Shallow Groundwater Table Research Articles

Streamflow and Groundwater Response to Stream Restoration Using Beaver Dam Analogues in a Semi‐Arid Perennial Stream

ABSTRACTDegradation of stream and riparian environments across the western United States has damaged critical ecosystems, water quality, and increased sedimentation of reservoirs. Low tech, process‐based restoration methods such as beaver dam analogues (BDAs) have been adopted by practitioners because they restore ecosystem function, improve habitat, and reduce downstream sediment delivery at a low cost. However, few studies have examined the potential impacts of beaver dam analogues on the quantity and timing of streamflow, which is of primary concern for water stakeholders. We address this gap with 2 years of streamflow and riparian groundwater observations before and after installing a series of 17 BDAs on Fish Creek, a first‐order stream in semi‐arid northern Utah. Within 8 weeks of BDA installation, and 1 year later, we found no significant change in streamflow compared with control and Regional Reference sites. Shallow groundwater table elevations within 7 m of the stream edge increased significantly, up to 14 cm, relative to the control reach. Our results suggest that the small, local hydrological changes from BDA installation are superimposed on much larger‐scale snowmelt and alluvial groundwater controls on streamflow, suggesting BDA installation can restore ecosystem function without deleterious impacts on streamflow. These findings are especially relevant to restoration and water stakeholders with concerns about impacts of BDAs on downstream flows.

Shallow groundwater table fluctuations: A driving force for accelerating the migration and transformation of phosphorus in cropland soil

Shallow groundwater table fluctuations: A driving force for accelerating the migration and transformation of phosphorus in cropland soil

Predictive simulation of groundwater contamination due to landfill leachate: A case study on the Robinson Deep Landfill, Johannesburg, South Africa

Groundwater contamination from municipal solid waste landfills is a global issue, including South Africa. The Robinson Deep landfill (RDL) in Johannesburg lacks necessary leachate collection and handling facilities, has a shallow groundwater table, and no groundwater quality forecast tool. This situation poses a risk of groundwater contamination. This study aimed to construct groundwater flow and contaminant transport models to predict contamination from leachate migration at RDL. Visual MODFLOW Flex software was used for model construction and verification. Heavy metal concentration observations (Al, Cd, Mn, and Pb) from boreholes BH-1, BH-2, BH-3, and BH-H near the RDL were used to calibrate and validate the contaminant transport model (CTM). The result of the CTM predictive simulations for 2030 show Mn and Pb concentrations in the BH-H groundwater could reach 4.28 mg/L and 6.85 mg/L, respectively, exceeding permissible limits of 0.01 mg/L for Pb and 0.4 mg/L for Mn. The simulations indicate that the RDL threatens groundwater quality, especially in the northern areas of the landfill. Based on these findings, a recommendation is made for future studies on assessment and modelling of groundwater quality to focus on areas where increased concentrations of Pb and Mn are predicted. Further, it is recommended that precautionary preventive measures be implemented to mitigate possible contamination of groundwater in the northern areas of the landfill.

Monitoring soil salinization and waterlogging in the northeastern Nile Delta linked to shallow saline groundwater and irrigation water quality

Soil salinization and waterlogging are critical environmental issues affecting agricultural productivity and cultural heritage preservation, particularly in arid regions. This study investigated soil degradation processes in the archaeologically and agriculturally significant northeastern Nile Delta of Egypt. The objective was to assess the severity of soil degradation and identify key drivers related to water resources and soil characteristics to aid in the development of management strategies. The research employed a multi-faceted approach, including hydrochemical analyses (of groundwater, irrigation water, and soil), water quality indices calculations, statistical analyses, and satellite data. The results revealed high levels of soil salinization in the northern and central areas, with 64% of soil samples classified as strongly and very strongly saline. Soil chemistry indicated salinization sources linked to sodium chloride dominance. Satellite data from Sentinel-2 images and SRTM digital elevation data showed widespread severe waterlogging in the northern lowlands. The Irrigation Water Quality Index (IWQI) values indicated that 87.5% of irrigation water samples posed severe restrictions due to high salinity and sodium hazards, which were mismatched with the low soil permeability observed in 81% of the collected samples exhibiting clay texture and covering most of the study area. Furthermore, shallow groundwater at depths of 0.5–3 m with high salinity was detected, where total dissolved solids exceeded 20,000 mg/L, and Na-Cl water types prevailed, indicating saltwater intrusion. A strong positive correlation (r > 0.83) was found between shallow saline groundwater and soil salinity. The combination of poor irrigation water quality, shallow saline groundwater tables, and low-permeability soils created a synergistic effect that severely compromised soil health and agricultural productivity. It also posed severe risks to the structural integrity of archaeological sites and buried artifacts through accelerated physical and chemical weathering processes. This necessitates an urgent mitigation strategy to combat soil degradation in this critical area.

Numerical Study on the Liquefaction Potential Analysis Using Constitutive Models for Sand and Silt in Mamuju, West Sulawesi

Background Sulawesi Island, located in the Eastern Indonesian archipelago, is known for its high seismic activity. In 2021, West Sulawesi experienced an earthquake with a mainshock of 6.2 MW, which resulted in liquefaction characterized by sand boil and lateral spreading at various locations, including near the North coast of Mamuju. Objective This study aims is to assess the potential for liquefaction at a nearshore location in Mamuju, West Sulawesi. The assessment focuses on the increase in pore water pressure in an area characterized by multiple layers of sand, silt, and clay soils. Methods Numerical analysis was conducted by modeling one-dimensional soil column using PM4Sand and PM4Silt constitutive models calibrated using PLAXIS 2D soil test feature with the Cyclic Direct Simple Shear (CDSS) test method. Furthermore, the study included spectral matching of the ground motion from the 2021 Mamuju earthquake to the spectral response at the research site as motion input. Results Analysis results indicate the potential for liquefaction in silty sand and sandy silt soils with sand-like behavior, as evidenced by an excess pore water pressure ratio exceeding 0.8. Meanwhile, sandy silt and sandy clay soils, with a plasticity index (PI) greater than 7, showed no liquefaction potential at a peak ground acceleration of 0.478 g. Conclusion In conclusion, soil relative density plays an important role in influencing pore water pressure and liquefaction susceptibility, which should be considered when planning and designing in earthquake-prone areas, shallow groundwater tables, sand, silt, and clay layers.

Modeling PFAS Subsurface Transport in the Presence of Groundwater Table Fluctuations: The Impact on Source‐Zone Leaching and Exploration of Model Simplifications

AbstractAir–water interfacial adsorption represents a major source of retention for many per‐ and poly‐fluoroalkyl substances (PFAS). Therefore, transient hydrological fluxes that dynamically change the amount of air–water interfaces are expected to strongly influence PFAS retention in their source zones in the vadose zone. We employ mathematical modeling to study how seasonal groundwater table (GWT) fluctuations affect PFAS source‐zone leaching. The results suggest that, by periodically collapsing air–water interfaces, seasonal GWT fluctuations can lead to strong temporal variations in groundwater concentration and significantly enhance PFAS leaching in the vadose zone. The enhanced leaching is more pronounced for longer‐chain PFAS, coarser‐textured porous media, drier climates, and greater amplitudes of fluctuations. GWT fluctuations and lateral migration above the GWT introduce a downgradient persistent secondary source zone for longer‐chain PFAS. However, the enhanced leaching and the secondary source zone are greatly reduced when subsurface heterogeneity is present. In highly heterogeneous source zones, GWT fluctuations may even lead to overall slower leaching due to lateral flow (in the GWT fluctuation zone and above the GWT) moving PFAS into local regions with greater retention capacities. Model simplification analyses suggest that the enhanced source‐zone leaching due to GWT fluctuations may be approximated using a static but shallower GWT. Additionally, while vertical 1D models underestimate source‐zone leaching due to not representing lateral migration, they can be revised to account for lateral migration and provide lower‐ and upper‐bound estimates of PFAS source‐zone leaching under GWT fluctuations. Overall, our study suggests that representing GWT fluctuations is critical for quantifying source‐zone leaching of PFAS, especially the more interfacially active longer‐chain compounds.

Distribution and redistribution of salt ions in saline soils with shallow groundwater table

Saline water resources are more abundant than freshwater. Bringing these resources into sustainable, productive use will offer opportunities to reduce competition for freshwater resources, especially in arid and semi-arid areas where freshwater is scarce. Hence, the primary objective of this study was to elucidate the dynamics of salt ions in saline profiles of various soil types (sandy Clovelly and sandy loam Bainsvlei) under malt barley cultivation across 2 seasons where no leaching between the seasons took place. Results of this lysimeter study investigating increasing irrigation salinity (ECi) set at 1.5, 4.5, 6, 9, and 12 dSꞏm−1 over 2 seasons were used to explore ion dynamics of a saline environment. The lysimeter set-up included a saline constant (1.2 m) groundwater table with its salinity corresponding to ECi. Findings showed that ion concentrations are higher closer to the water source only in the Bainsvlei soil and remain variable in the Clovelly soil. Salt dynamics were more predictable in sandy loam soil than in sandy soil, making management of saline sandy soils far more challenging when leaching is not possible. Therefore, our hypothesis that the absence of leaching between seasons will lead to a differentiated progressive accumulation of salt ions in the soil profile, with variable effects on the soil depending on soil texture, was true. We conclude that the desalinized zone, which we determined to be at a depth of 600 mm, should be used to guide crop selection. Furthermore, in addition to the apparent provision for leaching of saline profiles, fertilization should target restoring ion balances, especially provisioning for calcium deficiencies. Both soils were prone to nutritional disorders, most especially calcium deficiency. Therefore, in addition to provision for leaching saline profiles, fertilization should target calcium provisioning for crop production in arid saline environments.

Impact of organic mulch and exposure to shallow groundwater levels on Cnidoscolus aconitifolius in a tropical wetland, South Sumatra, Indonesia

Agricultural land in Indonesia is decreasing due to its conversion for various non-agricultural interests, which are economically more profitable. The remaining land available for agricultural activities is a suboptimal wetland. The reduction in cultivable areas has led to the evaluation of alternative crops in suboptimal land conditions. Chaya (Cnidoscolus aconitifolius) is a fast-growing perennial plant, its leaves are edible and rich in vitamins, minerals, and dietary fiber. However, the chaya plant has not been intensively tested for its adaptation to shallow groundwater tables in tropical lowlands. This study aimed to assess chaya’s adaptability to shallow groundwater table conditions and the benefits of using organic mulch. This research consisted of two separate parts, one part was related to organic mulch benefits (planting media without watering, with organic mulch but not watered, and with organic mulch and watering), while the other one was related to shallow groundwater table tolerance. The study followed a randomized complete block design consisting of three replications. Results showed that chaya plants negatively responded to the shallow groundwater table conditions. Growth retardation due to shallow groundwater levels is reflected in the averages of leaf length, leaf width, leaf area, canopy diameter, and canopy area; fresh and dry weight of stem, petiole, and leaf blade; development of roots; SPAD value at 7 weeks after transplanting and it was based on visual appearance. However, despite the increase in substrate humidity due to the application of organic mulch, the effects were not significant on most of the measured morphological traits. In conclusion, chaya plants are not able to adapt to shallow groundwater levels and do not require organic mulch on the soil surface.

Implementasi Sistem Pertanian Organik di Desa Karangrejo, Kecamatan Gumukmas, Kabupaten Jember

The Mulyo Farmer Group of Karangrejo village are the fostered villages of the University of Jember and have long been food producers, especially rice and corn, with the potential to become one of the providers of organic products according to SNI 6729:2016. Therefore it is essential to evaluate the implementation of gab against the standard requirements of organic farming systems. Some of the activities carried out are Evaluation and increasing understanding of the application of organic farming systems by continuing the practice of making biochar from agricultural waste for long-term organic fertilizer base materials; Focus Group Discussion and ongoing assistance by the Soil Biodiversity and Fertility Research Group UNEJ. The results of the activities show that the community and village officials are thrilled and open to several activities to be carried out. The results of the initial evaluation using the checklist for fulfilling the requirements of SNI 6729:2016 are based on eight variables related to fresh plants and plant products, indicating that there is no program yet to meet the needs of the organic farming system of SNI 6729:2016 or it has not yet been fulfilled. Even though it has not been fulfilled, the potential for implementing it remains open if based on its main potential, namely organic fertilizer sources and water sources (lowlands with relatively shallow groundwater tables). The existence of many livestock and agricultural waste (which is not harvested) available throughout the year can be used as a source of organic fertilizer in maintaining soil fertility or health.

Bio-economic analysis of irrigation schedules considering shallow groundwater: lessons from South Africa

Due to the pressure on South Africa’s irrigated agriculture to improve efficiency and optimal water use, irrigators must consider alternative water sources, such as root-accessible shallow groundwater tables, to supply the crop evapotranspiration requirement. Devising irrigation scheduling strategies that will optimize conjunctive water use is difficult because the contribution of shallow groundwater tables is not directly observed and is a function of irrigation management decisions; as a result, very few irrigators use these strategies. This paper aims to evaluate the profitability of using shallow groundwater tables as a source of irrigation water to satisfy crop evapotranspiration requirements. A bio-economic simulation model consisting of the soil–water–atmosphere–plant model and an economic accounting module was developed to calculate the profitability of conjunctive irrigation practices under different states of nature. The bio-economic simulation model was linked to a differential evolutionary algorithm to optimize the irrigation scheduling decisions. The results showed that irrigators could substantially increase profitability and water use efficiency if they consider the shallow groundwater table in their irrigation decision. About 51% of crop evapotranspiration could originate from shallow groundwater tables, reducing the irrigation requirements substantially without impacting crop yields. Sequential adaptive irrigation decision-making does not improve the bio-economic indicators much since using the shallow groundwater table mitigates the risk of undersupplying water. Therefore, conjunctive water use strategies using shallow groundwater tables economically benefit irrigators. However, a complex interplay exists between irrigation adjustments, crop yields and economic performance in different states, emphasizing the careful consideration of context-specific factors in irrigation management decisions.

Shallow groundwater table fluctuations weaken nitrogen accumulation in the thin layer vadose zone of cropland around plateau lakes, Southwest China

Excessive accumulation of nitrogen (N) in the soil profile in the intensive agricultural region will seriously threaten groundwater quality and safety. However, the impact of shallow groundwater table (SGWT) fluctuations driven by seasonal variations on the N accumulation characterizations in the soil profiles has not been well quantified, particularly in the regions with thin layer vadose zone. Through in-situ monitoring and simulation experiments, the changes in the SGWT and N accumulation of soil profile in intensive cropland around 7 plateau lakes in Yunnan were studied during the rainy season (RS) and dry season (DS), and the N loss in soil profile of cropland driven by SGWT fluctuations was estimated. The results showed that the SGWT and N accumulation in soil profile of cropland around the plateau lakes had obvious seasonal variation characteristics. The proportion of N storage in different forms in 60–100 cm soil layer in the RS was greater than that in the DS, particularly the proportion of NH4+-N storage was as high as 55 %, while N accumulation in surface soil was obvious in the DS. Compared with the DS, due to the rising SGWT in the RS, the maximum storages of TN and NO3−-N in the 0–100 cm soil layer decreased by17% and 36 %, respectively. The TN loss intensities from the 0–100 cm soil profiles of cropland around Fuxian Lake, Yilong Lake, Qilu Lake, Dianchi Lake, Yangzong Lake, Erhai Lake, and Xingyun Lake were 74, 54, 127, 105, 93, 72 and 207 kg/ha, respectively. Moreover, if the SGWT was <30 cm, the average TN loss intensity and amount could reach 177 kg/ha and 1250 t, respectively. Therefore, the SGWT regulation was one of the key measures to reducing soil N loss from the thin layer vadose zone of cropland around plateau lakes and improving groundwater quality.

Evaluating MONICA's capability to simulate water, carbon and nitrogen fluxes in a wet grassland at contrasting water tables

Wet grasslands, which are vital for water and nutrient regulation, are characterised by distinct water, carbon (C) and nitrogen (N) dynamics, and their interactions. Due to their shallow groundwater table, wet grasslands promote a strong interconnection between diverse vegetation and soil water. Researchers have investigated how wet grasslands respond to environmental changes, using various simulation models to understand how these sites contribute to water, C and N dynamics. However, a comprehensive, simultaneous study of all three of these dynamics is still lacking. This study makes use of a grassland lysimeter study with differently managed groundwater levels and employs the process-based MOdel for NItrogen and Carbon dynamics in Agroecosystems (MONICA) to simulate these dynamics. By using SPOTPY (Statistical Parameter Optimization Tool) to optimise the relevant parameters, we find that MONICA performs well in simulating vegetation growth (aboveground biomass), and elements of the water (evapotranspiration), C (gross primary productivity, ecosystem respiration) and N (N in aboveground biomass, nitrate in soil solution, Nitrous oxide emissions) balance, with Willmott's Refined Index of Agreement always larger than 0.35. This level of accuracy demonstrates that MONICA is ready to be applied for scenario simulations of groundwater management and climate change to evaluate their impact on greenhouse gas emissions and long-term carbon storage, as well as water and nitrogen losses in wet grasslands.

Shallow groundwater table fluctuations promote the accumulation and loss of phosphorus from surface soil to deeper soil in croplands around plateau lakes in Southwest China

The continuous excessive application of phosphorus (P) fertilizers in intensive agricultural production leads to a large accumulation of P in surface soils, increasing the risk of soil P loss by runoff and leaching. However, there are few studies on the accumulation and loss of P from surface soil to deep soil profiles driven by shallow groundwater table (SGT) fluctuations. This study used the intensive cropland around 7 plateau lakes in Yunnan Province as an example and conducted in situ monitoring of P storage in the soil profile and SGT during the rainy season (RS) and dry season (DS) as well as simulation experiments on soil P loss. The aim was to study the spatiotemporal variation in P accumulation in the soil profile of cropland driven by SGT fluctuations in the RS and DS and estimate the P loss in the soil profile driven by SGT fluctuations. The results showed that fluctuations in the SGT promoted P accumulation from the surface soil to deeper soil. The proportions of P stored in various forms in the 30–60 cm and 60–100 cm soil layers in the RS were greater than those in the DS, while the average proportion in the 0–30 cm soil layer in the DS was as high as 48%. Compared with those in the DS, the maximum decreases in the proportion of P stored as TP and Olsen-P in the 0–100 cm soil layer in the RS were 16% and 58%, respectively, due to the rise in the SGT (SGT <30 cm), while the soil TP storage decreased by only 1% when the SGT was maintained at 60–100 cm. The critical thresholds for soil Olsen-P and TP gradually decreased with increasing soil depth, and the risk of P loss in deeper soil increased. The loss of soil P was increased by fluctuations in the SGT. Based on the cropland area around the 7 plateau lakes, P storage, and SGT fluctuations, the average loss intensity and loss amount of TP in the 0–100 cm soil layer around the 7 plateau lakes were estimated to be 25 kg/ha and 56 t, respectively. Therefore, reducing exogenous P inputs, improving soil endogenous P utilization efficiency and maintaining deep soil P retention are the basic strategies for preventing and controlling P accumulation and loss in deep soil caused by SGT fluctuations.

Quantifying the impacts of varying groundwater table depths on cotton evapotranspiration, yield, water use efficiency, and root zone salinity using lysimeters

Determining the evapotranspiration (ET) of cotton as a water-intensive crop is crucial for effective irrigation planning and water management, especially in regions like Sindh province, Pakistan, where shallow groundwater table depths (WTDs) are prevalent. Despite the importance of cotton, a major cash crop in Sindh, previous studies on ET were conducted decades ago and may no longer be reliable due to ongoing climate change and the introduction of new crop varieties. Thus, we quantified cotton ET across two cropping seasons and at various WTDs (0.45, 0.60, 0.75, 1.50, 2.25, and 2.75 m). The experimental study was based on the data procured from 12 mini lysimeters and 12 large lysimeters for two years (2018 and 2019) and at two soil series. The findings revealed that cotton ET ranged from 1332 to 1437, 1114–1202, 988–1075, 781–821, 690–733, and 637–683 mm at WTDs of 0.45, 0.60, 0.75, 1.50, 2.25, and 2.75 m, respectively. WTDs from 0.45 to 0.75 m fulfilled 94–96 % of cotton ET through groundwater (GW) contribution in Sultanpur soil (silt loam) and 93–97 % in Miani soil (silty clay loam). At 1.50–2.75 m WTDs, irrigation water requirements (excluding rainfall and leaching) were 63–88 % in Sultanpur soil and 67–89 % in Miani soil. The highest yield was observed at a 1.50 m WTD, while the highest water use efficiency was identified at a 2.25 m WTD. However, soil salinity increased by 60–80 %, resulting in a 40–60 % lower cotton yield at 0.45–0.75 m WTD. Therefore, periodic flushing of salts is necessary to utilize shallow WTDs effectively. Considering GW contribution to ET when allocating water for irrigation channels and devising irrigation schedules is crucial. This approach can lead to water savings, prevent land from becoming waterlogged and saline, manage the groundwater table, and reduce the need for drainage channels and labor force for their preparation.

Alternate wetting and drying: a water-saving technology for sustainable rice production in Burkina Faso?

With emerging water scarcity and rising fertilizer prices, optimising future water use while maintaining yield and nutrient efficiency in irrigated rice is crucial. Alternate wetting and moderate soil drying irrigation (i.e., re-irrigation when the water level reaches 15 cm below the soil surface) has proven to be an efficient water-saving technology in semi-arid zones of West Africa, reducing water inputs without yield penalty. Alternate wetting and severe soil drying (AWD30), by re-irrigating fields only when the water table reaches 30 cm below the soil surface, may further reduce water inputs compared to farmers’ irrigation practices (FP). However, acute soil drying may impair fertilizer use efficiency and reduce the bio-availability of some key nutrients. This study assessed the potentials and risks associated with AWD30 for smallholder rice farmers in the semi-arid zones of West Africa. We conducted 30 on-farm field trials over three seasons (wet and dry seasons of 2019, and dry season of 2020), in Kou Valley, Burkina Faso. We assessed yield, water productivity, nutrient uptake, and use efficiency under AWD30 and FP. In FP, farmers maintained their fields submerged as frequently as possible according to the scheme-dependent water provision schedule. With AWD30, irrigation frequency was reduced by 30%, however, soils were seldom completely dried due to a shallow groundwater table. Compared to FP, AWD30 reduced irrigation water input by 37% with no significant effects on grain yields (average of 4.5 Mg ha−1), thus increasing average water productivity by 39%. Both irrigation management practices provided comparable crop uptake of N, P, and K, and use efficiencies of applied N and P. However, the N content in straw and the P concentration in grain generally increased with total water input (rain + irrigation). We conclude that at locations with a shallow groundwater table, AWD30 can effectively save irrigation water without significantly reducing the grain yield and the use efficiency of applied mineral nutrients.

Challenges of Including Wet Grasslands with Variable Groundwater Tables in Large-Area Crop Production Simulations

Large-scale assessments of agricultural productivity necessitate integrated simulations of cropland and grassland ecosystems within their spatiotemporal context. However, simultaneous simulations face limitations due to assumptions of uniform species distribution. Grasslands, particularly those with shallow groundwater tables, are highly sensitive to water availability, undergoing rapid species composition changes. We hypothesised that predicting above-ground biomass (AGB) remains challenging due to these dynamic responses. Ten years of data from four lysimeters at a German wet grassland site, with varying water table treatments, was utilised to test this hypothesis. Correlation analysis revealed a strong positive indirect effect of the water regime on AGB, with a one-year time lag (r = 0.97). The MONICA model initially exhibited fair agreement (d = 0.69) in simulating Leaf-Area-Index (LAI) but performed poorly in replicating AGB (d = 0.3). After removing the species composition change effect from the LAI and AGB datasets, the simulation notably improved, with the overall relative root mean square error (rRMSE) of AGB decreasing from 1.55 to 0.90 between the first and second simulations. This demonstrates MONICA’s ability to predict grass growth patterns amidst changing water supply levels for constant species composition. However, it needs a competition model to capture biomass growth changes with varying water supply.

A Science and Community-Driven Approach to Illustrating Urban Adaptation to Coastal Flooding to Inform Management Plans

Academic research plays a pivotal role in illustrating and testing potential future adaptation strategies to sea level rise in low-lying coastal communities and enhances local municipalities’ adaptation plans. In Waikīkī, Hawai‘i, the built environment is increasingly impacted by flooding from multiple drivers: sea level rise-induced direct marine inundation, storm-drain backflow, and groundwater inundation (GWI), compounded by high-wave runup, extreme tides, heavy rainfall, and a shallow groundwater table. Given Waikīkī’s economic and cultural importance, in-place accommodation of flooding is desired, yet implementation plans have not been developed. By combining current scientific research, urban design visualizations, and community feedback, the interdisciplinary research team advanced intentional communication between the many parties seeking increased flood resilience through the end of the 21st century. Site-specific architectural renderings were a key tool to prompt structured community input on the coordination, prioritization, policy, and feasibility of adaptation measures for buildings, utilities, transportation, and open space. Public outreach reports document that the majority of participants thought all adaptation strategies presented were applicable, especially relocating critical equipment in buildings and streets. Proposed methods to develop sea level rise-adjusted minimum building elevation requirements may inform local municipalities’ future codes to minimize coastal property damage. The multi-year iterative process fostered growing participation in hosted and invited events, further improving the publicly distributed research products.

Characterizing large‐scale preferential flow across Continental United States

AbstractUnderstanding preferential flow (PF) at large scales is critical for improving land management and groundwater (GW) quality. However, limited knowledge of this process, due to soil surface heterogeneity and observational constraints, hampers progress. In this study, we propose estimating effective PF at remote sensing footprint scale (4–9 km) by examining its impact on soil moisture (SM) distribution and shallow groundwater (SGW) table fluctuations (depth 5 m). Effective PF encompasses macropore, funnel, and finger flow pathways influencing SGW table fluctuations. We compiled daily SGW observations (2019–2021) from 19 Continental United States (CONUS) sites through United States Geological Survey. Using inverse modeling in HYDRUS‐1D, SGW data, and climate hazards group infrared precipitation with station data precipitation, we inversely estimated soil hydraulic parameters of the dual‐porosity model (DPM) simulating vertical flow from soil surface to subsurface. Effective PF presence was inferred using three criteria: (1) daily precipitation equal to or exceeding the site‐specific average across multiple (calibration) years, (2) daily observed SGW table increase, and (3) daily difference between observed and DPM simulated SGW tables 50% of the site‐specific root mean square error. Leveraging optimized DPM parameters and associated soil texture, classified PF events, and soil moisture active passive (SMAP L3E) satellite‐based SM, a random forest algorithm with 10‐fold cross validation predicted large‐scale effective PF events. Results indicate seasonal dependence, with spring having the highest occurrence of PF events. The random forest model achieved 98% accuracy in predicting large‐scale PF events, with SMAP SM and saturated hydraulic conductivity (Ks) among the four most impactful variables. Our approach provides a soil hydraulic property, site characteristic, soil texture, and remote sensing‐based generalized tool to analyze large‐scale effective PF.

A multi-scenario multi-model analysis of regional climate projections in a Central–Eastern European agricultural region: assessing shallow groundwater table responses using an aggregated vertical hydrological model

The 2022 drought highlighted Hungary's vulnerability to climate change, especially the Great Hungarian Plain. Soil moisture, which is crucial for agriculture, depends on the position of the shallow groundwater table. This study investigated the effects of climate change on groundwater table fluctuations in more than 500 wells on the plain. An integrated vertical hydrological model, assuming negligible horizontal subsurface flows, employed the Dunay–Varga-Haszonits methodology for evaporation and Kovács approach for the water retention curve. Verified with two meteorological databases, the model was accepted for 463 wells based on NSE > 0.4 and RMSE < 0.5 m criteria. The FORESEE HUN v1.0 dataset proved suitable after spatial consistency tests. Examining 28 bias- and discontinuity-corrected climate model projections on these wells revealed a general decline in the groundwater table. Differences between trends to 2050 and 2100 suggested lower groundwater levels by mid-century. This research highlights climate change impacts in a crucial Central-European agricultural region in the Carpathian Basin and emphasizes the importance of modeling climate change-induced changes in shallow groundwater levels in water resources management.

Understanding the impact of climate-induced sea level rise on groundwater inundation in a low-lying coastal area: A numerical simulation in Southeast India

Global warming has led to rising sea levels, severely threatening coastal areas, particularly in low-elevation coastal zones. The groundwater in coastal aquifers of lower elevation is susceptible to groundwater inundation (GWI), an emerging hidden long-term hazard earlier to marine inundation. The inundation is mainly due to the hydraulic connection between sea level and shallow unconfined aquifers, resulting in groundwater upsurging towards the ground surface. To understand the potential impact of sea level rise (SLR) induced GWI on low-lying coasts, a transient state model was simulated and predicted in the Cuddalore regions of South India under 0.3 m, 0.6 m, and 1 m SLR scenarios. The simulation reveals that the aerial extent of groundwater rise (GWR) was 331.9 km2, 566.2 km2, and 650.8 km2 for 0.3 m, 0.6 m, and 1 m SLR scenarios, respectively. About 50% of the response was observed in the northern and central parts of the study area within a 5 km buffer, which is attributed to the deeper groundwater table. In contrast, the southern region exhibited a 10% decline in response due to shallow groundwater discharge to drainage, which dampened the shoaling effect. The present-day shallow groundwater tables in the southern region are more vulnerable to GWI from rising sea levels. Specifically, a 0.3 m SLR could inundate 14.9 km2. In comparison, a 1 m SLR could inundate 40.5 km2 of the area, including the Pichavaram mangrove forest, agricultural land, municipal structures, and the other regions that flooding could threaten. These inundations could have potential impacts, such as wetland loss, agricultural flooding, deteriorating water quality, and infrastructural damage. The present study provides valuable insights into the subsurface hydrodynamic and exposure impacts of sea rise-induced inundations. This can aid coastal engineers, policymakers, and decision-makers to plan appropriate mitigation measures.