Critical appraisal of water quality model parameters for an urban city in lower Ganga basin during pre- and post-COVID19 Lockdown in India

Ramakar Jha,Kamakshi Singh

doi:10.17485/ijst/v14i29.242

Abstract

Objectives: To assess the impact of urban city Patna on water quality of the river Ganga during pre and post COVID-19 lockdown. Method: A study is done to assess the impact of point and nonpoint source pollution at different reaches of river Ganga for the years 2017 to 2020 (at a stretch of 40 km of a urban city in lower Ganga plains). A total of 450 datasets have been collected from eight river locations and two major drains. The equations of deoxygenation and reaeration coefficient used in water quality modelling have been tested for their applicability in the study area. Findings: Analysis of water quality data collected from 8 river locations and 2-drains for the year 2017-2020 shows significant improvement in water quality variables observed in river Ganga at Patna due to reduction in influx of point and non-point source pollution including floating population at Patna during COVID19 lockdown (March- June 2020). The use of BOD-DO developed by Streeter-Phelps (1925) as Oxygen-Sag curve is still valid, if input variables are limited. However, Camp (1963) and Jha et al. (2007) may be used effectively for comprehensive input data sets. Moreover, the refined model for predicting reaeration coefficient has been tested for the developed dissolved oxygen (DO) model and biochemical oxygen demand (BOD) model for pre- and post COVID19 lockdown individually. The water quality maps developed using satellite (Landsat-8) data provides the turbidity levels during pre and post COVID19 countrywide lockdown period and resulted in a significant improvement. Novelty: The study is unique due to water quality analysis during COVID19 and its comparison with previous year data. The deoxygenation and reaeration coefficients values are established for pre-and post COVID period. Also use of Landsat-8 data is used for assessing turbidity for pre- and post-COVID19. Keywords: point source pollution; COVID 19; BODDO modelling; nonpoint pollution

Highlights

3.2 Biochemical oxygen demand (BOD) and Dissolved oxygen (DO) Models In India, limited river water quality modelling efforts have been made during the recent past for biochemical oxygen demand (BOD) and dissolved oxygen (DO) simulations [1,3,4,4,5,5,6,6,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,13,13,14,14,14,15,15,15,16,16,16,17,17,18,18,19,19,20,20,21,21,22,23,23,24,25,26,27,28,29,34]
The water quality samples collected from different locations indicate variation in their values due to influx of point source pollution (Figures 2 and 3 )
The analysed data have been utilised for water quality modelling and establishing different parameters K1 and K2 in BOD-DO modelling

Summary

Introduction

Good quality of freshwater is essential for the human being, flora, fauna and other living things [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33]. Due to over exploitation of freshwater and disposal of waste water in River Ganga from mega and metro cities situated along the river Ganga, the water quality of river Ganga has been deteriorating in recent past. In most of the studies done in recent past, the variation of water quality parameters such as DO and BOD has been estimated. Very little work has been done for water quality modelling and establishment of water quality parameters such as deoxygenation rate constant and reaeration coefficient during pre as well as post COVID period

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Conclusion