Preliminary geochemical assessment of water from man-made waterways in coastal Andhra Pradesh and its implications for agriculture and public health with a new approach

This hydrogeochemical study examines surface water quality over a 1007 km² coastal area with Quaternary marine and fluvial sediments, highlighting the influence of natural and human factors on water chemistry and its spatial variability. Physico-chemical parameters such as Electrical Conductivity (EC), Total Dissolved Solids (TDS), and Total Hardness (TH) exhibit decreasing gradients from inland areas toward the coast, attributed to dilution by rainwater, tidal flushing, and lower mineral content in sandy coastal sediments. Major ion chemistry highlights contrasting water type: inland zones show elevated sodium and chloride concentrations suggestive of both salinewater encroachment and evaporative effects of fresh surface water while coastal samples are enriched in calcium and bicarbonate, indicating low saline water influenced by recharge dynamics. Piper and Wilcox diagrams corroborate this spatial variability from saline Na–Cl type in the north to mixed Ca–Mg–HCOff type in the south. Trace element concentrations (Fe, Mn, Pb, Ba, Zn) reflect both geogenic sources and localized anthropogenic inputs, including industrial discharge and agricultural runoff. Gibbs diagram shows physico-chemical characteristics of the water in this area is controlled by evaporation and precipitation. A novel Trend Feasibility Map (TFM) was developed to spatially visualize water quality trends and identify direction of suitability for drinking and irrigation. The TFM integrates hydrochemical and geospatial data, offering a practical tool for water resource planning in coastal settings. Overall, the study underscores the necessity of spatial and directional approach to water quality assessments in dynamic coastal environments.