Redemarcation of recharge area of stressed confined aquifers of Neyveli groundwater basin, India, through tritium tracer studies

Autor: G. K. Hodlur, T. Gangadhara Rao, D. Muralidharan, R. Rangarajan, S. D. Deshmukh
Rok vydání: 2005
Předmět:
Zdroj: Environmental Geology. 48:37-48
ISSN: 1432-0495
0943-0105
Popis: Natural recharge due to rainfall (annual average 1,200 mm) over an area of 1,500 km2 of the Neyveli groundwater basin was carried out for two consecutive hydrological years, using the tritium injection technique. The lignite seams, occurring within the Upper Miocene formation in the basin have been mined for the last 40 years. The confined aquifer underlying the lignite seams has been pumped continuously since 1961, for depressurization and safety around the mine. The recharge zone is identified as an elongated zone, oriented in a NE–SW direction within the basin. Natural recharge measurements were made at several sites (single and duplicate injections), covering the entire basin. They indicate a recharge rate of 333–556 mm/year (24–40% of rainfall) in the north and northeastern parts, covering the previously defined recharge areas as well as some adjoining areas. Soil moisture movement at several duplicate sites in these areas showed significant downward migration of tracer during the non-monsoon period, probably caused by pumping in the mine area. Isotopic data of ground water samples in the northern and northeastern part of the basin indicates modern ages. Concurrent field observations like deep water table with high annual fluctuations and exposure of pebble beds, enabled the redemarcation of the aggregate recharge area as 650 km2. The redefined recharge area includes the areas identified by earlier workers as well as the new area on the northeastern side of the lignite mine.
Databáze: OpenAIRE
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