Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

S. P. Rai ¹, Vijay Kumar ¹, Omkar Singh ¹, Bhishm Kumar ², S. K. Jain ²

Affiliations
1 National Institute of Hydrology, Western Himalayan Regional Centre, Satwari Jammu Cantt (J&K) 180 003, IN
2 National Institute of Hydrology, Jalvigyan Bhawan, Roorkee (U A ) - 247 667, IN

Abstract

An attempt has been made to workout the bathymetry, determine the rate of sedimentation and the physico-Chemical characteristics of the Mansar lake of Jammu region. The bathymetric survey conducted using Range-Line method shows present lake surface area is 0 59x10⁶ m² and volume to be 11 57x10⁶ m³. The rate of sedimentation determined using ¹³⁷Cs and ²¹⁰Pb radiometric dating technique in the lake varies between 0 14 cm/y to 0 37 cm/y with a mean rate of 0 23 cm/y±0 002 cm/y. The variation of temperature, pH, electrical conductivity, dissolved oxygen, hardness and alkalinity suggest that Mansar lake undergoes two distinct stages, viz complete mixing stage in the months of January and February and stratified stage in other months. The catchment lithology contributes a large part of the major constituents in lake water, Ca and Mg account 70 to 85% of the cations and HCO₃ accounts for 77 to 91% of the total anion, and equivalent ratio of Ca Mg varies from 0 45 to 6 40. The average (Ca+Mg)/HCO₃ equivalent ratio of 1 04, major contribution of (Ca+Mg) to total cations and high (Ca+Mg)/(Na+K) ratio indicate that weathering of calcareous sandstones and mudstones of the Siwalik Group could be the primary source of major ions in the lake water. Results of phosphorous show that Mansar lake has entered the eutrophic stage.

Keywords

Bathymetry, Sedimentation Rate, ¹³⁷Cs and ²¹⁰Pb Dating, Stratification, Hydrochemistry, Mansar Lake, Jammu and Kashmir.

Full Text

     

Rm. P. Nachiappan ¹, Bhishm Kumar ¹, Rm. Manickavasagam ², S. Balakrishnan ³

Affiliations
1 National Institute of Hydrology, Roorkee - 247 667, IN
2 Institute Instrumentation Centre, Indian Institute of Technology, Roorkee - 247 667, IN
3 Department of Earth Sciences, Pondicherry University, Pondicherry - 605 014, IN

Abstract

Hydrochemical characteristics of the groundwater occuring in and around the Nainital lake basin indicate that Ca²⁺/Mg²⁺ ratios are less than one. Statistical analyses reveal that the variation in Ca²⁺/Mg²⁺ ratios is mainly due to variation in Ca²⁺. The groundwater is geochemically undersaturated with respect to calcite and dolomite and has a tendency to dissolve the calcareous rocks more readily than it is expected in ideal dolomite terrain. The higher infiltration rates and lower surface runoff indicate that the groundwater will play a major role in the hillside stability. Further, the groundwater movement will enhance dissolution of carbonate rocks and lead to enlargement of fractures. Hence, the quantum of groundwater seepage and their hydrochemical character seem to play a crucial role in the landslide hazards as experienced by the lake basin frequently.

Keywords

Hydrochemistry, Dolomite, Landslide Hazard, Groundwater, Nainital, Uttaranchal.

Full Text