Evaluating Hydrological Responses to Urbanization in a Tropical River Basin: A Water Resources Management Perspective

The present study investigates the hydrological response of increase in urbanization on water stressed Upper Bhima River basin which lies in a semi-arid climatic zone of Maharashtra state, India. Land Use Land Cover (LULC) changes due to urbanization, industrialization and anthropogenic activities have reconfigured the waterscape of the river basin, which has affected its regional hydrology. Influence of urbanization on key hydrological components is studied using Soil and Water Assessment Tool model. Firstly, Object Based Image Analysis approach was used to prepare time series LULC maps of the years 1992, 2002, 2009 and 2014. Overall classification accuracy of 92.48% and Kappa Coefficient (K) of 0.87 were achieved. Urbanization indicators, e.g. population urbanization level (U-p) and spatial urbanization level (U-s), were used to quantify the growth patterns in population and urban areas respectively. Mann-Kendall trend test was performed on the average annual rainfall data (year 1985-2014) to study rainfall trends across the region. Further, combination of statistical analyses including correlation analysis and multivariate analysis of variance were performed to comprehend the causative connection and interrelationships between U-s and hydrological parameters. The results reveal that during 1992-2014, with increase in U-s of 0.05, the average annual surface runoff increased to 10.4mm [standard deviation (sigma)=4.40; sum of squares (SS)=58.20], whereas percolation decreased to 14.5mm [sigma=6.06; SS=110.10], and base flow decreased to 11.7mm (sigma=4.90; SS=72.00). These hydrological parameters are highly influenced by increase in urbanization. This study is relevant for various stakeholders such as water sources planners and policy makers for assessment of water resources to ensure sustainable development in the urbanizing tropical river basins. Remedial measures are suggested to minimize the adverse effect of urbanization on hydrological processes.