The study assesses the suitability of groundwater for drinking and irrigation use and examines the likely impact of Yamuna river water quality on groundwater. Delhi is faced with severe problems associated with groundwater quality and quantity. The quality varies spatially and seasonally, with depth and is primarily governed by the extent and composition of dissolved solids present in it. Surface water bodies play a role and the hydraulic gradient determines the lateral and vertical migration in the groundwater flow system.

Groundwater samples were collected through extensive field surveys covering entire Delhi area representing various geo-hydrological and land-use conditions. The data has been analysed with respect to BIS and WHO standards to examine its suitability for various uses. The area has a peculiar feature of infiltration of surface water to groundwater from river Yamuna and from various drains.

An attempt has been made to classify the groundwater on the basis of different classification schemes, such as Stiff, Piper trilinear and US Salinity Laboratory classifications. As per the Stiff classification, majority of the samples fall under sodium bicarbonate type followed by sodium sulphate and sodium chloride type. In the Piper trilinear and modified diagram, majority of the samples fall in the Na-K-Cl-SO4 followed by Na-K-HCO3 and Ca-Mg-Cl-SO4 hydrochemical facies. According to the US Salinity Laboratory's classification of irrigation water, more than fifty percent samples fall under water type C3-S1 (high salinity and low SAR) and such water cannot be used on soils with restricted drainage.

Even with adequate drainage, special management for salinity control may be required and plants with good salt tolerance should be selected. About thirty percent of the samples fall under water type C3-S2 (high salinity and medium SAR). Such water induces an appreciable sodium hazard in fine textured soils having good cation exchange capacity, especially under low leaching conditions.

The qualitative analysis of the data depicted higher concentration of various physico-chemical and bacteriological parameters in deep aquifers on the western side of Yamuna. However, due to paucity of hydro-chemical, geological and water level data no specific inferences could be drawn regarding the probable impact of river water quality on groundwater. Further studies are being planned to investigate the impact of Yamuna river water quality on the groundwater system.

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