Groundwater salinity studies were carried out in arid and semi-arid parts of northwest India’s Punjab and Haryana states. Hydro-geochemical processes and factors causing salinity were identified using environmental tracers. Analytical results show that the hydrogeological controls and salinity mechanisms are not the same in both study areas. It has been found that the shallow groundwater in southwest Punjab is influenced by canal and river water, but the shallow water table is causing salinity due to high evaporation. Salinity in Punjab decreases with depth, and extensive irrigation is responsible for the increase in salinity along with mineral dissolution. However, in the Mewat district of Haryana, higher salinity in shallow aquifers is due to the mineral dissolution, and saltiness increases with depth due to the continuous dissolution of minerals over time. Spatial distribution of salinity in groundwater varies due to possible movement/mixing of saline water due to hydrogeological controls and anthropogenic factors like drainage, irrigation, groundwater pumping etc. Therefore, there is an urgent need for continuous monitoring of groundwater salinity so that suitable control measures can be suggested to properly manage water resources in these areas.

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.

Dam is a hydraulic structure constructed across the river to impound water. Generally dams are used for multipurpose, thus dam stability is essential. Floods resulting from the failure have caused some of the most destructive catastrophes in the past decades (George and Nair  Aquat Procedia 4:853–860, 2015). The current study was undertaken to understand the Hydrological Review and Dam Break Analysis (DBA) of Suvarnavathi dam constructed across Suvarnavathi River. An unsteady flow simulation is done using HEC-RAS (Hydrological Engineering Center River Analysis System) model to determine, probable maximum flood, flood travel time and the affected villages. From hydrological review, it is clear that existing spillway capacity is inadequate. Hence dam height must be raised further to a height of 10.1 m. The results obtained from Dam break analysis under overtopping and piping criteria furnished proof to give statement that, 46 villages and a city will be under submergence and rehabilitation cost turns out to be 3440.64 crores under overtopping failure. 23 villages and a city will be under submergence and rehabilitation cost turns out to be 1802.73 crores under piping failure.

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.

Although the Ganga is an important fluvial system of India, the isotopic investigations of its water are limited and not reported for the whole length of the river. This limits the understanding of the hydrological processes of the river whose flow characteristics have been changed considerably over the years due to changes in the climate and land use/land cover patterns of the region. This study intends to fill this gap of data and knowledge. Hence, a robust isotope datasets were generated for a period of 2-3 years from 11 locations covering the entire length of the river (2250 km). These data were further analysed to study the controls on spatiotemporal patterns of river water isotopes and understand dominance of different hydrological processes affecting flow characteristics of the river in different reaches. The stable isotopes of oxygen and hydrogen in river water exhibited large spatial and temporal variation throughout the study periods. The most negative isotopic values (mean delta O-18: -15 parts per thousand to -9.7 parts per thousand) between 0 and 318 km in the mountainous region during pre-monsoon period attributes to the dominant glaciers melt contribution while the altitude effect in rainfall is mainly responsible during monsoon season. However, less negative isotopic values (mean delta O-18: -9.7 parts per thousand to -4.3 parts per thousand) between 318 and 1000 km correspond to the mixing of water from major tributaries. Other hydrological factors responsible for the increased isotopic values include evaporative enrichment and contribution of isotopically less negative groundwater. The observed relatively low isotopic values (delta O-18: -4.3 parts per thousand to -6.9 parts per thousand) in the downstream of 1000 km of the river are due to joining of tributaries originating from the Nepal Himalayas. Results substantiate that distinct isotopic values found in different reaches of the river are because of the variations in basin characteristics, hydro-meteorological processes, and water mixing. These findings would contribute in developing a better knowledge on hydrological behaviour of the Ganga River and help in taking appropriate measures for maintaining its sustainable flows.

To investigate paleoclimate conditions and mean annual ground temperatures at the time of infiltration, concentrations of dissolved atmospheric noble gases, O-18, H-2 and C-14 were studied in Sfax deep groundwater in southeastern of Tunisia. Carbon-14 corrected ages are up to 40 Ka BP suggesting that most of this water infiltrated during Late Pleistocene. Noble gas temperatures (NGTs) clearly show the presence of water that infiltrated under much cooler conditions than at present. According to the NGT's, the mean annual temperature in this mid latitude coastal site during the last glacial maximum (LGM) was 5.5 +/- 1.0 degrees C colder than during the Holocene. This transition of Holocene -Pleistocene is well marked by a depletion of oxygen-18 isotope composition by 1.5 parts per thousand when compared to the modern rain water signature. Furthermore, the amount of excess air, which is closely linked to the magnitude of groundwater table fluctuations, provides further information on drought and wet period alternations during Late Pleistocene in Northern Africa.

ABSTRACT Stable isotope data are presented for precipitation, spring and stream water in a headwater catchments in the Indian Lesser Himalaya. Isotopic contents of phreatic groundwater followed the local meteoric water line and showed minimal alteration by evaporation, suggesting fast recharge. Mean isotopic values for springs and the stream were close to the weighted annual mean for precipitation, indicating recharge was in synchrony with seasonal rainfall distribution. Precipitation exhibited isotopic declines of −0.6‰ and −0.2‰ δ18O per 100 m rise in elevation in July and August (monsoon), respectively. The time lag of one month between rainfall and spring discharge, combined with the isotopic lapse rate indicated a recharge elevation of 70–165 m above the spring outflow point, implying the water originated within the catchment. Time series of electrical conductivity and temperature of spring, seepage and stream waters confirmed the rapid recharge and limited storage capacity of the shallow aquifers.

The study evaluates the water vapor isotopic compositions and its controls with special reference to Indian Summer Monsoon (ISM) season at Roorkee, India. Precipitation is usually a discrete event spatially and temporally in this part of the country, therefore, the information provided is limited, while, the vapors have all time availability and have a significant contribution in the hydrological cycle locally or over a regional scale. Hence for understanding the processes altering the various sources, its isotopic signatures were studied. The Isotope Water Vapour Line (Iso Val) was drawn together with the Global Meteoric Water Line (GMWL) and the best fit line was delta D = 5.42 * delta O-18 + 27.86. The precipitation samples were also collected during the study period and were best fitted with delta D = 8.20( +/- 0.18) * delta O-18 + 9.04( +/- 1. 16) in the Local Meteoric Water Line (LMWL). From the back trajectory analysis of respective vapor samples, it is unambiguous that three major sources viz; local vapor, western disturbance and monsoon vapor are controlling the fate of moisture over Roorkee. The d-excess in ground-level vapor (GLV) reveals the supply of recycled moisture from continental water bodies and evapo-transpiration as additional moisture sources to the study area. The intensive depletion in isotopic ratios was associated with the largescale convective activity and low-pressure/cyclonic/depression systems formed over Bay of Bengal. (C) 2018 Elsevier B.V. All rights reserved.

Oxygen (\({\updelta }^{18}\hbox {O}\)) and hydrogen (\({\updelta }^{2}\hbox {H}\) and \(^{3}\hbox {H}\)) isotopes of water, along with their hydrochemistry, were used to identify the source of a newly emerged seepage water in the downstream of Lake Nainital, located in the Lesser Himalayan region of Uttarakhand, India. A total of 57 samples of water from 19 different sites, in and around the seepage site, were collected. Samples were analysed for chemical tracers like \(\hbox {Ca}^{++}\), \(\hbox {Mg}^{++}\), \(\hbox {Na}^{+}\), \(\hbox {K}^{+}\), \({\hbox {SO}_{4}}^{--}\) and \(\hbox {Cl}^{-}\) using an Ion Chromatograph (Dionex IC-5000). A Dual Inlet Isotope Ratio Mass Spectrometer (DIIRMS) and an Ultra-Low Level Liquid Scintillation Counter (ULLSC), were used in measurements of stable isotopes (\({\updelta }^{2}\hbox {H}\) and \({\updelta }^{18}\hbox {O}\)) and a radioisotope (\(^{3}\hbox {H}\)), respectively. Results obtained in this study repudiate the possibility of any likely connection between seepage water and the lake water, and indicate that the source of seepage water is mainly due to locally recharged groundwater. The study suggests that environmental isotopes (\({\updelta }^{2}\hbox {H}\), \({\updelta }^{18}\hbox {O}\) and \(^{3}\hbox {H}\)) can effectively be used as ‘tracers’ in the detection of the source of seepage water in conjunction with other hydrochemical tracers, and can help in water resource management and planning.

Tritium (3H) in natural waters is a powerful tracer of hydrological processes, but its low concentrations require electrolytic enrichment before precise measurements can be made with a liquid scintillation counter. Here, we describe a newly developed, compact tritium enrichment unit which can be used to enrich up to 2 L of a water sample. This allows a high enrichment factor (>100) for measuring low 3H contents of <0.05 TU. The TEU uses a small cell (250 mL) with automated re-filling and a CO2 bubbling technique to neutralize the high alkalinity of enriched samples. The enriched residual sample is retrieved from the cell under vacuum by cryogenic distillation at −20 °C and the tritium enrichment factor for each sample is accurately determined by measuring pre- and post- enrichment 2H concentrations with laser spectrometry.

RATIONALE Natural water samples artificially or experimentally enriched in deuterium ((2) H) at concentrations up to 10,000 ppm are required for various medical, environmental and hydrological tracer applications, but are difficult to measure using conventional stable isotope ratio mass spectrometry. METHODS Here we demonstrate that off-axis integrated cavity output (OA-ICOS) laser spectrometry, along with (2) H-enriched laboratory calibration standards and appropriate analysis templates, allows for low-cost, fast, and accurate determinations of water samples having δ(2) HVSMOW-SLAP values up to at least 57,000 ‰ (~9000 ppm) at a processing rate of 60 samples per day. RESULTS As one practical application, extremely (2) H-enriched samples were measured by laser spectrometry and compared to the traditional (3) H Spike-Proxy method in order to determine tritium enrichment factors in the batch electrolysis of environmental waters. Highly (2) H-enriched samples were taken from different sets of electrolytically concentrated standards and low-level (<10 TU) IAEA inter-comparison tritium samples, and all cases returned accurate and precise initial low-level (3) H results. CONCLUSIONS The ability to quickly and accurately measure extremely (2) H-enriched waters by laser spectrometry will facilitate the use of deuterium as a tracer in numerous environmental and other applications. For low-level tritium operations, this new analytical ability facilitated a 10-20 % increase in sample productivity through the elimination of spike standards and gravimetrics, and provides immediate feedback on electrolytic enrichment cell performance. Copyright © 2016 John Wiley & Sons, Ltd.

A geochemical assessment of seasonal dynamics in the groundwater chemistry of the National Capital Territory (NCT), Delhi, was attempted through geochemical modelling, mineral precipitation sequences with rainfall and water evaporation cycle. Saturation indices calculated using PHREEQC indicated that the degree of water–rock equilibrium changes significantly from pre-monsoon to post-monsoon. The schematic model of SI change with water table fluctuation showed that during monsoon, as rainwater percolates through the soil, partial pressure of CO2 becomes higher than that of the atmospheric value and led to the formation of more carbonic acid that react with the carbonate minerals to produce \({{{\text{HCO}}_{3}^{-} }}\), Mg2+ and Ca2+. The thermodynamic stability relationships of water chemistry in the Na, K, Ca and Mg silicate systems showed that for the samples with higher EC equilibrium between clay and primary minerals is not likely to be the main processes controlling variation in the groundwater chemistry. Chloro-alkaline indices (CAI) are positive when the groundwater level is high and become negative with the lowering of water level, i.e. when water level is high, reverse ion exchange is dominant. In case of pre-monsoon season, lower and negative value of CAI-1 and CAI-2 indicates dominance of ion exchange process and increases dissolved solid concentration in groundwater. The conceptual geochemical model depicted that water table fluctuation resulting from heavy pumping/withdrawal and recharge in association with the variation in DO, \({{{\text{HCO}}_{3}^{-} }}\) and Fe regulates the water–mineral equilibrium. The conceptual geochemical model explained the hydrogeochemical processes and their variations with water table fluctuation and, thus, highlighted the descriptive capabilities of PHREEQC. The study suggested that in the subsurface environment, complex interactions are simultaneously functioning, and hence, significant seasonal variations are likely to be very influential due to monsoonal recharge and subsequent changes in the saturation states of the water.

Present study has analysed stable isotopic composition (δ18O and δ2H) of cryospheric waters of Ladakh and Kashmir regions, located in Western Himalayas, India. The samples of glacier ice (11) and melt water stream (10) collected altitude ranging between 3168 and 5465 m a.s.l. have been analysed for δ18O and δ2H. The measured δ18O values of glacier ice varied between −16.5 and −13.8 ‰ in Ladakh, and between −12.8 and −9.6 ‰ in Kashmir region. Study shows that isotopic characteristics of ice samples collected from snout of glaciers in Ladakh and Kashmir region are distinctly different from each other. Melt water samples collected from streams near the snout during September have shown good resemblance with the glacier ice melt of respective region. The d-excess of glaciers and melt water of Kashmir region varied from 21.0 to 25.6 ‰ and from 18.0 to 21.5 ‰ respectively. The d-excess of glaciers of Ladakh region have been found between 13.5 and 16.7 ‰ and of the melt water between 11.6 and 12.6 ‰. Depleted δ18O signature and low d-excess value of glaciers of Ladakh in comparison with that of Kashmir region may be attributed to sublimation process triggered by cold arid climatic conditions. The present study of Kashmir and Ladakh region suggest that isotopic composition of glacier ice is influenced by post depositional alteration, such as sublimation, during snow to glacier ice transformation.

In the recent past, lake water is greatly deteriorated due to the global climate change and anthropogenic activities because they affect both quantity and quality of the available water. Lakes in mountainous regions are generally small, and therefore more sensitive to natural/human-induced perturbations. In this study, the effect of twentieth century global climate change and human interventions was analysed for Lake Nainital, located in a densely populated valley of Kumaun Himalaya. For this purpose, gridded (0.50 × 0.50 and 0.250 × 0.250) climatic (T Mean, T Max, T Min, DTR and rainfall) data of period 1901–2000 available on monthly time steps were employed for detecting an annual and seasonal pattern of change in the climatic variables in the lake region. The samples of water collected between February 1994 and July 1996 for different months from the lake were used for determining the physical and chemical characteristics of the lake water. The samples were analysed for: field parameters (temperature, pH, EC), major ions (Ca2+, Mg2+, Na+, K+, HCO3 −, SO4 2− and Cl−), and nutrients (NO3 − and PO4 −). Results derived from the chemical analysis of water reveal that anthropogenic activities, increased in recent past, have accelerated the deterioration and eutrophication processes of the lake. However, decrease in mean annual and monsoonal rainfall will affect the various components of water balance and may cause reduction in the lake volume in the future.

The problem of salinization in the Delhi aquifer, that currently exhibits rapid landuse change, is conspicuous and severe. Salinization may be caused either by a single process, or a combination of different processes; including anthropogenic related activities, water logging and evaporative concentration of salts, influx of natural saline water, upconing of brines from the deeper parts of the aquifer, and airborne salts depositions. However, there is a lack of well-proven theory that can explain the salinity of the order of 5000 mu S/cm in the deeper aquifers of Delhi. This work identifies inconclusiveness in the previous theories of marine ingression, evaporation enrichment and subsequent leaching of salt. Further, the study depicts a conceptual understanding of the origin of salinity in groundwater based on the integrated investigations of groundwater quality, age and stable isotopic fingerprinting as well as GIS based mapping of geomorphic features. In order to explain the salinity observed in groundwater of NCT Delhi, a phenomenological scenario is illustrated and supported by additional evidences. The highest average EC value was for the shallow aquifer and is strongly symptomatic of anthropogenic influences on groundwater chemistry. Piper diagram showed heterogeneous water type and sufficient recharge/mixing of the groundwater from different aquifers. The relationship between Cl-/Br- ratios vs. Cl- indicated dissolution of salt deposits containing evaporative fraction present in the unsaturated zones or in the sediments of deeper aquifers and leaching of evaporative minerals from dunes of the adjacent Thar Desert. Cl-/SO42- ratio suggested the presence of connate seawater, halite dissolution and concentration of dissolved salts by evapo-transpiration of river water diverted for irrigation. The results show, that the closed inland marine conditions developed and buried with the active sedimentation in the geological past in this region, and further intensive exploitation of groundwater, and enhanced evaporation have together resulted in saline playa condition in some part of the region. The scenario was further verified by matching the required condition for the formation of salt pan or playa with the existing geo-morphological conditions of the area. Isotopic results indicate that salinity flushing is possible and proceeds in the areas of freshwater recharge. (C) 2015 Elsevier Ltd. All rights reserved.

Isotopic composition and electrical conductivity (EC) of groundwater were analyzed to trace the source and transport of pathogenic microbes in shallow and deep groundwater wells over a depth range from 9 m to 75 m below land surface (bls). Stable isotopic composition was used for the identification of the source of water while environmental tritium contents were used to estimate the time elapsed since the recharge of the groundwater. The results revealed that drain water contaminates shallow groundwater and as a consequence increases microbial contamination as well as EC. Two potential bacterial pathogens, Staphylococcus aureus and Micrococcus spp., were found in old as well as modern groundwater. In contrast, the distribution of Escherichia coli (E. coli) and Bacillus spp. was confined to modern groundwater, predominantly in those locations where there is a mixing of local polluted water. The results of this study suggest that bacteria may persist and travel significant distances into the subsurface, thus posing a potential infectious risk to those who are consuming groundwater for drinking.