Characteristics of Rock–Water Interaction in Gangotri Proglacier Meltwater Streams at Higher Altitude Catchment Garhwal Himalaya, Uttarakhand, India

Home , Alaknanda River, Bhaironghati, Gangotri Glacier, Garhwal Himalaya, Harsil, Pindari Glacier

J. Earth Syst. Sci. (2020) 129:173 Ó Indian Academy of Sciences

https://doi.org/10.1007/s12040-020-01426-9 (0123456789().,-volV)(0123456789().,-volV)

Characteristics of rock–water interaction in Gangotri proglacier meltwater streams at higher altitude catchment Garhwal Himalaya, Uttarakhand, India

SARFARAZ AHMAD and ZABIULLAH ANSARI* Department of Geology, Aligargh Muslim University, Aligarh, India. *Corresponding author. e-mail: [email protected]

MS received 18 March 2019; revised 9 March 2020; accepted 23 April 2020

Proglacial streams play an important role in water–rock interaction due to different climatic conditions at different altitudes. The main objective of the present study is to analyze the variation of glacier hydrochemistry and sedimentation processes at different altitudes. The results show that the bed sediments in higher altitude streams are Bne sand, poorly sorted, leptokurtic in nature and dominated with high proportion of feldspar and biotite. At lower altitude, the bed sediment is coarse sand, moderately sorted and platykurtic in nature with relatively high proportion of quartz. The high concentration of biotite and feldspar in silt/lay size fraction are responsible for high proportion of magnesium in Gangotri proglacier meltwater than others. Meltwater is slightly acidic and hydrochemical facies shows Ca+2– +2 À +2 +2 + + Mg –HCO3 type. The concentration of Ca ,Mg ,Na, and K decreases with altitude due to dilution produced by augmentation of freshly monsoonal recharged groundwater from meadow and forest in downstream. The cation exchange, carbonate/silicate weathering and groundwater, subglacial water sources control the hydrochemistry of proglacial streams at lower altitude. Keywords. Gangotri proglacier streams; sediments texture; streams hydrochemistry; weathering processes.

1. Introduction an important source to supply sediments in the Cuvial ecosystem. Plucking, quarrying, crushing, Gangotri proglacial meltwater stream is the source shearing and abrasion are the main physical of the Ganges–Brahmaputra river system. This weathering processes in Himalayan glacier catch- river system plays an important role in world ments. Studies have demonstrated that the speciBc hydrological, sedimentological budget and aAect yield may increase downstream due to the remobi- the large human population of the world. The lization of sediments pushed by the glaciers (Fer- understanding of the glacier-fed meltwater streams guson 1984; Warburton 1990; Chauhan and processes are closely related with the comprehen- Hasnain 1993). The sediment loads of Himalayan sive knowledge of the sediment budget and hydro- rivers are reported to be highest in the world, logical composition of rivers in Himalaya. The delivering *17% of the global sediment input to the headwater of this river system is covered with gla- oceans (Milliman and Syvitski 1992). Along with cier/ice. In glacier cover catchments, physical sediment load, these rivers also contribute about weathering processes have long been recognized as 5% of the total dissolved solids in the ocean. The 173 Page 2 of 14 J. Earth Syst. Sci. (2020) 129:173 solute acquisition processes of the Himalayan rivers Garhwal Himalaya situated in the Uttarkashi in Ganga–Yamuna plains have been studied by district, Uttarakhand, India. It is bounded by lat- numerous scientists in last four decades (Abbas and itude 30°440–30°560N and longitude 79°040–79°150E Subramanian 1984; Subramanian 1985; Subrama- and streams draining in the south western direction nian et al. 1987; Sarin et al. 1989). Numerous studies (Bgure 1). The proglacial streams originate from have also been completed on hydrochemical aspect Gangotri glacier at an altitude of 4000 amsl and of small glaciers basins in Himalaya (Ahmad and Cow in deep glaciated valley. The famous Gangotri Hasnain 2000; Singh et al. 2012, 2013; Singh and temple is situated on the right side of the proglacial Ramanathan 2015). Most of these studies were river at the altitude of 3000 amsl. Hydrometero- conducted to investigate the hydrochemical pro- logical conditions in the catchment area of processes in high altitude region with the emphasis to glacial streams vary with altitude. The climate is revealing the rock–water interaction. The hydro- cold and mild warm at Gangotri town and severe logical and hydrochemical variability of glacier cold at Gangotri glacier. A variation with the meltwater streams have been studied in detail by altitude in the study area showing different eco- Singh and Hasnain (1998), Pandey et al. (1999) and logical zones in the catchment; above 3000 amsl Ahmad and Hasnain (2001). forest is sparse and represented by the Bhojpatra Hydrochemical researches in the glacier cover and near the glacier snout hardly any vegetation catchments of Himalaya have been conducted to survived except few herbs. The Gangotri proglacial characterize the hydrochemical species, temporal streams receive water mainly from two types of changes with season, glacial and subglacial path- sources; glacier meltwater and groundwater from ways. However, the interactions of proglacial melt- forest/meadows. water stream with channel sediments and forest The basement rocks of the Gangotri proglacial streams have found a little attention among hydro- stream catchment are Gangotri granite and chemists and hydrologists. In recent years, the Bhaironghati granite (Bgure 2). The Gangotri interactions of lithology, geomorphology, weather- granite is the western end of the Badrinath granite, ing kinetics and land cover with proglacial stream one of the largest bodies of the higher Himalayan have been studied (Wu et al. 2005; Baraer et al. 2009; leucogranite (HHL) belt in the Garhwal Himalaya. Chakrapani et al. 2009; Han et al. 2009; Panwar et al. It was exposed along the upper reaches of the 2016). The results indicated that the chemistry of Bhagirathi river around the Gangotri glacier meltwater controlled by groundwater interactions of region. The granite was Brst described by Heim the proximal environment has very high velocity in and Gannser (1939) from the higher Himalaya proglacial streams in headwater. The understanding along upper Alaknanda valley near Badrinath of evolution of the hydrochemical characteristics of tample. Later, Auden (1949) described, the Bne headwater stream water is crucial to predict the fate grain granite constituted by tourmaline, mus- of chemical interaction with pollutant in down- covite, biotite and garnet. The Gangotri granite is stream. These complex interactions cannot be intruded as lenses either the metamorphosed base identiBed in main composite streams in Ganga of the Tethyan sedimentary as mica porphyritic plains. Therefore, the higher altitude pristine envi- granite (Scaillet et al. 1990; Searle et al. ronment provides unique opportunity to reveal the 1993, 1999), which has been named as Bhairong- processes of sediment–water interaction. In the hati granite by Pant (1986) and mainly constituted present study, an integrated approach was applied by quartz, feldspar and muscovite. to investigate the variation in hydrochemical, geochemical, sedimentologoical and mineralogical characteristics with altitude to envisage the inter- 3. Materials and methods action of proglacial streams water in different environmental parameters. For revealing the rock–water interaction, different types of rock/water/stream bed samples were collected during 25–31 October, 2014 from Gangotri 2. Study area snout to Gangotri town during post-monsoon in proglacier environment. The altitude, longitude, The Gangotri proglacial stream drains from the and latitude information of the samples were doc- Gangotri glacier and the total catchment of the umented from GPS Garmin Etrex-10 and slope stream is 873 km2. It is the longest valley glacier in information along the meltwater stream were being J. Earth Syst. Sci. (2020) 129:173 Page 3 of 14 173

Figure 1. Sample location map along the Gangotri proglacial streams.

Figure 2. Geology and rock types in Gangotri region (after Jowhar 2010).

extracted from SRTM DEM (Shuttle Radar topo- different gravel samples were viewed and graphic Mission) using PCI Geomatica 9.1.1. photographed under the microscope with magniB- Stream bed sediment samples were collected in cation factor of 20 and 50 lm. The major mineral zip-lock polythene bags using a plastic scoop. The compositions were analyzed through Trinocular sediment grain size distributions were determined stereo zoom microscope (Nikon-SMZ1500). In each by sieve shaker (Fritsch Analysette 03.502) and sample, minerals were identiBed and perform based textural analysis was carried out by Folk and Ward on physical method for the 200 particles in a method (1957). The pebble size fraction of bed sample (Ingersoll et al. 1984). The mineralogy of sediment samples were analyzed under thin section clay fraction of bed sediments were studied using studies (Hamphries 1992). In thin sections, an X-ray diAractogram technique (Carrols 1970; 173 Page 4 of 14 J. Earth Syst. Sci. (2020) 129:173

Gibbs 1971). The samples were used as powder and ) run diAractometer along with Ni-Blter and Cu-Ka U ( À1 radiation with chart drive speed of 1 cm /min. Kurtosis Morphological features of the clay fraction of bed sediments were identiBed and studied under the scanning electron microscope (SEM) (Krinsley and ) U 0.35 0.16 0.020.09 0.54 0.79 0.470.22 4.99 0.47 ( – – – – Doornkamp 1973). The geochemical analysis was À carried out using Electron Dispersive X-ray Spec- Skewness troscopy (EDXRF) method. The geochemical

analysis error of major elements in sediments ) U considered about ±0.1% (Goldstein et al. 2003). ( Sorting The stream water samples were collected in pre- washed polyethylene bottle. Soon after the sample )

collection, electrical conductivity and pH of the U ( samples were measured using a conductivity meter Mean and pH meter. Bicarbonate was analyzed by the potentiometric titration method keeping 4.5 pH as the ) U ( end point. Sulphate concentration was determined by Mica the turbidimetric method, absorbance was measured at420nmbyusingaUV/VISspectrophotometer.ClÀ )

was determined by titration method. Dissolved silica U 0.64 0.74 0.36 0.35 ( was determined by the molybdosilicate method at 812 À Feldspar nm using a UV/VIS spectrophotometer. The concentration of Ca+2,Mg+2,Na+ and K+ in melt water was determined by one of the American Public Health ) U (

Association (APHA 1980) method. The cationic and Quartz anionicchargebalance(\10%) were checked for each water sample for precision.

4. Result and discussion 0.45 0.16 0.80 À degree STD

4.1 Grain size characteristics of the stream bed Slope in sediments

The bed sediment characteristics and their relationships with altitude and slope in glacier and (m) proglacial environment were presented in table 1. Altitude Fine sand is the characteristics of the bed sediments in glacier environment, but coarse sand size 400020 305780 318420 31970000 3328 9.87 13.8660 357220 3776 8.84 3.35 378280 4.43 6.92 386740 7.28 5.39 69.14 3904 5.89 75.71 3.88 3927 5.8 3.45 72.5 10.48 4089 12.76 2.45 73 10 7.42 68.88 4.06 1.89 6.8 60 12.5 18.08 8.63 6.48 63 64.42 14 14.28 14.44 0.51 7.79 4.46 15 54 15 1.75 16.66 15.38 66.66 0.96 13 46.66 15 1.3 0.25 1.55 15 20.19 25 13.54 28.33 1.65 0.89 22 0.77 3.14 1.51 19.79 31 1.2 25 1.43 1.27 0.37 1.23 1.53 0.86 0.43 1.24 2.63 1.24 1.29 1.28 0.53 1.34 0.62 0.76 1.25 0.3 0.35 0.73 0.29 0.68 0.48 0.48 is the characteristics of the proglacial environment 0 0 0 0 0 0 0 0 0 0 0 56 57 55 58 01 03 03 03 04 04 05 at lower altitude. The low slope near the glaciated ° ° ° ° ° ° ° ° ° ° ° environment indicated that strong levelling of the topography by the glacier action, while inactive 4000 78 40 78 00 78 80 78 00 79 00 79 00 79 40 79 80 79 80 79 79 glaciations and tectonic forces are responsible for 0 0 0 0 0 0 0 0 0 0 0 59 59 58 00 00 57 57 57 56 55 55 ° ° ° ° ° ° ° ° ° the high slope of proglacial streams at lower alti- ° ° tude area. These conditions lead to increasing stream velocity and subsequently increases drainage capacity in downstream direction. This process removes the selective Bne size particles and Sedimentological and mineralogical character (only sand) of the sediment in Gangotri proglacier streams. leads to increase grain size in downstream region. dence level 80% 60% 99% 99% 99% 95% 95% 95% 65%

The sorting of bed sediment increases down- B with elevation 130 330 530 231 431 630 730 830 930 Table 1. Sl. no. Latitude Longitude Correlation Con stream, less sorting in glaciated environment is the 1011 30 30 J. Earth Syst. Sci. (2020) 129:173 Page 5 of 14 173 characteristics of low energy conditions and also removing Bne material from the stream bed and some of the variable sources act as sediment pro- increased the skeweness in downstream (Bgure 3). duction such as slumping of unstable moraine and channelized system. However, high discharge in 4.2 Mineralogical characteristics of the stream downstream consequently lead to removal of Bne bed sediments sediment from stream bed caused to increase in sorting at lower altitude. The mineral compositions were evaluated for the The kurtosis of bed sediment shows the gravel, sand and clay fractions of bed sediment in peakedness of grain size distribution. In the melt- proglacier meltwater streams (table 2). The gravel water streams, the bed sediment kurtosis decreases and sand fraction are the most dominant sediment in with increasing altitude. At higher altitude in the streams bed. Petrographic study indicates that in glaciated environment, the bed sediments are gravel fraction, quartz (56 ± 4.6%) is the most showing leptokurtic nature and platykurtic in dominant mineral followed by biotite (17 ± 5.1%), downstream regions. Near the glacier, the Bne size muscovite (14 ± 4.3%), and feldspar (9 ± 5.7%), sediments are delivered to channel by subglacial respectively. The comparative analysis of country abrasion activity, unstable moraines and alluvial rock and gravel fraction indicates that major mineral cones. The limited sources of sediment environ- constituents in gravel fractionare intact and chemical ment resulted in leptokurtic nature of bed sediment weathering were not impacted on them. The sand near glacier. At lower altitude, the variable sources fraction is the most dominant in bed sediment and in indicate platykurtic nature of bed sediment. The sand, quartz is the most dominant component with skewness of bed sediments indicates positive average of 65 ± 8.7%, followed by biotite/muscovite skewed ranging from symmetrical to course-skewed constitute 20 ± 5.4% and feldspar constitute about in nature. At lower altitude, the carrying capacity 15 ± 4.2%. The high percentage of quartz in sand of meltwater streams increases due to augmenta- fraction than in gravel fraction suggests the rework- tion of groundwater and other streams along with ing of sand grade sediment in meltwater stream drain high slope in downstream regions. Enhanced from Gangotri glacier environment. Therefore, high carrying capacity at lower altitude resulted in percentage of quartz in glacier environment cannot be

3.5 y = 0.0008x - 1.5289 1.8 y = -0.0004x + 2.4436 R² = 0.1307 R² = 0.1251 3 1.6 1.4 2.5 1.2 2 1 1.5 0.8 Mean (ɸ) Mean

Sorting (ɸ) 0.6 1 0.4 0.5 0.2 0 0 3000 3500 4000 4500 3000 3500 4000 4500 Altitude (m) Altitude (m)

1 y = -0.0004x + 1.626 6 y = 0.0006x - 1.1238 R² = 0.1001 R² = 0.0287 0.8 5 0.6 4 0.4 3 0.2

Kurtosis (ɸ) Kurtosis 2

Skewnes (ɸ) Skewnes 0 1 -0.23000 3500 4000 4500 -0.4 0 3000 3500 4000 4500 -0.6 Altitude (m) Altitude (m)

Figure 3. Variation of textural characteristics of bed sediments with altitude in Gangotri proglacial streams. 173 Page 6 of 14 J. Earth Syst. Sci. (2020) 129:173

Table 2. Mineralogical composition of the gravel, sand and clay fraction in bed sediment of Gangotri proglacial environment.

Gravel fraction in bed Sand fraction in Clay fraction in bed Clay fraction in bed Mineral in sediment (Gaumukh) proglacial stream sediment (Gaumukh) sediment (Bhojwasa) percentage (n =4) (n = 11) (n =6) (n =3) Quartz 56 ± 4.6% 65 ± 8.7% 18.4 ± 3.1% 26.5 ± 5.8% Illite 5.8 ± 2.8% 18.1 ± 6% Feldspar 9 ± 5.7% 15 ± 4.2% 71.4 ± 11.4% 53.5 ± 4% Keolinite 0.7 ± 0.2% 1 ± 0.5% Muscovite 14 ± 4.3% 20 ± 5.4% 0.9 ± 0.2% Biotite 17 ± 5.1% 3.7 ± 1.4%

Table 3. Hydrochemical characteristics of the Gangotri proglacier streams meltwater (all the concentration in milli eq/litre except TDS in mg/l and EC in l/cm).

Sl. Altitude +2 +2 + + À À2 À no. Latitude Longitude (m) TDS pH EC Ca Mg Na K H4SiO4 HCO3 SO4 Cl 130°59040 78°057005 3088 52.17 6.3 52 0.56 0.49 0.1 0.03 0.1 1.05 0.06 0.16 230°59033 78°056023 3090 109.68 7 110 0.72 0.89 0.11 0.09 0.13 1.61 0.12 0.17 330°59023 78°055021 3170 105.64 7.3 106 0.96 0.89 0.11 0.14 0.18 1.86 0.17 0.15 430°59044 78°058051 3228 79.89 7.1 80 0.56 0.49 0.14 0.02 0.16 1.05 0.07 0.19 530°59024 78°055023 3246 126.13 7.1 126 1.44 0.81 0.13 0.15 0.22 2.01 0.19 0.08 630°59007 79°000052 3539 69.9 7.2 70 0.56 0.73 0.07 0.02 0.09 1.29 0.15 0.05 730°58007 79°002016 3742 124.03 6.9 124 1.04 0.57 0.13 0.1 0.16 1.81 0.14 0.07 830°56057 79°003005 3769 173.28 6.3 173 0.8 0.97 0.4 1.31 0.15 1.78 1.45 0.36 930°56000 79°004019 3916 166.84 6.4 167 0.96 1.06 0.31 0.22 0.13 2.02 0.42 0.2 10 30°55057 79°004024 3923 127.41 6.5 127 0.96 1.22 0.25 0.12 0.13 2.18 0.2 0.02 11 30°55034 79°004051 3967 147.63 6.8 148 0.96 1.22 0.4 0.14 0.13 2.18 0.28 0.26 12 30°55035 79°004055 4005 75.92 6.3 76 0.48 0.49 0.2 0.06 0.15 0.97 0.19 0.13 13 30°55031 79°005006 4065 115.94 6.7 116 1.2 1.14 0.27 0.09 0.09 2.59 0.2 0.02 regarded as indicator of stable cratonic conditions. studies conducted in Harsil sub-basin of Ganga The detritus mineralogy of the bed sediments of river headwater also suggested that the high stable slope in central Ganga basin also suggested that the detri- at lower altitude, high temperature and high vege- tus is mainly derived from recycled orogen prove- tation cover was responsible to intense chemical nance with granite-gneisses (Singh et al. 1993). The weathering at lower altitude than higher altitude clay fraction was least dominant and composed with (Ahmad and Hasnain 2007). The relationship feldspar and clay minerals (Illite). However, quartz between minerals percentage of sand fraction in bed was observed as the least abundant mineral in clay sediment samples and their altitude attributes fraction due to high viscosity of the meltwater in low exhibited by correlation matrix in table 1. The temperature conditions along with high hardness of strongest negative relationship was exhibited by quartz. feldspar fallowed by positive relation with quartz The changes in sand mineral constituents at and biotite/muscovite. Positive and negative rela- different altitude have been evaluated to reveal the tionships were observed due to change in percentage relationship of chemical weathering intensity pre- of quartz and feldspar with altitude. A sudden sented in table 1. In Gangotri valley the tempera- decrease in feldspar percentage from an altitude of ture changes with altitude, at the Gangotri town the 4089 to 3900 m a.s.l. suggests the quick mobilization climate was cold to mild warm and severe cold at of solute in this zone. The low gradient, poorly Gangotri glacier. Therefore, low temperature in sorting of bed sediment results indicate that sluggish glaciated environment lead to chemical weathering movement of water which provide sufBcient contact with low intensity. This result also indicates high time between rock meltwater interaction. The percentage of feldspar in the bed sediment near the chemical reactions during this time results degrad- glacier than bed sediments at Gangotri town. The ing the chemically susceptible minerals and caused J. Earth Syst. Sci. (2020) 129:173 Page 7 of 14 173 sudden decrease in volume percentage of feldspar at lower altitude in proglacier stream. Tracer studies conducted on subglacial aspect of the Gangotri glaciers revealed that the well developed subglacial channel exist beneath the glacier. The stream velocity in this subglacial channel is 0.6 msÀ1 and dispersivity value 2.1 m in post monsoon season. It reveals that the sluggish movement of meltwater in subglacial environment with freshly abraded material resulted in quick mobilization of solute in proglacier streams (Jose et al. 2014).

4.3 Chemical characteristics of the streams meltwater

The Gangotri proglacial basin altitude ranges from 3000 m near the Gangotri town to 4000 m amsl near Gangotri glacier. Therefore, the hydro meteorological conditions vary from cold to warm moist at Gangotri town and severe cold at Gangotri Figure 4. Impact of hydrogeochemical processes on chemical glacier. Hence, the hydrological and solute acqui- characteristics of proglacial meltwater streams in post-monsoon period (after Gibbs 1970). sition processes also changes from lower to higher altitude. Three major hydro-meteorological and hydro-morphological conditions can be distin- guished on the basis of climatic and geomorphic characteristics namely glaciated cover, meadow and sparse pine forest. The temporal and spatial dominance of particular hydrological processes in one or other geomorphic units inCuence the solute acquisition processes and inCuence the hydrochemistry of proglacial streams. The hydrochemical characteristic of meltwater was evaluated to investigate the solute acquisition processes in the basin during post-monsoon season (table 3). Average pH of the meltwater is 6.76 ± 0.38, mean EC (electrical conductivity) is 113 ± 36 lS/cmP and EC show strongP relationship between EC/ cations (TZ+) and EC/ anions (TZÀ) with r [ 0.999. The hydrochemical processes were identiBed through Figure 5. Hydrogeochemical facies diagram of meltwater using standard diagrams, i.e., Gibbs, Piper, scat- samples in proglacial streams. tered, etc., the Gibbs diagram indicated that water samples from higher altitude glacier stream show proglacial streams shows that calcium and magne- strong rock-water interaction (Gibbs 1970). How- sium were the most dominant cations and the order ever, the proglacier streams at lower altitude shown of abundance is Ca+2 [ Mg+2 [ Na+ [ K+ and less rock-water interaction and equal dominance of piper diagram indicate the meltwater is Ca+2– +2 À precipitation (Bgure 4). The concentration of TDS Mg –HCO3 type (Bgure 5). (Total Dissolved Solids) decreases with altitude A comparative analysis of the cations abundance (r [ 0.80) indicates that low concentration of with other proglacial streams in the Garhwal Hima- freshly recharged monsoon ground water leading to laya indicate the dominance of Ca+2 and Mg+2 (Ah- low concentration of ion concentration in proglacier mad and Hasnain 2000;Singhet al. 2015). However, streams during post-monsoon period. Average the difference between Ca+2 and Mg+2 concentra- chemical composition of meltwater in Gangotri tions is significant in other proglacial streams than 173 Page 8 of 14 J. Earth Syst. Sci. (2020) 129:173 the Gangotri proglacial streams. The substantial and resulted in high mobility of Ca+2 and Mg+2.The contribution of Mg+2 in proglacial streams were equivalent ratio of (Ca+2 +Mg+2)/TZ+ is about mobilized through geochemical weathering of biotite 0.83 ± 0.11, while (Na+ +K+)/TZ+ is 0.16 ± 0.1 mineral present in gravel, sand and clay fraction. (Bgure 6). A high level of r [ 0.8 between Ca+2/ +2 À Biotite/illite mineral in clay size fraction constitute Mg and HCO3 indicating carbonate weathering substantial part in bed sediments and contribute to process is the main solute acquisition mechanism in the high concentration of magnesium mobilization in basin.Further, the high silica concentrationin stream meltwater. Calcium is the most dominant cations in water suggests the active silicate weathering also the entire proglacial streams and mobilized through inCuencing. Hence, solute acquisition processes in the the geochemical weathering of feldspar, which is a proglacial environment can be a considered as mix- dominant mineral in clay fraction. Near the glacier ture of both the carbonate and silicate weathering environment, the bed sediments were characterized processes (Garzanti et al. 2010;Bickleet al. 2015; with small grain size with leptokurtic in nature. This Shukla et al. 2018;Ansariet al. 2019). mixture is highly geochemically active and made by The sources and characteristics of the solute in two components namely the Bne fraction of unsta- meltwater were also evaluated through correlation ble minerals and relatively stable gravel size inactive analysis among the variables (table 4). The result fraction. Chemical unstable material controls the indicates that silica is less significant and has solute acquisition processes in the subglacial envi- negative relationship with altitude, while the ronment. Fresh chemically active feldspar and biotite cations are showing positive relationship. The high mineral go under the chemical weathering processes concentration of silica at lower altitude is a func- tion of high intensity of chemical weathering of silicate rocks owe to high temperature and soil development. However, the Na+,Mg+2 positive relationship with altitude is related to augmentation of the sub-glacial solute enriched melt water and freshly recharged low TDS groundwater from meadows and forests. The best positive relationship with altitude was exhibited by Na+ and Mg+2, while K+ and Ca+2 show relatively weak positive relation. Highly mobile Na+ is a lithogenic element, which gets easily aAected by the dilution produced in the meltwater streams. However, Ca+2,Mg+2, and K+ have higher capacity to get exchanged on clay adsorption site and do not show the good

+2 +2 relationship with altitude. The rate of decrease Figure 6. Relative mobilization of (Ca +Mg ) and +2 +2 + (Na++K+) in proglacial meltwater streams. of Ca /H4SiO4,Mg /H4SiO4,Na/H4SiO4 and

Table 4. Correlation matrix of hydrogeochemical parameters of proglacial streams.

Altitude 2+ 2+ + + À 2À À Parameters (m) TDS pH EC Ca Mg Na K H4SiO4 HCO3 SO4 Cl Altitude (m) 1 TDS 0.47 1 pH À0.5 À0.21 1 EC 0.47 1 À0.2 1 Ca2+ 0.18 0.58 0.22 0.58 1 Mg2+ 0.47 0.71 À0.08 0.71 0.54 1 Na+ 0.71 0.77 À0.55 0.77 0.22 0.66 1 K+ 0.18 0.61 À0.38 0.61 0.05 0.24 0.6 1

H4SiO4 À0.29 0.25 0.32 0.25 0.42 À0.17 À0.11 0.14 1 À HCO3 0.46 0.71 0.05 0.71 0.84 0.86 0.51 0.15 0.02 1 2À SO4 0.29 0.65 À0.43 0.65 0.04 0.29 0.67 0.06 0.08 0.17 1 ClÀ À0.07 0.42 À0.29 0.42 À0.27 0.05 0.54 0.68 0.14 À0.17 0.68 1 J. Earth Syst. Sci. (2020) 129:173 Page 9 of 14 173

+ +2 K /H4SiO4 ratios with altitude shows that Ca / groundwater contribution to proglacial streams. +2 + H4SiO4 and Mg /H4SiO4 decrease sharply than But low exchange capacity of Na results in con- + the Na /H4SiO4. It further indicates the depletion tinuous mobilization of these ions in groundwater of Ca+2 and Mg+2 due to dilution of groundwater and further in proglacial streams. from freshly recharged meadow/forest augmenta- High concentration of calcium and magnesium in tion in proglacier streams. This groundwater was proglacial meltwater streams along with dissolved highly inCuenced by cations exchange capacity of silica in stream water may result in precipitation of clay fractions in forest and stream bed sediments. clay minerals in glaciogenic sediments. The silt and An investigation of relative silica concentration clay from lateral moraine also mobilized along with and positive relation with Ca+2,Mg+2, and K+ slope, and contributed Bne sediments in the pro- suggest that concentration of these cations have glacial environment (Plate 1a and b). Saturation been decreased ranging from 90 to 95% and Na+ index of the possible different mineral species is concentration decreased by 20% from higher calculated using USGS (PHREEQC). The results altitude to lower altitude. Further, a decrease in indicate that mineral sepiolite has saturated state +2 +2 + ratio of Ca /H4SiO4,Mg /H4SiO4,Na /H4SiO4 in proglacial stream water due to high concentra- + and K /H4SiO4 were observed (12 À 3 = 9), tion of magnesium and active silicate weathering (11 À 3=8),(2À 0.6 = 1.4) and (8 À 0.12 = 7.8), (Plate 2a and b). The studies conducted by respectively (Bgure 7). Mahaney et al. (2009) also found that soil and Nature of decrease in cations/H4SiO4 was related moraine have spediolite in cores of late glacial and to relative exchange processes of cations on clay neoglacial moraines of Humboldt glacier, north- particle in meadows/forest and bed sediment soil. western Venezuelan Andes. The present study also The high uptake of the Ca+2,Mg+2 and K+ suggest high possibility of Bnding such clay min- from the soil solution at adsorption sites of clay erals in Gangotri regions and further research is the particles results in Ca+2,Mg+2 and K+ deBcient need in this aspect.

Plate 1. (a) Gaumukh where Bhagirathi stream started and (b) Bhagirathi stream channel.

Plate 2. (a and b) Soil proBle near the glacier cover area at altitude of 3700 m amsl. 173 Page 10 of 14 J. Earth Syst. Sci. (2020) 129:173

14 y = 0.0029x - 4.1189 14 y = 0.0041x - 8.2377 R² = 0.2034 12 12 R² = 0.2813 4 4 10 10 SiO SiO 4

4 8 8 /H /H

6 +2 6 +2 Ca 4 Mg 4 2 2 0 0 3000 4000 5000 3000 4000 5000 Altitude (m) Altitude (m)

3.5 3 y = 0.0006x - 1.2975 y = 0.0019x - 5.2727 R² = 0.2574 3 R² = 0.5799 2.5

4 2.5 4 2

SiO 2 SiO 4

4 1.5 /H /H

+ 1.5 +

K 1 Na 1 0.5 0.5 0 0 3000 4000 5000 3000 4000 5000 Altitude (m) Altitude (m)

Figure 7. Impact of altitude on different ionic ratios in Gangotri proglacial streams.

4.4 Geochemical characteristics morphological features of sediments in the glacial environment are generally large and depends on Geochemical composition of the clay fraction, numerous factors such as rock types, rapid changes showing the order of abundance are Si [ Al [ in glacier motion, shifts in the subglacial drainage Na [ K [ Fe [ Mg [ Ca (table 5). A change was system, failure of channel banks, etc., (Collins observed with altitude in order of abundance and it 1989; Hammer and Smith 1983). The Scanning shows Na, K, Mg and Ca. The impact of elemental Electron Microscope (SEM) has been proved as a change with altitude shows decrease in ratio of Ca/ principal tool for examining surface texture of Si and Na/Si more significantly than the K/Si. sediment particle. Many researchers have attemp- However, Mg/Si ratio does not show any relation- ted the explanation of relief structure on quartz ship with altitude. The close behaviour of Na/Si sand grain to speciBc glacial sub-environment and Ca/Si with altitude was related to common based on different processes in those regimes source, and correlation matrix indicated that Ca (Margolis and Kennel 1971; Whalley and Krinsley and Na are strongly associated. A positive associ- 1974; Whalley 1978). ation of Mg, K, Al and strongly negative relation- The morphoscopic characteristics of sand parti- ship has been observed with Si (table 6). The cle in the supraglacial, subglacial and proglacial association reveals that chemistry of the clay environment have been identiBed in Himalayan fraction of bed sediment was largely governed by glacier environment by Singh et al. (1995). Sources feldspar and micas in geological rock material of suspended particle were identiBed based on which is abraded by glacier activity and hydraulic morphoscopical character of subglacial, supragla- reworked sediments. cial and proglacial environment in Pindari glacier basin (Pandey et al. 2002). These studies were 4.5 Morphoscopy limited to glacier regimes, which occupy few per- cent of the area in higher altitude basins and pro- The shape of sediment particles and textural duce large volume of sediment to the Cuvial patterns on their surfaces are good source of system. The systematic changes occurred on mor- information about the physical and chemical pro- phoscopy of sediments can be useful for under- cesses in the environment. Textural characters and standing the processes of sediment interaction J. Earth Syst. Sci. (2020) 129:173 Page 11 of 14 173

Table 5. Elemental composition % in clay fraction of bed sediments collected from Gangotri proglacial streams.

+ +2 +3 + +2 +2 Sl. no. Latitude Longitude Altitude (m) Na Mg Al SiO2 K Ca Fe 130°59040 78°56040 3100 7.4 1.8 17.1 64.1 5.5 1.4 2.7 230°58080 79°01020 3600 5.9 3.2 20.3 56.9 6.8 1.2 5.8 330°54.0 79°06000 4000 6.2 0.7 16.5 64.6 5.7 1.3 5.1 430°54.00 79°06000 4200 6.5 2.3 17.4 62.9 5.1 1.1 4.7 530°550.80 79°05040 4100 6.5 2 17.8 62.1 5.8 1.3 4.6

Table 6. Correlation analysis of clay fraction of bed sediments.

+ +2 +3 + +2 +2 Parameters Altitude (m) Na Mg Al SiO2 K Ca Fe Altitude (m) 1 Na+ À0.560 1 Mg+2 À0.146 À0.251 1 Al+3 À0.162 À0.528 0.890 1

SiO2 0.082 0.603 À0.867 À0.995 1 K+ À0.254 À0.593 0.518 0.845 À0.851 1 Ca+2 À0.629 0.586 À0.485 À0.353 0.401 0.020 1 Fe+2 0.589 À0.997 0.288 0.539 À0.613 0.567 À0.635 1

Figure 8. (a, b) Hazy poorly sorted mixed glacier stream bed sediment, cleaned well sorted grains from bed sediments from low altitude proglacial streams. between higher and lower altitude basins. The clay (Bgure 8a). However, the grain size distribution fraction of bed sediment samples were collected in shows moderate sorting of bed sediment in pro- post-monsoon from the Gangotri proglacial glacial streams near Gangotri town at lower alti- streams and examined by SEM for surface textural tude (Bgure 8b). In glacier environment, elongated studies. Grain morphoscopy and surface texture grains were also found and indicated stretching of were recognised and interpreted on the basis of the grains due to glacier movement (Bgure 9a). individual surface texture as well as particular Some grains show conchoidal followed by step-like combinations of texture diagnostic of speciBc sed- features along with chemical activities on the pre- iment transport mechanism and environment. In sent samples that are evident with surface etching this study, it indicates that the bed sediment in (Bgure 9b). Strong impacts of glacier abrasion on glacial environment was characterized by poorly grains are visible in the form of steps and stria- sorting along with sub-angular to sub- tions; sub-rounded to rounded particles with rounded shapes with variable size near the glacier smoothening of the conchoidal edges, elongated 173 Page 12 of 14 J. Earth Syst. Sci. (2020) 129:173

Figure 9. (a, b) Elongated grains and glacier abrasion resulting in conchoidal fracture, steps like striations and etching due to chemical weathering.

Figure 10. (a, b) Evidence of glacier strong abrasion on grains resulting breakage steps and curved striations. sub-rounded grain with secondary replacement melt water streams. At higher altitude, the bed dissolution, secondary growth in sediments col- sediments were characterized by Bne sand, poorly lected from lower altitude (Bgure 10a and b). The sorting, leptokurtic in nature and dominated by bed sediment in glacier environment shows etching feldspar and micas. While at the lower altitude, on the surface, these grains are showing hazy type. coarse sand, moderate sorting, platykurtic, and However during transportation, the etching surface quartz dominate in the bed sediment. was removed and surface of grain in downstream The subglacial abrasion produces highly chemi- shows polished and less striation along with grains cal active clay fraction feldspar and biotite grains. with secondary growth and replacement. These chemical active grains in sluggish subglacial and gentle slope in proglacial environment releases the solute in meltwater streams. High Mg+2,Ca+2 and H4SiO4 in melt water may produce saturation 5. Conclusions of sepiolite in glaciogenic sediments. The concentration of Ca+2,Mg+2,Na+, and K+ decreases with An integrated approach has been reported in this altitude due to dilution eAect produced by aug- paper to investigate the spatial change in min- mentation of freshly monsoonal recharged eralogical, sedimentological and hydrochemical groundwater from meadow and forest in down- characteristics of proglacier streams with differ- stream. The cation exchange, chemical weathering ent altitude in Gangotri basin. The altitude plays and mixing of groundwater from forest/meadows an important role in determining the composition control the hydrochemistry in lower altitude and physical character of the bed sediment in during post-monsoon time. J. Earth Syst. Sci. (2020) 129:173 Page 13 of 14 173

Acknowledgements Collins D N 1989 Seasonal development of sub-glacial drainage and suspended sediment delivery to meltwater beneath an The authors would like to express their thanks to alpine glacier; Ann. Glaciol. 13 45–50, https://doi.org/10. Chairman, Department of Geology, Aligarh Mus- 3189/S026030550000762X. Ferguson R I 1984 Sediment load of the Hunza river, In: lim University for providing the laboratory and International Karakoram project (ed.) Miller K J, Cam- library facilities. The authors would like to appre- bridge University Press, Cambridge, UK, pp. 581–598. ciate the Bnancial assistance provided by UGC, Folk R L and Ward W C 1957 Brazos river bar: A study in the Ministry of HRD, Govt. of India to conduct the significance of grain size parameters; J. Sedim. Res. 27(1) present research work (F. No. 41-1041/2012 SR). 3–26, https://doi.org/10.1306/74D70646-2B21-11D7-86480 00102C1865D. We are also thankful to anonymous reviewers who Garzanti E, Ando S, France-Lanord C, Vezzoli G, Censi P, Galy helped in improving the manuscript quality. V and Najman Y 2010 Mineralogical and chemical variability of Cuvial sediments. 1. Bedload sand (Ganga–Brahmaputra, References Bangladesh); Earth Planet. Sci. Lett. 299 368–381. Gibbs R J 1970 Mechanisms controlling world water chemistry; Science 170(3962) 1088–1090, https://doi.org/10. Abbas N and Subramanian V 1984 Erosion and sediment 1126/science.170.3962.1088. transport in the Ganges river basin (India); Hydrogeol. J. 9 Gibbs R J 1971 Procedures in sedimentary petrology (ed.) 173–182, https://doi.org/10.1016/0022-1694(84)90162-8. Carver R E, John Wiley Inc., New York, pp. 531–540. Ahmad S and Hasnain S I 2000 Melt water characteristics of Goldstein J, Newbury D E, Joy D C, Lyman C E, Echlin P, Garhwal Himalayan glaciers; J. Geol. Soc. India 56(4) Lifshin E, Sawyer L and Michael J R 2003 Scanning 431–439. Electron microscopy and X-ray microanalysis; Kluwer Ahmad S and Hasnain S I 2007 Textural, mineralogical and Academic, Plenum Publishers, New York 710, https:// geochemical characteristics of sediments and soil at high doi.org/10.1017/S0016756803238838. altitude catchment in the Garhwal Himalaya; J. Geol. Soc. Hammer K M and Smith N D 1983 Sediment production and India 69(2) 291–294. transport in a proglacial stream: Hilda creek, Alberta, Ahmad S and Hasnain S I 2001 Snow and stream-water Canada; Boreas 12 91–106, https://doi.org/10.1111/j. chemistry of the Ganga headwater basin, Garhwal Hima- 1502-3885.1983.tb00441.x. laya, India; Hydrol. Sci. J. 46(1) 103–111, https://doi.org/ Hamphries D W 1992 The preparation of thin section of rocks, 10.1080/02626660109492803. minerals and ceramics; Royal Microscopic Society, Oxford Ansari Z, Ahmad S and Khan M A 2019 Seasonal variations of Science Publications, Microscopy Handbook 24 83. streams hydrochemistry and relationships with morphome- Han D, Liang X, Jin M, Currell M, Han Y and Song X 2009 tric/landcover parameters in the Bhagirathi watersheds, Hydrogeochemical indicators of groundwater Cow systems Garhwal Himalaya, India; J. Geol. Soc. India 94 493–500. in the Yangwu River Alluvial Fan, Xinzhou Basin, Shanxi, APHA/AWWA/WPCF 1980 Standard Methods for the China; Environ. Manag. 44 243–255, https://doi.org/10. Examination of Water and Waste Water. 15 edn, Public 1007/s00267-009-9301-0. Health Association/American Water Works Association/ Heim A and Gannser A 1939 Central Himalaya: Geological Water Pollution Control Federal, Washington DC, 1134p. observations of the Swiss Expedition 1936; Zurich,€ Mem- Auden J B 1949 Tehri Garhwal and British Garhwal; Rec. oires de la Societ e Helvetique des Sciences Naturelles 73(1) Geol. Surv. India 76 74–78. 245. Baraer M, Mckenzie J M, Mark B G, Bury J and Knox S 2009 Ingersoll V, Bullard T F, Ford R L, Grimm J P, Pickle J D and Characterizing contributions of glacier melt and ground- Sares S W 1984 The eAect of grain size on detrital modes: A water during the dry season in a poorly gauged catchment test of the Gazzi–Dickinson point-counting method; J. of the Cordillera Blanca (Peru); Adv. Geosci. 22 41–49, Sedim. Petrol. 54 103–116, https://doi.org/10.1306/ https://doi.org/10.5194/adgeo-22-41-2009. 212F83B9-2B24-11D7-8648000102C1865D. Bickle M J, Tipper E D, Galy A, Chapman H J and Harris N Jose P G, Ramanathan A L, Singh V B, Sharma P, Azam F W B 2015 On discrimination between carbonate and silicate and Linda A 2014 Characterization of sub-glacial pathways inputs to Himalayan rivers; Am. J. Sci. 315 120–166, draining two tributary meltwater streams through the https://doi.org/10.2475/02.2015.02. lower ablation zone of Gangotri glacier system, Garhwal Carrols D 1970 Clay minerals a guide to their identiBcation; Himalaya, India; Curr. Sci. 107 613–621. Geol. Soc. Am. Bull. 126 48–65, https://doi.org/10.1130/ Jowhar T N 2010 Chemistry of tourmalines from the Gangotri SPE126-p1. Granite, Garhwal Higher Himalaya; Earth Sci. India 3(3) Chakrapani G J, Saini R K and Yadav S K 2009 Chemical 181–194. weathering rates in the Alaknanda–Bhagirathi river basins Krinsley D I I and Doomkamp J 1973 Alias of quartz sand in Himalayas, India; J. Asian Earth Sci. 34 347–362, grain surface textures; Cambridge University Press, Cam- https://doi.org/10.1016/j.jseaes.2008.06.002. bridge, UK, 176p. Chauhan D S and Hasnain S I 1993 Chemical characteristics, Mahaney W C, Kalm V, Kapran B, Milner M W and Hancock solute and suspended sediment loads in the meltwaters R G V 2009 A soil chrono sequence in Late Glacial and draining Satopanth and Bhagirath Kharak glaciers, Ganga Neoglacial moraines, Humboldt Glacier, northwestern basin India; In: Snow and glacier hydrology (ed.) Young J, Venezuelan Andes; Geomorphology 109(3–4) 236–245, IAHS 218 403–410. https://doi.org/10.1016/j.geomorph.2009.03.005. 173 Page 14 of 14 J. Earth Syst. Sci. (2020) 129:173

Margolis S V and Kennel J P 1971 Cenozoic paleoglacial Singh A K and Hasnain S I 1998 Major ion chemistry and history of Antarctica recorded in sub Antarctic deep-sea weathering control in a high altitude basin: Alaknanda cores; Am. J. Sci. 271 1–36. river, Garhwal Himalaya, (India); Hydrol. Sci. J. 43(6) Milliman J D and Syvitski J P M 1992 Geomorphic tectonic 825–843, https://doi.org/10.1080/02626669809492181. control of sediment discharge to the ocean – the importance Singh P, Ramasastri K S, Gergan J T and Dhobal D P 1995 of small mountainous rivers; J. Geol. 100(5) 525–544. Hydrological characteristics of the Dokriani Glacier in the Pandey S K, Singh A K and Hasnain S I 1999 Weathering and Garhwal Himalayas; Hydrol. Sci. 10(2) 243, https://doi. geochemical processes controlling solute acquisition in org/10.1080/02626669509491407. Ganga headwater–Bhagirathi river, Garhwal Himalaya, Singh V B and Ramanathan A L 2015 Assessment of solute India; Aquatic Geochem. 5 357–379, https://doi.org/10. and suspended sediments acquisition processes in the Bara 1023/A:1009698016548. Shigri glacier meltwater (Western Himalaya, India); Env- Pandey S K, Singh A K and Hasnain S I 2002 Grain-size iron. Earth Sci. 73(1) 387–397, https://doi.org/10.1007/ distribution, morphoscopy and elemental chemistry of s12665-015-4584-3. suspended sediments of Pindari Glacier, Kumaon Hima- Singh V B, Ramanathan A L and Kuriakose T 2015 Hydro- laya, India; Hydrol. Sci. J. 47(2) 213–226, https://doi.org/ geochemical assessment of meltwater quality using major 10.1080/02626660209492925. ion chemistry: A case study of Bara Shigri glacier, Pant R 1986 Petrochemistry and petrogenesis of the Gangotri Western Himalaya, India; Natl. Acad. Sci. Lett. 38(2) granite and associated granitoids, Garhwal Himalaya; 147–151. Ph.D. Thesis, University of Roorkee, India. Singh V B, Ramanathan A L, Pottakkal J G, Linda A and Panwar S, Khan M Y A and Chakrapani G J 2016 Grain size Sharma P 2013 Temporal variation in the major ion characteristics and provenance determination of sediment chemistry of Chhota Shigri glacier meltwater, Lahaul–Spiti and dissolved load of Alaknanda River, Garhwal Himalaya, Valley, Himachal Pradesh, India; Natl. Acad. Sci. Lett. India; Environ. Earth Sci. 75 91, https://doi.org/10.1007/ 36(3) 335–340. s12665-015-4785-9. Singh V B, Ramanathan A L, Pottakkal P G, Sharma P, Linda Sarin M M, Krishnaswamy S, Dilli K, Somayajulu B L K and A and Azam M F 2012 Chemical characterisation of Moore W S 1989 Major ion chemistry of the Ganga–Brahma- meltwater draining from Gangotri glacier, Garhwal Hima- putra river system: Weathering processes and Cuxes to the laya, India; J. Earth Syst. Sci. 121(3) 625–636, https://doi. Bay of Bengal, Geochim.Cosmochim. Acta 53 997–1009, org/10.1007/s12040-012-0177-7. https://doi.org/10.1016/0016-7037(89)90205-6. Subramanian V 1985 Water chemistry of the Ganga, Science Scaillet B, France-lanord C and Lefort P 1990 Badri- Today (September), 52. nath–Gangotri plutons (Garhwal, India): Petrological and Subramanian V, Sitasawad R, Abbas N and Jha P K 1987 geochemical evidence for fractionation processes in a high Environmental geology of the Ganga river basin; J. Geol. Himalayan leucogranite; J. Volcanol. Geotherm. Res. 44 Soc. India 30 335–355. 163–188, https://doi.org/10.1016/0377-0273(90)90017-A. USGS (PHREEQC), https://wwwbrr.cr.usgs.gov/projects/ Searle M P, Metcalfe R P, Rex A J and Norry M J 1993 Field GWC˙coupled/phreeqc/phreeqc3-tml/phreeqc3.htm. relations, petrogenesis and emplacement of the Bhagirathi Warburton J 1990 An alpine pro-glacial Cuvial sediment leucogranite, Garhwal Himalaya; In: Himalayan Tectonics budget; GeograBska Annular 3 261–272. https://doi.org/ (eds) Treloar P J and Searle M P, Geol. Soc. London Spec. Publ. 10.2307/521154 74 429–444, https://doi.org/10.1144/GSL.SP.1993.074.01.29. Whalley W B 1978 An SEM examination of quartz grain from Searle M P, Noble S R, Hurford A J and Rex D C 1999 Age of sub-glacial and associated environments and some methods crustal melting, emplacement and exhumation history of for their characterization. In: Scanning Electron Micro- the Shivling leucogranite, Garhwal Himalaya; Geol. Mag. scopy (ed.) O’llara A M, Part I, pp. 353–358. 136 513–525. Whalley W B and Krinsley D I I 1974 A scanning electron Shukla T, Sundriyal S, Stachnik L and Mehta M 2018 microscope study of surface texture of quartz grains from Carbonate and silicate weathering in glacial environments glacial environments; Sedimentology 21 87–105, https:// and its relation to atmospheric CO2 cycling in the doi.org/10.1111/j.1365-3091.1974.tb01783.x. Himalaya; Annals Glaciol. 59(77) 159–170, https://doi. Wu L L, Huh Y, Qin J H, Du G and Vanderlee S 2005 org/10.1017/aog.2019.5. Chemical weathering in the Upper Huang He (Yellow Singh A, Bhardwaj B D and Ahmad A H M 1993 Tectonic River) draining the eastern Qinghai–Tibet Plateau; Geo- setting and sedimentology of Ganga river sediments, India; chim. Cosmochim. Acta 69(22) 5279–5294, https://doi. Boreas 22(1) 38–46. org/10.1016/j.gca.2005.07.001.

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