Heavy metal contamination of sediments is often observed as a result of the expansion of industrial sectors and agro-economic systems, especially in developing regions. The high pollution of the river Yamuna in India, especially the substantial heavy metal contamination not only to the river but also increasingly to groundwater in Mathura and Agra regions is of concern for the production of drinking water. Consequently, this study focused on a prognosis of the risk of heavy metal contamination during the investigations for a new riverbank filtration (RBF) site in the cities of Mathura and Agra. Twenty sediment samples were taken at each site during the drilling of an exploratory well for RBF up to a depth of 30 m. The heavy metals As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were analysed in soil and aquifer sediments and water from the exploratory wells. Principal component analysis (PCA) was subsequently performed for the heavy metal concentrations in the soil and sediment samples. In general, the heavy metal concentrations found in the aquifer sediments were significantly lower compared to concentrations in riverbed material reported in literature, lower than WHO limits for agricultural soils (except Cd and Pb in Agra) and lower than values in other literature sources. While the heavy metal concentrations found in the exploratory well water in Mathura were generally found to be within the WHO drinking water guideline limits, the mean concentrations of Cd and Pb in the exploratory well in Agra significantly exceeded the WHO guideline values. The study concluded that the risk of leaching of heavy metals and consequent contamination to groundwater by the vertical movement of irrigation water is expected to be significantly greater compared to the movement of infiltrated river water through the riverbed during the RBF. Consequently, caution should be exercised when selecting flood-plain areas for new RBF sites that have been irrigated in the past with surface water impacted by heavy metals. The major sources of heavy metals identified by PCA were mainly natural and to a certain extent anthropogenic, especially in the upper layers of the soil/aquifer and is also indicative of a lesser risk of heavy metal contamination during RBF. Nevertheless, for RBF to be effective at new sites impacted by extreme environmental conditions, well-head and source-protection zones have to be implemented to avoid contamination of the aquifer from above ground anthropogenic activities. Furthermore, frequent water quality monitoring for not only heavy metals, but also other parameters in the RBF well(s), river and ambient (landward side) groundwater is important.

The present study dealt with understanding hydrogeochemical evolution, ascertaining distribution, fate and spatio-temporal variation of arsenic along with comprehending recharge processes and quantification of recharge rate in the central Gangetic plain, India. The arsenic enriched area was observed mostly in the fluvial deposits with younger alluvium. The depth to water levels maps for 1996 and 2016 showed marked spatiotemporal variation and the groundwater recharge rate was estimated to be varied between 0.05 m/year and 0.07 m/year in the study area. The elevated arsenic concentration was noticed in the region, having declined groundwater recharge. A total of 147 water samples were collected from hand pumps (n = 141) and rivers (n = 6) during the pre-monsoon period (May 2016). In addition, about 81 groundwater samples were collected from 27 locations during the pre-monsoon, monsoon and winter 2019 for studying seasonal variability in the hydrogeochemical parameters and isotopic composition of water. Arsenic concentration was found more in the area where deposits of coarser sediment of the Quaternary period was present along the rivers Ganga and Ghaghra. The arsenic concentration was observed higher in the pre-monsoon (maxm. As 641 mu g/L), followed by the post-monsoon (425 mu g/L) and monsoon season (375 mu g/L). The depleted isotopic value and higher D-excess values in groundwater suggested active recharge conditions with precipitation as the major source of recharge in the study area. It is hypothesized that rainwater induced oxygenated water into the aquifer by the process of recharge, which may prompted various biogeochemical reactions due to change in redox conditions and endorsed arsenic sorption in the monsoon season. Thereafter, anoxic conditions prevailed in the post-monsoon season, and finally, in the pre-monsoon season, reducing conditions continued and arsenic released at a rapid rate, which was justified with the seasonal variation of arsenic concentration.

The state of Punjab has a dominant agrarian economy and is considered India's bread basket. However, it is now under the problem of falling agro-economy primarily because of pervasive depletion of groundwater levels and deteriorating groundwater quality in south-west Punjab, but increasing salinity is a major concern. The irrigation requirements of crops are fulfilled by groundwater and canal water but the introduction of canal irrigation has led to waterlogging and subsequent salinization rendering large fertile-land areas becoming unproductive mainly in the south-western part of Punjab. There was an apprehension that excessive withdrawal of groundwater might have caused a reversal of natural groundwater flow pattern that might have caused ingress of saline water into fresh groundwater region of central Punjab. To address the apprehension related to the rise in groundwater salinity and its subsequent ingression in the fresh-water zone and suggest suitable management solutions, a study was undertaken to analyse the data related to salinity, isotopes, land-use and land cover (LULC) along with field and laboratory experimental results. The depth-wise isotope analysis shows that there is a large variation in isotopic signatures of shallow and intermediate aquifers and it decreases with the depth of aquifers (150-250 m). It appears that very deep groundwater (>250 m) is relatively isolated and does not show a large variation or mixing effect. Tritium analysis shows that dynamic groundwater is actively recharged through canal, river, and/or rain. The presence of modern groundwater at deeper depth indicates a good interconnection between shallow and deep groundwater. Interpretations of the results show that the canal is the main source of groundwater recharge in south-west Punjab and the evaporation process is responsible for increasing the salinity hazard. In the central parts of Punjab, groundwater and rain are the main sources of groundwater recharge, while rain is the main source of groundwater recharge in the Kandi area. In the south-west Punjab, some primary salinity has formed as a result of mineral dissolution which has further increased due to evaporative enrichment.

The state of Punjab has a dominant agrarian economy and is considered India's bread basket. However, it is now under the problem of falling agro-economy primarily because of pervasive depletion of groundwater levels and deteriorating groundwater quality in south-west Punjab, but increasing salinity is a major concern. The irrigation requirements of crops are fulfilled by groundwater and canal water but the introduction of canal irrigation has led to waterlogging and subsequent salinization rendering large fertile-land areas becoming unproductive mainly in the south-western part of Punjab. There was an apprehension that excessive withdrawal of groundwater might have caused a reversal of natural groundwater flow pattern that might have caused ingress of saline water into fresh groundwater region of central Punjab. To address the apprehension related to the rise in groundwater salinity and its subsequent ingression in the fresh-water zone and suggest suitable management solutions, a study was undertaken to analyse the data related to salinity, isotopes, land-use and land cover (LULC) along with field and laboratory experimental results. The depth-wise isotope analysis shows that there is a large variation in isotopic signatures of shallow and intermediate aquifers and it decreases with the depth of aquifers (150-250 m). It appears that very deep groundwater (>250 m) is relatively isolated and does not show a large variation or mixing effect. Tritium analysis shows that dynamic groundwater is actively recharged through canal, river, and/or rain. The presence of modern groundwater at deeper depth indicates a good interconnection between shallow and deep groundwater. Interpretations of the results show that the canal is the main source of groundwater recharge in south-west Punjab and the evaporation process is responsible for increasing the salinity hazard. In the central parts of Punjab, groundwater and rain are the main sources of groundwater recharge, while rain is the main source of groundwater recharge in the Kandi area. In the south-west Punjab, some primary salinity has formed as a result of mineral dissolution which has further increased due to evaporative enrichment. (c) 2021 Elsevier B.V. All rights reserved.

The 'Normalized Antecedent Precipitation Index (NAPI)' model developed based on water balance equation was found capable to predict runoff yields from ungauged catchment when its parameters estimated from the gauged catchment are updated using the linear relationship of geomorphologic parameters of an ungauged to that of the gauged catchment, and cumulative geomorphologic index (CGI). The CGI was developed by assigning a relative weight on each geomorphologic parameter multiplied by the ratio of characteristic value of that parameter of the ungauged and gauged catchment. Influence of land-use and land-cover (LULC) on the model's parameters was also analyzed by developing an index for LULC. The NAPI model has three parameters and its mathematical structure has rational form and the parameters possessed resonance with curve number (CN) of the SCS (Soil Conservation Services) model. The NAPI model demonstrated ability to simulate rainfall-runoff events both as direct and inverse problem. Performances of the model to predictions of runoffs from ungauged catchments were also tested with the data of two observation sites of the Bina basin in Madhya Pradesh (India) considering the data of one site as the runoffs from the ungauged catchment. The results exhibited a close match between the computed and observed values when the model's parameters were also updated by the index of LULC.

The potential impacts of climate change on the water resources of the Narmada basin in central India has been investigated using the Soil and Water Assessment Tool (SWAT). The existing dams in the river basin have been incorporated in the model setups, calibration and validation. The COordinated Regional climate Downscaling EXperiment datasets for South-Asia (CORDEX-SA) at 0.5 degrees x 0.5 degrees resolution for four-time horizons, viz., 1970-05 (historical), 2006-40 (near-term), 2041-70 (mid-term) and 2071-99 (end-term) under Representative Concentration Pathways (RCP) scenarios, RCP4.5 and RCP8.5 has been used to investigate the changes in the future climate and simulation of future streamflow. The proposed dams have also been incorporated for modeling the future developmental scenarios. The scenario analysis based on the projected climate variables has led to the inference that the change in the precipitation pattern coupled with the warming trends, maybe contributing towards higher variability in water availability. A future scenario of lower water availability and higher water demands thus calls for optimal utilization of available water resources in the future, so that the higher water demands can be satisfied with lower anticipated future flows. Various alternatives were explored for devising adaptation strategies using the engineering/technical solutions in which the optimal water resources management approaches were explored using the simulation-only and the genetic algorithm based simulation-optimization approaches. The simulation-optimization framework based integrated reservoir operation of four reservoirs has led to better reservoir performance and the number of irrigation failures has decreased substantially from 92 to 12 during 2006-40, 86 to 22 during 2041-70 and 89 to 10 during 2071-99. The hydropower failures have also decreased considerably from 202 to 96 during 2006-40, 192 to 28 during 2041-70 and 179 to 67 during 2071-99 under the RCP8.5 scenario. There were no failures in meeting the domestic water supply and environment flow demands. This may be an important adaptation measure to address the issues of climate change impacts on the water resources in the future in the Narmada basin.

Improving numerical accuracy of the finite difference (FD) models of groundwater transport is achieved here by removing the truncation error associated with advection-dispersion equation with first-order reaction and sink/source (ADERS). This chapter presents theoretical and numerical truncation error associated with ADERS for the first time. The truncation errors associated with the FD models of the ADERS are formulated from Taylor series analysis. The error expressions are based on a general form of the corresponding FD equation. A temporally and spatially weighted parametric approach is applied to differentiate among the various FD models. The study revealed that all the FD models (explicit, Crank-Nicolson, implicit) suffer from truncation errors and formulated an expression for error from sink/source term for the first time. The effects of these truncation errors on the solution of ADERS are demonstrated by comparison of numerical solution from different FD models with the analytical solution. The results revealed that these errors are not negligible and correcting the FD schemes for truncation error can result in a more accurate solution in groundwater transport models which are applied for environmental management as well as hydrological investigations.

Groundwater plays a pivotal role in India, particularly in hard rock and semi-hard rock regions of the country to support domestic, agricultural, and industrial requirements of water in addition to environmental needs. Rising demands of groundwater for rapidly increasing population, developmental activities and urbanization have resulted in unsystematic over extractions of groundwater that led to the decline of groundwater levels in many parts of the world including India. Many areas have even no proper groundwater development program that has given rise to problems of waterlogging and salinity. Approximately, 25% area of the Indo-Gangetic basin has saline water with TDS more than 1000 mg/L (as per WHO 2004) or conductivity more than 1500 mu S/cm. In Indo-Gangetic basin, the problems of salinity in Indus and upper Gangetic parts covering northwestern states of India are different than the salinity of coastal areas. The major problem of groundwater salinity in the northwestern states, namely Delhi, Haryana, Punjab, and Rajasthan, is of terrestrial origin. The order of salinity affected state, in terms of magnitude, is Rajasthan > Haryana > Punjab > Delhi. Over-abstraction of groundwater can also spread saline water into the freshwater zones due to the presence of evaporative sequences from deeper to shallower depths. Modern irrigation practices with dense canal distribution network may lead to very shallow water tables, hence may increase waterlogging and salinization due to the leakage. The impacts of groundwater salinity largely hamper the crop productivity and thereby can affect the food security. Management of groundwater salinity is thus essential for the sustainability of food security and to remediate health hazards and ecosystem services in the northwestern region of India. To obviate the problem and for better management of groundwater resources in the area, one has to know the interaction between the aquifers and surface water sources.

Mewat district in Haryana located in the semi-arid region of India has been reported continual increase of groundwater salinity. Stable isotopes, δ 18 O and δ D, of groundwater and rain water were successfully used for characterization and source identification of salinity affected groundwater in the area. Eleven representative groundwater samples were of the pre-monsoon (May), monsoon (August) and post-monsoon (November) seasons were analyzed for determining EC, δ 18 O, δ D and other parameters. The mean EC of the samples was determined 6712 μS/cm for the pre-monsoon, 4743 μS/cm for the monsoon and 6602 μS/cm for the post-monsoon. The slope of LMWL (8.13) obtained from the bivariate plot showed a very close to the GMWL (8) and the slope of rain water (7.47) and groundwater samples found lied on the right of the LMWL for all the seasons. Slopes observed for the pre-monsoon (6.76), monsoon (5.63) and post-monsoon (6.11) seasons indicated some evaporative enrichment of water before the groundwater recharge. The increase of d -excess values from 0.74 in pre-monsoon to 3.75 in monsoon and 4.46 in post-monsoon seasons suggested modern recharge with low evaporation. The recharge by meteoric water was noted from the decrease in the mean value of EC in the monsoon season and its increase in the post-monsoon season, which suggested possible ‘mechanism of mixing’. All these processes qualitatively predicted the recharge and discharge locations in the study area.

In the upper Ganga basin particularly in Himalayan terrain, precipitation and/or snow/glacial melt contribute towards the flow of the Ganga river in the form of surface and sub-surface water. In the present study, river-subsurface water chemistry is compared to infer river-subsurface water interactions in higher Himalayan region. Forty-one water samples from the Ganga river and its small tributaries between Gomukh and Dabrani section as well as subsurface water were collected during the months of March, May, September, October and November 2016 with in-situ measurements of pH, Electric Conductivity, temperature and bicarbonates. The samples were analysed for major ions and isotopes of oxygen and hydrogen. The results revealed that major ion chemistry of sub-surface water and river water is influenced by seasonal mineral dissolution and rock weathering reactions in the sub-surface water. A dominance of Calcium (36-43% in surface and 61-71% in sub-surface water), bicarbonate (13-66% in surface water and 45-85% in sub-surface water) and sulphate (31-86% in surface water; 15-47% in sub surface) is observed. High carbonate dominance is observed in surface water during the pre-monsoon (May 2016) suggesting more carbonate dissolution while high sulphates are found in March and September. The isotopes characterization of the surface and sub-surface water indicated highly evaporated sub-surface water in pre-monsoon season while in post monsoon season the slope and intercept values of delta O-18 and delta D plot was more close to that of surface water suggesting its influence. The study helps understand to river-subsurface water interactions in the Himalayan terrain of the Ganga basin. The understanding of river-subsurface water interactions can help in management of the Ganga river water and in addressing downstream environmental issues associated with the river.

This paper presents a hybrid approach for stormwater runoff modelling and pollutant load estimation in a hilly catchment. The stormwater runoff hydrograph was simulated by developing a conceptual hybrid model (HM) using transfer function. Model parameters were estimated by non-linear optimization. The simulated runoff hydrographs showed an excellent match with the observed data. Next, a relationship was developed between runoff and pollutant load and the developed relationship was used for estimation of pollutant load. A novelty of this hybrid approach is that it could bring out a generic HM. By using the derived model, the pollutant load was successfully predicted from simulated runoff (R-2 > 0.75) by considering rainfall as the only input. In addition, assessment, characterization and analysis of the first flush of urban runoff also form part of the study. The HM was tested and validated by applying it to 25 storm events monitored during two monsoon seasons in the Nainital Lake catchment (approx. 1900 m a.m.s.l.), India.

Submarine groundwater discharge (SGD) acts as major pathway to transport solute-laden terrestrial-sourced fresh groundwater, as well as re-circulated marine water to the global oceans. The study area, Bay of Bengal (BoB), a part of the Indian Ocean, receives one of world's highest terrestrial riverine fresh water discharge, sediment and solute flux from the adjacent Himalayan and cratonic South Asia. Thus, together with the monsoon-dominated tropical climate, it forms one of the most complicated, productive and interactive global hydrological systems. However, understanding such topical phenomena needs intricate mechanistic understanding, based on high resolution data, which are barely available from the BoB. Delineation of stable isotopic and chemical signature of hydrologic-sourced components in the SGD to the BoB would help to identify the intra-annual to diurnal-scale impact of seasonality and tidal cycles, as well as interactions with other surface water bodies. This study provides one of the first documentation of such high-resolution, temporally-variable, stable isotope patterns of SGD in coastal systems of the BoB, and possibly of any tropical ocean. During post-monsoon season, the discharging groundwater was observed to have depleted delta O-18 (ranges - 2.12 parts per thousand to - 4.19 parts per thousand) and low Cl- concentrations (745 to > 11,500 ppm) (seepage water), which is closely associated with the groundwater delta O-18 composition (-3.18 parts per thousand to -4.05 parts per thousand) and Cl- content (775 to > 5900 ppm) range. In pre-monsoon season depleted delta O-18 values suggests that regional groundwater contributes up to 45 m from high tide line (HTL) (up to 88%), and re-circulated seawater-sourced SGD dominates 45 m to 110 m (extent of study transect) offshore. In post-monsoon season, terrestrial-sourced groundwater predominates the SGD composition (up to 99%) till 110 m. Changes in delta O-18 and Cl- content, in pre-monsoon season indicates enhanced infiltration of seawater in the seepage face, due to lower terrestrial-sourced freshwater discharge, whereas, in post-monsoon terrestrial-sourced, resident freshwater dominates in the seepage face. The study suggests that SGD are sourced to interactions between local-regional hydrological systems, and do reflect their compositional variability. It also provides insight of influencing physico-chemical mechanisms, ranging from seasonal to daily-tidal time-scales. The outcome of this study thus may provide intricate insights in delineating the coastal hydrologic and biogeo-chemical processes, as well as detecting, carbon sinks, nutrient sources and primary productivity in a tropical ocean.

Process based semi-analytical models for surface and ground water management of a recharge basin, based on the concept of managed aquifer recharge (MAR) and aquifer storage treatment and recovery (ASTR), are presented. The model for simulation of aquifer responses due to recharge and extraction of recharged water is developed by integrating the hydrologic components into basic water balance equation; and the models for simulation of contaminants’ fate in the recharge basin and through the soil column beneath are developed by considering: (i) in-basin mass balance with decay of contaminant and, (ii) 1-dimensional advection-dispersion-decay equation coupled with linearized sorption isotherm equation, respectively. The estimate of hydrologic components included: inflow to the recharge basin from its catchment by SCS-CN model, water surface evaporation by combination of Priestley-Taylor and Penman method, recharge by Hantush’s analytical equation for water table rise due to recharge from a rectangular spreading basin in absence of pumping well, and drawdown due to pumping by Theis’s well function equation. The contaminant’s fate estimate included: time varying changes in concentration due to assimilation and detention of contaminant in the recharge basin and transport of assimilated materials through saturated soil column until they reached the groundwater table. The performances of recharge-pumping and contaminants’ transport models are illustrated by examples. These models can successfully be used and upscale as potential tools for MAR and ASTR.

Water quality indices are mathematical equations that transform water quality data into a particular number which describe the status of water. A number of water quality indices have been developed by various researchers for categorizing the water quality for different uses. These indices are developed based on classification criteria, sub-indices, and aggregation function. In the present study, a generalized Composite Water Quality Index (CWQI) is developed to classify the water into five categories, viz excellent, good, fair, poor, and polluted. For this purpose, the concentration ranges have been categorized on the basis of the Indian Standards (IS) and Central Pollution Control Board (CPCB) standards and considering International standards of World Health Organization (WHO) and European Commission (EC). Twenty-five water quality parameters are selected based on the social and environmental impacts, and weights are computed using the Saaty’s Analytic Hierarchy Process (AHP) Multiple Criteria Decision Analysis (MCDA) tool. These parameters are selected such that the same indices can be used to assess the quality of both surface and ground water. The computed weights minimize the subjectivity in assigning the parameter weights. The proposed index improves understanding of water quality issues by integrating complex data and generates a score which describes the status of water quality. The index will be very useful for the water management authorities to maintain good health of surface water resources.

Stormwater runoffs are one of the primary causes for deteriorating water quality in the Nainital Lake, India – a prominent tourist attraction and the sole drinking water source for the habitants of Nainital City. Treatment of fluctuating runoffs and contaminant influxes before mixing with the lake's water by conventional methods would require a large land footprint, which is a big constraint in the Nainital because of the hilly region. Ballasted sand flocculation (BSF) technology requires much less land footprint; a full-scale 1 MLD capacity pilot plant was applied for treatment of stormwater runoffs of the Nainital Lake. Twenty-eight storm events were monitored for runoff characterization and for evaluating the performance of BSF technology. The runoff water showed marked variation especially for total suspended solids (TSS), total phosphorus (TP), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total coliform (TC) and fecal coliform (FC) with maximum concentrations of 964 mg/l, 2.35 mg/l, 520 mg/l, 299 mg/l, 21 × 105 MPN/100 ml and 14 × 104 MPN/100 ml. The performance analyses results of the pilot plant revealed that the contaminants including trace metals in the stormwater runoff were reduced appreciably and the pollutant removal efficiencies were found to be largely unaffected by fluctuation of the influent contaminants' concentration.

Assessment of spatio-temporal variation provides a principal source of information regarding groundwater recharge, storage and discharge. Spatio-temporal variation of groundwater level (GWL) in Raipur city has been studied using statistical and graphical methods. Monthly trend of GWL has been investigated using Mann–Kendall test and Sen’s slope estimator. The monthly GWL data of thirty observation wells (dug well) of Raipur city for the period 2010–2014 have been used for the study. The minimum and maximum GWL has been found out to be 0.84 m below ground level (bgl) which is 267.98 m above mean sea level (amsl) and 16.61 m bgl (271.53 m amsl). Contour map shows that average GWL varies between 1.74 and 13.80 m bgl (i.e. 280.34 m to 287.12 amsl) during pre-monsoon and 1.64 m to 6.75 m bgl (i.e. 279.92 m to 282.54 m amsl) during post-monsoon. GWL is shallower in central part of the city, whereas deeper GWL has been observed in western and northern part of the city. The groundwater contour maps depict that the groundwater flow direction is towards north and west. The results of trend analysis reveal that no significant trend is detected at 5% significance level except few locations.

•Phosphorous is the limiting nutrient in Lake Nainital.•Naina Devi drain with a catchment area of 49% of the lake’s catchment area is the major source of pollutants.•Runoff into the lake during the rainy season is the major source of nutrients and other pollutants.

River bank filtration is a sustainable solution for drinking water quality and quantity problems in Haridwar, Uttarakhand. Riverbank filtration (RBF) is an efficient and low-cost natural alternative technology for water supply application, in which surface water contaminants are removed or degraded as the infiltrating water moves from the river/lake to the pumping wells. The removal or degradation of contaminants is a combination of physicochemical and biological processes. This paper presents an investigation to the full set-up of 22 RBF large diameter (10 m) caisson wells located along the bank of River Ganga in order to supply portable drinking water for Haridwar (112,617 persons residing permanently in the main city). These 22 RBF large diameter (10 m) caisson wells were constructed along the bank of River Ganga at Haridwar, each 7–10 m deep, and are located 50–450 m from the Ganga River or the Upper Ganga Canal. Water samples from River Ganga as induced surface water, from Upper Ganga Canal (UGC), groundwater (open well) and from RBF wells were collected and analysed for pre-monsoon and post-monsoon period. Quality measurements of physical, chemical and microbiological characteristics were obtained. Comparison of water supplied from RBF wells with surface, UGC and background natural groundwater for the investigated Haridwar site has proven the effectiveness of RBF technique for potable water supply in Haridwar district of Uttarakhand. Physicochemical and microbiological characteristics of the produced water are better than the allowable standards (IS 10500) for drinking purposes or recommended WHO limits. The results prove effectiveness of RBF method for sustainable drinking water supply in feasible locations.