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The present research based on 39 cross sections, historical maps, satellite images, and intensive field investigations intends to portray the changes in the cross-sectional morphology and channel efficiency of the lower Bhagirathi River (Katwa to Nabadwip) after the Farakka barrage was constructed over the Ganga River in 1975. The study reveals that majority of the cross sections have undergone significant changes in terms of higher width/depth ratio (1972:71.4 and 1984:85.1), higher channel form index (1972:28.06, 1984:33.44), and higher areal asymmetry (1972:0.244, 1984:0.287). Thus, discriminant analysis based on the principal component analysis Z-score of the derived indices shows a reversal of the quadrant reflecting a definite change in cross-sectional morphology in the post-Farakka barrage condition. Though the Reynolds number and specific stream power increased due to the increase in the lean period (January to May) discharges by the controlled hydrology, channel efficiency has decreased which is reflected through the higher Chezy roughness factor (1972:0.095 and 1984: 6.802) and increasing braiding index (1994:0.103, 2019:0.294). This is due to the emergence of the transport-limited condition triggered by the inadequate discharge compared to the huge sediment load contributed by Bhagirathi bank erosion and the Ajay–Mayurakshi system. Moreover, the role of erosion permitting sand and silt facies triggering higher channel oscillation along the left bank and presence of plug bar deposits coupled with the suspected attraction of subsurface fault are also noted on the relative stability and channel orientation of the middle part of the study reach.

The present work intends to assess the suitability of groundwater for agricultural use based on 110 samples collected from 52 community development blocks in the Gangetic West Bengal, India. The dominant hydrochemical facies of the studied samples is Ca2+–Mg2+–HCO3− (57.27%) followed by Mg2+–Ca2+–HCO3−–Cl− (19.09%). The undesirable electrical conductivity (EC) and total dissolved solids (TDS) for about 25% of the samples have introduced a high salinity problem for crops. Moreover, the irrigation hazards measured in terms of sodium adsorption ratio, % Na, soluble sodium percentage, residual sodium carbonate, potential salinity, and permeability index indicate that more than 80% of the groundwater samples are suitable for agriculture. However, the magnesium adsorption ratio exhibits that about 39% of water samples are unsuitable for agriculture. A one-way ANOVA finds a statistically significant difference in irrigation hazards between samples located on the western and eastern banks of the Bhagirathi–Hooghly River. In general, the evolution of groundwater hydrochemistry and associated irrigation hazards is principally governed by rock dominance and silicate weathering as natural forcing. However, anthropogenic interventions in the form of sand mining from the river bed of the Ajay–Mayurakshi promote the high magnitude of silicate weathering and thereby inducing major hotspots of the irrigation hazards located on the western bank of the Bhagirathi–Hooghly River. Moreover, the high loadings of EC, TDS, and Cl− registered in the first principal component indicate deterioration of groundwater quality largely due to the change of land use and land cover while the significant loadings of NO3− in the second principal component indicate groundwater pollution due to agricultural practice.

In recent years, groundwater pollution has become increasingly a serious environmental problem throughout the world due to increasing dependency on it for various purposes. The Damodar Fan Delta is one of the agriculture-dominated areas in West Bengal especially for rice cultivation and it has a serious constraint regarding groundwater quantity and quality. The present study aims to evaluate the groundwater quality parameters and spatial variation of groundwater quality index (GWQI) for 2019 using the fuzzy analytic hierarchy process (FAHP) method. The 12 water quality parameters such as pH, TDS, iron (Fe−) and fluoride (F−), major anions (SO42−, Cl−, NO3−, and HCO3−), and cations (Na+, Ca2+, Mg2+, and K+) for the 29 sample wells of the study area were used for constructing the GWQI. This study used the FAHP method to define the weights of the different parameters for the GWQI. The results reveal that the bicarbonate content of 51% of sample wells exceeds the acceptable limit of drinking water, which is maximum in the study area. Furthermore, higher concentrations of TDS, pH, fluoride, chloride, calcium, magnesium, and sodium are found in few locations while nitrate and sulfate contents of all sample wells fall under the acceptable limits. The result shows that 13.79% of the samples are excellent, 68.97% of the samples are very good, 13.79% of the samples are poor, and 3.45% of the samples are very poor for drinking purposes. Moreover, it is observed that very poor quality water samples are located in the eastern part and the poor water wells are located in the northwestern and eastern part while excellent water quality wells are located in the western and central part of the study area. The understanding of the groundwater quality can help the policymakers for the proper management of water resources in the study area.

The present study exhibits a critical outlook on the poverty and livelihood vulnerability of the fisherman community in the context of persistent water pollution of the Churni River. The logistic regression model has identified eight factors influencing the poverty of the study area while the entropy weight method identifies the livelihood vulnerability of the fishermen. The livelihood vulnerability index of the upper stretch of the river is higher (0.65–0.67) compared to that of the lower stretch (0.46–0.57). The typical spatiality in poverty and livelihood vulnerability is triggered by the fragility of fishing livelihoods in the wake of lower concentrations of dissolved oxygen (DO), and higher BOD, COD, ammonia, nitrate and phosphate mainly due to industrial water pollution. For example, average DO ranges from 1.65 mg/l (upper stretch) to 2.50 mg/l (lower stretch) while the average BOD ranges from 5.44 mg/l (lower stretch) to 9.42 mg/l (upper stretch). This pollution induces acute ecological stress concerning declining fish diversity (from 41 to 16 fish species at the upper stretch and 41 to 23 fish species at the lower stretch during 1980–2018) as well as productivity of the existing fish species. Therefore, paralysed fishing economy and high dependency of the fishermen on the Churni River have forced them to revolve into the vicious cycle of poverty and enduring fragile livelihoods. Thus, the fishermen adopt few coping strategies like access to the nearby wetland for fishing, diversity in earning strategy and environmental movements against pollution to reduce the intensity of vulnerability. The present study would help the regional planners to frame the participatory plans for the sustainability of the riverine ecology and economy.

The flood hazard is very severe in the lower stretch of the Mayurakshi River Basin (MRB) in West Bengal, India. During the last 20 years (1998–2017), average flood frequency accounted for 9–12 times in the different community development blocks of the lower MRB. An empirical socio-economic survey has been executed over a randomly selected 2382 households across 43 villages of Murshidabad District to assess the impact of the flood on the economic conditions of the villages. The economic transformation is reflected through the increasing occupational diversification (e.g. Herfindahl–Hirshman index: 1.94 in 1998 and 2.26 2018 in Kandi), increasing per capita income (e.g. 1998: Indian National Rupee (INR) 502.23; 2018: INR 1203.70 in Kandi), decreasing poverty level (e.g. head count ratio 63.41% in 1998 and 42.42% in 2018 in Kandi) and more savings and lesser amount loan due to flood. This typical economic transformation is driven by five major in situ factors (decreasing cropping intensity and diversity, seasonal unemployment, increasing flood-induced expenditure and damages to properties and assets) that act as push factors for the traditional agrarian economy and one ex situ factor (international labour migration) that acts as the pull factor for the non-agrarian economy. The per capita per month receipt of remittances for the families having the labour migrants in the Middle East countries ranges from INR 2000 (Ibrahimpur) to INR 5375 (Dakshin Gopinathpur) that absorbs the shocks induced by flood. Thus, local economy flourishes in the areas of frequent flood and consequent labour migration compared to less flood-prone areas.

The elevated concentrations of heavy metals in soil considerably threaten ecological and human health. To this end, the present study assesses metals pollution and its threat to ecology from the mid-channel bar’s ( char ) agricultural soil in the Damodar River basin, India. For this, the contamination factor (CF), enrichment factor (EF), geoaccumulation index (I geo ), pollution index, and ecological risk index (RI) were measured on 60 soil samples at 30 stations (2 from each station, i.e., surface and sub-surface) in different parts of the mid-channel bar. The CF and EF indicate that both levels of char soil have low contamination and hence portray a higher potential for future enrichment by heavy metals. Moreover, I geo portrays that soil samples are uncontaminated to moderately contaminated. Further, pollution indices indicate that all the samples (both levels) are unpolluted with a mean of 0.062 for surface soils and 0.048 for sub-surface soils. Both levels of the char have a low potentiality for ecological risk with an average RI of 0.20 for the surface soils and 0.19 for the sub-surface soils. Moreover, Technique for order preference by similarity to ideal solution (TOPSIS) indicates that the sub-surface soils have lower pollution than the surface soils. The geostatistical modeling reveals that the simple kriging technique was estimated as the most appropriate interpolation model. The present investigation exhibits that reduced heavy metal pollution is due to the sandy nature of soils and frequent flooding. However, the limited pollution is revealed due to the intensive agricultural practices on riverine chars . Therefore, this would be helpful to regional planners, agricultural engineers, and stakeholders in a basin area.

The present study has been a pioneering effort examining the role of an annual flood as a potent stimulus inducing changes in channel geomorphology of the Mayurakshi River, India. Twenty cross sections have been considered for the measurement of various hydro-geomorphic attributes of the river in both the pre- and post-flood conditions in 2018. The study sensed an escalating trend for channel width, width/depth ratio, and wetted perimeter while the reverse was also detected for average depth, maximum depth, cross-sectional area, and hydraulic radius. For example, the width/depth ratio recorded an increase of ~ 11%, and the hydraulic radius depicted a decrease of ~ 8%. Furthermore, channel asymmetry, bed asymmetry and bed relief index experienced a decrease after the flood. The sudden hydraulic impulse during monsoon flood as manifested in velocity, discharge, specific stream power, Reynolds number, Froude number increases the erosivity of the fluid. Besides the hydraulic factors, bank material (massive sandbank susceptible to hydraulic action and mixed bank constituted by alternate bands of sand and silt, and vulnerable to failure by piping action) brings substantial changes in channel morphology. Moreover, anthropogenic interventions such as sand mining are found to play a significant role in channel behaviour. The role of the multiple factors driving the morphological changes of the cross sections has been unpacked using canonical component analysis.

In recent years groundwater contamination through nitrate contamination has increased rapidly in the managementof water research. In our study, fourteen nitrate conditioning factors were used, and multi-collinearity analysis is done. Among all variables, pH is crucial and ranked one, with a value of 0.77, which controls the nitrate concentration in the coastal aquifer in South 24 Parganas. The second important factor is Cl − , the value of which is 0.71. Other factors like—As, F − , EC and Mg 2+ ranked third, fourth and fifth position, and their value are 0.69, 0.69, 0.67 and 0.55, respectively. Due to contaminated water, people of this district are suffering from several diseases like kidney damage (around 60%), liver (about 40%), low pressure due to salinity, fever, and headache. The applied method is for other regions to determine the nitrate concentration predictions and for the justifiable alterationof some management strategies.

Determining the degree of high groundwater arsenic (As) and fluoride (F − ) risk is crucial for successful groundwater management and protection of public health, as elevated contamination in groundwater poses a risk to the environment and human health. It is a fact that several non-point sources of pollutants contaminate the groundwater of the multi-aquifers of the Ganges delta. This study used logistic regression (LR), random forest (RF) and artificial neural network (ANN) machine learning algorithm to evaluate groundwater vulnerability in the Holocene multi-layered aquifers of Ganges delta, which is part of the Indo-Bangladesh region. Fifteen hydro-chemical data were used for modelling purposes and sophisticated statistical tests were carried out to check the dataset regarding their dependent relationships. ANN performed best with an AUC of 0.902 in the validation dataset and prepared a groundwater vulnerability map accordingly. The spatial distribution of the vulnerability map indicates that eastern and some isolated south-eastern and central middle portions are very vulnerable in terms of As and F − concentration. The overall prediction demonstrates that 29% of the areal coverage of the Ganges delta is very vulnerable to As and F − contents. Finally, this study discusses major contamination categories, rising security issues, and problems related to groundwater quality globally. Henceforth, groundwater quality monitoring must be significantly improved to successfully detect and reduce hazards to groundwater from past, present, and future contamination.

Social psychology of people affected by hazards is different from normal psychology. For example, severe bank erosion in the lower reach of the Bhagirathi River in West Bengal has resulted in significant land loss (∼60% of all households lost land over last 20 years) and affected the livelihoods of the people in the study villages along the river. Per capita income has almost halved from 1970–2012 due to land loss. This stark nature of land erosion and vulnerability of livelihood has had far-reaching repercussions on the fabric of society and the psychology of the people in this region. Results showed that erosion-affected villages have registered comparatively larger average family sizes (∼4.1 as compared to ∼3.9 in non-affected villages), lower literacy levels (< 50% compared to > 65% for the non-affected villages), and poor health. Reports of poor health as a result of land erosion include ∼60% of the respondents having reported physical ailments such as headache and abdominal discomfort, as well as 3%–5% reporting loss of emotional and psychological balance. Villages suffering from erosion showed higher positive loadings in average-coefficient of variation (CV) differential (25%–40%) depicting objectivity in their opinions for select variables of social processes. Principal component analysis (PCA) portrayed maximum eigenvalues in the first principal component for interpersonal processes (∼98%) and a minimum for intergroup processes (∼80%). Categorical principal component analysis (CATPCA) depicted a cluster between interpersonal and intergroup processes and another between intra-individual and group categories. The positive loadings in female-male differences in CV of perceptions portrayed relative consistency of males over the females concerning fear/phobia and physical stress while negative loadings exhibited higher consistency for females regarding psychological stress and shock. Lastly, the Tajfel matrix portrayed a distinction between hazard psychology characterized by maximum joint profit as found in Rukunpur, and normal psychology characterized by in-group favoritism as found in Matiari.