Water quality assessment of Noyyal river using water quality index (WQI) and multivariate statistical techniques

ABSTRACT Noyyal River is an important river that flows through the districts of Coimbatore, Tirupur, and Erode in Tamil Nadu, India. This river is the prime source of water for agricultural and domestic purposes in the above districts. This study evaluates the surface water quality of the Noyyal river and its suitability for drinking and agricultural uses. For this study, samples were collected from 27 locations along the Noyyal river from its source to sink. The water quality index (WQI) values were designated and, except for two samples out of 27, all the other samples were categorized as poor, very poor, and unfit for consumption. The parameters evaluated to assess the water quality of the Noyyal river for irrigation include Electrical conductivity (EC), Sodium adsorption ratio (SAR), Soluble sodium percentage (SSP), Residual sodium carbonate (RSC), Magnesium hazard (MH), Kelly’s ratio (KR), and Permeability index (PI). USSL (U.S. Salinity Laboratory) diagram analysis helped to classify the samples 1 and 2 of the Noyyal river in the C1S1 and C2S1 category, which indicates low salinity-low sodium and medium salinity-low sodium, respectively. The rest of the samples fall under the category of very high salinity and very high sodium waters. Other indices like RSC, magnesium hazard, soluble sodium percentage, Kelly’s ratio, and permeability index signified that majority of the collected samples fall in the category of unsuitable for agricultural use and they need special management practices. The Principle component analysis determined the four PCs that explained 84.88% of the total variance in the data structure. The present study concludes that we cannot use the surface water of the Noyyal river directly without treatment and strict management practices should be implemented for the sustainable use of the resource.