Groundwater quality assessment for irrigation use in the Godavari Delta region of east coast India using IRWQI and GIS

The present work was carried out in the deltaic region of the river Godavari in coastal Andhra Pradesh of southern India to evaluate the status of groundwater quality for irrigation. Groundwater is predominantly used in these productive agricultural fields. Saline water intrusion in fresh groundwater aquifers, which is mainly due to the excess withdrawal of groundwater, was recorded in the study area. A total of 80 groundwater samples were analyzed for physical and chemical parameters using standard chemical procedures. The groundwater mainly represents Na+–Cl− type, which shows the mixing of fresh water with saline water. The high correlation between Na+–Cl− and Mg2+–HCO3− explained that the intermixing of aquifer waters and the leaching of secondary salts influenced the region. Evaporation-fractional crystallizations are the main processes in the groundwater of the study area. The irrigation water quality index was calculated using different quality indices including Na%, sodium adsorption ratio, residual sodium bicarbonate (RSBC), permeability index (PI), magnesium hazard (MH), Kelly's ratio (KR), and potential salinity (PS), Cl−:HCO3−, Mg2+:Ca2+ and Na+:Ca2+ to estimate the suitability of groundwater quality for irrigation. Spatial distribution maps were prepared using raster interpolation in GIS. The assessment revealed that the areas covering 67.6% of electrical conductivity, 100% of total dissolved solids, 57.5% of Na%, 21.3% of RSBC, 66.3% of PI, 16.3% of MH, 65% of KR, and, 100% of PS required severe to moderate restrictions. Overall, the groundwater in the study region showed potential salinity due to geogenic and anthropogenic activities, and thus it must be monitored for sustainable agriculture. HIGHLIGHTS Geochemical evaluation of groundwater explains that evaporation is the main controlling factor of geochemistry along with rock dominance. The irrigation water quality index (IRWQI) was calculated using different quality indices to estimate groundwater quality for irrigated waters.; The calculated indices were found to be in the moderate to unsuitable category of groundwater for irrigation.;