142-Modelling of Dissolved Oxygen Behaviour in Fast Moving Shallow Hilly Streams.

Abstract

Surface water is highly susceptible to contamination with ever growing urbanization and industrialization worldwide. A variety of wastewaters are discharged into streams/rivers leading to depletion of Dissolved Oxygen (DO) of water due to organics stabilization by aerobic activities. DO in river water is a prime consideration for assessing rivers health and to support aquatic lives therein. The domain of DO modelling is too extensive to cover each and every aspect, influencing DO behavior in streams. Earlier researchers worked upon modeling of DO using experimental data on a number of slow moving streams or rivers, but devoted less efforts towards fast moving shallow hilly streams. Also, the existing models do not account for some important factors like turbulence, geometry of streams etc., which are essential parameters in case of fast moving shallow hilly streams. The present paper attempts to formulate and modify the existing Bhargava's (1986) model for DO deficit by accounting the parameters like turbulence, width, depth and length of course of streams for the application in fast moving shallow hilly streams. The modified equatins were tested using the data available from literature on river Ganga in India. Experimental observations were also taken on Dikrong river, a shallow fast moving hilly stream in the state capital of Arunachal Pradesh in India, by introducing synthetic soluble glucose waste as pollutant and these observations were used to validate the developed model equations for the fast flowing shallow streams. The results indicate that agreement between the experimental and predicted DO deficits using Bhargava's (1986) model tested on Ganga river was found within ±30%, which reduced to ±23% with modified model. The agreement using simplified model was found even much better (within ±18%) when tested on fast moving shallow Dikrong river. Thus, the present modified model gives certainly a better prediction over the existing model and has a practical utility in assessing river's health, especially in case of fast moving shallow hilly streams.