Environmental study on water quality of Mayur River with reference to suitability for irrigation

The farmers residing in the western fringe of Khulna city in Bangladesh use the sewage-fed water of the Mayur River for irrigation as good quality surface water is not available as well as higher cost in groundwater irrigation. The present study was undertaken to evaluate the suitability of this river water for irrigation during the hot summer months (March to May) since this period is more sensitive to crop agriculture in the study area. A total of 30 water samples, 10 in each month from 10 stations, were collected and analyzed for pH, EC, TDS, major cations (Na, K, Ca, Mg) and anions (Cl, HCO3, NO3, PO4, SO4), Chemical data were used for calculation of SAR, Na%, RSC, PI, KI and MR for better understanding the suitability of river water for irrigation use. Wilcox diagram and USSL diagram were also adopted in the present study to verify the suitability of river water quality for irrigation. The results revealed that water of the Mayur River was alkaline in nature like major world rivers. Sodium was the most dominant cation throughout the sampling period, whereas sulfate was the most dominat anion in March and May, and chloride in April. The river water was found to be safe for irrigation with respect to pH and PI. However, some usual and calculated parameters like EC, TDS, hardness, alkalinity, chloride, sulfate, nitrate, sodium, Na%, SAR, KI, MR and Ca/Mg restricted the Mayr River water for use in irrigation. The RSC values indicated the water to be safe during April and May and permissible to severe in March. The USSL and Wilcox diagrams indicated high salinity in the water with high sodium being unsuitable for irrigation. The findings call for an immediate management plan to protect this invaluable resource.