Integration of Surface River Water Quality Model Using QUAL2K, Water Quality Index, and GIS For Evaluating River Water Quality of Bhadra River System, India.

Author: Himanshi Singh 2019710001
Date: 2023-09-25
Report no: IIIT/TH/2023/134
Advisor:Shaik Rehana


River water quality is a vital component of the ecosystem which is the main source for drinking, irrigation and more. In recent years, increasing urban growth and expansion have resulted in structural deterioration and functional degradation of river systems, resulting in significant volumes of harmful contaminants being discharged into the water. River pollution substantially impedes long-term economic and social growth and endangers human health. In order to enhance the water environment, it is essential to examine the reasons for water quality deterioration. River water quality modeling is the finest way to assess and monitor water quality. River water quality models are mathematical models that simulate the behavior of pollutants in surface water bodies used to predict the concentration of pollutants in the water and assess the overall river water quality. QUAL2K is a widely-used water quality model that can simulate water quality parameters, such as Dissolved Oxygen (DO), nutrients, and pH, in streams and rivers. However, simulation of many water quality parameters through water quality model does not assess the status and overall pollution extent of any river system. Single river water quality index is required for evaluation of overall pollution extent and to adopt necessary water quality control measures. Therefore, a holistic approach which can integrate river water quality simulation model and pollution extent characterization model is necessary. Thus, this study aims to develop an integrated, holistic model approach to estimate the pollution extent in terms of river water quality index utilizing various river water quality model parameters. Furthermore, the study aimed to analyze the spatial variability of river pollution extent using Geographic Information System. In this present study, the river water quality model, QUAL2K, is used to assess the quality of Bhadra river stretch, one of the major tributaries of the Tunga-Bhadra River situated in Karnataka. The study stretch considered is around 27 km which is divided into three reaches with elements of 1km as 3,4,20 for each reach respectively. In this current study, we analysed the effects of wastewater discharge from the monitoring stations such as the Mysore Paper Mill (MPM), the Visveshvarya Industrial Steel Limited (VISL), and the Bhadravathi city to simulate the Dissolved Oxygen by varying the Biochemical Oxygen Demand (BOD) loads (25%, 50%,70%,100%) coming from different pollutant sources within the study stretch. The observed water quality parameter data from 2006 to 2017 for those monitoring stations has been obtained from Advanced Centre for Integrated Water Resource (ACIWR). The water quality parameters like flow rate and pollution point sources discharge are the highly sensitive water quality parameters for modelling the QUAL2K model. There must be a reduction of 25% of BOD effluent to reach the minimum standards set by the Central Pollution Control Board (CPCB). It is noted that a 75% reduction of BOD effluent from point sources will lead to an increase of 15% average DO throughout the study stretch. The weighted Average Water Quality Index (WAWQI) method is used in estimating Water Quality Index (WQI) by using QUAL2K simulation results for the study stretch. QUAL2K model was calibrated from April 2006 to October 2013 and validated from November 2013 to March 2017. The estimated WQI values range from 92.35 to 112, indicating the quality classification ranges from very poor to unfit for consumption for the Bhadra river. It was observed that the quality status of Bhadra river water was very poor in upstream and downstream segments, while unfit for consumption in the middle segment indicating access to industrial and anthropogenic activities. For spatial analysis, Arc-Geographical Informal System (GIS) software and Inverse Distance Weighted (IDW) interpolation technique is used to generate water quality parameters concentration level and WQI maps. In context to this, it was found that the middle segment of Bhadra study stretch falls into the category of unfit for consumption due to the combination of effluents from industries like MPM and VISL and domestic effluents from Bhadravathi city. Overall, this study revealed that the MPM water quality station was a hotspot for river water quality degradation. Based on all these analyses, we provide a framework for the integration of the three components, i.e., QUAL2K calibration, WQI and spatial visualization for water quality management and policymakers to take decisions about water quality management in Bhadra river stretch .

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Centre for Spatial Informatics