This reprint focuses on the application of groundwater models developed with the aim of optimizing the management of water resources in urban environments, coastal areas, karst aquifers, and riparian ...zones, among other environments. The testing of innovative techniques applied to traditional models, including machine learning techniques, is of particular interest. Special attention is given to the application of tools for the evaluation of climate change effects on groundwater.
Science, society, and the coastal groundwater squeeze Michael, Holly A.; Post, Vincent E. A.; Wilson, Alicia M. ...
Water resources research,
April 2017, 2017-04-00, 20170401, Letnik:
53, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Coastal zones encompass the complex interface between land and sea. Understanding how water and solutes move within and across this interface is essential for managing resources for society. The ...increasingly dense human occupation of coastal zones disrupts natural groundwater flow patterns and degrades freshwater resources by both overuse and pollution. This pressure results in a “coastal groundwater squeeze,” where the thin veneers of potable freshwater are threatened by contaminant sources at the land surface and saline groundwater at depth. Scientific advances in the field of coastal hydrogeology have enabled responsible management of water resources and protection of important ecosystems. To address the problems of the future, we must continue to make scientific advances, and groundwater hydrology needs to be firmly embedded in integrated coastal zone management. This will require interdisciplinary scientific collaboration, open communication between scientists and the public, and strong partnerships with policymakers.
Key Points
Coastal hydrogeology addresses important societal problems
Scientific advances have created tangible societal benefits
Collaborations between scientists, policymakers, and the public are essential for coastal water resource sustainability
Global threat of arsenic in groundwater Podgorski, Joel; Berg, Michael
Science (American Association for the Advancement of Science),
2020-May-22, 2020-05-22, 20200522, Letnik:
368, Številka:
6493
Journal Article
Recenzirano
Odprti dostop
Naturally occurring arsenic in groundwater affects millions of people worldwide. We created a global prediction map of groundwater arsenic exceeding 10 micrograms per liter using a random forest ...machine-learning model based on 11 geospatial environmental parameters and more than 50,000 aggregated data points of measured groundwater arsenic concentration. Our global prediction map includes known arsenic-affected areas and previously undocumented areas of concern. By combining the global arsenic prediction model with household groundwater-usage statistics, we estimate that 94 million to 220 million people are potentially exposed to high arsenic concentrations in groundwater, the vast majority (94%) being in Asia. Because groundwater is increasingly used to support growing populations and buffer against water scarcity due to changing climate, this work is important to raise awareness, identify areas for safe wells, and help prioritize testing.
Groundwater is an important water source for agricultural irrigation in Penyang County. Some traditional methods such as irrigation coefficient, sodium adsorption ratio, total alkalinity, total ...salinity and total dissolved solids were employed to assess groundwater quality in this area. In addition, an improved technique for order preference by similarity to ideal solution model was applied for comprehensive assessment. The origin of major ions and groundwater hydrogeochemical evolution was also discussed. Groundwater in Penyang County contains relative concentrations of dominant constituents in the following order: Na
+
> Ca
2+
> Mg
2+
> K
+
for cations and HCO
3
−
> SO
4
2−
> Cl
−
> CO
3
2−
for anions. Groundwater quality is largely excellent and/or good, suggesting general suitability for agricultural use. Calcite and dolomite are found saturated in groundwater and thus tend to precipitate out, while halite, fluorite and gypsum are unsaturated and will dissolve into groundwater during flow. Groundwater in the study area is weathering-dominated, and mineral weathering (carbonate and silicate minerals) and ion exchange are the most important factors controlling groundwater chemistry.
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•Groundwater related research papers from 1978 to 2017 were collected.•The number of published studies increased by >10% per year on average.•Institutions based in developed countries ...have led groundwater research output.•China and India have experienced strong growth in output in recent years.•Depletion and sustainability have increased as a percentage of groundwater studies.
Long-term over-exploitation and unsustainable practices have caused severe groundwater depletion and deterioration across many regions throughout the world. This has triggered a series of negative impacts on human populations and the natural environment. To understand groundwater-related processes and explore ways to mitigate pertaining issues, large numbers of groundwater-related studies have been performed by the research community. In this study, all research papers published between 1978 and 2017 incorporating “groundwater” in the title, keywords, or abstract, were retrieved from the Web of Science Core Collection (WSCC). Of these, a total of 80,763 papers were identified as being groundwater-related publications. Our analysis revealed that groundwater research output increased significantly during this period, at average annual rate of 10.1%, exceeding the general trend for the WSCC (3.4%). Institutions based in developed countries have held predominance in publishing groundwater research, however, research output from developing countries, such as China and India, experienced much growth in recent years. Development trends were assessed among the research topics of groundwater depletion, contamination, remediation technology, and sustainable management, all of which experienced increased research output. Among sub-topics, groundwater depletion and sustainable management research have increased as a percentage of total groundwater studies, while studies of arsenic, chlorinated solvents, BTEX, bioremediation, and natural attenuation have dropped off in recent years. Additionally, as groundwater-related research output has increased rapidly, robust secondary analyses and meta-analyses are called for in order to make sense of the rapidly expanding body of groundwater research literature. Moreover, owing to the many complexities surround groundwater issues, greater interdisciplinary collaboration is also called for.
In the arid inland basins of China, the long-term unregulated agricultural
irrigation from surface water diversion and groundwater abstraction has
caused the unsustainability of water resources and ...the degradation of ecosystems.
This requires the integrated management of surface water (SW) and groundwater (GW) at basin scale to achieve scientific decisions which support sustainable water resource allocation in China. This study developed a novel multi-objective simulation-optimization (S-O) modeling framework. The
optimization framework integrated a new epsilon multi-objective memetic
algorithm (ε-MOMA) with a MODFLOW-NWT model to implement
real-world decision-making for water resource management while pondering
the complicated groundwater–lake–river interaction in an arid inland basin. Then the optimization technique was validated through the SW–GW management in Yanqi Basin (YB), a typical arid region with intensive agricultural irrigation in northwest China. The management model, involving the maximization of total water supply rate, groundwater storage, surface runoff inflow to the terminal lake, and the minimization of water delivery cost, was proposed to explore the trade-offs between socioeconomic and environmental factors. It is shown that the trade-off surface can be achieved in the four-dimensional objective space by optimizing spatial groundwater abstraction in the irrigation districts and surface water diversion in the river. The Pareto-optimal solutions avoid the prevalence of decision bias caused by the low-dimensional optimization formulation. Decision-makers are then able to identify their desired water management schemes with preferred objectives and achieve maximal socioeconomic and ecological benefits simultaneously. Moreover, three representative runoff scenarios in relation to climate change were specified to quantify the effect of decreasing river runoff on the water management in YB. Results show that runoff depletion would have a great negative impact on the management objectives. Therefore, the integrated SW and GW management is of critical importance for the fragile ecosystem in YB under changing climatic conditions.
How topography controls topography‐driven groundwater flow is investigated with varying rainfall and topography using a two‐dimensional groundwater‐surface water coupled model. Results show that the ...penetration depths of local flow systems present a good relation with capture zone size (Cl) and topography rise (Hl) of local flow systems, but poor and opposite relation with the two topographic indices of the surface water watershed. The stagnant zones are formed due to the movement of stagnation points, whose velocity magnitude is almost zero. The area and depth of stagnant zones below the mountains have a good or no relation with the mountain size, depending on the hydraulic conductivity. The fractal behavior of penetration depth variations with rainfall presents a good or no relation with Cl and Hl, depending on the rainfall rate and hydraulic conductivity. The topography control may be less important when rainfall rate or hydraulic conductivity is significantly reduced.
Plain Language Summary
This study explains which topographic indices control topography‐driven groundwater flow. Our study demonstrates that the groundwater subsystems are not controlled by the size and topography rise of a surface water watershed, but by the size and topography rise of each groundwater subsystem. In previous studies, identifying surface water divide was usually thought to be important before setting up a model to investigate groundwater flow patterns, but this study indicates that groundwater divide is totally independent of surface water divide. And it comes to an opposite conclusion when we base on capture zone size of groundwater subsystems. Our research also indicates that the control of topography on stagnant zones and variations of groundwater flow system can become weakened when the hydraulic conductivity or rainfall rate is reduced. The combined effect of topography, climate, and geology on groundwater flow patterns should be considered to fully understand the dominant factors on topography‐driven groundwater flow.
Key Points
Stagnant zones are formed due to the movement of stagnant points with rainfall fluctuation
Penetration depth of local flow systems is controlled by the capture zone size and topography rise of local flow systems
When the rainfall or hydraulic conductivity is reduced, climate or geology may control groundwater flow systems much more than topography
Managing fragile island freshwater resources requires identifying pumping strategies that trade off the financial cost of groundwater supply against controlling the seawater intrusion (SWI) ...associated with aquifer pumping. In this work, these tradeoffs are investigated through a sensitivity analysis conducted in the context of an optimization formulation of the groundwater management problem, which aims at minimizing the groundwater supply operation cost associated with groundwater pumping and desalination treatment, subject to constraints on SWI control, as quantified by the water table drawdown over the well (∆s), the reduction in freshwater volume (∆FV) in the aquifer, or the salt mass increase (∆SM) in the aquifer. This study focuses on a simplified two‐dimensional model of the San Salvador Island aquifer (Bahamas). Pumping strategies are characterized by the distance of the pumping system from the shoreline (WL), the ion screen depth (D) and overall pumping rate (Q), constituting the decision variables of the optimization problem. We investigate the impacts of pumping strategies on the operation cost, ∆s, ∆FV and ∆SM. Findings indicate increasing D or decreasing WL reduces ∆s, ∆FV and ∆SM, thus preserving the aquifer hydrogeologic stability, but also leads to extracting saltier groundwater, thus increasing the water treatment requirements, which have a strong impact on the overall groundwater supply cost. From a financial perspective, groundwater ion near the island center and at shallow depths seems the most convenient strategy. However, the analysis of the optimization constraints reveals that strategies where the pumping system approaches the island center tend to cause more severe SWI, highlighting the need to trade off groundwater supply cost against SWI control.
Key Points
Effects of pumping patterns (pump depth, rate and well location) on island groundwater supply cost and seawater intrusion (SWI) are studied
Shallow pumping near the island center is cost‐effective but causes more severe SWI, that is, a conflict between economic cost and SWI control
Controlling SWI by limiting water table drawdown usually leads to selecting more expensive groundwater supply strategies
Streamflow of the Colorado River Basin is the most overallocated in the world. Recent assessment indicates that demand for this renewable resource will soon outstrip supply, suggesting that limited ...groundwater reserves will play an increasingly important role in meeting future water needs. Here we analyze 9 years (December 2004 to November 2013) of observations from the NASA Gravity Recovery and Climate Experiment mission and find that during this period of sustained drought, groundwater accounted for 50.1 km3 of the total 64.8 km3 of freshwater loss. The rapid rate of depletion of groundwater storage (−5.6 ± 0.4 km3 yr−1) far exceeded the rate of depletion of Lake Powell and Lake Mead. Results indicate that groundwater may comprise a far greater fraction of Basin water use than previously recognized, in particular during drought, and that its disappearance may threaten the long‐term ability to meet future allocations to the seven Basin states.
Key Points
Groundwater depletion in the Colorado River Basin is greater than we thoughtAs GW disappears, the basin will struggle to supply water to the seven basin statesIt is time to bring groundwater under the water management umbrella
Warming in the Arctic is occurring at twice the rate of the global average, resulting in permafrost thaw and a restructuring of the Arctic hydrologic cycle as indicated by increased stream discharge ...during low‐flow periods. In these cold regions, permafrost thaw is postulated to increase low‐flow discharge, or baseflow, through either: (a) localized increases in groundwater storage and discharge to streams due to increased aquifer transmissivity from thickening of the freeze–thaw layer above permafrost known as the active layer or (b) long‐term increases in regional groundwater circulation via enhancement of groundwater–surface water interactions due to extensive permafrost loss over decades. While increasing baseflow has been observed throughout northern Eurasia, the precise mechanistic causes remain elusive. In this study, we differentiate between where these two subsurface physical mechanisms of baseflow increase are occurring by performing a baseflow recession analysis using daily streamflow records from 1913 to 2003 for 139 stations in northern Eurasia underlain by varying permafrost areal extents. Results indicate that from 1913 to 2003, the majority of catchments underlain by continuous permafrost have an increasing trend in their recession flow intercepts, a proxy for increasing active layer thickness. Alternatively, the majority of catchments underlain by permafrost types that are less spatially extensive (e.g., discontinuous, sporadic, isolated, or no permafrost) have decreasing trends in their recession flow intercepts, indicating that a potential increase in active layer thickness is not the driving factor of baseflow variations in these catchments. This may indicate that in catchments underlain by continuous permafrost, active layer thickening correlates with increases in baseflow, whereas, in other catchments with less extensive permafrost, increases in baseflow may be caused by wholesale permafrost loss and vertical talik expansion that enhances regional groundwater circulation. The results of this work may inform our understanding of the subsurface mechanisms responsible for the changing Arctic hydrologic cycle.
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