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River Ganga covers around 26% of India’s land area and sustains diverse ecosystems in this overly populated area. The globally accepted coherent approach of water quality indices (WQIs) and multivariate statistical models (principal component analysis (PCA) and cluster analysis (CA)) were applied on the dataset to evaluate the spatial-temporal variation and pollution source identification and apportionment. Twenty-two hydro-chemical parameters were analyzed by collecting the samples from 20 different vertically elevated monitoring locations for different seasons. The CA evaluation of data, grouped the monitoring locations into five clusters of varied water quality with human perturbations and geo-genic inputs. The PCA analysis of an extensive dataset indicated the seven significant principal components (PCs) explaining 93.0% of the total variance and finalized 8 water quality parameters out of preselected 22 to represent good aspects of the water quality. The seasonal variation in river water quality by the Canadian Council of Ministers for Environment Water Quality Index (CCMEWQI) showed the quality class at a marginal level in summer (62.16), monsoon (59.96), and post-monsoon (60.20) season, whereas in winters (71.18), water quality was in fair condition. The response of National Sanitation Foundation Water Quality Index (NSFWQI) classified the river water in medium quality class for summer, monsoon, post-monsoon, and winter season, respectively. The present observations contribute in the usefulness of these statistical methodologies to interpret and understand large dataset and also provide reliable information to reduce the tedious and cost of water quality monitoring and assessment programs.

We characterize here the saline‐alkaline soils composed of Na2CO3 and NaHCO3 in the Ganga floodplain and the peninsular basin using various chemical proxies and the isotopic composition of Sr. Abundance of saline‐alkaline soils in the Ganga floodplain and their higher solubility make them an important source of non‐chloride Na and other dissolved ions including Sr to the river waters. Inverse model based source apportionment of dissolved ions indicates ∼26%–71% of Na at the Ganga outflow is influenced by the saline‐alkaline soils; however, in some of the tributaries of the Ganga in the floodplain, for example, in the Gomti, this contribution exceeds 85%. The estimated silicate erosion rate by correcting for the saline‐alkaline soil contribution in the Ganga floodplain (∼5 tons km−2 yr−1) is less than one third of that of the Himalayan headwaters (16 tons km−2 yr−1) emphasizing the important role of physical erosion in controlling the chemical erosion in the mountain catchments compared to higher temperature and residence time in the floodplain. The silicate sourced dissolved fluxes from the floodplains are comparable to those from the Himalaya because of the vast drainage area of the floodplains and peninsular catchment. The findings of this study have direct relevance to studies on the determination of silicate weathering rates of not only the Ganga system, but also of other basins infested by saline‐alkaline soils such as the Columbia, the Colorado, the upper Rio Grande, the Missouri‐Mississippi river system, the Parana river, the Niger, the Nile, and the Orange. Plain Language Summary The saline‐alkaline soils containing Na2CO3 and NaHCO3 are present abundantly in the plain and peninsular drainages of the Ganga. Their higher solubility contribute significantly to the dissolved ions budget of the river waters which was earlier considered as the part of silicate weathering resulting in overestimation of silicate weathering and hence the CO2 consumption in the Ganga System. Chemical and isotopic characterisation of these salts in the Ganga system allowed us to estimate actual silicate weathering of the system and associated CO2 consumption impacting the carbon cycle. This study estimates three times higher silicate erosion rate in the mountainous catchment of the Ganga, 16 tons km−2 yr−1 compared to its plain catchment, ∼5 tons km−2 yr−1. This study puts the hotly debated topic of importance of mountain versus plain erosion of the Ganga on rest and emphasizes the role of higher physical erosion in contributing to the higher chemical erosion in the hilly terrain compared to higher temperature and residence times in the plain catchment. Key Points The Ganga Plain is infested by saline‐alkaline soils, Na2CO3 and NaHCO3 minerals If not corrected, they overestimate the silicate erosion rates (SERs) in the Ganga Basin SER in the Ganga Plain is one third of that in the Himalaya

National river of India, Ganga River, nurturing ecological, economic, and socio-cultural aspects defining the last long history of country. Forming the largest catchment, fulfil the needs of millions of people for fresh water used in domestic, agriculture, commercial and industrial sectors. Therefore, River Ganga is always the center of attraction to the administrative authorities, institutions, academicians and researchers for its quality issues. The periodically examination of the river water quality for its conservation, restoration or rejuvenation is essential and conducted by many researcher on different quality aspects. The aim of the present investigation is to estimates the spatio-temporal variability in the Ganga River System's hydrology in upstream regions in the Himalayan Region of Uttarakhand state, India. The result clearly explains considerable variation in water quality index (WQI: 29.39–71.60) screening seasonal variation, defining the deterioration of water quality (WQ) of Ganga River from good to moderate polluted level through the overall index of pollution (OIP). Moreover, principal component analysis (PCA) has implied to identify the pollution sources. The PCA generates seven components and contributes (85.1%) to influencing river water's hydrochemistry. These outcomes give detailed information to understand the water quality affecting factors in the Ganga River system. The management and remedial practices are an urgent task required to conserve WQ in the upstream region to check WQ's further deterioration in the future.

Background The Ganga River System (GRS) is a biodiversity hotspot, its ecological richness is shaped by a complex geological history. In this study, we examined the genetic diversity, spatial connectivity, and population structure of the Asian Silurid catfish, Wallago attu , across seven tributaries of the GRS. Methods and results We employed three mitochondrial DNA (mtDNA) regions: cytochrome c oxidase subunit I (COX I ), cytochrome b (Cyt b ), and control region (CR). Our comprehensive dataset encompassed 2420 bp of mtDNA, derived from 176 W. attu individuals across 19 sampling sites within the seven rivers of GRS. Our findings revealed high gene diversity (Hd:0.99) within W. attu populations. Analysis of Molecular Variance (AMOVA) highlighted that maximum genetic variations were attributed within the populations, and the observed genetic differentiation among the seven populations of W. attu ranged from low to moderate. Network analysis uncovered the presence of three distinct genetic clades, showing no specific association with seven studied rivers. Bayesian skyline plots provided insights into the demographic history of W. attu , suggesting a recent population expansion estimated to have occurred approximately 0.04 million years ago (mya) during the Pleistocene epoch. Conclusions These results significantly enhance our understanding of the genetic diversity and spatial connectivity of W. attu , serving as a vital foundation for developing informed conservation strategies and the sustainable management of this economically valuable resource within the Ganga River System.

Ganga River system is a life support system to sustain the people of northeast region, India, by providing freshwater resource. In this study, the seasonal heavy metal concentrations of Ganga River system at Haridwar region (India) have been characterised for metal pollution. The collection of water samples was done from 10 different locations and analysed for various metal parameters (Zn, Pb, Mn, Fe, Cu, Si, Al, Ni, Cd, Mg and Co) using a standard laboratory procedures. The pollution level was assessed from the observed concentrations by using Heavy Metal Pollution Index (HPI) for nine heavy metals. The observed values of HPI were found lower than the Critical Pollution Index value of 100 (average value 78.62 and 81.18) during the study period. The concentration of Fe and Mg is exceeding the desirable limits of the World Health Organization, Bureau of Indian Standards and US Environmental Protection Agency in all water samples throughout the study period. The levels of all the metals were higher in the monsoon season and lower in the winter season. The Karl Pearson’s correlation matrix was developed by using the mean values of all parameters and showed the light intensity positively correlated with biochemical oxygen demand (BOD) and sulphate which indicate good microbial activity. Dissolved oxygen and BOD is found negatively correlated. From this study, it is easy to understand the various harmful effects of metal pollution to irrigation water and health of local people.

The Ganga River plays a major role in the transfer of materials from the Indian sub-continent to the Bay of Bengal, both in dissolved and particulate forms. To understand the present elemental dynamics of the Ganga River system, it is important to assess the hydrogeochemical contribution of its tributaries. In this paper, we present an updated database on dissolved and particulate fluxes and denudation rates of the Himalayan tributaries of the Ganga River (Ramganga, Ghaghara, Gandak and Kosi). Dissolved trace element concentrations, their fluxes and suspended sediment-associated elemental fluxes of the Himalayan tributaries have been reported for the first time. Total dissolved flux of the Ramganga, Ghaghara, Gandak and Kosi was estimated as 4, 19.1, 10.3 and 8.8 million tons year−1 accounting for ~ 5.7, ~ 27.3, ~ 14.7 and ~ 12.6%, respectively, of the total annual dissolved load carried by the Ganga River. The total particulate flux of the Ramganga, Ghaghara, Gandak and Kosi was computed as 8.2, 81.6, 30.9 and 19.5 million tons year−1, respectively. Compared to earlier studies, we have found a significant increase in the total dissolved flux and chemical denudation rate of the studied tributaries. The estimated particulate fluxes were found to be low in comparison to the previous studies. We suggest that a significant increase in the dissolved fluxes and a decrease in the particulate fluxes are an indication of the increasing anthropogenic disturbances in the catchment of these tributaries.

Ganga river basin is the most populated and among the worst water-stressed river basins in the world. The basin contributes to 40% of India’s gross domestic product. Despite the Ganga basin’s cultural, heritage, and economic importance, the interplay among the crucial factors that make the basin one of the global groundwater depletion hotspots is not well understood. Using observations from wells and Gravity Recovery and Climate Experiment satellites and simulations from a hydrological model, here we show that the Ganga river basin has lost 226.57 ± 25.22 km3 groundwater during 2002–2016, which is about 20 times the storage capacity of the largest (Indira Sagar) reservoir in India. A significant (p-value < 0.05) decline (∼11%) in the summer monsoon (June–September) during 1951–2016, severe and frequent droughts (2009, 2014, 2015), and groundwater pumping for irrigation have contributed to groundwater depletion. However, the non-renewable groundwater abstraction is the most significant (relative contribution = 80%) contributor to the groundwater depletion in the basin. Renewable groundwater pumping contributed to only 20% of the total groundwater depleted during the 2002–2016 period. Severe and frequent droughts in the basin pose a double whammy of reducing groundwater recharge and increasing withdrawal. Changes in cropping patterns, groundwater metering, and improved water use efficiency are needed to reduce the non-renewable groundwater abstraction for irrigation, which is crucial for water sustainability in the basin.

The present study aimed to assess the impact of anthropogenic stressors on the physico-chemical characteristics and water quality of the River Ganga employing a GIS-based approach in the middle Gangetic Plain at Patna, India. After the survey, sand mining, bridge construction, and disposal of untreated domestic and sewage wastes were selected as major anthropogenic stressors. A total of 48 samples were collected in pre-monsoon and post-monsoon seasons of 2022 and were analyzed for 16 physico-chemical parameters, namely water temperature (WT), pH, electrical conductivity (EC), total dissolved solids (TDS), turbidity, dissolved oxygen (DO), biological oxygen demand (BOD), total hardness (TH), Ca2+, Mg2+, Na+, K+, Cl- and SO42− ions, following standard protocols. The WQI was calculated using the Weighted Arithmetic Water Quality Index (WAQWI) method and spatial maps were created using ArcGIS software. The result revealed significant seasonal variation in several physico- chemical parameters except for Ca2+, K+ and TA (p > 0.05). ANOVA revealed significant variation for BOD and COD at Ghagha and Triveni, whereas for nitrate at Gai Ghat reference and impact sites, respectively. The Water Quality Index (WQI) revealed a deterioration in water quality by 60% in post-monsoon season. HCA revealed that the WQI was mostly governed by TDS, TH, TA, and EC.

In-situ hydrometric gauges are considered the most trusted source of information in hydrology. They are crucial for effective planning, designing and management of water-related projects. In this study, we aim to identify important gauge locations of streamflow and sediment in the Ganga River Basin: (1) by identifying critical nodes (CN) which serve as pathways for the transport of water and sediment using the linear integer programming algorithm and (2) by identifying unique gauges among the 207 existing stream gauges based on the streamflow and sediment data using the complex network measure of clustering coefficient. We use 30 years of precipitation and temperature data to generate the streamflow and sediment data at the 207 stream gauge locations using the Soil and Water Assessment Tool (SWAT). Results show that the highest number of CN is found in the eastern zone of the basin, followed by the northern and southern zones. A total of 126 CN, 51 unique streamflow gauges, and 85 unique sediment gauge locations are identified. Combining the critical nodes and unique gauges, we identify 177 and 211 potential streamflow and sediment gauge locations in the basin, respectively. Results suggest the scope for adding streamflow and sediment gauges at the identified 126 CN locations. The study is important for policymakers for collecting and managing hydrological data, flood forecasters, and river management authorities for detecting sources of pollution, wastewater, etc.

The Ganges River holds a vital status within India as a cornerstone of the nation's ecological and socio-economic fabric. Flowing through diverse terrains like the Himalayas, Gangetic plains, and coastal regions, it fosters an incredibly rich biodiversity, supporting a myriad of life forms ranging from microorganisms to mammals. Beyond its ecological significance, the river sustains the livelihoods of millions, contributing significantly to the economy of northern India. However, rampant human development over recent decades has posed grave threats to its well-being. Pollution from sewage and industrial waste has tainted its waters with heavy metals, posing risks of bioaccumulation and magnification within aquatic life. Infrastructure projects like dams and bridges disrupt natural habitats and impede the migration of aquatic species, further jeopardising the river's ecological balance. Despite these challenges, there have been glimmers of hope, particularly noted during the COVID-19 lockdown when industrial activities ceased, offering the river a temporary reprieve. Moving forward, effective measures are imperative, including reducing industrial and domestic effluent discharge, scrutinising sources of heavy metal contamination, and prioritising the restoration of the river's natural flow. Preserving the Ganges’ ecological integrity is paramount, necessitating concerted efforts to ensure its health and vitality for future generations.