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INTRODUCTION
Freshwater resources are essential for the survival of various life forms. The freshwater resources contribute only 3% of the total water resources, out of which only 1% is available for human usage (Deep et al. 2020). Due to the population explosion and higher human dependency on freshwater sources, these resources are under tremendous stress and are deteriorating at a faster rate (Bassi et al. 2014). The area of fresh water sources is shrinking and is also being polluted by anthropogenic influences, thus both quantity and quality are under threat. Today, the world is struggling with basic consumptive water usages like drinking, manufacturing, livestock rearing, and agriculture due to the dilapidated condition of freshwater resources and their distribution (Singh et al. 2017). Wetlands as an important freshwater resource are transition areas between land and water ecosystems and have unique features in terms of soil, vegetation, flora and fauna. Wetlands deliver many ecosystem services including flood control, food and water supply, water for irrigation, groundwater recharge, biodiversity support, nutrient cycling, pollution abatement, and livelihood support (Verma & Negandhi 2011). Ramsar Convention on wetlands (2021) points out that more than 35% of natural wetlands have been lost globally between 1970 and 2015 and the loss of inland wetlands is higher than the coastal ones. The wetlands are under continuous threat from various anthropogenic activities including encroachment for urbanization, industrialization, agricultural land expansion and alteration of hydrological regimes (Gopal 2013). The discharge of untreated or partially treated wastewaters emanating from sewage treatment plants (STPs), industries, municipalities, agricultural and urban runoff into wetlands are also reasons for the poor condition of the wetlands (Bassi et al. 2014; Shan et al. 2021). The inflow and outflow of the water from wetlands is an important factor that governs various wetland processes and their hydrological regimes (Mitsch & Gossilink 2000). The hydrological condition of the wetlands causes variations in the hydro-geochemistry of the water of the wetlands; at times these variations are influenced by human–wetlands relations. Hydro-geochemical assessment of wetlands water is thus conducive to the understanding of its nature, source of ions, pollution status and its suitability for water usage, mostly for irrigation.
North Bihar (northern side of the River Ganges) is blessed with plenty of wetlands locally known as chaurs...