Rajendrakumar D. Deshpande

Distribution of oxygen and hydrogen isotopes in shallow groundwaters from Southern India: influence of a dual monsoon system

Oxygen and hydrogen isotopic investigation of groundwater and river water samples from the southern Indian peninsula was undertaken to characterise the isotopic nature of the near surface water sources and provide basic framework for future hydrological studies. It is assumed that the shallow groundwater retains the isotopic signature of the local precipitation averaged over a few tens of years except in a few cases where the same gets modified by post precipitation evaporation and/or recharge contribution from surface water bodies. Therefore, isotopic character of the groundwater can, in principle, be used to determine the relative influence of the different vapour sources contributing to the local/regional precipitation and to characterise the modifications before groundwater recharge. In the present context, vapour sources for two rainy seasons, namely, southwest (SW) and northeast (NE) monsoon, are respectively, the Indian Ocean/Arabian Sea and the Asian continental sources together with the Bay of Bengal. This study shows that: (i) The regions dominated by NE monsoon have distinctly depleted isotopic composition compared to those dominated by SW monsoon. (ii) The δ18O–δD regression line slope of ∼6 in the east coast region is lower than that expected for local precipitation suggesting secondary evaporation. (iii) The orography of the Western Ghats hill ranges plays a significant role in controlling the isotopic distribution along the west coast region. (iv) The low ‘d-excess’ values in most part of study area indicate secondary evaporation. (v) The high ‘d-excess’ values over the Deccan Plateau region in the NW part of the study area suggest admixture of recycled moisture with the inflowing oceanic vapour.

Estimation of snow and glacier melt contribution to Liddar stream in a mountainous catchment, western Himalaya: an isotopic approach

ABSTRACT Snow- and glacier-dominated catchments in the Himalayas are important sources of fresh water to more than one billion people. However, the contribution of snowmelt and glacier melt to stream flow remains largely unquantified in most parts of the Himalayas. We used environmental isotopes and geochemical tracers to determine the source water and flow paths of stream flow draining the snow- and glacier-dominated mountainous catchment of the western Himalaya. The study suggested that the stream flow in the spring season is dominated by the snowmelt released from low altitudes and becomes isotopically depleted as the melt season progressed. The tracer-based mixing models suggested that snowmelt contributed a significant proportion (5–66 %) to stream flow throughout the year with the maximum contribution in spring and summer seasons (from March to July). In 2013 a large and persistent snowpack contributed significantly (∼51 %) to stream flow in autumn (September and October) as well. The average annual contribution of glacier melt to stream flow is little (5 %). However, the monthly contribution of glacier melt to stream flow reaches up to 19 % in September during years of less persistent snow pack.

Influence of southwest monsoons in the Kashmir Valley, western Himalayas

ABSTRACT The regional climate of the Himalayas is predominated by the southwest monsoons and the western disturbances. The uplift of the Pir Panjal to its present height is believed to restrict the southwest monsoons from entering into the Kashmir Valley in the western Himalayas. In the present study, monthly precipitation samples were collected across the Kashmir Valley from June 2013 to May 2014 for δ18O and δ2H analyses to constrain the influence of southwest monsoons in the valley. Except in August, the precipitation is enriched in 18O and 2H from June to September and depleted from October to May. The sharp depletion of 18O in precipitation along with the decrease in d-excess in August confirm the maximum intrusion of southwest monsoons into the valley. A significant temperature – δ18O relationship was found during October and May (westerlies period) decreasing during June and September (southwest monsoon period). The local meteoric water line for the whole Kashmir Valley based on the precipitation-weighted monthly samples is . Higher intercept of the regression equation suggested dominant contribution of precipitation from western disturbances. The study suggested that the southwest monsoons enter the Kashmir Valley from southwest through the mountainous passes.

Isotope fingerprinting of precipitation associated with western disturbances and Indian summer monsoons across the Himalayas

Precipitation samples were collected across the Himalayas from Kashmir (western Himalaya) to Assam (eastern Himalaya) to understand the variation of the stable isotopic content (

Synoptic variation of stable isotopes in precipitation and ground level vapour in a humid tropical region, Kerala, India

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Isotopic composition of daily precipitation along southern foothills ofthe Himalayas: impact of marine and continental sources ofatmospheric moisture

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Origin of high fluoride in groundwater in the North Gujarat-Cambay region, India

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