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Evaluation of Spatial and Temporal Variations in Water Quality of River Ganga

J. Joshi, A. A. Abhyankar

Abstract



In this study, statistical hypothesis tests are carried out to identify spatial and temporal patterns in Ganga river water quality. Data for eight water quality components - Temperature, pH, Dissolved oxygen, Biological Oxygen Demand, Chemical Oxygen Demand, Total Coliform, Fecal Coliform and Total Kjeldahl Nitrogen measured at 34 stations along the river for each month of the year 2004 and 2009 were used for analysis. In order to obtain meaningful water quality information that is understandable to legislative decision makers, Water Quality Index (WQI) was computed from the measured values of water components. A custom R package was written to compute the unweighted arithmetic water quality indices. The hypothesis for spatial, temporal, and seasonal changes in computed WQI values were defined. These were tested using Moran’s I, Mann Kendall, and Wilcoxon tests. The result from hypothesis tests revealed significant spatial correlation in values of WQI whereas WQI values were not found to vary significantly for the year 2004 and 2009.

Keywords


Mann Kendall test, Moran I’s test, seasonality, spatial autocorrelation, water quality assessment, Water Quality Index (WQI), Wilcoxon test.

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