Implications of demographic changes and land transformations on surface water quality of rural and urban subbasins of Upper Bhima River basin, Maharashtra, India

For sustainable development in a river basin, it is crucial to understand population growth–land use/land cover (LU/LC) transformations–water quality nexus. This study investigates the effects of demographic changes and LU/LC transformations on surface water quality of rural (Ghod) and urban (Mula-Mutha) subbasins of Upper Bhima River basin. Population data (1981–2011) and LU/LC data {October 2002 [Landsat Enhanced Thematic Mapper (ETM+) data] and October/November 2009 (Indian Remote Sensing 1C Linear Imaging Self Scanner III data]} were analysed using statistical, remote sensing and geographic information system techniques to study demographic and LU/LC changes, respectively. Further, overall indices of pollution (OIPs) developed specifically for rural subbasin (OIPr: Hardness CaCO and Total Dissolved Solids), urban subbasin (OIPu: Biological Oxygen Demand, Chlorides, Coliform Total, Colour, Dissolved Oxygen%, pH and Turbidity) and single OIP considering all parameters (OIPa) were used for spatio-temporal water quality assessment of pre-monsoon and post-monsoon periods. Results revealed that from 1981 to 2011, population increase was higher in urban subbasin than in rural subbasin. Subsequently, from 2002 to 2009 mainly increase in built-up lands (3.82%) and agricultural lands (15.35%) in urban and rural subbasins respectively, affected their water quality. From 2002 to 2009, the highest increase in OIPr and OIPu was observed at Kashti (3.37–6.52 due to fertilizers) and Bundgarden Bridge (3.03–7.83 due to municipal and industrial wastes) stations of rural and urban subbasins, respectively. With significant increase in OIPa of 2.74–6.70, Bundgarden Bridge station affected by urbanization had the most polluted water quality.