Temporary fluoride concentration changes in groundwater in the context of impact assessment in the Vaniyar sub-basin,South India

India's surface water and groundwater distribution is temporally variable due to the monsoon.Agriculture is one of the dominant economic sectors in India.Groundwater quality is regularly assessed to determine usability for drinking and irrigation.In this study,World Health Organization and Bureau of Indian Standards guidelines were used to determine suitability of groundwater near artificial recharge structures(ARS) with a focus on the structures impact on groundwater quality.Groundwater resources were evaluated for irrigation suitability using electrical conductivity(EC),sodium adsorption ratio,the US Salinity Laboratory diagram,sodium concentration,Wilcox's diagram,Kelly's index,and Doneen's permeability index.EC and major ions were tested in recharge areas at different distances from the ARS.The construction of ARS at optimal distances along major streams has improved groundwater quantity and quality in the subbasin.Before construction of ARS,fluoride concentrations were higher;after construction,fluoride was reduced in most locations.Water stored in the check dam and groundwater in the wells closer to the structure were suitable for both drinking and irrigation purposes.Impact of ARS on nearby groundwater quality was observed at Pallipatti,Mulayanur,Venkadasamuthram,Pudupatti,Poyyappatti,Harurl,and Sekkampatti.More distant sites included Pappiredipatti,Nambiyappati,Menasi,Harur,Todampatti,and Adikarapatti.Data demonstrated improved groundwater quality in the area of the ARS.Through recharge,the non-potable fluoride in the region is reduced to the permissible limit for human consumption.