Evaluation of hydrogeochemical processes and dissolve ion chemistry in Satopanth Tal,

To grasp meltwater chemistry and geochemical processes influencing hydrogeochemistry, major ion chemistry of the glacial lake Satopanth Tal was carried out to provide relevant details on the dissolved ions sources, weathering, and hydrogeochemical processes as well as anthropogenic activities taking place throughout the lake setting. Twenty-one surficial water samples were collected and 12 different physicochemical parameters were analyzed to understand the hydrogeochemistry of the study area. The mean pH value was estimated to be 6.9 in the lake water, which indicates a marginally acidic. The ionic contribution through the organic matter decomposition has been indicated by the observation of dominancy of the total anions over the total cations. The most abundant anion was Cl − in Satopanth Tal, while Ca 2+ and Mg 2+ were significant cations in the water. The high ratios of (Ca 2+ + Mg 2+ )/TZ + , (Ca 2+ + Mg 2+ )/(Na + + K + ), HCO 3̶ /(Ca 2+ + Mg 2+ ), and the higher Ca + / Na + , Mg + / Na + and HCO 3̶ / Na + ratio indicate the supremacy of the weathering of carbonate as a significant source of dissolved ions in the study area's lake water. The lower equivalent ratios of Na + /Cl − and K + /Cl − are measured and substantially comparable results are observed that have been expected from the Gibbs plot and the stable isotope analysis suggests a reasonably significant contribution to the chemical composition of the Satopanth Tal water by these ions from atmospheric precipitation. The correlation and factor analysis show that water chemistry at Satopanth Tal is primarily influenced by weathering processes such as weathering of carbonate and silicate, pyrite oxidation. Bhambri et al. proposed the area type by using the satellite imageries and Kumar et al. (2017) on water quality index alone. Thus, the present study has attempted to assess the combined study on hydro-geochemical characteristics, and the stable isotopic investigation of The Garhwal Himalayan lake Satopanth Tal to understand the sources of dissolved ions and hydrogeochemical processes. critical source of ion dissolution in Satopanth Tal with comparison to silicate weathering. The higher Ca + / Na + , Mg + / Na +, and HCO 3̶ / Na + ratio than the highest ratio predicted for the silicate weathering suggest the exposure of carbonate weathering action. The trilinear plot indicates that the Satopanth Tal is influenced by the major hydrogeochemical facies of Ca-Cl type of water. The dominancy of alkaline earth metal over alkali metals suggests the mechanism of carbonate weathering, which regulating the hydrogeochemistry of Satopanth Tal. Several investigations like Gibbs boomerang and stable isotopic analysis indicate that the predominant samples fall in the precipitation dominance zone, suggesting that precipitation is the dominant process that controls the lake water chemistry, which has been supported by the low ratio of Na + /Cl − and K + /Cl − concerning marine aerosols. The calculated C-ratio suggests the carbonate dissolution and derivation of the proton (H + ) from sulphide oxidation in the Satopanth Tal region. The cation exchange study infers the processes influencing the direct exchange reaction rather than the reverse exchange in the study area. The PCA study suggests the carbonate weathering, sulphate mineral dissolution, and sulphide oxidation along with atmospheric precipitation contribution of atmospheric precipitation to govern the major ion chemistry.


Introduction
Lakes are an imperative part of the cycling of components. The components brought to the lake are not principally fixed on the sediments and can be delivered back to the water-segment with the change in environmental conditions (Forstner et al., 1983;Håkanson, et al., 2004;Singh et al., 2005;Khadka and Ramanathan et al., 2021).
"The investigational research of hydrogeochemistry is indispensable to decide the genesis of the chemical constitution of groundwater as well as surface water" (Zaporozec, 1972). Thus, estimating the lake water chemistry is crucial as it assists us with assessing the disintegration rate, and the geochemical changes of that specific area. Papatheodorou et al (2006) has suggested that besides several important natural processes like precipitation and weathering activities, other different activities such as industrial, rural, and urban activities are also the major parameters on which the quality of water depends, as the chemistry of water is a crucial index to understand the catchment lithology, soil erosion, and anthropogenic activities, etc. Vasudevan et al (2013) infer the different lithologies can alter the chemistry of surface water, as water passes through them. Therefore, precipitation water penetrates directly into the soil zones causing the dissolution of soil particles. Hence, during the flowing of water from the recharge point to the discharge point, several geochemical processes act to affect the water quality (Peiyue et al., 2014). "High altitudes lakes are endangered to atmosphere inputs than the lowland lakes due to different components like environment, shallow soil, little watershed, and so on" (Rosha et al., 2012).
Different water chemistry research has been carried out by several researchers on high-altitude lakes of the Indian Himalayas (Chakrapani 2002;Das 2005;Jeelani and Shah 2006;Dash et al. 2008;Saini et al. 2008;Sarah et al. 2011;Purushothaman et al. 2012;Najar and Khan 2012;Khan et al. 2012;Singh and Jain 2013;Sheikh et al. 2014;Singh et al. 2016;Khadka et al. 2021). However, no low down assessment has been done in the morainedammed lake Satopanth Tal in advance beside Bhambri et al. (2013) proposed the area type by using the satellite imageries and Kumar et al. (2017) on water quality index alone. Thus, the present study has attempted to assess the combined study on hydro-geochemical characteristics, and the stable isotopic investigation of The Garhwal Himalayan lake Satopanth Tal to understand the sources of dissolved ions and hydrogeochemical processes.

Study area and its geological extent
The Satopanth Tal is situated in the Chamoli district of Uttarakhand, India (Fig. 1). This lake is drawn nearer from a distance of 25 km away from Badrinath in Garhwal Himalaya. Satopanth Tal is a triangular-shaped pristine lake located at 79°21'21.74"E and 30°44'38.30"N, occupying an area of 0.0 25km 2 at an altitude of about 4600 m above mean sea level. The maximum length of the lake is 0.262km; while the maximum width is 0.211km with a maximum depth of 17.5m. The climate in Satopanth Tal region is cooler throughout the year, as its summer temperature measured around 10 0 to 12 0 C during the day and 5 0 to ̶ 5 0 C during the night time, and the temperature drops to ̶ 20 0 to ̶ 25 0 C in the day hours, while between ̶ 30 0 to ̶ 35 0 C during night hours in winter. Geologically, the study area falls under Central Crystalline Zone. Lithologically, the study region is controlled by calc-silicate with sillimanite-kyanite-garnet-biotite gneiss and schist with tourmaline granite belonging to Pindari Formation (Valdiya, 1973 andSharma, 2019). The Badrinath Granite nothing but the leucogranitic tourmaline bearing rocks and the crystalline rocks of metasediments and acidic intrusive are exposed in the study area grouped under Badrinath formation and Vaikrita group respectively.

Analytical Procedure
The 21 surficial water samples from Satopanth Tal were collected during post-monsoon in 500ml narrownecked, clean polyethylene bottles covering all parts of the lake. Parameters such as pH, EC, and TDS were analyzed by utilizing the multi-parameter meter Hanna instrument (HI98194) adopting the standard methods adopted by APHA (1995). Collected water samples were filtered by 0.45μm Millipore membrane filter papers to remove the floating fine particles. Na + and K + were determined by using a flame photometer (CL-378), whereas Result and Discussion

Hydrogeochemistry
The study of water chemistry is one of the most vital investigations opted to evaluate the chemistry of water and the dominance of several cations and anions and their enrichment to recognize the geochemical processes.
The physicochemical characteristics of the lake water are given in that the lake water is of slightly acidic (6.4±0.2) to little alkaline (7.1±0.2) nature. The addition of all ions in water solution is termed total dissolved solids (TDS), which suggests the intensity of chemical weathering in the catchment . In Satopanth Tal, TDS ranged from 7.3±3.5 to 20.4±3.5mg/L with an average of 11.75±3.5mg/L, indicating freshwater (Table 1). "EC is an indirect measure of mineralization and ionic strength of natural water" (Chidambaram et al. 2011). In Satopanth Tal, EC values were recorded from 14±7 to 42.2±7 µS/cm having a mean of 21.02±7 µS/cm indicating the least amount of dissolution of minerals in the lake water.
The average Ca 2+ and Mg 2+ concentration in the water of Satopanth Tal were observed to be 32.9±7.2mg/L and 11.7±4mg/L, respectively, whereas the Na + and K + ion concentration in the lake water was observed as an average of 2.1±0.7mg/L and 1.4±0.2mg/L respectively (Table 1). Generally, the dominance of HCO 3 ̶ in water indicates intense chemical weathering, while the rich concentration of Chloride infers the anthropogenic sources (Meybeck, 1983). In Satopanth Tal, the average HCO 3 ̶ and Clconcentrated was observed to be 37.18±7.1 mg/L and 60.96±9.7 mg/L respectively, which satisfy the permissible limit suggested by WHO(2011) ( Table 1). Thus, the lower value of HCO 3 ̶ and Cl − in Satopanth water might be accredited to the dilution effect of the meltwater. The calculated mean of SO 4 2− , PO 4 2− as well as H 4 SiO 4 concentration in the lake water were found to be 19.04±1.1 mg/L, 9.58±0.5 mg/L, and 5.1±3.97 mg/L respectively. So the water sample collected from Satopanth Tal glacial lake were analyzed and found to be fall under the advisable limit of WHO (2011) indicate the lake is holding pure and fresh water in it.
The use of semi-logarithmic graph paper to map anion and cation concentrations were suggested by Schoeller (1967) (Fig. 2). In milliequivalent per liter (meq/L), the concentration of dominant anions and cations are plotted on six evenly spaced logarithmic scales. This type of graph depicts not only the absolute value of each ion, but also the concentration differences (Khan and Jharia et al., 2018

Fig.2 Schoeller diagram representing the concentration of anions and cations
Hydrogeochemical processes on the lake water The reaction within surface water and surrounding minerals plays a major role in the water quality and is also useful in understanding the genesis of surface water and its sources. To identify the hydrogeochemical processes operating in the Satopanth Tal region, the hydrogeochemical data is subjected to various conventional graphics plots.

Major dissolved ions sources in water
Rock weathering, precipitation, and anthropogenic activities are the important sources from which the ion got derived and dissolve in water. (Das and Kaur 2001;Jeelani and Shah 2006). The mean distribution of total cations (TZ + ) and total anions (TZ − ) in Satopanth Tal water were recorded as 48.01±5.25 and 127.41±14.16 ( Table   2). The higher mean concentrations TZ − than TZ + indicate the contribution of total anions to the lake by the organic compound decompositions (Dalai et al. 2002). The second most abundant element in Earth's crust is Silicon, very much essential for life and available in the form of H 4 SiO 4 for phytoplankton and algae. The content of H 4 SiO 4 in the water of Satopanth Tal ranged from 1.9± 3.9 to 15.8± 3.9 meq/L. These high values indicate a significant vertical gradient of temperature due to the mixing, which leads to the death and decomposition of diatoms, except the silicate weathering (Håkanson, 1984;Anshumali and Ramanathan, 2007). This argument is also supported by the high H 4 SiO 4 / Na + + K + ratio, as in Satopanth Tal water samples the it is high with a mean of 1.05±0.47. Subramanian et al (1979) classified the dissolved silica into two categories; the Indian Himalayan river average (9.6meq/L) and the global average (12.0meq/L). The present results show H 4 SiO 4 value (5.1± 3.9meq/L) is substantially lower compared to the above said two classes indicates silicate minerals are resistant to the prevailing weathering conditions.
"The recorded (Ca 2+ +Mg 2+ ) / (Na + +K + ) ratio in the silicates of the upper crust is 1.0" (Taylor and McLennan 1985). In the present study, this means the equivalent ratio is estimated as 13.42±3.50 (Table 2) and the scatter plot indicates all the points fall above 2:1 equiline, infers the dominancy of Ca 2+ and Mg 2+ over Na + and K + in the lake water (Fig 3a). The Ca 2+ +Mg 2+ /TZ + scatter plot (Fig. 3a) for the lake water has a linear spread adjacent to "Similarly, the (Na + + K + )/TZ + ratio is used as an index to assess the contribution of cations via silicate weathering" (Stallard and Edmond 1983). The (Na + + K + ) against TZ + exhibits an average ratio of 0.07± 0.02 (Table   2) indicating the silicate weathering contributes the least as a source for the dissolve ions in lake water. The plot of (Na + + K + ) versus TZ + (Fig. 3b) shows all samples clustered just underneath the 1:1 line reflecting the deficiency of Na + and K + in the water. The high (Ca 2+ +Mg 2+ )/(Na + +K + ) and (Ca 2+ +Mg 2+ )/TZ + ratios and low (Na + + K + )/TZ + ratios of the water samples, therefore, suggest that the weathering of carbonates is the dominant mechanism and the negligible contribution of silicate weathering that regulates the Satopanth Tal's major ion chemistry. This weathering is carried out by the meltwater generated from the precipitation processes. The plot for (Ca 2+ + Mg 2+ ) against HCO 3 − of lake water samples fall close to the equivalent of 1:1 indicating the predominance of alkali matter over bicarbonate, i.e., HCO 3 − is balanced by Ca 2+ and Mg 2+ (Fig 4a). The scatter plot of (Ca 2+ + Mg 2+ ) upon (HCO 3 − +SO 4 2− ) (Fig 4b) shows all the water sample points are clustered above 1:1 equiline needing apportion of the bicarbonate(HCO 3 − ) and Sulphate (SO 4 2− ) over Calcium (Ca) and Magnesium (Mg) to be balanced by Sodium (Na + ) and Potassium (K + ) from weathering of silicate rocks (Pandey et al 1999. While, (Ca 2+ +Mg 2+ ) versus SO 4 2̶ scatter plot (Fig. 4c) indicates a very weak correlation of R 2 =0.013 between (Ca 2+ +Mg 2+ ) and SO 4 2− inferring negligible amount contribution from CaSO 4 and MgSO 4 to the meltwater of Satopanth glacier which feeds the lake Satopanth.
The carbonate dominant rocks through which water draining is characterized by high Ca + / Na + , Mg + / Na + and HCO 3 ̶ / Na + by exhibiting Ca + / Na + nearly 50, Mg + / Na + nearly 10, and HCO 3 − / Na + nearly 120 (Stallard et al. 1980;Meybeck et al. 1986;and Negrel et al. 1993). Whereas, in case of silicate dominant rocks low ratio of Ca + / Na + nearly 0.35±0.12, Mg + / Na + nearly 0.24±0.12 and HCO 3 − / Na + nearly 2±1 (Gaillardet et al. 1999). The water samples from Satopanth Tal exhibit an average ratio of Ca + / Na + = 17.79± 8.21, Mg + / Na + = 5.80±2.09, and HCO 3 − / Na + = 19.61±7.22 (Table 2). The observed ratio in the Satopanth Tal water is lower than that of water draining out from carbonate lithology and much higher than that of from silicate rock type. These ratios therefore suggest that Satopanth Tal water's major ion chemistry is governed by carbonate weathering followed by silicate weathering as reported by other researchers for different Himalayan glacial feed lakes (Singh et al. , 2015(Singh et al. , and 2016). The HCO 3 − / TZ + of the study area varied between 0.53±0.12 to 0.98±0.12, with an average of 0.77±0.12 (Table 2). This high ratio indicates the dominancy of HCO 3 − anion in the water with a mean of 37.0±7.1 meq/L (Table 1). The proton sources are unavoidable parameters that influence carbonate weathering. Hence, to estimate these sources and to confirm its genesis whether from carbonation or oxidation, the C-ratio (HCO 3 − / HCO 3 − + SO 4 2− ) is adopted (Brown et al., 1996). Where the C-ratio of 1 implies weathering by carbonate reactions as shown in Eq.
This Na + /Cl − and K + /Cl − of lake water can be compared with the ratio of Na + /Cl − and K + /Cl − of marine aerosols to estimate the contribution of atmospheric precipitation to the chemical composition of the lake. The ratio of Na + /Cl − and K + /Cl − for marine aerosols according to Singh et al. (2016) is 0.85 and 0.02 respectively. As the estimated Na + /Cl − and K + /Cl − ratio for Satopanth Tal water are relatively lower than that of marine aerosols, this infers the chemical composition of the lake can be affected by the noticeable contribution from atmospheric precipitations. Ca 2+ and Mg 2+ ions are exchanged with Na + and K + ions in the water, which indicates chloro-alkaline disequilibrium (reverse exchange) as expressed in Eq. (10) (Wang Q, 2020) ( Fig.6a and b).
Ca 2+ + 2NaX = 2Na + + CaX 2 (10) In the Satopanth Tal, CAI 1 value ranges from 0.91 to 0.96 with an average of 0.94 whereas CAI 2 value ranges from 0.82 to 1.43 with an average of 1.04. The predominantly positive CAI value of Satopanth Tal indicates that the Na + and K + ions from the water get exchanged with Ca 2+ and Mg 2+ ions from the rocks. Therefore, the most significant mechanism responsible for the water chemistry of Satopanth Tal is the cation exchange in the water .  Fig. 7a), indicate that Ca +2 -Cl − is the major hydrogeochemical facies, suggesting the dominancy of alkali and strong acids, and as the percentage values of alkaline earth metal (Ca 2+ + Mg 2+ = 44.5±5.3) significantly higher than the alkali metals (Na + + K + = 3.5±0.7), inferring the dominancy of carbonate weathering mechanism as well which regulating the hydrogeochemistry of Satopanth Tal. The piper plot was further modified (Fig 7b) by Johnson et al (1975), where all three components of the Piper trlinear plot are individually projected in rectangular coordinates to produce a pattern similar to the Piper plot to study and interpret the changes in water hydrogeochemical phases. Fig.   7b reveals that all samples fell into the class 1 suggesting high Ca 2+ +Mg 2+ and So 4 2− +Cl − indicates dominance of carbonate weathering in the study area with acidic to alkaline water type. To understand the dominance of several processes such as either precipitation, weathering, or evaporation in the geochemical evolution of water bodies, two semilog plots were being proposed by Gibbs (1970) widely known as the Gibbs diagrams (Fig. 7c). This simple boomerang plot provides information regarding the importance of different natural major mechanisms that a b controlling surface water chemistry. In Satopanth Tal, the Gibbs diagram demonstrates that precipitation controls the major ion chemistry as estimated from Na + /Cl − and K + /Cl − ratio study. Statistical analysis of the data has been tried to divulge the hidden relationship between every parameter (Singaraja et al. 2013). The correlation matrix is commonly used to explain the relationship between various ionic species (Mondal et al. 2011). Correlation matrices are applied to clarify the lake water samples and to use SPSS software to classify the geochemical processes controlling surface water geochemistry. The average value of all the variables is determined and tabulated as a matrix in Table 3. A very strong positive correlation of 0.73 has been obtained between PO 4 2− and Na + and good positive correlations between Cl − , Mg 2+, and HCO 3 − having values of c a b 0.46 and 0.47, respectively indicating their common sources. Strong correlations were found between EC and TDS, PO 4 2− , Na + suggesting that dissolved solids, Na + and PO 4 2− contribute to the EC of the lake water. Moreover, the positive correlation between EC and TDS (r = 0.58) shows that electrical conductivity also increases as the concentration of dissolved constituents or ions increases  and suggest that by snow melting, lake water originally receives much of the water. The low pH is due to a lower rate of silicate weathering, which is supported by the positive correlation between pH and H 4 SiO 4. The positive correlation Ca 2+ and Mg 2+ (r = 0.68) infers their similar sources. Ca 2+ revealed a positive correlation with HCO 3 ̶ (r = 0.36), showing common provenance and may be due to carbonate weathering. A good correlation was found between Na + and K + (r = 0.13), while H 4 SiO 4 was significantly and negatively correlated with the K + and Na + indicating the absence of silicate weathering. A good correlation between SO 4 2− and Ca 2+ indicates their similar origin like pyrite oxidation, sulphate minerals dissolution, and Sulphur compounds oxidation in the bottom sediment of the lake at the transition zone between aerobic and anaerobic environments (Singh et al 2016;Khadka et al. 2021). The principal components analysis (PCA) is used to define trends in the data set and to explain the data in such a way that their similarities and differences are highlighted (Smith LI, 2002). With the assistance of main component analysis, which is responsible for explaining much of the intimation within the original data, the big data  (Ranjan, 2013). Eigenvalue more than one is recognized as an important contributing factor . Varimax rotation was utilized for factorial investigation (Gotelli and Ellison 2004) to amplify the amount of variance in factor coefficients, which ideally depicted the sources that influence the water system (Prasanna et al. 2012). The relationship level between each factor and each variable is shown by the load on that factor (Deka et al. 2015a). Table 4 displays the outcomes of the factor analysis of meltwater from Satopanth Tal. In factor analysis of meltwater samples, four factors were recognized as Eigenvalues of more than one. Around 65.01% of the overall variability in the data set was illustrated by these four the principal source for these ions. Factor 2 also infers sulphate dissolution and oxidation of pyrite. Factor 3 has good loading for Cl − represents a variance in the data of 12.42%, this factor signifies the role of atmospheric precipitation in Satopanth Tal's meltwater. There is no notable variable in Factor 4, which illustrated about 10.74% except a higher variable at pH value inferring the lake water is acidic to slightly alkaline (Table 4). Generally, two stable isotopes such as deuterium ( D) and oxygen ( 18 O) were investigated for water samples to understand several geological processes includes streamflow, evaporation as well as precipitation which influence the chemical composition of water. Flaim et al (2013) infer that lower altitude regions were high isotopically enriched than higher and vice versa. Then the relation between 18 O and D in global fresh surface waters has been established by Craig (1961) and termed as Global Meteoric Water Line (GMWL) (Eq. 4). GMWL line is the global application line and is a mean of various local or regional meteoric water lines known as Lake water line (LWL) which have different from GMWL in terms of slope and intercept (Clark and Fritz, 1997), due to different climatic and geographic parameters. Craig (1961) also inferred that waters associated with cold regions experience isotopically depletion, whereas water from warm regions exhibits isotopically enrichment. Hence, this variation in presence of stable isotopes in the water of different regions concerning their climatic conditions helps to emphasize the recharge environment of groundwater from the surface water. "Stable isotope study ( 18 O and 2 H) in the precipitation and glacial stored water of the study area allow us to demark how much these waters are moving away from GMWL and what the climatic processes are" (Giovanna et al., 2017). Fig. 8a shows that 18 O and D values of the surface water samples distributed parallel to the LWL line, indicating an influence of precipitation as a major source to the lake. The correlation coefficient (R 2 = 0.97) of the LWL is nearly the same as that of the correlation of GMWL (R 2 =1) nullified the probability of any anthropogenic activities, and the significant linear relationship between 18 O and D suggests the dominancy of precipitation process in the lake (Zhu S et al. 2019).
The slope of GMWL (8) is much higher than the slope of LWL (2.97), indicates the lake is fed employing precipitation and supplied by ice and snow meltwater from Satopanth glacier and plays a major role in ion exchange phenomenon as well as during their dissolution. Hence, exhibiting negative values (Fig. 8a).
Deuterium-excess, which is widely adopted for re-predicting of ancient climatic changes and several definite sources that influence the water by investigating the measure of relative proportions of 18 O and D in the water has been proposed by Dansgaard, (1964) (Eq. 5). "It is an index of deviation from GMWL in which the values are usually close to 10% for the meteoric water line on a global scale" (Ayuba et al., 2019). High positive deuterium excess is characterized by precipitation (Yurtsever and Gat 1981;Pande et al., 2000), whereas evaporation by high negative d -excess values. Negative d-excess values were reported in a few samples, while strong positive values were reported in the majority of the water samples, resulting in partial evaporation and heavy precipitation action either when the precipitation falls from the cloud or during storage (Ayuba et al., 2019). Nevertheless, Fig. 8b indicates that the gradual depletion of δ 18 O has contributed to the gradual enrichment of d-excess, reflecting the impact of precipitation on lake water. Therefore, the large difference in the d-excess with maximum positive values and only two negative values indicates that the characteristics of Satopanth Tal water are influenced by little evaporation and strong precipitation sources.

Conclusion
This paper concentrates on several processes influencing the surface water. The hydrogeochemical study of Satopanth Tal indicates that water is slightly acidic to alkaline in nature. Among the anions, Cl − is the major ion accounting for 57% followed by HCO 3 − of 27% of the whole anionic budget. While, from cations, Ca 2+ is the dominant ion compromising 85% and Mg 2+ constituting 31% of the total cationic budget. The high (Ca 2+ + Mg 2+ ) /TZ + , and (Ca 2+ + Mg 2+ ) / (Na + + K + ) ratio, and strong positive correlation between Ca 2+ and HCO 3 − , and Ca 2+ and Mg 2+ and the low (Na + + K + ) / TZ + ratio suggest that carbonate weathering is the dominant mechanism serving as the a b critical source of ion dissolution in Satopanth Tal with comparison to silicate weathering. The higher Ca + / Na + , Mg + / Na +, and HCO 3 ̶ / Na + ratio than the highest ratio predicted for the silicate weathering suggest the exposure of carbonate weathering action. The trilinear plot indicates that the Satopanth Tal is influenced by the major hydrogeochemical facies of Ca-Cl type of water. The dominancy of alkaline earth metal over alkali metals suggests the mechanism of carbonate weathering, which regulating the hydrogeochemistry of Satopanth Tal. Several investigations like Gibbs boomerang and stable isotopic analysis indicate that the predominant samples fall in the precipitation dominance zone, suggesting that precipitation is the dominant process that controls the lake water chemistry, which has been supported by the low ratio of Na + /Cl − and K + /Cl − concerning marine aerosols. The calculated C-ratio suggests the carbonate dissolution and derivation of the proton (H + ) from sulphide oxidation in the Satopanth Tal region. The cation exchange study infers the processes influencing the direct exchange reaction rather than the reverse exchange in the study area. The PCA study suggests the carbonate weathering, sulphate mineral dissolution, and sulphide oxidation along with atmospheric precipitation contribution of atmospheric precipitation to govern the major ion chemistry.