Abstract:The observed retreat of several Himalayan glaciers and snow packs is a cause of concern for the huge population in southern Asia that is dependent on the glacial-fed rivers emanating from Himalayas. There is considerable uncertainty about how cryospheric recession in the Himalayan region will respond to climate change, and how the water resource availability will be affected. As a first step towards quantifying the contribution of glacier-melt water, hydrograph separation of River Ganga at Rishikesh into its constituent components, namely (i) surface runoff, (ii) glacial ice-melt and (iii) groundwater discharge has been done in this paper. A three-component mixing model has been employed using the values of υ 18 O and electrical conductivity (EC) of the river water, and its constituents, to estimate the time-varying relative fraction of each component. The relative fraction of the surface runoff peaks (70-90%) during winter, due to the near-zero contribution of glacial ice-melt, essentially represents the melting of surface snow from the catchment. The contribution of glacial ice-melt to the stream discharge peaks during summer and monsoon reaches a maximum value of ¾40% with an average of 32%. The fraction of groundwater discharge varies within a narrow range (15 š 5%) throughout the year. On the basis of the variation in the d-excess values of river water, it is also suggested that the snow-melt and ice-melt component has a significant fraction derived from winter precipitation with moisture source from mid-latitude westerlies (also known as western disturbances).

[1] Results of a 4 year (2005)(2006)(2007)(2008)) study of stable isotopic composition of daily rain and ground-level vapor (GLV) at a semiarid station in western India are reported. The GLV samples were collected by complete cryogenic trapping. The sampling was mostly limited to the rainy season (June, July, August, and September) and about a month before and after. The maximum number of samples was collected during the year 2007. The GLV has a steady baseline d18 O and dD composition without distinguishable seasonal differences. The d-excess of GLV indicates that its isotopic composition has a significant contribution from kinetic evaporation of nonlocal water sources. During a rain event, GLV rapidly interacts with raindrops and tends to move toward isotopic equilibrium. On cessation of rain, the d18 O and dD of GLV quickly return to the typical baseline values. Therefore, use of isotopic composition of monthly rainfall for estimating average monthly isotopic composition of GLV can lead to erroneous results. Within a rainy season, certain large rain events have depleted d18 O and dD values compared to other equally large rain events with significantly enriched d18 O and dD. These isotopic differences are apparently not related to amount of rainfall. Variable magnitude of evaporation from falling raindrops and/or cloud liquid water fraction cannot explain the observed differences. Instead, it is shown that varying source regions (Arabian Sea or Bay of Bengal) and cloud top temperature may be responsible for observed differences.Citation: Deshpande, R. D., A. S. Maurya, B. Kumar, A. Sarkar, and S. K. Gupta (2010), Rain-vapor interaction and vapor source identification using stable isotopes from semiarid western India,

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The present study investigated the chemical composition of rainwater at Kabir nagar, Nari, Nagpur, Maharashtra, India. The rainwater samples were collected on event basis during June-July-August-2006 and were analyzed for pH, major anions Cl, NO(3), SO(4)) and cations (Ca, Mg, Na, K, NH4). The pH value varied from 6.0 to 7.3 (avg. 6.3 +/- 0.3) indicating alkaline nature of rainwater. The pH of the rainwater was found well above the reference pH (5.6), showing alkalinity during the monsoon season. The average and standard deviation of ionic composition was found to be 98.1 +/- 10.6 micro eql(-1). The total anions contribute 45.1% and cations 54.9%, respectively to rainwater. Neutralization factors (NF) followed a sequence of NF(Ca) > NF(Mg) > NF(NH4) with factors of 1.1, 0.38 and 0.15 indicating the crustal components are responsible for neutralization of anions. The average ratio of (NO(3) + Cl)/SO(4) observed as 1.1 indicates that nitric and hydrochloric acid influences the acidity of rainwater. The ratio of NH(4)/NO(3) and NH(4)/SO(4) was observed as 0.68 and 0.34 indicate that the possible compounds which may predominate in the atmosphere are NH(4)NO(3) and (NH(4))(2)SO(4). Ionic correlation was established to identify sources of origin. A good correlation was seen between Ca and Mg (r = 0.95); suggesting the common occurrence of these ions from crustal origin. Similarly, the acidic ions SO(4) and NO(3) correlated well (r = 0.60) indicating their origin from similar sources. Other relatively significant correlations were observed between Ca and SO4 (r = 0.92), Mg and SO(4) (r = 0.83), Ca and NO(3) (r = 0.09), Ca and Cl (r = 0.34) and Mg and Cl (r = 0.31), and Mg and NO(3) (r = 0.71). The observed rainwater ratio of Cl/Na (1.1) is closer to that of seawater ratio (1.16) indicates fractionation of sea-salt and modifications by non-marine constituents as the site is 834 km away from the sea coast. The nss-Ca contribution was observed as 95.7% suggesting their crustal origin whereas nss-Mg and nss-K shows their contribution as 87.9% and 83.2% indicating influence of soil sources. The nss-SO(4) contributed as 87.4% shows anthropogenic origin.

The study was conducted in the summer season (April-May 2007). The fluoride concentration along with physico-chemical parameters in ground water samples was determined in various villages of Kadi tehsil at Mehsana district of Gujarat state (India), since in most of the villages it is the only source of drinking water. The fluoride concentrations in these villages varied from 0.94 to 2.81 mg/L (1.37+/-0.56) with highest fluoride level at Visalpur (2.08 mg/L) and lowest at Adaraj (0.91 mg/L). There was found a positive correlation of pH with fluoride and a negative relationship of fluoride with bicarbonate which is generally observed in deep ground water.

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