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Conservation of embankment soil along the rivers is a global challenge. The existing solutions including rigid structures and cement-based techniques pose risks to the sensitive river ecology. The trending biopolymer (Bp) based soil stabilisation technique has shown enormous potential to stabilise loose and soft soils. The rheology of such biopolymer solutions is expected to play a critical role in soil stabilisation, especially in a wet environment such as riverbanks. In this study, four different levels of xanthan gum treatment (0.5 to 1.25% by soil weight) are investigated for stabilising the soil collected from an erosion-prone bank of the Brahmaputra River basin. The rheological properties of the intended biopolymer solutions are investigated extensively prior to their application. Later, the degree of stabilisation of the biopolymer-treated soil is determined by evaluating their unconfined compressive strength (UCS) and secant modulus. The erosion characteristics of the treated samples were evaluated using an in-house built apparatus. The shear-thinning and viscoelastic parameters of the biopolymer solutions have been quantified with the rheological analysis. The UCS strength test revealed a consistent increase up to 1.6 MPa with an increase in the biopolymer treatment of 1.25%. The erosion test revealed that the biopolymer treatment delayed the erosion process. However, it did not completely cease the erosion. The microstructure analysis revealed that the strong biopolymer bridging acts as a dampener in the soil pores to delay erosion. This study unravels the critical role of rheological factors, which are essential in reproducing the desired results from the geotechnical laboratories to field-scale applications. [ABSTRACT FROM AUTHOR]

Soil erosion is a complex natural process that occurs by either individual or combined actions of wind, hydraulic currents, waves, and rain. This study comprehensively reviews biocementation-based soil stabilisation techniques for developing erosion-resilient landforms through an ecologically conscious strategy. The different pathways for biocementation occurring in nature are discussed with a focused view on the microbially induced carbonate precipitation (MICP) technique. MICP relies on biogenic calcium carbonate (CaCO3) precipitation via the urea hydrolysis route to bind the soil grains. The kinetics and factors affecting MICP are succinctly discussed to highlight the practical challenges associated with biocementation. This study emphasises the influence of MICP on erosion resistance (aeolian and hydraulic) and geotechnical properties of soils. The critical assessment of the previous studies revealed that aeolian and hydraulic erosion can be effectively controlled with a small to moderate quantity of biogenic CaCO3 (2% to 10% of soil weight). MICP marginally influences the hydraulic conductivity of soils with a substantial improvement in compressive strength, making it desirous over traditional soil cementation agents for erosion control due to the limited intervention to natural groundwater flow. However, the scientific design and findings of the previous laboratory-scale and pilot-scale research are still inconsistent for standardising biocementation techniques to transition towards upscaling. This study presents critical insights to the researchers of the environmental, geotechnical and geoenvironmental engineering domains to design their upcoming studies to tackle the challenges required for upscaling biocementation technology. [ABSTRACT FROM AUTHOR]

Although geogenic Arsenic (As) contamination is well-recognized in northern Chile, it is not restricted to this part of the country, as the geological conditions favoring As release to the human environment exist across the country as well, although not at the same level, based on comparatively fewer studies in central and southern Chile. The present work provides a critical evaluation of As sources, pathways, and controls with reports and case studies from across the country based on an exhaustive bibliographic review of its reported geogenic sources and processes that affect its occurrence, systematization, and critical revision of this information. Arc magmatism and associated geothermal activities, identified as the primary As sources, are present across the Chilean Andes, except for the Pampean Flat Slab and Patagonian Volcanic Gap. Metal sulfide ore zones, extending from the country's far north to the south-central part, are the second most important geogenic As source. While natural leaching of As-rich mineral deposits contaminates the water in contact, associated mining, and metallurgical activities result in additional As release into the human environment through mining waste and tailings. Moreover, crustal thickness has been suggested as a principal controlling factor for As release, whose southward decrease has been correlated with lower As values. [ABSTRACT FROM AUTHOR]

Elevated fluoride in groundwater is a severe problem in India due to its extensive occurrence and detrimental health impacts on the large population that thrives on groundwater. Although fluoride is primarily a geogenic pollutant, existing model-based studies lack the amalgamation of the influence of geologic factors, specifically tectonics, for identifying groundwater fluoride distribution. This drawback encourages the present study to investigate the association of the tectonic framework with fluoride in a multi-model approach. We have applied three machine learning models (random forest, boosted regression tree, and logistic regression) to predict elevated groundwater fluoride based on fluoride measurements across India. The random forest model outperformed other models with an accuracy of 93%. Tectonics was found to be one of the most important predictors alongside "depth to water table." Two major areas of high risk identified were the northwest parts and the south–southeast cratonic peninsular region. The random forest model also performed significantly well over the validation dataset. We estimate that nearly 257 million people are exposed to elevated fluoride risk in India. We endeavor that the findings of our study would be an effective tool for identifying the areas at risk of elevated fluoride and also assist in undertaking effective groundwater management strategies. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Increased frequency of extreme weather events has made the conservation of riverbanks and coastlines a global concern. Soil stabilisation via microbially induced calcite precipitation (MICP) is one of the most eco-suitable candidates for improving resilience against erosion. In this study, the erosion characteristics of soil treated with various levels of biocementation are investigated. The samples were subjected to hydraulic flow in both tangential and perpendicular directions in a flume to simulate riverbank and coastal situations. Soil mass loss, eroded volume, and cumulative erosion rates of the treated soil against the applied hydraulic energy density have been reported. Post erosion exposure, the residual soil has been assessed for its properties using needle penetration resistance, precipitated calcium carbonate content and microstructure. It was observed that soil erosion declined exponentially with the increase in calcium carbonate content against the perpendicular waves. However, biocementation leads to brittle fracture beyond a threshold, limiting its efficacy, especially against the tangential waves. Additional composite treatment with a biopolymer was found to improve the resilience of the soil specimens against erosion. The composite treatment required half of the quantity of the biocementing reagents in comparison to the equally erosion-resistant plain biocemented sample. Therefore, stoichiometrically the composite treatment is likely to yield 50% lesser ammonia than plain biocement treatment. This investigation unravels a promising soil conservation technique via the composite effect of biocement and biopolymer. [ABSTRACT FROM AUTHOR]

Reutilisation of the construction and demolition (C&D) wastes as aggregate in concrete is a vital step towards sustainability as it prevents depletion of natural resources as well as alleviates wastes. However, the attached mortar on the aggregate surface renders certain shortcomings like excessive water absorption, high porosity, and weak interfaces. Recycled aggregates can be treated to improve these shortcomings. However, the minimisation of the drawbacks involves huge energy, materials, and cost. Moreover, the efficacy of such adopted method is sometime questionable, and which needs further research. This study demonstrates bio-treatment of recycled coarse aggregate (RCA) as a means of upcycling and compares it with conventional cement slurry treatment. A novel spraying technique has been applied that significantly economises biocement treatment. The experimental results show that biocement treatment reduced the water absorption by 70%. The treatment has filled the pores of RCA and has prevented water absorption. In contrast, cement slurry coating treatment shows increase in water absorption of RCA by 19%. The compressive strength of concrete with 100% biocement treated RCA surpasses that of concrete with natural coarse aggregates. The genesis of this dramatic improvement in case of biocement has been established through micro-scale studies including scanning electron microscopy and energy-dispersive X-ray spectroscopy. The cost analysis demonstrates that RCA upcycled with biocement treatment is more economical than natural aggregates or cement treated ones. Findings of the present study led to the conclusion that 100% replacement of natural coarse aggregates can be achieved by upcycling C&D wastes as coarse aggregate through bio-treatment. [ABSTRACT FROM AUTHOR]

Microbially induced calcium carbonate precipitation (MICP)/Biocementation has emerged as a promising technique for soil engineering applications. There are chiefly two methods by which MICP is applied for field applications including biostimulation and bioaugmentation. Although bioaugmentation strategy using efficient ureolytic biocementing culture of Sporosarcina pasteurii is widely practiced, the impact of native ureolytic microbial communities (NUMC) on CaCO3 mineralisation via S. pasteurii has not been explored. In this paper, we investigated the effect of different concentrations of NUMC on MICP kinetics and biomineral properties in the presence and absence of S. pasteurii. Kinetic analysis showed that the biocementation potential of S. pasteurii is sixfold higher than NUMC and is not significantly impacted even when the concentration of the NUMC is eight times higher. Micrographic results revealed a quick rate of CaCO3 precipitation by S. pasteurii leading to generation of smaller CaCO3 crystals (5–40 µm), while slow rate of CaCO3 precipitation by NUMC led to creation of larger CaCO3 crystals (35–100 µm). Mineralogical results showed the predominance of calcite phase in both sets. The outcome of current study is crucial for tailor-made applications of MICP. [ABSTRACT FROM AUTHOR]

Riverbank erosion is a global problem with significant socio-economic impacts. Microbially induced calcite precipitation (MICP) has recently emerged as a promising technology for improving the mechanical properties of soils. The present study investigates the potential of selectively enriched native calcifying bacterial community and its supplementation into the riverbank soil of the Brahmaputra river for reducing the erodibility of the soil. The ureolytic and calcium carbonate cementation abilities of the enriched cultures were investigated with reference to the standard calcifying culture of Sporosarcina pasteurii (ATCC 11859). 16S rRNA analysis revealed Firmicutes to be the most predominant calcifying class with Sporosarcina pasteurii and Pseudogracilibacillus auburnensis as the prevalent strains. The morphological and mineralogical characterization of carbonate crystals confirmed the calcite precipitation potential of these communities. The erodibility of soil treated with native calcifying communities was examined via needle penetration and lab-scale hydraulic flume test. We found a substantial reduction in soil erosion in the biocemented sample with a calcite content of 7.3% and needle penetration index of 16 N/mm. We report the cementation potential of biostimulated ureolytic cultures for minimum intervention to riparian biodiversity for an environmentally conscious alternative to current erosion mitigation practices. [ABSTRACT FROM AUTHOR]

The rapid decline of groundwater levels (GWL) due to pervasive groundwater abstraction in the densely populated (~1 billion) Indus-Ganges-Brahmaputra-Meghna (IGBM) transboundary river basins of South Asia, necessitates a robust framework of prediction and understanding. While few localized studies exist, three-dimensional regional-scale characterization of GWL prediction is yet to be implemented. Here, 'support vector machine', a machine-learning-based method, is applied to data from the Gravity Recovery and Climate Experiment (GRACE) and data on land-surface-model-based groundwater storage and meteorological variables, to predict the GWL anomaly (GWLA) in the IGBM. The study has three main objectives, (1) to understand the spatial (observation well locations) and subsurface (shallow vs. deep observation wells) variability in prediction results for in-situ GWLA data for a large number of observation wells (n = 4,791); (2) to determine its relationship with groundwater abstraction, and; (3) to outline the advantages and limitations of using GRACE data for predicting GWLAs. The findings, based on individual observation well results, suggest significant prediction efficiency (median statistics: r > 0.71, NSE > 0.70; p < 0.05) in most of the IGBM; however, the study identifies hotspots, mostly in the agriculture-intensive regions, having relatively poor model performance. Further analysis of the subsurface depth-wise prediction statistics reveals that the significant dominance of pumping in the deeper depths of the aquifer is linked to the relatively poor model performance for the deep observation wells (screen depth > 35 m) compared with the shallow observation wells (screen depth < 35 m), thus, highlighting the limitation of GRACE in representing spatial and depth-dependent local-scale pumping. [ABSTRACT FROM AUTHOR]

Worldwide, >2 billion people (~1/3 world population), mostly living in economically stressed areas of Africa and South Asia, still do not have access to basic sanitation, and ~1 billion still practice open defecation. Water pollution due to open defecation may primarily be linked to economy, and other factors such as social and hygiene practices, land use and hydrogeological parameters could also have sufficient influence. The present study describes the effect of human development index (HDI, 2001–2015) and economic development (NL, 1992–2013) on groundwater microbial pollution (FC, 2002–2017) across India. Economic development pattern suggested discernable inverse relationship with FC in most areas, although areas with inferior water quality, improper human practices were found to outweigh economic development. Vulnerability modelling, using these data, along with measured FC in groundwater-sourced drinking water locations (n = 235) demonstrated the heterogeneity of FC distribution potential in areas of homogenous economy, social practices, and land use. High-resolution numerical modelling of the advective transport of the hypothetical FC particles in the aquifers, suggest up to ~24 times faster movement of pollutants under irrigation-induced pumping regimes. Hence, the results of our study highlight and quantify the potential pitfalls that are possible hindrance for achieving the United Nations sustainable development goal, despite social and economic development, across the spatial scales. [ABSTRACT FROM AUTHOR]

The removal of the harmful carcinogen arsenic from drinking water by a green technology is a major concern in the field of environmental engineering. The sorptive profile of arsenic remediation by calcined Mg-Fe-layered double hydroxide, fabricated by a one-pot synthesis technique, was investigated to delineate its applicability in real-life water. The physicochemical properties of adsorbent, as demonstrated from spectroscopy and microscopy, which described the existence of amorphous material with significant surface roughness possess selectivity towards arsenic. The isotherm and kinetic along with thermodynamic modeling exhibited the occurrence of spontaneous (ΔG0 value = − 8.084 kJ/mol to − 10.942 kJ/mol), endothermic (ΔH0 value = 12.135 kJ/mol), and physisorption reactions (Ead = 4.103–5.832 kJ/mol, Ea = 11.546 kJ/mol, S* = 0.0005 << 1, and ΔHx = 9.23–16.29 kJ/mol) with high uptake rate and adsorption potential of adsorbent. The isotherm and kinetics were demonstrated by Temkin (R2 = 0.944–0.969) and Elovich (R2 = 0.996–0.998) models, respectively, with high statistical significance. The intraparticle diffusion model which established the rate-limiting step is the combination of both film and pore diffusions. The applicability of layered double hydroxide (LDH) material in the real-life water was confirmed by isotherm and kinetic modeling along with the regeneration/reuse potential. The adsorptive removal of arsenic by the LDH material exhibited to be a promising technique without creating any secondary hazard. [ABSTRACT FROM AUTHOR]

Bacterially induced precipitation of minerals leading to cementation of natural geological formations has been well recorded in a variety of environments. A range of microbial pathways and geochemical processes have been found to influence the cementation processes; but detailed formation mechanisms and biogeochemical relationships are still not very clear. There has been a growing demand for the application of bacterially driven biocementation in a number of geotechnical engineering applications recently. Here, we aimed to unpin the mechanisms behind the formation of actively mineralising beachrock sediments at Lucky Bay in Western Australia to understand the natural accretionary processes and potential of indigenous bacterial communities in biocementation. We observed ferruginous, aluminosilicate and carbonate cements along with extensive extra polymeric substances, borings with possible microbial activities in certain sections of native beachrock sediments. Cement precipitation under calcium- and iron-rich microenvironments sourced from seawater and iron creek seems to be driven by both biogenic and abiogenic processes in nature. Native microbial communities with a dominance of the genera Halococcus and Marinobacter were recorded. Enrichment of native bacterial communities under seawater media conditions was conducted which lead to successful biomineralisation of calcitic and ferruginous cements under in vitro conditions although the community composition changed significantly. Nanomechanical properties of natural and laboratory synthesised cement crystals showed that engineered biocement is highly promising. The results of this study clearly demonstrate biological influence in the formation of natural cements and hint significant potential of biostimulation which can be harnessed for different engineering applications including coastal erosion. [ABSTRACT FROM AUTHOR]

In 2020, we are in the doorstep of a new decade, during which the UN Sustainable Development Goals (SDG) are to be achieved, collectively as one nation and one human-hood, where availability of safe, sustainable and clean water and air forms the core of multiple goals. However, the emergence of the COVID-19 pandemic across the globe has resulted a newer challenge and paradigm for an evolving socio-scientific priorities. It is generally expected that the impacts of the pandemic would be in shorter time-scale, while the planned time and pathway for attaining the SDG are typically mandated in longer-term, hence may remain mostly unaffected. However, the stringent lockdown measures, isolated economies and financial burden to contain the pandemic emergency have resulted to slowdown of socio-economic development, which if continues for a longer period, would put a question mark on developing plans and pathways to achieve the SDGs, even in decadal-scale. Hence, in these newer times, it is important to understand the real priorities of availability of clean water and air, which are already stressed worldwide and in India, because of various natural and human-influenced triggers. This ongoing pandemic has provided an unprecedented opportunity to evaluate the impact of human development and consequent feedback of nature and human society in pre- and post-COVID scenarios on water–air–human life, which can help to re-think and re-orient the societal development priorities. It is a rare opportunity for scientists to impress the policy-makers with real-time examples on the efficacies of potential mitigation strategies for climate change, water and air pollution, and the importance of enduring investment on environmental causes and consequent benefits that can secure health and development for our future generations. Highlights: Environmental pollution and climate change pose a high risk for human survival. Develop resilience to attain SDGs in spite of economic constraints caused by COVID-19. Set real priorities of availability of clean water and air for future, in a unified world. [ABSTRACT FROM AUTHOR]

The present study is undertaken in the eastern coast of India, along the coastal tract of Bay of Bengal (BoB), to delineate the submarine groundwater discharge (SGD)-borne nutrient flux at temporal scale and their impact to coastal ecology and biogeochemical processes. Solutes chemistry, seepage meter study, stable-isotopic signature, and geophysical techniques were used to identify the surface water–groundwater interaction zone, SGD rate and nutrient flux. The estimated rate of major annual discharge of nutrient fluxes were 240 and 224 mM m−2 day−1 for NO3− and Fetot. The variation of solute and nutrient fluxes was depending on the load of terrestrial water masses, which is triggered by the local monsoonal meteoric recharge. The ecohydrological response to this solute flux results in spatio-temporal patterns of N and P-sensitive algal blooms in the intertidal zones. Most algae were identified as dinoflagellates and some haptophytes, with greenish and brownish hue that provides a distinct look to the coastal landscape. The algal blooms were found to be substantially influenced by the seasonal-nutrients flux and discharge location. Our study is expected to increase the understanding of a rarely reported eco-hydrological response to terrestrial–marine water interactions and their implications in the tropical ocean adjoining the Indian Subcontinent. [ABSTRACT FROM AUTHOR]

Coastal barrier dynamics is a complicated system which mainly involves shoreline changes due to accretion and erosion of the coast. Erosional activity in the coastal area of Paradeep, Odisha is risking the lives of the people and the community/factory infrastructures of this major port city, adjoining to the Bay of Bengal. So, understanding of the complex barrier dynamics is more important in this study area. The purpose of this study was to identify several erosional features within sedimentary beddings by Ground Penetrating Radar (GPR) survey and to understand the processes involved in this microtidal barrier from obtained GPR facies/radar facies. GPR reflection survey, with 200 MHz antenna, along (17 profiles) and across (21 profiles) the barrier was done to delineate shapes and sizes of the sedimentary features, erosional surfaces, channels, scour-and-fill structures, progradational beddings and internal geometry of the beach ridge deposits. GPR facies analyses of the beach ridge have established the longshore drift of sediments from nearby river mouths e.g. Mahanadi and Devi river mouths. This interpretation technique has also characterized the palaeo-tidal channels of the study area into two types - (a) larger channels which are perpendicular to the shoreline having channel width of about 400 m with maximum depth of 3.4 m from the surface and (b) smaller channels (width up to 60 m) flow parallel to the shoreline. Here, seaward-dipping beach progradational facies is positioned within oblique erosional surfaces below the facies boundary. This describes the cyclicity of erosion and accretion activity at Paradeep coastal barrier. [ABSTRACT FROM AUTHOR]

Western Himalaya is a strategically important region, where the water resources are shared by China, India and Pakistan. The economy of the region is largely dependent on the water resources delivered by snow and glacier melt. The presented study used stable isotopes of water to further understand the basin-scale hydro-meteorological, hydrological and recharge processes in three high-altitude mountainous basins of the western Himalayas. The study provided new insights in understanding the dominant factors affecting the isotopic composition of the precipitation, snowpack, glacier melt, streams and springs. It was observed that elevation-dependent post-depositional processes and snowpack evolution resulted in the higher isotopic altitude gradient in snowpacks. The similar temporal trends of isotopic signals in rivers and karst springs reflect the rapid flow transfer due to karstification of the carbonate aquifers. The attenuation of the extreme isotopic input signal in karst springs appears to be due to the mixing of source waters with the underground karst reservoirs. Basin-wise, the input–output response demonstrates the vital role of winter precipitation in maintaining the perennial flow in streams and karst springs in the region. Isotopic data were also used to estimate the mean recharge altitude of the springs. [ABSTRACT FROM AUTHOR]

Copyright of Hydrogeology Journal is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Road traffic noise pollution is a global hazard, and rapid urbanization has aggravated the problem. This paper explores a novel approach which involves a smartphone user community to monitor the prevalent noise. The system involves a client application on smartphones that records noise, processes the information and communicates to a server and shares the information as visual noise levels on Google® Maps. A fuzzy logic-based classification of noise is proposed. Results from residential, commercial, and industrial areas of the northern region of India are demonstrated. The noise levels are generally found to be higher than the prescribed standards. The experiment demonstrates the huge potential of user community participation in monitoring noise pollution. [ABSTRACT FROM AUTHOR]

Sulfate reducing bacteria (SRB) mediated treatment of acid mine drainage is considered as a globally accepted technology. However, inadequate information on the role of nitrogen source in the augmentation of SRB significantly affects the overall treatment process. Sustenance of SRB depends on suitable nitrogen source which is considered as an important nutrient. This review focuses on the different nitrogen rich growth substrates for their effectiveness to support SRB growth and sulfate reduction in passive bioreactors. Compounds like NHCl, NHHCO, NO, aniline, tri-nitrotoluene, cornsteep liquor, peptone, urea, and chitin are reported to have served as nitrogen source for SRB. In association with fermentative bacteria, SRB can metabolize these complex compounds to NH, amines, and amino acids. After incorporation into cells, these compounds take part in the biosynthesis of nucleic acids, amino acids and enzyme co-factor. This work describes the status of current and the probable directions of the future research. [ABSTRACT FROM AUTHOR]

Microbially induced calcium carbonate precipitation is an immensely growing technology for restoration and remediation of building materials. The investigation on role of exopolymeric substances and biofilms in microbially induced calcium carbonate precipitation suggested that these exopolymeric materials play major role in carbonate precipitation in Bacillus megaterium SS3 along with enzymes urease and carbonic anhydrase. The concentration of EPS directly affects the precipitation of carbonate precipitates which might be due to capturing of Ca ions by acting as nucleation site. Components of the media and presence of calcium also play crucial role in production of exopolymeric substances along with affecting the morphology of carbonate precipitates. [ABSTRACT FROM AUTHOR]

This paper describes a non-contact and non-invasive health monitoring strategy for submerged plate structures using guided waves. The structure under consideration is immersed in water and subjected to longitudinal ultrasonic waves at specific angles of incidence using a cylindrical piezoelectric transducer using the surrounding water as coupling medium. Suitable ultrasonic guided wave modes with optimum scanning capabilities have been generated and identified in submerged plate system. Finally, the propagation of selected modes through submerged notched plates is investigated. Sensitivity of leaky waves to the notches has been studied. The methodology would help in identifying damages in the submerged plate structures. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

The Brahmaputra is a unique dynamic river in the world with intense braiding and critical bank erosion. Both erosion and deposition are continuous processes in the river in an attempt to reach a new equilibrium in channel geometry and morphology by the ever dynamic nature of flow. Erosion and deposition of the river have link to land use and land cover (LULC) as the land cover is under constant change in a dynamic landscape constantly shaped by continuous erosion and deposition. The objective of the present work is to evaluate the extent of erosion and deposition along the Brahmaputra river and change in the LULC of the Brahmaputra river in Assam, India. Remote sensing and geographic information system (GIS) techniques were utilised to extract information from Landsat images. Total area of erosion and deposition during 1973–2014 was 1557 and 204 km2, respectively. Increase in area (28%) of the Brahmaputra during 1973–2014 is not solely due to bank erosion, but also for the bifurcation of streams without the loss of land. LULC study has revealed that 29% area was occupied by active channels and 71% was occupied by bars in 2014. Maximum reaches experienced reduction of the submerged part in 2014 compared to 1994 in the post-monsoon months with an overall decrease from 37% to 29%. A reduction in natural grassland and forest has been observed with a corresponding increase in agricultural practices in different bars and islands of the Brahmaputra in Assam during 1994–2014. [ABSTRACT FROM AUTHOR]

Globally, ~1 billion people, mostly residing in Africa and South Asia (e.g. India), still lack access to clean drinking water and sanitation. Resulting, unsafe disposal of fecal waste from open-defecation to nearby drinking water sources severely endanger public health. Until recently, India had a huge open-defecating population, leading declining public health from water-borne diseases like diarrhoea by ingesting polluted water, mostly sourced to groundwater. However, in recent past, sanitation development to achieve Sustainable Development Goals (SDGs) has been encouraged throughout India, but their effect to groundwater quality and human health conditions are yet-unquantified. Here, for the first time, using long term, high-spatial resolution measurements (>1.7 million) across India and analyses, we quantified that over the years, groundwater fecal coliform concentration (2002–2017, −2.56 ± 0.06%/year) and acute diarrheal cases (1990–2016, −3.05 ± 0.01%/year) have significantly reduced, potentially influenced by sanitation development (1990–2017, 2.63 ± 0.01%/year). Enhanced alleviation of groundwater quality and human health have been observed since 2014, with initiation of acceletated constructions of sanitation infrastructures through Clean India (Swachh Bharat) Mission. However, the goal of completely faecal-pollution free, clean drinking water is yet to be achieved. We also evaluated the suitability of using satellite-derived night-time light (NLan, 1992–2013, 4.26 ± 0.05%/year) as potential predictor for such economic development. We observed that in more than 80% of the study region, night-time light demonstrated to be a strong predictor for observed changes in groundwater quality, sanitation development and water-borne disease cases. While sanitation and economic development can improve public health, poor education level and improper human practices can strongly influence on water-borne diseases loads and thus health in parts of India. [ABSTRACT FROM AUTHOR]

More than quarter of underprivileged global population, who lack access to basic sanitation and clean drinking water, live in India. Consequently, every year, millions suffer with enteric diseases from drinking faecal-contaminated groundwater. The UN Sustainable Development Goal lists access to safe water and basic sanitation for all by 2030, as their sixth goal. For the first time, the role of economic improvement on decrease in water-borne faecal pathogens was studied across Indo-Ganges–Brahmaputra river basin (IGB) for almost last three decades, to delineate the long-term improvement trends of groundwater quality across India, as a consequence of development. Long-term temporal (1990–2017) and high-resolution spatial (administrative block scale, n = 2217 ) datasets of water-borne faecal pathogen concentration in groundwater and satellite-based nightlight (NL) were used to investigate the statistical trends and causal relationships. Linear and nonlinear (Hodrick–Prescott) trend analyses, panel data analyses, Bayesian vector autoregression (VAR) and lead–lag causality (LLC) analyses were performed on aforesaid culled datasets. However, the efficiency of development in alleviating the water quality and public health, and relationship with economic development, has not been well understood. Here, for the first time, using long-term, high-spatial resolution ( n = 2217 ), annual in-situ measurements and multivariate statistical models, we show that the spatially variable groundwater faecal pathogen concentration (FC, 2002–2017, - 1.39 ± 0.01 %/yr) has been significantly decreased across the basin. In most areas, increasing satellite-based NL plays a significant role (NL , 1992–2013, 3.05 ± 0.01 %/yr) in reduction of FC. However, in areas with low literacy rate surpass development. Enhanced decrease of faecal coliform concentration in groundwater possibly signifies the implementation of Clean India Mission since 2014. [ABSTRACT FROM AUTHOR]

In summer (pre-monsoon) of recent years, low water level among the last few decades, has been observed in several lower Indian reaches of the Ganges (or Ganga) river (with estimated river water level depletion rates at the range of −0.5 to −38.1 cm/year between summers of 1999 and 2013 in the studied reaches). Here, we show this Ganges river depletion is related to groundwater baseflow reduction caused by ongoing observed groundwater storage depletion in the adjoining Gangetic aquifers (Ganges basin, −0.30 ± 0.07 cm/year or −2.39 ± 0.56 km3/year). Our estimates show, 2016-baseflow amount (~1.0 × 106 m3/d) has reduced by ~59%, from the beginning of the irrigation-pumping age of 1970s (2.4 × 106 m3/d) in some of the lower reaches. The net Ganges river water reduction could jeopardize domestic water supply, irrigation water requirements, river transport, ecology etc. of densely populated northern Indian plains. River water reduction has direct impact on food production indicating vulnerability to more than 100 million of the population residing in the region. The results of this study could be used to decipher the groundwater-linked river water depletion as well as the regional water security in other densely populated parts of the globe. [ABSTRACT FROM AUTHOR]