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This review manuscript addresses hydro-meteorological correlations of various glaciers situated in the Himalayan region. Meteorological parameters influence the discharge pattern of the glacier. A strong correlation has been observed between discharge and air temperature of the studied Himalayan glaciers. Whereas, other meteorological parameters such as wind speed and wind direction etc. were not significantly correlated with the meltwater runoff of different glaciers in this region. In general, variability (Cv) in discharge from the various Himalayan glaciers such as Chhota Shigri and Gangotri glaciers follow the variability (Cv) in the temperature of these glaciers. Maximum variability (Cv) in meltwater runoff from the Chhota Shigri glacier has been reported in the month of September, which might be due to the fast decline in stream runoff and air temperature of the study area during the month of September. A strong relationship has been observed between suspended sediment concentration and temperature of the majority of studied Himalayan glaciers. Such type of result shows that the suspended sediment concentration in the glacial meltwater has increased with rising air temperature in this region.

Improving the knowledge on Himalayan glaciers mass balance is a key to understand the present and past annual atmospheric variations and future water availability in the region. Here, we present glaciological mass balance for Patsio Glacier, located in Himachal Pradesh (India), western Himalaya. Annual glacier-wide mass balance was measured for 7 consecutive years (2010/11 to 2016/17) and winter mass balance for 6 years (2011/12 to 2016/17). The cumulative mass balance over this period was −2.35 ± 0.37 m w.e. The corresponding mean mass balance was −0.34 m w.e. a−1. The mean annual ablation gradient excluding the debris-covered area was 0.47 m w.e. (100 m)−1. The annual ablation over the debris-covered area is reduced by an average of −1.0 m w.e. compared to the clean ice surface. Winter mass balance was consistently positive with a maximum of 1.34 m w.e. in 2014/15 and a minimum of 0.88 m w.e. in 2011/12. Multiple regression analysis between annual mass balance versus annual and winter precipitation of the Lahaul-Spiti region shows a significant positive correlation. Our results highlight the importance of monitoring seasonal mass balance and consideration of non-climatic parameters (debris and aspect) while estimating the glacier-wide mass balance.

The Himalayan glaciers contribute significantly to regional water resources. However, limited field observations restrict our understanding of glacier dynamics and behaviour. Here, we investigated the long-term in situ mass balance, meteorology, ice velocity and discharge of the Chhota Shigri Glacier. The mean annual glacier-wide mass balance was negative, −0.46 ± 0.40 m w.e. a−1 for the period 2002–2019 corresponding to a cumulative wastage of −7.87 m w.e. Winter mass balance was 1.15 m w.e. a−1 and summer mass balance was −1.35 m w.e. a−1 over 2009–2019. Surface ice velocity has decreased on average by 25–42% in the lower and middle ablation zone (below 4700 m a.s.l.) since 2003; however, no substantial change was observed at higher altitudes. The decrease in velocity suggests that the glacier is adjusting its flow in response to negative mass balance. The summer discharge begins to rise from May and peaks in July, with a contribution of 43%, followed by 38% and 19% in August and September, respectively. The discharge pattern closely follows the air temperature. The long-term observation on the ‘Chhota Shigri – a benchmark glacier’, shows a mass wastage which corresponds to the slowdown of the glacier in the past two decades.

This study mainly focuses on the source identification of various ions in meltwater and estimation of CO2 consumption rate by chemical weathering in the Batal glacier basin on the basis of 2 years of study (2015 and 2017). The glacier meltwater has been monitored as slightly acidic in nature having mean pH value of 6.6. Ca2+ was observed as the most dominant cation contributing about 76% of TZ+ (total cations), whereas SO42− was observed as the most dominant anion contributing about 70% of TZ− (total anions) in the stream meltwater. High ratios of (Ca + Mg) versus TZ+ (mean value: 0.89 ± 0.02) and (Ca + Mg) versus (Na + K) (mean value: 8.51 ± 2.07) elucidate that stream water chemistry of the Batal glacier is largely controlled by carbonate weathering. Concentration of total dissolved solid in the glacial stream water was higher during the low-melt season (September) and lower during the high-melt period (July). The average value of daily mean TDS flux of the study area was calculated to be 12.4 t/day. The mean values of CWR (carbonate weathering rate) and SWR (silicate weathering rate) for the Batal glacier basin were calculated to be 97.4 and 22.8 t/km2/year, showing higher contribution of CWR as compared to SWR in the investigation area. CO2 consumption rate by the combined silicate and carbonate (chemical) weathering was estimated to be 11.1 × 105, 28.8 × 105 and 35.5 × 105 mol/km2/year during the study period September 2015, June 2017 and July 2017, respectively. The annual CO2 drawdown by the Batal glacier basin on the basis of CO2 consumption rate by chemical weathering is much lower as compared to the Gangotri glacier, which may be due to bigger size and higher meltwater runoff of the Gangotri glacier as compared to the Batal glacier.

Groundwater samples via tubewells were collected from the district Saharanpur, Uttar Pradesh (India). The study aimed to analyse groundwater quality and potential sources of trace metal contamination using the multivariate statistical tool, and the level of contamination by applying contamination index (Cd) and heavy metal pollution index (HPI). The groundwater was found to be enriched with Fe and contaminated with the trace and toxic elements like Al, As, B, Cu, Mn and Pb having mean values of 2786, 152, 9, 1033, 107, 199 and 15 µL respectively. Arsenic exceeded the WHO (2011) guidelines and BIS (2012) standard (10 µg/L) for 30% of the groundwater samples. For B, 46% of the samples were found having concentration higher than BIS (2012) permissible limit (1000 µg/L) and 3% to WHO (2011) guideline values (2400 µL). Lead level exceeded the BIS (2012) standard value and WHO (2011) guideline value in 46% of the samples. Multivariate analysis identified three factors responsible for data composition explaining 81% of the total variance in groundwater samples. Factor analysis (PCA and CA) allowed grouping of parameters according to the common features; Fe, Mn and Pb were associated with PC1 and controlled by the mixed origin such as geogenic sources as well as anthropogenic activities. Boron and Cu (PC2) were controlled by anthropogenic activities while As (PC3) was derived from the geogenic sources. The northern part of study area has higher Pb and Mn concentration than the southern part associated with small industrial activities. Degree of contamination and heavy metal pollution index supported the results and higher contamination was found to be in the vicinity of industrial setups. The overall quality (estimated using HPI values) of groundwater in the northern area is poor, and may cause potential health risk from the analyzed tubewells to the local population if the water is consumed for longer time.

The hydrogeochemical study on glacial meltwater gives important information about the quality of meltwater and weathering processes controlling dissolved ions chemistry in the glacierized area. Anionic abundance in the Manimahesh Glacier meltwater shows a trend of HCO3− > SO42− > Cl− = NO3−, whereas cationic abundance in the meltwater shows a trend of Ca2+ > Mg2+ > K+ > Na+. On the basis of high equivalent ratios of (Ca + Mg) versus (Na + K) and (Ca + Mg) versus TZ+ (total cations) and low equivalent ratio of (Na + K) versus TZ+, carbonate-type weathering has been identified as a major hydrogeochemical process regulating solute chemistry of the Manimahesh Glacier meltwater followed by silicate weathering. About 80% of bicarbonate in the meltwater of investigation area was mainly generated from carbonate weathering, whereas 20% of bicarbonate was produced from silicate weathering. The result of statistical methods (correlation, principal component and cluster analysis) shows that meltwater quality of the Manimahesh Glacier is mainly governed by carbonate and silicate-type weathering, oxidation of pyrite, dissolution of sulphate minerals and atmospheric input. The average value of suspended sediment concentration (SSC) in the glacier meltwater was calculated to be 46 mg/l and 63 mg/l during the month of June and July 2014, respectively, showing higher concentration of SSC during the month of July (peak-flow period) followed by June (low-flow period).

Present study shows suspended sediment dynamics in the meltwater of Chhota Shigri glacier, Himachal Pradesh, India for different melt seasons during the period 2011-2014. Maximum suspended sediment concentration in the meltwater was found during the month of July 2011, 2012 and 2014 constituting to 55.2%, 48.3% and 46.9%, respectively. Whereas in 2013, maximum suspended sediment concentration was observed in August accounting for 46.1% of the total. On the other hand, maximum suspended sediment load was monitored in the month of July 2011, 2012 and 2014 constituting 59.5%, 63% and 55.7% of the total, respectively. Whereas in 2013, maximum suspended sediment load was observed in the month of August accounting for 49.8% of the total suspended sediment load. Annual distribution of suspended sediment concentration (SSC) and suspended sediment load (SSL) in the Chhota Shigri glacier shows higher value of SSC and SSL during the study period 2012 and 2013, which may be due to the presence of high glacial runoff and negative mass balance of the studied area during these time periods. Marked diurnal variation has been observed in the SSC of meltwater. Strong correlation was observed between SSC and SSL with discharge. On the other hand, SSC and SSL also showed strong exponential correlation with air temperature of the studied area. Sediment yield from the catchment of Chhota Shigri glacier is high during the peak melt season (July and August) and low during the late melt season (September and October). The average value of erosion rate for Chhota Shigri glacier basin during the study period 2011-2014 was calculated to be 1.1 mm/yr, which is lower than the average erosion rate of other Himalayan glaciers such as Rakiot, Chorabari and Gangotri glaciers, which may be caused by its geological setting containing high erosion resistant rocks such as granite, granite gneiss and porphyritic granite.

This manuscript discusses about the solute acquisition processes controlling hydrogeochemistry and suspended sediment characteristics of meltwater of the Batal glacier, Western Himalaya, India. The predominance of anions and cations in meltwater follows the order: SO4 2− > HCO3 − > Cl− > NO3 − and Ca2+> Mg2+> Na+> K+, respectively. High excess of (Ca + Mg) over (Na + K), high input of (Ca + Mg) to the TZ+ (total cations) and very low input of (Na + K) to the total cations (TZ+) demonstrate that meltwater chemistry of Batal glacier is predominantly regulated by carbonate type weathering along with minor input from silicate type weathering. Sulphide oxidation is the dominant mechanism responsible for delivery of hydrogen ions (protons) for weathering in the glacier environment, which is revealed by C-ratio of meltwater. The Piper trilinear plot indicates that Ca–SO4 is the prevalent water type in the study area with dominancy of (Ca + Mg) (alkaline earth metals) over (Na + K) (alkali metals) and dominancy of (SO4 + Cl) (strong acid) over (HCO3) (weak acid). Interrelation among the different chemical constituents of meltwater and various factor regulating meltwater chemistry of the Batal glacier are evaluated by multivariate statistical analysis. Average suspended sediment concentrations in meltwater of the study area for August and September 2014 were computed to be 706 and 98.3 mg/l, respectively. These results show that in August suspended sediment concentrations is high and in September its concentration is low.

The hydrochemical study of meltwater draining from a catchment dominated by snowmelt in a cold-arid trans-Himalayan region of Ladakh, India, was carried out for an entire melting season (May–September) during the year of 2010. Cation concentration in the meltwater shows a consistent trend of Ca > >Mg > Na > K for this period. Carbonate weathering has been identified as the dominant process controlling the dissolved ion chemistry of meltwater in the study area. There are indications that atmospheric aerosols contain alkaline dust, sea salt and anthropogenic aerosols like NO3 and SO4 that might have also added some solute to the system. Meltwater chemistry has been showing an intra-annual variation with highest concentration for most of the dissolved solutes during the late melt period, pointing towards the contribution of ground ice melt to the catchment runoff. The lowest concentration during the peak melt period is due to higher contribution from snow melt which has less residence time to interact with rock. Cationic denudation rate for this catchment has been estimated as 778 meq m−2 a−1, while the average total dissolved solids flux for early, peak and late melt period is 0.64 t day−1, 3.02 t day−1, 1.31 t day−1, respectively.

We present the updated glaciological mass balance (MB) of Chhota Shigri Glacier, the longest continuous annual MB record in the Hindu-Kush Karakoram Himalaya (HKH) region. Additionally, 4 years of seasonal MBs are presented and analyzed using the data acquired at an automatic weather station (AWS-M) installed in 2009 on a lateral moraine (4863ma.s.l.). The glaciological MB series since 2002 is first recalculated using an updated glacier hypsometry and then validated against geodetic MB derived from satellite stereo-imagery between 2005 (SPOT5) and 2014 (Pléiades). Chhota Shigri Glacier lost mass between 2002 and 2014 with a cumulative glaciological MB of –6.72mw.e. corresponding to a mean annual glacier-wide MB (Ba) of –0.56mw.e. a–1. Equilibrium-line altitude (ELA0) for the steady-state condition is calculated as ~4950ma.s.l., corresponding to an accumulation–area ratio (AAR0) of ~61%. Analysis of seasonal MBs between 2009 and 2013 with air temperature from AWS-M and precipitation from the nearest meteorological station at Bhuntar (1050ma.s.l.) suggests that the summer monsoon is the key season driving the interannual variability of Ba for this glacier. The intensity of summer snowfall events controls the Ba evolution via controlling summer glacier-wide MB (Bs).

Various physico-chemical parameters of meltwater samples from Bara Shigri glacier collected during 2012–2013 were analysed to understand the dissolved ion chemistry and solute acquisition processes regulating major ion chemistry of the study area. Ionic dominance of anions followed the trend as HCO3 − > SO4 2− > Cl− > NO3 −, whereas ionic dominancy of cations varied as: Ca2+> Mg2+> K+> Na+ for both the years. High share of (Ca + Mg) in the total cations and also dominancy of (Ca + Mg) over (Na + K) for both the years demonstrate that solute acquisition processes in the meltwater of Bara Shigri glacier are mainly governed by the weathering of carbonates. The Piper plot identified Ca-HCO3 as the dominant water type followed by CaSO4 type of water in the study area. The average value of partial pressure of carbon dioxide (Pco2) for meltwater of the Bara Shigri glacier was 10−2.6 atm in 2012 and 10−2.3 atm in 2013 and were higher than the Pco2 value of atmosphere (10−3.5 atm). It indicates that the meltwater is in disequilibrium with respect to the atmosphere. Contents of suspended sediment in the meltwater were 1432 mg/l in July and 596 mg/l in September 2012, whereas in 2013, suspended sediment contents were 1093 mg/l in August and 425 mg/l in September, following discharge pattern of the Bara Shigri glacier. We found that Bara Shigri and Gangotri glaciers demonstrate the higher rate of regional melting.

Discharge and transportation of suspended sediment from the Patsio glacier have been studied for 2 years. During the study period 2011 and 2012, daily mean discharge was measured to be 0.70 and 0.94 m 3 /s, respectively. Daily mean suspended sediment concentra- tion during the study period 2011 and 2012 was found to be 28.1 and 48.8 mg l -1 , respectively. Whereas, daily mean suspended sediment load during the study period was estimated to be 1.70 and 3.96 t day -1 . Suspended sediment concentrations generally follow the discharge pattern of the glacier for both years. High average TDS/TSM ratio of the Patsio glacier meltwater for both years shows the domi- nancy of chemical weathering over the physical weath- ering. The physical weathering rate of the study area during year 2011 and 2012 was estimated to be 79.3 and 185 t km -2 year -1 , respectively. The chemical (cation) weathering rate of the Patsio glacier is much higher than other Himalayan glaciers, which may be due to high intensity of chemical weathering in this glacier.

The current study was focused on the characterization of recharge, weathering processes and to check the aptness of groundwater for household and agriculture utility in the Chhaprola industrial area located in Gautam Buddha Nagar district of Uttar Pradesh, India. Groundwater samples (n = 33) were analyzed for major cations and anions from which (n = 22) were analyzed for stable isotopic records (δ2H and δ18O). Solute chemistry revealed neutral to moderately basic nature (pH ranged 6.4–8.8) and showed a higher (ranged 552–3130 µS/cm) of electrical conductivity. Isotopic signals ranged from − 8.7 to − 3.3‰ for δ18O and − 60.1 to − 37‰ for δ2 H. Bivariate plot of stable isotopes (δ 18O and δ2 H) showed that majority of the samples fell below the global meteoric water line (GMWL) and local meteoric water line (LMWL) of New Delhi, indicating enrichment of heavier isotopes in the aquifers, which explain that recharging water, has undergone evaporation before recharging the aquifer. Monsoonal precipitation was observed as the major source of aquifer recharge in the surveyed area. Vertical hydraulic connectivity of the aquifer layers was traced with the help of isotopic record which exhibited a more negative intercept for shallow depth tube well than the middle depth tube well. About 76% of the samples exhibited negative Schoeller index thereby indicated cation-anion exchange reactions while the remaining samples depicted the Base Exchange Reactions. Sodium-normalized Ca versus Na-normalized Mg and HCO 3, indicated an equal contribution of silicate and carbonate type weathering on global-average weathering system. About 52% of the groundwater samples fell into the Ca-HCO3- water type while remaining samples fell into 33% and 15% of Na-HCO3 and Mg-HCO3 type, respectively. Water quality indices (viz. residual sodium carbonate, Kelly index, permeability index, magnesium hazard, and Chloroalkaline indices) revealed unsuitability of the groundwater for drinking and irrigation purpose at few locations.

The chemical compositions of various ions in meltwater of the Chhota Shigri glacier were analysed during the observation period from May to October 2010. Total 164 samples of meltwater were collected in two times a day at 8.0 a.m and 6.0 p.m. Bicarbonate and calcium were the dominant anion and cation in meltwater of the investigation area. High ratios of (Ca + Mg) versus TZ+ and (Ca + Mg) versus (Na + K) demonstrate that hydrogeochemistry of the study area was mainly governed by carbonate type weathering. The average sulphate mass fraction of meltwater was computed to be 0.31 ± 0.12, showing dominancy of bicarbonate over sulphate. This excess bicarbonate would be generated by an alternative proton supply mechanism due to biological activities in the bed rock lithology and sulphide oxidation may be about the same as carbonation as a driver of chemical weathering at Chhota Shigri glacier. In general, major ions and total dissolved solid concentrations showed decreasing trend with increasing discharge from the study area. The average daily mean dissolved load of this glacier was much lower than that of the Gangotri glacier, which may be due to low meltwater runoff and lithology of the investigation area. The cation weathering rates of study area for early, peak and late melt seasons were computed to be 694, 1631 and 481 meq m−2 a−1, respectively. The average value of chemical denudation rates of the Chhota Shigri glacier meltwater was found lower than that of the Dokriani glacier.

A hydrochemical analysis of meltwater draining from Chaturangi glacier was conducted to determine the dissolved ions chemistry and to evaluate the geochemical processes controlling major ions chemistry of the study area. Ca2+, Mg2+ and SO4 2− are the dominant ions in the glacier meltwater. The ratio of (Ca + Mg) versus TZ+ varied from 0.79 to 0.86 with an average value of 0.82 ± 0.02 indicating larger contribution of Ca and Mg to the total cations. (Ca + Mg)/(Na + K) ratio is also high, varying from 3.77 to 6.33 with an average value of 4.77 ± 0.79. This shows the dominancy of carbonate weathering in the study area. The scatter diagram between (Ca + Mg) versus SO4 2− shows a linear trend throughout the range of data, indicating the dissolution of sulphate minerals as one of the possible source of SO4 2− in the Chaturangi glacier meltwater. The C-ratio of meltwater of the study area shows that sulphide oxidation is the major proton producing mechanism. Correlation matrix and principal component analysis (factor analysis) were applied for identification of various processes controlling solute acquisition in the Chaturangi glacier meltwater.

Hydrogeochemical assessment of meltwater quality draining from Bara Shigri glacier was carried out in the year 2011. The concentration of cations varied as Ca2+ > Mg2+ > K+ > Na+. Whereas, anions concentration followed the pattern HCO3 − > SO4 2− > Cl− > NO3 − > PO4 3−. High values of Ca+Mg/TZ+ and (Ca+Mg)/(Na+K) indicate that carbonate weathering is the most dominant mechanism controlling the major ions chemistry of the study area. However, the low ratio of (Na+K)/TZ+ also shows relatively smaller contribution of dissolved ions in the meltwater by silicate weathering as compared to carbonate weathering. The ratios of Na/Cl and K/Cl are higher than marine aerosols, indicating relatively small contribution from atmospheric precipitation to the chemical composition of meltwater of the study area.

In the past few years, seabuckthorn plants have gained special attention due to their ability to grow in the harshest of the environment. This adaptability may be con- tributed by various antioxidants present in the plants besides other morphological adaptation. As in vivo studies cannot be justified without in vitro studies, the present investigation carried out evaluation of both in vitro and in vivo antioxidant potentials of aqueous and alcoholic extracts of the leaves of Hippophae salicifolia (HS) and Hippophae rhamnoides mongolica (HRM) in comparison with Hippophae rhamnoides turkestanica (HRT). The results had clearly depicted that in vitro antioxidant potential of the extracts was responsible for the in vivo adaptogenic performance in animals during cold and hypoxia exposure under restraint stress. Total phenolic content (TPC), total flavonoid content (TFC), total protein content, and antioxidant potential were determined. For adaptogenic studies, rats with oral drug sup- plementation were exposed to Cold-hypoxia-restraint (C-H- R) stresses-induced hypothermia, as a measure of endurance. Aqueous extracts of HS showed maximum (99 %) resistance compared to HRT (81 %) and HRM (29 %). The levels of biochemical parameters such as malondialdehyde (MDA), reactive oxygen species (ROS), lactate dehydrogenase (LDH), superoxide dismutase (SOD), glutathione (GSH/ GSSG), and catalase (CAT) in blood samples also revealed that the aqueous leaf extract of HS has better antioxidant and adaptogenic potential compared to HRM.

Major ion chemistry of meltwater draining from Patsio glacier was carried out between 2010 and 2012 to understand the meltwater chemistry and geochemical processes controlling hydrogeochemistry of the study area. Among the anions, bicarbonate is the major anion on average accounting for 52.5 % in 2010, 58.5 % in 2011 and 58.9 % in 2012 of the total anions (TZ−). Sulphate is the next dominant anion after bicarbonate on average accounting for 45.9 % in 2010, 36.3 % in 2011 and 39.8 % in 2012 of the total anions (TZ−). On the other hand, calcium is the major cation on average accounting for 71.9 % in 2010, 70.3 % in 2011 and 72.5 % in 2012 of the total cations (TZ+). The comparatively higher contribution of (Ca + Mg) to the total cations (TZ+), high value of (Ca + Mg)/((Na + K), good positive correlation between Ca-HCO3 and low value of (Na + K)/TZ+ for all 3 years indicate that carbonate weathering is a dominant geochemical process controlling meltwater chemistry of the study area. The average Na/Cl and K/Cl ratios in the meltwater draining from Patsio glacier are much higher than marine aerosols indicating comparatively minor contribution from atmospheric precipitation to the chemical composition of meltwater of the study area. The average pCO2 (effective CO2 pressure) values of the meltwater of study area are higher than the atmospheric pCO2 showing disequilibrium with respect to atmosphere and open system weathering. Statistical analysis (correlation matrix and factor analysis) was applied for identification of different factors controlling hydrochemistry of the Patsio glacier meltwater.

A systematic study on the seasonal variation of major cations and anions was carried out to understand the source of dissolved ions as well as the geochemical weathering processes controlling the meltwater chemistry of Gangotri glacier. Calcium and magnesium are the major cations while sulphate is the dominant anion followed by bicarbonate. The high ratios of (Ca + Mg)/(Na + K), Ca/Na, Mg/Na, HCO3/Na and low ratio of (Na + K)/TZ+ for pre-monsoon, monsoon and post-monsoon seasons indicate the dominance of carbonate weathering, which is a major source of the dissolved ions in the meltwater of Gangotri glacier followed by silicate weathering. High equivalent ratios of Na/Cl and K/Cl as compared to sea water indicate relatively lesser contribution from atmospheric input to the chemical composition of meltwater. Correlation matrix and factor analysis were used to identify various factors controlling the major ion chemistry. Marked seasonal and diurnal variations were observed in the dissolved ions and suspended sediment concentration. Daily mean suspended sediment concentration for pre-monsoon, monsoon and post-monsoon was observed as 1719, 3281 and 445 mgl−1, respectively. Highest suspended sediment load was observed in monsoon season followed by pre-monsoon and post-monsoon seasons. The cation denudation rates of Gangotri glacier meltwater were calculated to be 42.2, 46.5 and 15.9 t km−2 y−1 for pre-monsoon (June only), monsoon and post-monsoon respectively. These values are higher than that of other Himalayan glaciers. Whereas physical weathering rate of the Gangotri glacier catchment was observed to be 7056, 15,344 and 588 t km−2 y−1 for pre-monsoon (June only), monsoon and post-monsoon respectively, much higher than the Indian and world averages of river.

Studies on dissolved ion chemistry and suspended sediment concentration of meltwater draining from Chhota Shigri Glacier were carried out in the year 2008 and 2009. The cationic and anionic concentrations follow the trend: Ca2+ > Mg2+ > Na+ > K+ and HCO3 − > SO4 2− > Cl− > NO3 − > PO4 3−, respectively. The higher ratios of (Ca + Mg)/TZ+ and (Ca + Mg)/(Na + K); strong correlations between Ca-Mg, Ca-HCO3 and Mg-HCO3; and low ratio of (Na + K)/TZ+ for both the years indicate that chemical characteristics of Chhota Shigri Glacier meltwater are mostly controlled by carbonate weathering followed by silicate weathering. The C ratio shows that dissolution and dissociation of atmospheric CO2 is the major proton producer for glacier meltwater. Statistical analysis was used to identify different factors controlling dissolved ions chemistry of study area. There have been marked seasonal and diurnal variations in the total dissolved solid (TDS) and suspended sediment concentration of glacier meltwater observed during the sampling periods. TDS of meltwater is high during October (low discharge) and low during August (high discharge) in both years, implying that TDS is inversely correlated with discharge. On the other hand, suspended sediment concentration is higher during August (high flow regime) and low during October (low flow regime) during the sampling periods, generally following the discharge pattern of the glacier.

Glaciers, while commonly regarded as sensitive indicators of climate change, can also be affected by various factors like atmospheric deposition. Study of major ions (Mg2+, Ca2+, Na+, K+, HCO3 −, SO4 2− and Cl−) of meltwater draining from Chhota Shigri glacier was carried out to understand weathering and geochemical processes controlling the major ion chemistry of the glacier meltwater. Chhota Shigri glacier meltwater was sampled in August 2008. Mg2+ is the dominant cation followed by Ca2+, K+ and Na+. Whereas HCO3 − is the dominant anion followed by SO4 2− and Cl−. The high ratio of Ca + Mg/TZ+ i.e. 0.77 and low ratio of Na + K/TZ+ i.e. 0.23 shows that carbonate weathering is the dominant mechanism controlling major ion chemistry followed by silicate weathering in the study area. In this paper we aim to evaluate the possible effect of various processes that affect the chemistry of meltwater of Chhota Shigri glacier. Decadal variation in the major ion chemistry of Chhota Shigri glacier meltwater was carried out by comparing the hydrochemistry of August 2008 with previous study carried out in 1987. Comparison between the two data sets shows that cations like Ca2+ increased nearly 6 times, Mg2+ 87 times, Na+ 10 times and K+ 19 times, while anions like Cl− increased nearly 12 times, HCO3 − 85 times and SO4 2− 49 times between 1987 and 2008. This could be attributed to increased weathering rates due to climate warming, atmospheric deposition or a combination of both. Annual specific mass balance of Chhota Shigri glacier was often sharply negative during 2002–2010, pointing to glacier recession, which may be also attributed to global climatic change.

Glaciers are the largest reservoir of fresh water on the earth. They play a vital role in the hydrological cycle (Sangewar 2012). Snow field areas of the Himalayan glaciers store about 12,000 km3 of fresh water and are the main source of water for great Asian rivers: Ganga, Brahmaputra and Indus (Cruz et al. 2007). There are approximately 9600 glaciers found in the Indian Himalayan region, covering an area of about 40,000 km2 (Raina and Srivastava 2008). Himalayan glaciers control the global climate change and are considered as a sensitive indicator for climate change (Sharma et al. 2013a). Since last century, majority of the Himalayan glaciers have been retreating significantly due to climate change (Kulkarni and Bahuguna 2002; Kulkarni and Alex 2003; Kulkarni et al. 2005) and effecting the meltwater runoff from the glaciers of Himalaya (Kulkarni et al. 2002). Discharge from the Himalayan glaciers is important for the generation of hydroelectric power, irrigation and drinking water supply (Singh et al. 2006).

Available published literatures on glacier mass loss and climate studies like temperature and precipitation are reviewed for Lahaul and Spiti region in northern India, which is a part of the western Himalayas. Chhota Shigri and Hamtah Glaciers are both located in the Lahaul and Spiti region and have the longest record of in situ glaciological mass balance (MB) measurements. We have compiled and compared all the dataset (different methods) related to glacier change with climate in the past few decades. Both the glaciers have experienced a significant mass loss during the study period. Different methods show diverse results for the glaciers studied for the same year; however, all results depicts overall unsteady state of both the glaciers. Data of Indian Meteorological Department (IMD) shows a significant increase in average temperature for the entire country and huge variability in precipitation particularly in the state of Himachal Pradesh. Temperature and precipitation are found to be the two main governing factors controlling the glacier health in this region. Thus, it can be said that the glaciers of Lahaul and Spiti region are losing mass due to changing weather conditions, especially the increasing air temperature. However, long-term MB and climate data will give a better insight into understand and predict the future scenario of glacier health in this region.

Glacial runoff and suspended sediment transport characteristics of the Chhota Shigri glacier were studied during the whole ablation period (May–October 2010). Discharge patterns of this glacier show that August experiences maximum runoff accounting for 34.2 % of the total runoff, followed by July 32.9 %, June 14.3 %, September 12.5 %, May 5.2 % and October 0.9 %. During the study period, the maximum runoff (Q max) was observed in the evening (4–6 p.m.), whereas minimum runoff (Q min) was observed in the morning (7–9 a.m.). The lag time between generation of meltwater from the glacier and its emergence as runoff varied from 1 to 4 h depending on the condition of melting during the melt season. A good correlation (r 2 = 0.71) was found between daily mean glacier-specific runoff and air temperature of the study area. Daily mean concentrations of suspended sediment for May, June, July, August, September and October were found as 155, 506, 577, 591, 80.9 and 30.8 mg l−1, respectively, showing maximum concentration of suspended sediment in August, followed by July. Suspended sediment load also follows a similar trend. Diurnal variations in the concentration of suspended sediment of the investigation area are directly associated with diurnal variations in meltwater runoff. There is a strong relationship between concentration of suspended sediment and discharge (r 2 = 0.79) and suspended sediment load with discharge (r 2 = 0.94). The average sediment yield of the Chhota Shigri glacier basin was computed as 1689 t km−2 year−1 during the melt season, much higher than the worldwide and Indian averages.

Major ion chemistry of lake water provides important information about the sources of dissolved ions, weathering, and hydrogeochemical processes as well as anthropogenic activities taking place in the lake environment. Surface water samples were collected from 23 different locations of the Chandra Tal (Lake) situated in the Western Himalaya and analyzed for 12 different physicochemical parameters for understanding hydrogeochemistry of the study area. The average value of pH in the lake water was measured to be 8.1, showing alkaline nature. HCO3 − was the most dominant anion and Ca2+ and Mg2+ were major cations in the Chandra Tal water. The high ratios of (Ca2+ + Mg2+)/TZ+ (total cations), (Ca2+ + Mg2+)/(Na+ + K+), Ca2+/Na+, Mg2+/Na+, and HCO3 −/Na+ show the dominancy of carbonate weathering as a major source of dissolved ions in the lake water of the study area. On the other hand, equivalent ratios of Na+/Cl− and K+/Cl− are significantly higher than the sea aerosol indicating relatively minor contribution of these ions from atmospheric fallout to the chemical composition of the Chandra Tal water. The carbon dioxide partial pressure (Pco2) of the lake water (10–2.9 atm) was significantly higher than Pco2 value of the atmosphere (10–3.5 atm), showing disequilibrium with respect to the atmosphere and open system weathering in the catchment. The correlation and R-mode principal component analysis indicate that Chandra Tal water chemistry is mainly controlled by weathering processes such as carbonate and silicate weathering, oxidation of pyrite, dissolution of sulphate minerals along with small contribution from atmospheric precipitation, and anthropogenic activities.

A detailed analytical study of major cations (Ca2 + , Mg2 + , Na + , K + ) and anions (SO $_{4}^{2-}$ , HCO $_{3}^{-}$ , Cl − , NO $_{3}^{-})$ of meltwater draining from Gangotri Glacier was carried out to understand major ion chemistry and to get an insight into geochemical weathering processes controlling hydrochemistry of the glacier. In the meltwater, the abundance order of cations and anions varied as follows: Ca2 + > Mg2 + > K + > Na + and SO $_{4}^{2-}$ > HCO $_{3}^{-}$ > Cl − > NO $_{3}^{-}$ , respectively. Calcium and magnesium are dominant cations while sulphate and bicarbonate are dominant anions. Weathering of rocks is the dominant mechanism controlling the hydrochemistry of drainage basin. The relative high contribution of (Ca+Mg) to the total cations (TZ + ), high (Ca+Mg)/(Na+K) ratio (2.63) and low (Na+K)/TZ + ratio (0.29) indicate the dominance of carbonate weathering as a major source for dissolved ions in the glacier meltwater. Sulphide oxidation and carbonation are the main proton supplying geochemical reactions controlling the rock weathering in the study area. Statistical analysis was done to identify various factors controlling the dissolved ionic strength of Gangotri Glacier meltwater.

Tectonic evolution of Himalayas is related to high erosional potential and substantial sediment transport. Fluvial deposition of clastic material in the Middle Gangetic plain (MGP) is mainly governed by crustal deformation and climatic condition of Himalayas (Singh M, Singh IB, Muller G, Geomorphology 86:144–175, 2007). Seven large Asian rivers—Ganga, Indus, Brahmaputra, Yangtze, Huang He or Yellow River, Salween and Mekong—are fed by Himalayan glaciers which are supplying ~30 % of the global sediments to the ocean (Milliman JD, Meade RH, J Geol 9:1–19, 1983; Singh VB, Ramanathan AL, Pottakkal JG, Kumar M, J Asian Earth Sci 79:224–234, 2014, 2005). High flux of sediment transported from different terrain of Himalayas is product of geologically young rock formation (Singh VB, Ramanathan AL, Pottakkal JG, Kumar M, J Asian Earth Sci 79:224–234, 2014). It provides an opportunity to study the fluvial system and post-depositional changes in sediment water interaction depending on the degree of mobility of element under the altered environmental conditions. Arsenic (As) contamination of groundwater is a global problem. Understanding of As mobilization from sediments to As-contaminated aquifers is important for water quality management in areas of MGP of India.

The global climate system is a consequence of and a link between the atmosphere, oceans, ice sheets (cryosphere), living organisms (biosphere), and soils, sediments and rocks (geosphere). The role of glaciers as sensitive climatic indicators and natural buffers of hydrological cycle is well established. In this era of much talked about climate change and global warming, glaciers have been correctly recognized as a thermometer and a crucial freshwater resource. Glaciers release meltwater during summers and early autumn, and, therefore, act as a water resource downstream by recharging river fed aquifer and influencing runoff (Bolch et al., 2012).

In the present investigation, the Late Neogene deep-sea benthic foraminiferal diversity at ODP Site 762B has been measured by using Hurlbert's diversity index ( S m ). This index measures the expected number of species to a common sample size ( m ). Here, m is put equal to 100. This method is relatively more advantageous than other commonly used diversity indices because it eliminates differences in sample size. The Late Neogene section at Site 762B is characterised by marked variations in species diversity ( S 100 ) of the deep-sea benthic foraminiferal assemblages. Species diversity broadly exhibits an inverse relationship with the values of Uvigerina proboscidea abundance and percentage of infaunal taxa in the examined section of the site. This suggests that temporal variations in primary productivity of the overlying surface waters are reflected in the Late Neogene deep-sea benthic foraminiferal diversity trends. The species diversity pattern explains that the trophic level of the bottom water changed at the beginning of the Late Pliocene (∼3.5 Ma) due to an increased surface water productivity. The higher values of species diversity during the Early Pliocene was due to a stable deep-sea environment with low trophic resource levels. However, the Late Pliocene and Pleistocene interval is largely characterised by low diversity reflecting an unstable deep-sea environment with higher surface water productivity. A distinct increase in the values of species diversity along with low percentages of U. proboscidea and infaunal taxa during the latest Pliocene (∼2.3–1.9 Ma) suggests low organic carbon influx in the bottom waters due to a decrease in the surface water productivity.

This study presents a reconstruction of the mass balance (MB) of Chhota Shigri glacier, Western Himalaya, India, and discusses the regional climatic drivers responsible for its evolution since 1969. The MB is reconstructed by a temperature-index and an accumulation model using daily air-temperature and precipitation records from the nearest meteorological station, at Bhuntar Observatory. The only adjusted parameter is the altitudinal precipitation gradient. The model is calibrated against 10 years of annual altitudinal MB measurements between 2002 and 2012 and decadal cumulative MBs between 1988 and 2010. Three periods were distinguished in the MB series. Periods I (1969-85) and III (2001-12) show significant mass loss at MB rates of -0.36±0.36 and -0.57±0.36mw.e.a-1 respectively, whereas period II (1986-2000) exhibits steady-state conditions with average MBs of -0.01 ±0.36mw.e.a–1. The comparison among these three periods suggests that winter precipitation and summer temperature are almost equally important drivers controlling the MB pattern of Chhota Shigri glacier at decadal scale. The sensitivity of the modelled glacier-wide MB to temperature is -0.52 m w.e. a–1 °C–1 whereas the sensitivity to precipitation is calculated as 0.16mw.e.a-1 for a 10% change.

Mass-balance and dynamic behaviour of Chhota Shigri glacier, western Himalaya, India, has been investigated between 2002 and 2010 and compared to data collected in 1987-89. During the period 2002-10, the glacier experienced a negative glacier-wide mass balance of -0.67 ± 0.40 m w.e. a-1. Between 2003 and 2010, elevation and ice-flow velocities slowly decreased in the ablation area, leading to a 24-37% reduction in ice fluxes, an expected response of the glacier dynamics to its recent negative mass balances. The reduced ice fluxes are still far larger than the balance fluxes calculated from the 2002-10 average surface mass balances. Therefore, further slowdown, thinning and terminus retreat of Chhota Shigri glacier are expected over the next few years. Conversely, the 2003/04 ice fluxes are in good agreement with ice fluxes calculated assuming that the glacier-wide mass balance is zero. Given the limited velocity change between 1987−89 and 2003/04 and the small terminus change between 1988 and 2010, we suggest that the glacier has experienced a period of near-zero or slightly positive mass balance in the 1990s, before shifting to a strong imbalance in the 21st century. This result challenges the generally accepted idea that glaciers in the Western Himalaya have been shrinking rapidly for the last few decades.