Seasonal dynamics and hydrogeological assessment of Najafgarh drain and its irrigation channels for agricultural purposes in Southwest Delhi, India

This research paper focuses on evaluating the suitability of drain water, whether untreated or treated, for irrigation purposes in a peri-urban region of southwest Delhi, India. A total of 11 drain water samples were collected during the pre-monsoon (PRM) and post-monsoon (POM) seasons. A comprehensive assessment of various water quality parameters, including pH, EC, major cations (Na+, Ca2+, Mg2+, K+), anions (Cl-, HCO3-, SO42-, NO3-, F-), heavy metals, and irrigation water quality (SAR, Na%, RSC, KR, MH, PI) were analyzed. The results revealed that the drain water was highly unsuitable and marginally suitable for irrigation in PRM and POM. The Wilcox diagram classified 91% of samples as doubtful to unsuitable during PRM but only 63% during POM due to the rainfall. Heavy metal concentrations often exceeded permissible limits, with Fe ranging from 0.98 to 8.65 ppm (PRM) and 0.004 to 10.32 ppm (POM). Other metals like Mn (0.12-0.98 ppm PRM), Zn (0.02-2.54 ppm POM), Cd (0-0.031 ppm POM), and Cu (0.07-0.345 ppm POM) also showed elevated levels. The chemical composition of the water was influenced by evaporation and rock-water interactions as indicated by Gibbs diagrams in both the seasons. The results highlight the need for proper treatment to address salinity, sodicity, and heavy metal issues.