SESSION-7: Monitoring and Modelling
PAPER-5: Water Quality Management in Rivers using Water Quality Models for Assessment and Prediction
Sudhira H. S., Praveen S. Gurukar, and Anurita

Abstract:

Water quality assessment in rivers has attained considerable importance in recent years. This is because of the deterioration of river water quality due to pollution from different sources attributed to human activities on the pretext of economic development. Water quality modeling and subsequent prediction can be one of the most potential tools for water quality management in rivers. In this regard, the current paper highlights the importance of water quality assessments in rivers with a thrust on water quality management of the rivers.

This paper presents such study on water quality assessment and modeling studies undertaken for River Cauvery at Srirangapatna. The water sampling was done at six transects selected for sampling along the river stretch over a distance of 5 km. Water quality monitoring was done over a period of three months extending from February 2002 to April 2002. The water quality parameters and upstream flow characteristics were analyzed for review and validation of available water quality model under steady-state conditions.

Water quality model developed by Gowda (1983) was applied in the present study. In particular the model MIXPIPOX for single effluent discharge is used here. The river water quality and hydrologic characteristics were used as inputs for this program. The low river flow analysis was also carried to determine the design flow for the least flow in the river representing the critical flow conditions. These data were further used to calibrate and validate the MIXPIPOX computer model for the conditions prevailing in the river. The non-dimensional diffusion factor value (b) was arrived at by using the conservative parameters (conductivity, TDS) for model calibration and validation was done using non-conservative parameter (BOD).

The decay rates reaeration coefficients and b values for each transect were used to compare the observed and predicted values by plotting graphs for the same. From these plots, it was found that observed and predicted values correlate well with three transects and agree with the trend of the rest of the transects. Finally, the study evaluated the viable engineering option of setting up effluent treatment plant for River Cauvery near Srirangapatna considering the b rates, decay rates and reaeration coefficients. This was carried for the options of providing primary and secondary treatments only. From the water quality assessments the extent of pollution on the river is not very significant. The paper discusses some aspects accounting for this phenomenon as well as other options available for safe and efficient disposal of wastewater.