Excess fluoride in groundwater-based drinking water supply is a growing concern in semi-arid tropical (SAT) regions of India. More than 16 states in India are facing the fluorosis problem. Several southern-peninsular states are experiencing monsoon climate condition, where the rainwater is harvested through tanks and used for agriculture. Presence of millions of such tank systems in these regions and their interception in the fluoride cy-
cle has been studied here on a pilot level in several tanks.