Assessment of river water quality for agricultural irrigation

Monitoring was conducted during 2009-2014 in the river Ganga to evaluate water quality for irrigation. Sampling was done every month at four locations in West Bengal, India, viz. Berhampore, Palta, Dakshineswar and Uluberia from two positions (middle of the river and one discharge point) at each location and analysed for different parameters. Electrical conductivity and sodium adsorption ratio of river water during the period were obtained in the range of 0.15-0.88dS/m and 0.07-2.84 with average of 0.32dS/m and 0.92, respectively. The pH was in the range of 6.85-8.47 showing an increasing trend over the years. Spatial changes were evident for chloride exhibiting higher mean concentrations (mg/L) at Palta (17.29) and Uluberia (19.02). Significant temporal changes were observed in case of, electrical conductivity, sodium adsorption ratio, sodium, calcium, chloride, sulphate and nitrate, exhibiting higher values during dry seasons than monsoon. The trace elements concentrations were well within the permissible limit for irrigation. Fe, Mn, Zn and Pb were detected in more than 90% of the samples, whereas Cu, Cr, Ni, Cd and F were detected in 70, 71, 58, 25 and 64% samples, respectively. The manganese concentration exceeded the limit in about 60% of detected samples. The dominance pattern of ions was in the order Ca2+>Na>SO4(2-)>Mg2+>Cl->NO3->B>HCO3->CO32- and that of trace elements Fe>Mn>Zn>Pb>F>Cr>Cu>Ni>Cd.