Water Quality Assessment of Various forms of Rainwater and Statistical Studies on Physico-Chemical Characteristics of Stormwater in Coimbatore, India

Rain water harvesting, irrespective of the technology used, essentially means harvesting and storing water in days of abundance, for use in lean days. It has been construed as the most sustainable method for managing water scarcity situations, incorporating all type of water demands. Though rainwater is considered as a contamination free source, human activities particularly in the industrial and agricultural sectors pollute this pure form of water. The quality of various forms of rainwater, viz. direct rainfall, rooftop water and stormwater were assessed by analysing various physico-chemical parameters. The physico-chemical characteristics of stormwater were further subjected to statistical and correlation analyses. The results showed that the direct rainwater samples collected were pure and safe as drinking water. The surface stormwater runoff samples collected from the study location, which is mainly an urban and industrialised catchment, contained undesirable amount of sediment load and other chemical parameters; most of them are not within safe limits for drinking and irrigation use. The electrical conductivity and sediment concentration in samples collected from roofs were slightly above the desirable limit for drinking purpose. The mean, standard deviation (SD) and coefficient of variation (CV) of various physico-chemical parameters of stormwater were computed and compared. Similarly correlation coefficients were worked out to find out the relationship amongst physico-chemical characteristics of the water samples and a large number of significant correlations were obtained.