Physico-Chemical and Oxygen-Hydrogen Isotopic Assessment of Bagmati and Bishnumati Rivers and the Shallow Groundwater along the River Corridors in Kathmandu Valley, Nepal

Abstract

The direct dumping of solid wastes into the rivers, discharge of industrial effluents together with direct discharge of domestic sewage have excessively polluted the major rivers Bagmati and Bishnumati. Groundwater along these river corridors is also affected from pollution of these rivers. Two major rivers: Bagmati and Bishnumati and shallow tube wells adjacent to these rivers were monitored for 2 years. Samples were analysed for the stable isotopes of hydrogen and oxygen (δD and δ 18 O) and selected physico-chemical parameters to investigate the possible interrelationship between river water and shallow groundwater along these river corridors. The physico-chemical values revealed that shallow groundwater and river water along the Bishnumati River corridor were heavily mineralized due to direct discharge of sewage wastes into this river. The isotope compositions of river water and shallow groundwater clustered together revealed possible interrelationship between them. Some of the isotopic compositions of groundwater and river water deviated below the Local Meteoric Water Line (LMWL) indicating that the water has undergone evaporation. The isotopic and chemical results suggested possible interrelationship between river water and groundwater. Fractional contribution of the river water to groundwater was calculated based on isotopic data using mass balance approach. Results showed that shallow groundwater

The Correlation and Regression Analysis of Physicochemical Parameters of River Water for the Evaluation of Percentage Contribution to Electrical Conductivity

“…It indicates that there is not only one source of origin of these ions. Natural and anthropogenic sources are responsible for the higher concentration of Cl − irrespective to Na + concentration [19].…”

“…Nepal being a Himalayan country, numerous investigations have been carried out all over the country to access the quality of water by analyzing the physicochemical and microbial parameters of the major river basins [12][13][14][15][16][17][18]. In recent years, statistical tools such as correlation and regression analyses also have been extensively used for evaluating, monitoring, and predicting the concentration of impurities in water [19][20][21][22][23][24]. But, no such works have been obtained in the literature, especially in Jhapa-based rivers of eastern Nepal.…”

Identifying Groundwater and River Water Interconnections Using Hydrochemistry, Stable Isotopes, and Statistical Methods in Hanumante River, Kathmandu Valley, Central Nepal

“…The stable isotopes of hydrogen (δD) and oxygen (δ 18 O) were analyzed using cavity ring-down spectroscopy (L1102-i, Picarro, Santa Clara, CA, USA). VSMOW (Vienna Standard Mean Ocean Water) is the standard water used to calculate isotopic ratios (δ) of D and 18 O of water samples. The results were reported in parts per thousand (per mill deviation) with respect to these standards with precision 0.5% for δD and 0.1% for δ 18 O.…”

“…VSMOW (Vienna Standard Mean Ocean Water) is the standard water used to calculate isotopic ratios (δ) of D and 18 O of water samples. The results were reported in parts per thousand (per mill deviation) with respect to these standards with precision 0.5% for δD and 0.1% for δ 18 O. The isotopic ratios of hydrogen and oxygen were calculated by using the formula given by Craig [45]:…”

“…Previous research conducted in the Kathmandu Valley reported the presence of an interconnection between river water and groundwater, showing a recharge of the groundwater by river water [17][18][19]. Additionally, a number of previous studies on river water quality have also reported heavy contamination of the downstream section of major rivers [20][21][22][23], inducing the occurrence of various water-borne diseases such as diarrhea, cholera, and dysentery among the people of riverside areas [24].…”