Groundwater sustainability in the face of urban expansion: A case study on Kolkata's ongoing challenge

This study investigates the impact of urbanization on groundwater sustainability in the megacity of Kolkata, India, amidst the global trend of increasing urban populations. Utilizing a site-specific approach and multidisciplinary framework, the research analyses three decades (1990-2020) of urban development, correlating the expansion of built-up areas with changes in groundwater levels. Remote sensing and Geographic Information System (GIS) techniques, specifically the Normalized Difference Built-up Index (NDBI), are employed to assess built-up area dynamics. Groundwater data from governmental sources, combined with spatial analysis using Geographically Weighted Regression (GWR), reveal a complex relationship. Descriptive analysis indicates a significant rise in average built-up areas over the decades, with a notable increase in 2020. Correlation coefficients shift from negative in 1990 to strongly positive in 2020, signifying a growing dependence of groundwater levels on built-up areas. Spatial autocorrelation showing a strong clustered pattern in case of groundwater scenario over the years. Geographical analysis highlights varying impacts across different wards, especially in the southern part of Kolkata. Time series analysis forecasts a continued increase in built-up areas, potentially leading to a decline in groundwater levels. The study emphasizes the urgent need for site-specific interventions to ensure the sustainability of groundwater resources in Kolkata, as urbanization continues