Abstract
Reconnaissance on the suitability of the available groundwater resources for irrigation in Thakurgaon District of northwestern Bangladesh was done by determining pH, TDS, EC, hardness, alkalinity, major cations and anions. The pH values suggest that the water is slightly acidic to strongly basic. The dominant cation and anion in the study area are Ca2+, Mg2+ and HCO3−, respectively. Calcium bicarbonate, calcium–magnesium–bicarbonate and calcium carbonate are the dominant hydrochemical facies among the water samples. The groundwater system in the study area may be recharged through infiltration of rain. The above statement is further supported by Gibbs plot where most of the samples fall within the rock-dominance zone. The evolution of these waters may be controlled by precipitation and dissolution of carbonate minerals. The USSL, SAR–EC classification schemes and Wilcox plot confirm that the groundwater samples are good to excellent as irrigation water. However, the groundwater evolution in this study is mainly the result of weathering of carbonate minerals and cation exchange within the aquifer materials, confirming the shallow porous groundwater hydrochemistry characteristics.
Highlights
Groundwater quality is important for determining its use for domestic, irrigation and industrial purposes
A relation of alkaline earths with weak acids is expressed in terms of Residual sodium carbonate (RSC) for assessing the quality of water for irrigation (Richards 1954)
When the weak acids are greater than the alkaline earths, a precipitation of alkaline earths occurs in soils, which damages the permeability of soil (Rao et al 2012)
Summary
Groundwater quality is important for determining its use for domestic, irrigation and industrial purposes. It is degraded by several factors related to human activities and geochemical changes. In floodplain areas degradation generally occurs owing to hydrogeochemical processes, arsenic contamination, aerosols deposited on the top soil and interaction of groundwater with brines and sedimentary formation (Sanford et al 2007). Hydrogeochemical processes that are responsible for changing the chemical composition of groundwater differ due to variation of time and space. The study of hydrogeochemical processes of the groundwater system helps to obtain the contributions of rock/soil–water interaction in aquifer. The geochemical processes are responsible for the spatio-temporal variations in groundwater chemistry (Kelly 1940; Wilcox 1948; Matthess 1982; Kumar et al 2006). Apart from the natural process, anthropogenic contaminations such as industrial effluents, agrochemicals, municipal wastewater, septic tank effluent and landfills are other major sources of water quality deterioration (Mondal et al 2008, 2011; Selvam et al 2013)
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