Solute dynamics of meltwater of Gangotri glacier, Garhwal Himalaya, India

Proc. Natl. Acad. Sci., India, Sect. A Phys. Sci.

Ramanathan

Pottakkal

2014

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. Ca 2? , Mg 2? and SO 4 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 SO 4 2-shows a linear trend throughout the range of data, indicating the dissolution of sulphate minerals as one of the possible source of SO 4 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.

Section: Hydrogeochemistrysupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Hydrogeochemistry of Meltwater of the Chaturangi Glacier, Garhwal Himalaya, India

Proc. Natl. Acad. Sci., India, Sect. A Phys. Sci.

Ramanathan

Pottakkal

2014

“…Gangotri glacier system geologically falls in the higher and Tethys Himalayan zone (Kumar et al 2009) and mainly comprises granite, mica (sericite) schist, quartzites and phyllites. The average seasonal temperature near the snout of the glacier is about 9.4°C while average seasonal rainfall is about 260 mm.…”

Section: Study Areamentioning

confidence: 99%

ANN modelling of sediment concentration in the dynamic glacial environment of Gangotri in Himalaya

Chakrapani

2015

Environ Monit Assess

The present study explores for the first time the possibility of modelling sediment concentration with artificial neural networks (ANNs) at Gangotri, the source of Bhagirathi River in the Himalaya. Discharge, rainfall and temperature have been considered as the main controlling factors of variations in sediment concentration in the dynamic glacial environment of Gangotri. Fourteen feed forward neural networks with error back propagation algorithm have been created, trained and tested for prediction of sediment concentration. Seven models (T1-T7) have been trained and tested in the non-updating mode whereas remaining seven models (T1a-T7a) have been trained in the updating mode. The non-updating mode refers to the scenario where antecedent time (previous time step) values are not used as input to the model. In case of the updating mode, antecedent time values are used as network inputs. The inputs applied in the models are either the variables mentioned above as individual factors (single input networks) or a combination of them (multi-input networks). The suitability of employing antecedent time-step values as network inputs has hence been checked by comparative analysis of model performance in the two modes. The simple feed forward network has been improvised with a series parallel non-linear autoregressive with exogenous input (NARX) architecture wherein true values of sediment concentration have been fed as input during training. In the glacial scenario of Gangotri, maximum sediment movement takes place during the melt period (May-October). Hence, daily data of discharge, rainfall, temperature and sediment concentration for five consecutive melt periods (May-October, 2000-2004) have been used for modelling. High Coefficient of determination values [0.77-0.88] have been obtained between observed and ANN-predicted values of sediment concentration. The study has brought out relationships between variables that are not reflected in normal statistical analysis. A strong rainfall: sediment concentration and temperature: sediment concentration relationship is shown by the models which are not reflected in statistical correlation. It has also been observed that usage of antecedent time-step values as network inputs does not necessarily lead to improvement in model performance.

“…These ratios are higher than marine aerosols (i.e. Na/Cl = 0.85 and K/Cl = 0.0176) showing relatively less contribution from atmospheric input to the chemical characterisation of meltwater of the study area [5,[17][18][19]. NO 3 -and PO 4 3-do not play a significant role in the meltwater chemistry of the study area, which shows that quality of the meltwater is good.…”

mentioning

confidence: 97%

“…A few works have been published on the importance of atmospheric contribution to the chemical composition of glacier meltwater [1,5,17,18]. The average ratios of Na/Cl and K/Cl for Bara Shigri glacier meltwater are 3.07 and 3.08, respectively.…”

mentioning

confidence: 99%

Hydrogeochemical Assessment of Meltwater Quality Using Major Ion Chemistry: A Case Study of Bara Shigri Glacier, Western Himalaya, India

Ramanathan

Kuriakose

2014

Natl. Acad. Sci. Lett.

Hydrogeochemical assessment of meltwater quality draining from Bara Shigri glacier was carried out in the year 2011. The concentration of cations varied as Ca 2? [ Mg 2? [ K ? [ Na ? . Whereas, anions concentration followed the pattern HCO 3 -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. Keywords Major ion chemistry Á Weathering Á Bara Shigri glacier Á Western Himalaya Hydrogeochemistry of meltwater draining from glaciers is useful to understand the weathering dynamics operating in the glacier environment [1]. The relative proportions of the dissolved ions in the solution are dependent on their relative dominance of the host rock and their solubility [2].There are various processes (such as carbonate and silicate weathering, dissolution of sulphate minerals, pyrite oxidation and evaporates dissolution) responsible for production of dissolved ions in the glacier environment depending upon the geology of the study area [3][4][5].