Hydro-geochemical evaluation of groundwater for irrigation in the Ganges river basin areas of Bangladesh Md Shajedul Islam University of Rajshahi Md. Golam Mostafa (
[email protected] ) University of Rajshahi Original Manuscript Keywords: Ganges river basin, Hydro-geochemistry, irrigation water quality, rock weathering, statistical analysis Posted Date: February 9th, 2021 DOI: https://doi.org/10.21203/rs.3.rs-161359/v1 License: This work is licensed under a Creative Commons Attribution 4.0 International License. Read Full License Page 1/33 Abstract Groundwater is a vital source of irrigation water, and it provides over 80% of the irrigated water supply in Bangladesh. The study aimed to assess the status of irrigation water of the Ganges river basin areas in the middle-west part of Bangladesh through the hydrogeochemical characterization and classication of 2+ 2+ + + − − groundwater. The study parameters were pH, EC, TDS, Ca , Mg , total hardness, Na , K , B, Cl , HCO3 , 2− − 3− SO 4 , NO3 , and PO4 along with irrigation water quality index (IWQindex), Na%, soluble sodium percentage, sodium adsorption ratio, residual sodium bicarbonate, magnesium adsorption ratio, permeability index, and Kelley’s ratio. The results showed that most of the water samples were acidic in the pre-monsoon and alkaline in the post-monsoon seasons, and the water type was Ca-HCO3. The signicant geochemical process in the area determined was calcite and dolomite mineral dissolution, and there was no active cation exchange, and silicate weathering occurred. The statistical analyses showed that both the geogenic and anthropogenic sources were controlling the chemistry of the groundwater aquifers. Concerning irrigation water quality, the results revealed that all the quality parameters and IWQindex (32.04 to 45.39) were within the safety ranges, except for the EC and total hardness.