Low Groundwater Table Research Articles

Deciphering Farm Pond Adoption Dynamics and Operational Efficiency in Drought-Prone Regions of Maharashtra, India

The study delves the dynamics of farm pond adoption and operational efficiency in the Vidarbha and Marathwada regions of Maharashtra during 2022-23. Through a combination of quantitative and qualitative methods, data were collected from 160 beneficiaries and 160 non-beneficiaries, employing focus group discussions and structured interviews. Agricultural risks were examined, revealing a significant impact on farm income. Challenges such as low ground water table (MS 0.978), high temperatures (MS 0.966), and least evapotranspiration (MS 0.759) affected farmers' livelihoods, underscoring the need for a multidisciplinary approach to address these issues. The study highlights factors influencing farm pond adoption, with high awareness (96.56%) contrasting with lower adoption rates (51.56%). Adopters cited increased water access (22.81%), and relief from water scarcity (20%) as motives. Non-adopters faced barriers like financial constraints (21.88%) and land shortage (18.75%). Farm pond characteristics were comprehensively explored, revealing variations in size, structure, year of adoption, and irrigation sources. Maintenance activities were examined, showcasing key areas for pond health. Regular inspection (31.88%), vegetation management (17.50%), sediment removal (25.63%), and erosion prevention (19.38 %) emerged as crucial tasks, with variations between the regions. Financial aspects of pond construction and maintenance were elucidated, indicating a need of subsidies. Despite widespread awareness of farm pond benefits, adoption rates remained constrained by financial limitations, land availability, and awareness gaps. The study underscores the importance of targeted interventions, including financial aid, technical guidance, and capacity-building. These efforts are essential for promoting widespread adoption, enhancing agricultural productivity, water management, and the resilience of farming communities in both regions.

Ditch cleaning in boreal catchments: Impacts on water chemistry and dissolved greenhouse gases in runoff

Ditch cleaning (DC) is a forestry practice commonly conducted in boreal regions that aim to lower groundwater tables (GWT) in waterlogged soils, thereby maintaining or improving forest growth. However, there is limited information on the impact of DC on water chemistry and dissolved greenhouse gases (GHG) in draining ditch networks. Based on a repeated synoptic sampling of a paired catchment design we here evaluated water chemistry and GHG data in ditch waters from 25 cleaned sites (being cleaned 1–4 years prior to sampling) and 25 non-cleaned reference sites (REF). The sampled sites were further selected to test whether there were any differences in the DC effect if the operations were conducted in forested or clear-cut areas. Across all sites, we found that DC sites exhibited higher pH, sulfate and calcium concentrations than REF sites. Also, lower dissolved carbon dioxide and higher nitrous oxide concentrations were observed in DC sites. In forested areas, DC sites exhibited significantly higher calcium and potassium concentrations, along with reduced levels of methylmercury and carbon dioxide. In clear-cuts, sulfate concentrations were significantly elevated in the DC sites. We suggest that the observed differences in water chemistry and GHG´s between DC and REF sites were induced by the DC and largely driven by lower GWT following DC, resulting in deeper groundwater flow paths through more mineral-rich soil layers, and altered redox conditions. Also, the removal of organic rich sediments and vegetation from the ditches themselves may affect water chemistry and GHG´s e.g. by decreasing the formation of methylmercury and carbon dioxide.

Anatomical Characteristics of the Xylem of Populus euphratica at Different Groundwater Burial Depths in the Lower Tarim River (China) and Its Response to Temperature Extremes

The anatomical characteristics of xylem and their relationship with temperature during the year can be studied at the cellular scale by using micro-coring technology and the wood anatomy method. In this study, we used Populus euphratica Oliv. trees with different groundwater burial depths in the lower Tarim River as the research subjects. Micro-core samples of Populus euphratica were collected near two sampling sites, TY1 and TY2, which have different groundwater burial depths. We analyzed the differences in xylem anatomical characteristics and their relationship with extreme temperatures under these varying groundwater conditions using wood anatomy methods. The results showed that the anatomical parameters at TY1, with a higher groundwater table, were greater than those at TY2, which had a lower groundwater table. Specifically, the conduit density, total conduit area, average conduit area and maximum conduit area of Populus euphratica xylem were significantly and positively correlated with both maximum and minimum temperatures. The principal components of xylem parameters at TY1, with the higher water table, were significantly and positively correlated with both maximum and minimum air temperatures. In contrast, the principal components of xylem parameters at TY2, with the lower water table, were not significantly correlated with either maximum or minimum air temperatures. The sensitivity analysis indicated that the sensitive maximum air temperature for the principal component parameter index change of Populus euphratica xylem was 34.1 °C, and the sensitive minimum air temperature was 16.1 °C. Therefore, different moisture conditions affected the sensitivity of xylem parameter growth to temperature, with the temperature threshold for Populus euphratica xylem growth being between 16.1 °C and 34.1 °C.

Spatial allocation of bioretention cells considering interaction with shallow groundwater: A simulation-optimization approach

Green infrastructure (GI), as one type of ecological stormwater management practices, can potentially alleviate water problems and deliver a wide range of environmental benefits in urban areas. GIs are often planned and designed to reduce runoff and mitigate pollution. However, the influence of GI on groundwater hydrology and that of shallow groundwater on GI performance was seldom considered. This study utilized a calibrated surface-subsurface hydrological model, i.e., Storm Water Management Model coupled with USGS's modular hydrologic model (SWMM-MODFLOW) to consider the interaction between GI and groundwater into the process of GI planning. The optimal implementation ratio, aggregation level and upstream-downstream location of bioretention cells (BC, one type of GI) under different planning objectives and hydrogeologic conditions was explored. The consideration of groundwater management exerted a significant impact on the optimal spatial allocation of BCs. The results showed that when groundwater management was more concerned than runoff control, BCs were recommended to be allocated more apart from each other and more upstream in the catchment because more-distributed and upstream BCs can result in lower groundwater table rise which is beneficial. BCs were overall recommended to be allocated in areas of deeper groundwater tables, coarser soils, and flatter topographies. However, the spatial features of BCs are related to each other, the choice of them are affected by various hydrogeologic factors simultaneously. The exact location of BCs should be determined by considering the trade-off between runoff control efficiency and groundwater impact. The findings obtained in this study can provide guidance on GI planning in shallow groundwater areas.

Soil salinity management practices in coastal area of Bangladesh: a review

Soil salinity is a significant threat to agriculture and livelihood, particularly in the Southern coastal areas of Bangladesh. Soil salinity is extended from 0.833 to 1.056 million hectares (about), with an increase of 26% between 1973 and 2009. Out of about 1.689 million hectares of coastal land, about 1.056 million hectares are affected by soil salinity of various degrees covering 49 Upazila (sub-district) of 19 districts. About 0.328, 0.274, 0.189, 0.161, and 0.101 million hectares of land are affected by very slight (S1), slight (S2), moderate (S3), strong (S4), and very strong salinity (S5), respectively. Data recorded by SRDI manifests new ingression of salinity in Narail (18.71 ha), Jashore (14.99 ha), Barishal (13.96 ha), Gopalgonj (6.27 ha), Jhalakati (4.69 ha), and Madaripur (0.72 ha) districts. Soil salinity also encroached a large area of Bhola (53.84 ha), Patuakhali (40.08 ha), Khulna (27.92 ha), and Bagerhat (23.14 ha), besides minor ingression in other districts. The salinity level is almost double (2.8-18.5 to 4.0-42.8 dS/m) from 1973 to 2009 in Sharankhola Upazila of Bagerhat district, Dumuria Upazila of Khulna district and Shyamnagar Upazila of Satkhira district (SRDI, 2010). Different causes are involved in increasing the water and soil salinity of the coastal area of Bangladesh, like withdrawal of fresh river water from upstream, irregular rainfall, faulty management of sluice gates and polders, regular tidal water flooding in an unprotected area, the capillary rise of soluble salts, decreased surface water availability, lowered ground water table, reduced soil moisture content, the introduction of unplanned shrimp cultivation, lack of drainage facilities. Some of the widespread soil and land management techniques adopted in the saline areas of Bangladesh to cope with the salinity are polder (123), farm-pond (khamar-pokor), sarjan procedure, usage of raised shrimp farm bund for year-round cropping, mulching (keeping land covered in winter and summer months), land leveling, pitcher (kolosh) irrigation to grow watermelon, dibbling method, the addition of organic matter, chemical fertilizers and cultivation of saline tolerant crop varieties, particularly rice. Vol. 10, No. 1, April 2023: 1-7

Vertical Transportation Diversity of Petroleum Pollutants under Groundwater Fluctuations and the Instructions for Remediation Strategy

Based on the information from an actual petroleum-contaminated site, a one-dimensional soil column was used to examine the vertical transportation diversities of different petroleum components under the influence of water table fluctuations, and the results revealed the following: (1) There were two obvious pollution accumulation zones under the condition of water table fluctuations: (i) The pollution infiltration zone dominated by the residual phase was formed at the leakage position, and (ii) the floating zone dominated by the free phase was formed near the water table. Combined with the viscosity of the organic components, the concentrations of the residual phase were octanoic acid > hexadecane > cyclohexane > toluene. Compared to coarse sand, clay can adsorb more components. (2) Different fluctuation frequencies had a great influence on the migration process of components. The free phase can transfer into the residual phase during the low groundwater table fluctuation. In the case of high-frequency groundwater fluctuations, there were more free phase components that can be carried by the water flow. However, due to the continuous flushing by the water, pollutants were finally spread to the whole underground system. (3) A cost-effectiveness remediation strategy is based on the difference in pollutant transportation. Therefore, the conclusions in this paper are fully applied in the actual contaminated sites. Specifically, the air-sparing (AS) and soil vapor extraction (SVE) devices were installed in the vadose zone to remove volatile substances (such as toluene). The permeable reactive barriers (PRBs) were set in the groundwater fluctuation zone to repair the residual pollutants (alkanes, cyclane, and asphaltenes hydrocarbons) that are continuously converted from the residual phase to the dissolved phase and free phase due to water level fluctuations. Hence, the results of this study provided a specific, targeted, and comprehensive strategy for petroleum pollution treatment.

Cost-benefit analysis of mitigating subsidence damage in Semarang and Demak, Indonesia

Since the early 1990s, the coastal Semarang City in Indonesia has been undergoing rapid industrialization and population expansion. To meet growing water demand, groundwater is abstracted with an ever-increasing number of abstraction wells. This has led to lower groundwater tables in the largely unconsolidated substrate and this, in turn, causes land subsidence in the area. This has led to significant direct and indirect economic damage. In the context of limited public resources, this study aims to analyze the economic rationale of alternative (public) investment strategies to reduce subsidence impact in the Semarang-Demak region. With Cost-Benefit Analysis (CBA), three alternative strategies to replace groundwater abstraction wells are analyzed: (1) Installment of a piped clean water supply system with 1,000 L/s capacity, (2) a new 2 km2 coastal freshwater reservoir in West Semarang, (3) installment of a piped clean water supply system with 2,000 L/s capacity. All strategies have a positive (>1) benefit-cost ratio, which indicates that there is an economic rationale for investment to mitigate subsidence in Semarang and Demak. Under a low water demand scenario, the best strategy is strategy 1; under a high water demand scenario, the best strategy is strategy 3. As strategy 3 gives the highest economic benefit in the worst-case scenario, this is the most robust strategy.

Groundwater Fluctuation of a Meliorated Forest Catchment in Connection with the Climate and the Growth of Forest Stands—30 Years of Monitoring

Hydromelioration networks aim to expand the vadose zones of waterlogged and peaty sites, which is expected to provide more soil space for trees’ roots, thus improving forest stand stability and production. However, the recent climate is manifested by increasing air temperatures, changed distribution of precipitation and frequent droughts. This raises the issue of the suitability of such measures. Additionally, the impacts on the ground water table (GWT) level, drainage, and forest health are disputed. This study deals with the behaviour of the shallow-aquifer GWT level in a formerly deforested headwater catchment named U Dvou louček (UDL) which had been monitored for 30 years and placed at a mountain site in north-eastern Bohemia, Czech Republic. GWT (84 m long transect with 22 probes), precipitation, throughfall, discharge, air temperatures and stand parameters were measured. Young Norway spruce stands now dominate within the UDL area. Average precipitation of the open area reached 1285 mm, and precipitation in years 2003, 2015 and 2018 was minimal (910 to 950 mm). Calibration of the GWT measurement took place in 1992–1995. After a 5-year stabilisation period in 1996–2001 with gradually falling GWT levels, following the digging of new ditches, the GWT no longer fluctuated significantly. The discharge and GWT change responses to stand growth were modest, and the impact of forest tending was limited. Lower GWTs in dry years were temporary. The inter-annual water levels in the immediate vicinity of the ditches fluctuated the least. The small-scale technical hydromelioration intervention neither had a negative impact on the GWT level, nor threatened the water supply of growing forest stands even in dry years. The results confirmed the long-term potential of such measures to improve the water regime of reforested clear cuts on waterlogged forest soils in mountains with a minimal risk of threat in warming environments.

The Long-Term Hydraulic Efficiency of Green Infrastructure under Sea Level: Performance of Raingardens, Swales and Permeable Pavement in New Orleans

Greater New Orleans is surrounded by wetlands, the Mississippi River and two lakes. Excess rain can only be drained off with pumping systems or by evaporation due to the bowl-like shape of a large part of the city. As part of the solution to make New Orleans climate adaptive, green infrastructure has been implemented that enable rainfall infiltration and evapotranspiration of stored water after Hurricane Katrina in 2005. The long-term efficiency of infiltrating water under sea level with low permeable soils and high groundwater tables is often questioned. Therefore, research was conducted with the full-scale testing method measuring the infiltration capacity of 15 raingardens and 6 permeable pavements installed in the period 2011–2022. The results show a high variation of empty times for raingardens and swales: 0.7 to 54 m/d. The infiltration capacity decreased after saturation (ca 30% decrease in empty time after refilling storage volume) but all the tested green infrastructure met the guideline to be drained within 48 h. This is in contrast with the permeable pavement: only two of the six tested locations had an infiltration capacity higher than the guideline 10 inch/h (254 mm/h). The results are discussed with multiple stakeholders that participated in ClimateCafe New Orleans. Whether the results are considered unacceptable depends on a number of factors, including its intended purpose, site specific characteristics and most of all stakeholder expectations and perceptions. The designing, planning and scheduling of maintenance requirements for green infrastructure by stormwater managers can be carried out with more confidence so that green infrastructure will continue to perform satisfactorily over the intended design life and can mitigate the effects of heavy rainfall and droughts in the future.

Probabilistic Soil Liquefaction Assessment: A Case Study for Agartala City in Tripura in North-East India

A sudden increase in pore water pressure causes the effective stress to decrease significantly, which in turn causes a loss of shear strength and the subsequent outcome of allowing the soil to behave as a liquid, resulting in soil liquefaction. Agartala, the capital of Tripura, is located in northeastern India, and the entire region is considered seismically active according to the seismic zoning map of India as per IS 1893:2002 (Part 1); the entire region is classified as Zone-V. Significant earthquakes have struck this region, including the 1897 Shillong and 1950 Assam earthquakes. The city is vulnerable to liquefaction due to alluvial soil and a low groundwater table. Several parameters are involved in assessing liquefaction potential in the deterministic method and have different input parameter uncertainties, resulting in inconsistent outcomes. As a result, evaluating liquefaction susceptibility requires a thorough probability approach that considers parameter uncertainty. In this work, the soil liquefaction potential of Agartala City is assessed using fuzzy logic and compared to the conventional Reliability technique using the first-order second-moment method. Soil liquefaction potential was properly calculated using both approaches for the 71 boreholes in and around Agartala city. The outcomes are shown as contour maps representing spatial variations of the probability of liquefaction at different depths. In this study, Fuzzy logic is used to model the relationships between different soil parameters, which can help better understand the soil\'s behaviour during liquefaction. This developed method can assess the vulnerability of liquefaction potential and select appropriate materials and construction processes.

Geochemistry and palaeo-hydrogeology of the weathered zone in the Opalinus Clay

The effects of weathering and decompaction on the Opalinus Clay in northern Switzerland were studied on the basis of a 146 m long drillcore profile. Below 6 m of Quaternary sediments, the rock down to 16 m depth is affected by partial or complete dissolution of siderite, calcite, pyrite and organic matter, with goethite as the only identified product. The reduction level of Fe (Fe2+/Fetot) in the rock increases with depth from <20% to >80% in unweathered rock below 24 m. Porosity reaches 0.39 in the shallowest samples before dropping to normal values of around 0.13 below 30 m. Pore-water composition obtained by rock squeezing evolves with depth from fresh water of the Ca-SO4-HCO3 type to a 10–12 g/L Na-SO4-Cl type in unweathered rock below 40 m. Ground-water samples taken in the weathered zone indicate reducing conditions at present and therefore reflect a remaining redox buffering capacity even in the strongly oxidised rock. The interpretation of the rock properties, in conjunction with the chemical and isotopic signatures of ground and pore waters, suggests that substantial weathering occurred primarily during stages with a lower ground-water table in the Pleistocene, providing access to oxygen via gas diffusion across the partially unsaturated zone. Three evolutionary stages can be distinguished: 1) Long-term pyrite oxidation during Pleistocene surface exposure under dry climate and diffusive transport of SO42− into the formation. This explains the higher SO42− pore-water concentrations even in the unweathered rock at depth when compared to regional data from deep boreholes. 2) Build-up of the curved Cl− and water-isotope diffusion profiles since ∼50–60 ka with a depth penetration of 40–80 m. 3) Holocene rise of the water table, leading to self sealing of fractures and the establishment of a diffusive regime in the weathered zone. Under saturated conditions, the depth penetration of rock oxidation is quite limited, which illustrates the substantial buffering capacity of the Opalinus Clay against external geochemical disturbances.

Monitoring Shoreline and Land Use/Land Cover Changes in Sandbanks Provincial Park Using Remote Sensing and Climate Data

Climate change-driven forces and anthropogenic interventions have led to considerable changes in coastal zones and shoreline positions, resulting in coastal erosion or sedimentation. Shoreline change detection through cost-effective methods and easy-access data plays a key role in coastal management, where other effective parameters such as land-use/land-cover (LULC) change should be considered. This paper presents a remotely sensed shoreline monitoring in Sandbanks Provincial Park, Ontario, Canada, from 1984 to 2021. The CoastSat toolkit for Python and a multilayer perceptron (MLP) neural network classifier were used for shoreline detection, and an unsupervised change detection framework followed by a postclassification change detection method was implemented for LULC classification and change detection. The study assessed the recent coastal erosion and accretion trends in the region in association with spatiotemporal changes in the total area of the West and East Lakes, the transition between LULC classes, extreme climate events, population growth, and future climate projection scenarios. The results of the study illustrate that the accretion trend apparently can be seen in most parts of the study area since 1984 and is affected by several factors, including lake water-level changes, total annual precipitations, sand movements, and other hydrologic/climatic parameters. Furthermore, the observed LULC changes could be in line with climate change-driven forces and population growth to accelerate the detected accretion trend in the East and West Lakes. In total, the synergistic interaction of the investigated parameters would result in a greater accretion trend along with a lower groundwater table amid even a low carbon scenario. The discussed findings could be beneficial to regional/provincial authorities, policymakers, and environmental advocates for the sustainable development of coastal communities.

Water Demand Estimation in Service Areas with Limited Numbers of Customer Meters—Case Study in Water and Sanitation Agency (WASA) Lahore, Pakistan

The Water and Sanitation Agency (WASA) of Lahore, Pakistan, supplies water to 5.29 million people through 598 tube wells but faces difficulties in meeting rapidly increasing water demand, lowering groundwater table, high energy costs, and low water tariffs. However, the actual water consumption and water loss have never been estimated due to water meter outages. This study aimed to estimate the actual water consumption, production, and water losses for the WASA Lahore service area, using the limited number of working water meters and pump operation data. The actual water consumption was estimated by 14,030 working customer meters; the population census was 44.02 m3 per connection per month, or 200 L per capita per day, while the water production was 79.8 m3 per connection. The actual water loss was significantly higher than non-revenue water, with an average of 45.4% (ranging from 35.9–69.4%). Due to high electricity costs, WASA has had to cut their supply hours. Therefore, leakage reduction programs must be implemented in the high-water-loss townships found in this study in order to meet the increasing water demand, reduce electricity consumption, and alleviate groundwater table drawdown.

Bottom-Up Control of the Groundwater Microbial Food-Web in an Alpine Aquifer

Groundwater ecosystems are typically poor in organic carbon and productivity sustaining a low standing stock of microbial biomass. In consequence, microbial food webs in oligotrophic groundwater are hypothesized to be bottom-up controlled. To date, quantitative information on groundwater microbial communities, food web interactions, and carbon flow is relatively lacking in comparison to that of surface waters. Studying a shallow, porous alpine aquifer we collected data on the numbers of prokaryotes, virus-like particles and heterotrophic nanoflagellates (HNFs), the concentration of dissolved (DOC) and assimilable organic carbon (AOC), bacterial carbon production (BCP), and physical-chemical conditions for a 1 year hydrological cycle. The potential effects of protozoan grazing and viral lysis onto the prokaryotic biomass was tested. Flow of organic carbon through the microbial food web was estimated based on data from the literature. The abundance of prokaryotes in groundwater was low with 6.1 ± 6.9 × 104 cells mL–1, seasonally influenced by the hydrological dynamics, with higher densities coinciding with a lower groundwater table. Overall, the variability in cell numbers was moderate, and so it was for HNFs (179 ± 103 HNFs mL–1) and virus-like particles (9.6 ± 5.7 × 105 VLPs mL–1). The virus to prokaryotes and prokaryote to HNF ratios ranged between 2–230 and 33–2,084, respectively. We found no evidence for a viral control of prokaryotic biomass, and the biomass of HNFs being bottom-up controlled. First estimations point at carbon use efficiencies of 0.2–4.2% with prokaryotic production, and carbon consumed and recycled by HNFs and phages to be of minor importance. This first groundwater microbial food web analysis strongly hints at a bottom-up control on productivity and standing stock in oligotrophic groundwater ecosystems. However, direct measurement of protozoan grazing and phage mediated lysis rates of prokaryotic cells are urgently needed to deepen our mechanistic understanding. The effect of microbial diversity on the population dynamics still needs to be addressed.

Impact of surface-applied liquid manure on the drainage resistance profile of an agricultural tile-drained clay till field.

Dissemination of antibiotic resistance genes (ARGs) in aquatic environments is a concern due to human and animal health. Application of liquid manure on agricultural land is an important source of ARGs, where pathogens, antibiotic-resistant bacteria, and selective agents are released. To improve our understanding of ARGs spreading through soils, our main objective was to evaluate the effectiveness of the soil as a barrier protecting water resources. Over the course of a year, profiles and abundances of ARGs and mobile genetic elements in soil and drainage from an agricultural tile-drained clay till field were investigated upon liquid pig manure application by applying high-throughput quantitative polymerase chain reaction targeting 143 genes. The findings were as follows: (a) 97 genes were detected, where only the transposon gene tnpA-03/ IS6 was shared between the genes detected in drainage and those in acidified liquid manure or fertilized soils, indicating that liquid manure application had a limited impact on the drainage resistance profile; (b) intI1 gene was present in ∼60% of drainage samples in concentrations up to 1,634intI1 ml-1 ; and (c) evapotranspiration from barley (Hordeum vulgare L., 'KWS Irina') and a low groundwater table appeared to reduce preferential transport to drainage during the first 3 mo of liquid manure application. Interestingly, the first preferential transport to drainage was observed immediately after the harvest of spring barley. Overall, during the monitoring year we found the soil to be an effective barrier against the spread of fecal ARGs even though the occurrence of the intI1 gene questions the barrier effect from previous years.

Response and contribution of shallow groundwater to soil water/salt budget and crop growth in layered soils

Shallow groundwater affects crop growth and yield by altering the root zone water and salt budgets, with the process being more complicated in layered soils. To gain insights into the role of shallow groundwater in layered soils, LAWSTAC, a physically-based agro-hydrological model, was employed to simulate soil water, salt, and groundwater fluxes and crop yield in three soil profiles: loam (L), loam with a sand interlayer (LSL), and loam with a clay interlayer (LCL). The model was verified using data collected in 2007 and 2008 from a spring wheat field with shallow groundwater tables. The model predictions matched well with the measured soil water content, salt concentration, groundwater table depth (GWD), leaf area index, biomass, and crop yield. Further simulations were conducted for the L, LSL, and LCL profiles with varying GWDs in the crop growth seasons and initial values specified at 130, 150, 170, 190, 210, 230, and 250 cm. The groundwater table showed greater fluctuations in LCL, with smaller fluctuations in LSL in comparison to L. When starting with smaller initial GWDs (of 130, 150, 170, and 190 cm), the coarse-textured soil under the root zone facilitated water and salt fluxes at the bottom of the root zone, resulting in larger averages for root zone water storage and more salt content during the crop growth seasons and lower crop yield due to salt stress. Meanwhile, in cases with an initial GWD larger than 210 cm, the coarse-textured soil inhibited the fluxes and improved crop yield due to the reduced salt stress. Fine-textured soil under the root zone inhibited water and salt fluxes, reducing root zone salt content and favoring crop yield; however, the effect decreased with larger initial GWDs. Thus, the groundwater table should be lowered to a level where coarse-textured soil acts as a capillary barrier for salt control and crop growth in soil profiles similar to LSL. Keeping a high groundwater table to sustain water for crop growth is acceptable in soil profiles similar to LCL, while keeping a lower groundwater table could be an effective practice to control salt and improve crop production in salinized croplands.

Monitoring of construction-induced urban ground deformations using Sentinel-1 PS-InSAR: The case study of tunneling in Dangjin, Korea

The construction of underground tunnels can prime or trigger ground subsidence, and thus surface deformation monitoring is required during and post-construction. Freely available satellite data allow significant possibilities for the use of remote sensing techniques, particularly multi-temporal interferometric synthetic aperture radar (Mt-InSAR), for surface deformation monitoring. However, track records and field demonstrations of InSAR-based tunneling-related deformation monitoring are limited, particularly in identifying the spatiotemporal evolution of ground deformation and causal factors thereof from construction activities. Therefore, this study explores the feasibility of using satellite SAR data to monitor the surface deformation associated with different tunnel construction phases. Tunneling-related surface deformation was analyzed using the persistent scatterer InSAR (PS-InSAR) technique and Sentinel-1B SAR data; the PS-InSAR results were compared with those from the conventional leveling method. The velocity map of the study site revealed a localized subsidence trough associated with the construction of vertical shafts and shield tunneling. The cumulative time-series displacement map successfully tracked the spatial and temporal progression of ground deformations related to the phases of tunnel construction activities. The maximum subsidence rate in the radar line-of-sight direction was estimated to exceed 40 mm/yr, with maximum cumulative subsidence of ∼ 200 mm. The results clearly showed that dewatering during tunneling aggravated the subsidence phenomenon. The consequent compaction and consolidation of the compressible soil layers due to the lowered groundwater table were the main causes of subsidence. Our results demonstrate the viability of the PS-InSAR technique based on the C-band Sentinel-1 product as a monitoring method to examine the spatiotemporal evolution of ground deformation patterns during tunneling activities and as a possible preliminary surveying tool to identify ongoing abnormal settlement prior to tunnel construction.

The late-Holocene relationship between peatland water table depth and summer temperature in northern Poland

Although the contribution of current summer warming to the widespread drying of European peatlands is undeniable, summer temperature fluctuations alone are unable to explain all the hydrological shifts of these ecosystems. We aim to determine whether the current coupling of high summer temperatures and low water tables of peatlands in northern Poland is recent or has been stable over long timescales, and to infer the climatic context driving past relationships between temperature and peatland hydrology. We compare the previously published 4000-year long paleohydrological record from Kusowo bog with a new chironomid-based summer temperature record covering the last 4.5 ka from nearby (~7 km) Lake Spore. Although several simultaneous shifts in our hydrological and temperature reconstructions are evident on multi-decadal to centennial timescales, for instance during the peak cooling of the Migration Period or Little Ice Age (~1.4 and 0.4 cal ka, respectively), the records reveal mostly independent fluctuations. However, the relatively high uncertainty of our quantitative estimates suggests caution is warranted when inferring the strength of the relationship between the reconstructed variables at this temporal resolution. However, at centennial to millennial timescales, the relationship between the records is surprisingly strong. Overall, warmer summers (mean July temperature = 18.7 °C) before ~2.3 cal. ka corresponded well with lower ground water tables at Kusowo bog (mean = 11.2 cm), whereas cooler summers in the following period (mean = 17.4 °C) were accompanied by higher water tables (mean = 7.9 cm). Particularly wet bog conditions during the last ~0.7 ka were also the coldest. The finding that on long timescales the drying of Kusowo bog coincided with warming suggests a persistent regional climate pattern in which drought conditions change along with summer temperatures. If this millennial-scale pattern holds for the projected warming, further peatland drying can be expected in northern Poland. • We compare paleohydrological record from a bog with a summer temperature reconstruction • On millennial timescales, dry conditions at the bog were concurrent with high temperatures • Conditions at the bog were generally drier before 2.3 cal. ka BP and wetter thereafter • Temperature rise above the late-Holocene maximum can result in unprecedented drying

Evaluation of wetland ecosystem health using geospatial technology: evidence from the lower Gangetic flood plain in India.

The floodplain wetland habitat in the lower Gangetic plains of West Bengal played a significant role in protecting from environmental degradation like pollution, lowering groundwater table, natural hazards, and others as well as supports for human wellbeing. Thus, it is needed to investigate the health status of wetlands and suggest restoration strategies to protect the livelihood patterns dependent on wetlands. This paper presents the health of the wetland ecosystem by comprising the wetland ecosystem health index (WHI) in 2011 and 2018 at the block level of Malda district, as a part of the lower Gangetic flood plain using the pressure-state-response model (PSR model) and AHP method. A total number of six Landsat satellite images and statistical census data were used to determine the wetland health. Wetlands are classified as very healthy (2.81-3.33), healthy (2.41-2.80), sub-healthy (2.01-2.40), unhealthy (1.61-2.00), and sick (0-1.60) category on the basis of the wetland ecosystem health index score. The results of this study showed that the wetlands located surrounding English Bazar, Manikchak, Ratua-II, and Kaliachak-II blocks have a sub-healthy to very healthy condition in 2011 but changed to unhealthy to sick category in 2018 due to the increase of rapid urbanization, population density, and development activities. These areas have belonged to the sub-healthy to sick category in the year 2011 as well as 2018 due to high wetland pressure. Our observation reveals that the ecosystem service value provided by wetlands decreased by 62.51% and 20.46 in the observed period. Management of WEH should emphasize on large (>100 ha) and medium (51-100 ha) sizes of wetlands in the Diara region of West Bengal. Developing local-level institutions and setting restoration goals are useful strategies to manage wetland resources, and protecting biodiversity should be guided by the Government organization and NGOs.

Conventional subsoil irrigation techniques do not lower carbon emissions from drained peat meadows

Abstract. The focus of current water management in drained peatlands is to facilitate optimal drainage, which has led to soil subsidence and a strong increase in greenhouse gas (GHG) emissions. The Dutch land and water authorities proposed the application of subsoil irrigation (SSI) system on a large scale to potentially reduce GHG emissions, while maintaining high biomass production. Based on model results, the expectation was that SSI would reduce peat decomposition in summer by preventing groundwater tables (GWTs) from dropping below −60 cm. In 2017–2018, we evaluated the effects of SSI on GHG emissions (CO2, CH4, N2O) for four dairy farms on drained peat meadows in the Netherlands. Each farm had a treatment site with SSI installation and a control site drained only by ditches (ditch water level −60 / −90 cm, 100 m distance between ditches). The SSI system consisted of perforated pipes −70 cm from surface level with spacing of 5–6 m to improve drainage during winter–spring and irrigation in summer. GHG emissions were measured using closed chambers every 2–4 weeks for CO2, CH4 and N2O. Measured ecosystem respiration (Reco) only showed a small difference between SSI and control sites when the GWT of SSI sites were substantially higher than the control site (&gt; 20 cm difference). Over all years and locations, however, there was no significant difference found, despite the 6–18 cm higher GWT in summer and 1–20 cm lower GWT in wet conditions at SSI sites. Differences in mean annual GWT remained low (&lt; 5 cm). Direct comparison of measured N2O and CH4 fluxes between SSI and control sites did not show any significant differences. CO2 fluxes varied according to temperature and management events, while differences between control and SSI sites remained small. Therefore, there was no difference between the annual gap-filled net ecosystem exchange (NEE) of the SSI and control sites. The net ecosystem carbon balance (NECB) was on average 40 and 30 t CO2 ha−1 yr−1 in 2017 and 2018 on the SSI sites and 38 and 34 t CO2 ha−1 yr−1 in 2017 and 2018 on the control sites. This lack of SSI effect is probably because the GWT increase remains limited to deeper soil layers (60–120 cm depth), which contribute little to peat oxidation. We conclude that SSI modulates water table dynamics but fails to lower annual carbon emission. SSI seems unsuitable as a climate mitigation strategy. Future research should focus on potential effects of GWT manipulation in the uppermost organic layers (−30 cm and higher) on GHG emissions from drained peatlands.