Evaluation of spatial characteristics of groundwater hydrochemical constituents across different geomorphic units of the�Imphal Valley in Northeast India
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Date
2021-07-05T00:00:00
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Springer Science and Business Media Deutschland GmbH
Abstract
The assessment of hydrochemical constituents across different geomorphic units of the Imphal valley of Northeastern India has been carried out. Geomorphologically, the valley is broadly demarcated as the�residual hill, piedmont zone, alluvial plain, and flood plain. The Scholler diagram and Box and Whisker plots suggest that the distribution of ions is characterized by dispersed concentrations owing to variation in the�lithologies in the�geomorphic units. The pH value ranges from 6.90 to 7.21 with a mean value of 7.04, indicating neutral water in the residual hill. In the piedmont zone, it ranges from slightly acidic (4.83) to neutral (7.40) with a mean of 6.58. In the alluvial and flood plains, the values range from 6.15 to 7.44, with a mean of 6.84 and 6.07 to 7.14 with an average of 6.73, respectively suggesting neutral water. TDS range shows slight reduction in the�alluvial plain and flood plain owing to effluent water supply from the�rivers whereas, oxidation�reduction potential (Eh) ranges from 8 to ?�19�mV with highest in the�residual hill, indicating reducing condition. Higher Ca2+ and Mg2+ in the�residual hill and piedmont zone are associated with the�cation-exchange process. Na+ and HCO3? are highest in the�alluvial and flood plains due to weathering of sodium-rich montmorillonite or dissolution of halite or nahcolite (NaHCO3) minerals from clay. The scatter plots indicate that the hydrogeochemical processes throughout the geomorphic units are mainly controlled by the�ion exchange, silicate weathering, carbonate weathering, and evaporate dissolution. The hydrochemical facies are characterized by (i) Na�K�Cl, (ii) Ca�Cl, and (iii) Na�K�Ca�Mg�Cl�SO4�HCO3. The residual hill and piedmont zones are dominated by Ca�Cl facies, implying recent meteoric water coupled with halite riched source of water. The alluvial plain is dominated by Na�K�Cl facies, while the flood plain is characterized by Na�K�Ca�Mg�Cl�SO4�HCO3 facies, suggesting the�mixed type resulted from the ion exchange process. These facies suggest that the groundwater belongs to the initial and intermediate stages of chemical evolution indicating fresh quality. � 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.
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Keywords
Facies, Geomorphic units, Groundwater, Hydrochemistry, Imphal valley, NE India