential for sustaining human life and ecosystems as a freshwater resource. However, intensive groundwater pumping (GWP) can deplete groundwater levels, and exacerbate issues such as sea-level rise and saltwater intrusion in coastal areas, further affecting the availability and accessibility of groundwater. To address these challenges, accurate monitoring and modeling of water table depth (WTD), a key indicator of groundwater storage, is useful for sustainable groundwater management. This work studies the implementation of a regression-enhanced random forest (RERF) model to predict WTD anomalies with pumping as a major input for New Jersey, a coastal state in the United States. The predicted WTD anomalies align well with observations, with a test Nash-Sutcliffe Efficiency (NSE) of 0.49, a test Pearson correlation coefficient (r) of 0.72, and a test root-squared mean error (RMSE) of 1.61 m. Based on a permutation feature importance, the most important input variables in the model for predicting WTD anomalies were long-term mean WTD, precipitation minus evapotranspiration (PME), and GWP. Using the trained RERF model, we generated 90 m spatial resolution WTD anomaly maps for New Jersey for January and July 2015, showing areas of increasing and decreasing WTD. We then inverted the RERF model to predict GWP using WTD anomalies, land cover, and a cross metric as additional inputs. This approach was less effective, yielding a test NSE of 0.40, a test r of 0.65, and a test RMSE of 15.44 million liters/month. A permutation feature importance revealed the most important input variables to be PME, long-term mean WTD, and topographic slope. Again we generated 90 m GWP maps for New Jersey for January and July 2015, offering finer resolution than the previous maps at the subwatershed level. Focusing on New Jersey, the study provides insights into the relationship between WTD anomalies and its critical input variables including GWP in coastal areas. Moreover, significant gaps in WTD observations persist in New Jersey, highlighting the need for comprehensive monitoring efforts. Thus, by employing ML techniques and leveraging available data, this study contributes to improving groundwater management practices and informing future decision-making.

BackgroundAssessing cumulative effects of anthropogenic and natural disturbances on forest carbon (C) stocks and fluxes, because of their relevance to climate change, is a requirement of environmental impact assessments (EIAs) in Canada. However, tools have not been developed specifically for these purposes, and in particular for the boreal forest of Canada, so current forest C assessments in EIAs take relatively simple approaches. Here, we demonstrate how an existing tool, the Generic Carbon Budget Model (GCBM), developed for national and international forest C reporting, was used for an assessment of the cumulative effects of anthropogenic and natural disturbances to support EIA requirements. We applied the GCBM to approximately 1.3 million ha of upland forest in a pilot study area of the oil sands region of Alberta that has experienced a large number of anthropogenic (forestry, energy sector) and natural (wildfire, insect) disturbances.ResultsOver the 28 years, 25% of the pilot study area was disturbed. Increasing disturbance emissions, combined with declining net primary productivity and reductions in forest area, changed the study area from a net C sink to a net C source. Forest C stocks changed from 332.2 Mt to 327.5 Mt, declining by 4.7 Mt at an average rate of 0.128 tC ha−1 yr−1. The largest cumulative areas of disturbance were caused by wildfire (139,000 ha), followed by the energy sector (110,000 ha), insects (33,000 ha) and harvesting (31,000 ha) but the largest cumulative disturbance emissions were caused by the energy sector (9.5 Mt C), followed by wildfire (5.5 Mt C), and then harvesting (1.3 Mt C).ConclusionAn existing forest C model was used successfully to provide a rigorous regional cumulative assessment of anthropogenic and natural disturbances on forest C, which meets requirements of EIAs in Canada. The assessment showed the relative importance of disturbances on C emissions in the pilot study area, but their relative importance is expected to change in other parts of the oil sands region because of its diversity in disturbance types, patterns and intensity. Future assessments should include peatland C stocks and fluxes, which could be addressed by using the Canadian Model for Peatlands.

Water scarcity is the major problem faced by today’s world. Groundwater is the most valuable resource of drinking water due to the scarcity of good quality surface water. Groundwater occurs in hard rock layers whose thickness may vary from few meters to 100 m. Aquifer stores the groundwater and yielded the water at the time of pumping. A groundwater model was developed for Kanpur city, a fast growing City of Uttar Pradesh, India. Progressive increase in the land reclamation projects, continuous population growth and increasing industrial water demand, an efficient water resource management plan was needed for the city. Groundwater extraction is increasing excessively due to the high river water contamination. For the better management of groundwater, steady state groundwater flow model was conceptualized for 10 years from January 2007 to December 2017. This three-layer model was calibrated for 7 years to symbolize the actual field condition and validated for 3 years. In groundwater flow model preparation, Geographic Information System (GIS) techniques were integrated to simulate the groundwater flow. This integration of GIS and groundwater flow model was very helpful in evaluating the groundwater potential zones and generating the various possible scenarios for management and prediction of groundwater. The results of the current study confirm that the ground-water aquifer in Kanpur city is prone to significant water head reduction, especially in the high elevation zones. Therefore, there is need of an efficient integrated and sustainable management plan for the groundwater resources to minimize the impact of too much extraction of groundwater in the study area.

PurposeThis paper aims to define the current and potential extent of seawater intrusion in Manukan Island under different scenarios of varying recharge and pumping rates. The calibrated model was also used to predict the extent of seawater intrusion in low lying area of Manukan Island for two years with all conditions assumed to remain the same as those in December 2009.Design/methodology/approachDifferent scenarios of varying recharge and pumping rates based on threats received by Manukan Island were investigated. El‐Nino events and overpumping are represented by varying recharge and pumping rates. Simulation was done using SEAWAT‐2000, the latest modeling software available in groundwater modeling that couples flow and transport together.FindingsThe seawater‐freshwater mixing ratio moves landwards after two years of simulation in Scenario 1. In order to control overpumping in this study area, Scenario 2 has resulted in backward movement of the 1.4 percent seawater‐freshwater mixing ratio toward the coast after two years of prediction. The current contamination of the coastal aquifers by seawater intrusion will be more severe with an impact of El‐Nino events on groundwater resources depletion in Scenario 3. Reductions of pumping and recharge rates in Scenario 4 have worsened the seawater intrusion problem. With the aid of artificial recharge in Scenario 5, highest hydraulic heads and lowest chloride concentration were observed.Practical implicationsThe sustainable groundwater management selected for Manukan Island's current situation will be Scenario 2. In view of the effects of El‐Nino events in the future, Scenario 5 can be implemented to restore groundwater resources. The numerical model has showed the groundwater condition during El‐Nino events and overpumping illustrated that simulation modeling is an excellent tool to understand the behavior and management of an aquifer system. The output of simulation modeling via numerical model provides a framework toward groundwater management. Thus, current study output with similar approach which will restore groundwater (artificial recharge and reduction of pumping rate) can be applied in other small islands of similar hydrogeological condition and stresses for the purpose of groundwater resource protection.Originality/valueBriefly, these findings will effectively contribute to water policy analysis, planning and management in the study area to combat current as well as future seawater intrusion problem.

Reversibility of seawater intrusion in a coastal aquifer: Insights from long-term field observation and numerical modeling

Disturbances are a common occurrence in coastal ecosystems and can provide opportunity for adaptation and renewal in healthy systems; hurricanes bring mineral accretion to a marsh, floods provide a pulse of freshwater and nutrients to estuaries, and fires increase species diversity and abundance in forests. Humans, however, have depleted the resiliency of many coastal systems via top down and bottom up mechanisms, leaving these ecosystems more vulnerable to both natural and anthropogenic disturbances. Louisiana’s wetlands have been modified for centuries via canals, levees, agricultural impoundments, etc., leading to a decreased resiliency to land loss. The Deepwater Horizon (DWH) oil spill had the potential to further reduce marsh resiliency, potentially precipitating a “regime shift” where natural disturbances that were once a subsidy to the system are now a stress. The DWH oil spill released 4.9 million barrels of oil into the northern Gulf of Mexico, covering 2,000 km of shoreline from Florida to Texas in the world’s largest accidental marine oil spill. I examined the direct and indirect impacts of the oil spill on salt marsh erosion rates in southeastern Louisiana on varying spatial (from cm to km) and temporal scales (from hours to years). I chronicled the effects using multiple techniques of documentation including field data collection of the marsh edge for 5 years, GIS analysis spanning 15 years, and time-lapse photography for one year. The DWH oil spill directly increased erosion rates for 2 years and also left a continuing land loss legacy of cascading erosional effects lasting for 3+ years. The salt marsh shoreline eroded unevenly, leaving behind micro-headlands that eroded at an accelerated rate, leading to cascading heightened land loss along the study area. The shoreline erosion rates immediately after the DWH oil spill that included Hurricane Isaac were higher than any time period in the last 15 years, including after the hurricane seasons of 2004 and 2005. The oil depleted the resiliency of the marsh, making it more susceptible to erosion precipitated by natural disturbances, and leaving a land loss legacy much greater than the initial impacts.

Mental models are the dynamic, internal cognitive representations of people's interaction with the world. Such models can be used to gain insights into how humans structure their beliefs and actions about environmental issues. This research paper aims to understand the mental models of sustainable groundwater management among farmers in semi-arid regions of Maharashtra, India. Using a mixed method approach of qualitative interviews and systems mapping, we assess how past experiences with drought and water scarcity have influenced farmers' beliefs, perceptions, and actions and develop mental models that highlight the dynamic processes that guide farmer actions regarding groundwater use and management. We identify policy triggers that can nudge farmers toward sustainable groundwater management in the future. Our results reveal three key insights: i) Farmers who experience higher water scarcity have a higher desire for groundwater conservation and higher consciousness towards future groundwater sustainability, ii) Farmers' actions towards either increased groundwater extraction or conservation are shaped by complex social, environmental, and institutional dynamics rather than self-interested individual will, and iii) Supply-driven water policies and initiatives can lead to maladaptive outcomes such as an increase in groundwater extraction in the long run. Current water policies need a transformative shift from focusing on short-term groundwater supply to those that facilitate long-term sustainable groundwater management by influencing the norms, values, and behavior toward groundwater conservation. Future interventions that allow and encourage collective mobilization, enhanced ownership and participation, adequate training, financial resources, and decentralized management structures with enhanced accountability are likely to be more effective in developing long-term solutions for sustainable groundwater management.

Groundwater irrigation plays an important role in sustainable agricultural development through protective shield during droughts and dry spells and intensifying and diversifying of the cropping system. The measuring, monitoring, and modeling of groundwater availability, condition, and distribution are the major step to formulate a sustainable groundwater management plan for agricultural use. The conventional methods to manage groundwater are tedious and costly. However, the modernization of geospatial techniques, namely, remote sensing (RS), geographic information system (GIS), Global Positioning System (GPS), etc., along with differential proximity sensing has enabled groundwater management both spatially and temporally. It can help in surveying, analyzing, detecting, differentiating, characterizing, mapping, monitoring, and modeling of the groundwater quantity, quality, distribution, extent, and association of groundwater resources. The major interventions of geospatial techniques in groundwater management are groundwater quality assessment, spatial zonation for irrigation, groundwater prospects mapping, dynamicity of groundwater storage, saltwater intrusion, etc. These applications have made a huge impact on groundwater management for crop and land resources on a sustainable basis. The multiparametric approach of geospatial techniques can minimize the time, labor, and money and thereby enable quick decision-making for efficient water resources management. However RS data has some inherent limitations of spatial, spectral, and temporal resolution, which sometimes makes it difficult to understand and asses the groundwater condition. Still, it is very important for the areas/regions especially developing nations where data scarcity in terms of quantity and quality is often an obstacle for solving real-world water problems. This chapter highlights the various approaches of groundwater management for irrigated agriculture using geospatial tools and techniques.

The economic expansion of Niger Delta region depends on groundwater resource for various uses. Therefore, there is need for an understanding of the hydrogeological and hydrochemical characteristics as an integral for management of the resource. Hence, this study was aimed at delineating areas of saltwater intrusion in the area. Geological and hydrogeological data were used to delineate two aquifers: alluvial aquifer (upper designated as A and lower designated as B) and a coastal plain aquifer (designated as C). Groundwater in the area was classified as fresh (<1500 μS/cm), brackish (1500–3000 μS/cm), and saline (>3000 μS/cm). Among the groundwater samples (n = 105), 95% from A, B, and C were classified as fresh, while 2 and 3% of the samples from A were classified as brackish and saline, respectively. The main groundwater facies were Na–Cl, Mg–Cl, and Na–HCO3 respectively, for A, B, and C aquifers. The enrichment of Na+ and Cl−, freshwater–seawater mixing ratio, cross plots, and classifications by means of different schemes indicated that seawater intrusion was occurring in the A aquifer. In terms of drinking and irrigation use, the A aquifer water is of poor quality relative to the groundwater from B and C aquifers. The study highlights the potential danger of contaminated groundwater in the coastal areas occupied by low income dwellers. Hence, seawater intrusion should be continuously monitored for sustainable development and management of groundwater in coastal areas.KeywordsCoastal aquiferContaminationSaltwaterNiger DeltaNigeria