Urban Growth Impact on Cauvery River: A Geospatial Perspective

Rivers are essential for the survival of all living organisms and crucial for balancing the ecosystem as they are the lifeline of any civilization. Various anthropogenic activities are contaminating the river water through point and non-point sources of pollution, mainly from domestic sewage and industrial effluents. Cauvery River is one of the most important water sources for the states of Karnataka and Tamil Nadu. Geospatial technology offers great promise for generating spatial information on natural resources and assessing the dynamics through multi-temporal remote sensing data. This study is aimed at understanding the long-term land use/land cover changes in Cauvery basin for nearly last 2 decades (2001–2019), location of point and non-point sources of water pollution along the river, along with assessing impact of urbanization and industrialization. Satellite imageries from Landsat-5 TM (30 m), Landsat-8 OLI (30 m) and Resourcesat-2 LISS IV MX (5.8 m) were utilized to understand and assess the temporal changes in the study region. Stream network was derived from Open Street Maps (OSM)/India-Water Resources Information System (India-WRIS) using Digital Elevation Model (DEM). River course and major cities/towns were delineated in the buffer region. From the land use/land cover analysis, the conversion of cropland and vegetation into settlements was quite evident. To assess the river water quality for pollution parameters, available field datasets of National Water Quality Monitoring Programme (NWMP) from river water quality monitoring stations of Central Pollution Control Board (CPCB)/Karnataka State Pollution Control Board (KSPCB)/Tamil Nadu Pollution Control Board (TNPCB) were analysed for temperature, pH, Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), Total coliform and Faecal coliform. Field survey, water sample collection and chemical analysis were also carried out for additional datasets during the study period in 2019. Based on the decadal population growth rate, the total current population (as in 2019) in the study region was also estimated. Based on the overall study, it was inferred that over the years, river water in selected stretches has become highly contaminated, especially in Srirangapatna (Karnataka) and in Bhavani, Pallipalayam, Trichy and Tiruppur (Tamil Nadu). This study helped to understand how the Cauvery River is getting polluted, identifying polluted stretches of river and possible point and non-point sources of pollution. The main reason for the deterioration in river water quality is attributed to increasing population in Cauvery River basin, which inturn generates increased waste (mainly sewage), making its way into the river in mostly untreated or partially treated form. Suitable remedial measures are also suggested to reduce river pollution and control its adverse impact on living organisms.