The Hydrochemistry of a Tropical Perennial River and its Adjoining Wells as Influenced by Seasonal Rains

Abstract

The Cauvery river's present dwindling annual flow of less than 50 per cent of normal prompted the study of its hydrochemistry and those of its adjoining well waters as influenced by seasonal rains. At Musiri gauging station the river hydrochemistry showed quiescent behavior during winter and summer, exhibiting dilution with increase in discharge during southwest monsoon and concetration during northeast monsoon. Wells in alluvium had rapid responses regaining their water levels and hydrochemistry. Hardrock wells exhibited rapid declines. Dilution took place in the nearby adjoining alluvial wells and distant hardrock wells after the northeast monsoon. Concentration tookplace in the nearby hardrock wells after the northeast monsoon. Long term river hydrochemistry revealed that due to steady decrease in river discharge the concentrations were on the increase. WATSPEC effective soeciation confirmed that the river and well waters were supersaturated with respect to calcite and dolomite and undersaturated with respect to gypsum and halite.