Impact of urbanization on land use and land cover change in Guwahati city, India and its implication on declining groundwater level

Urban environment continues to expand at an unprecedented rate to meet the demand of increasing population and economic development. The resulting changes to landscapes have increased stress to hydrological cycles, biogeochemical processes, and environmental sustainability of natural resources. This study evaluated spatio-temporal changes of land use and land cover (LULC) between 1990 and 2020 in Guwahati city, India. Time-series Landsat satellite images were analyzed using supervised classification schemes followed by quantification of LULC change over time. Five broad LULC classes were identified on the basis of spectral reflectance signature. Confusion matrix determined high classification accuracy with Kappa Coefficient >0.81 in all cases. The results showed that the urban built environment has doubled in area in 30 years (1990-2020). The urban environments have increased at the expense of vegetation, fallow land, and open areas and to some extent wetlands. Notably, the expansions of urban areas have taken place from city center to the south, to the southeast, and along the east-west National Highway 37 connecting other NE States of India. There is no clear indication of change in the amount of precipitation in response to urbanization. However, analysis of long-term groundwater level data suggests a steady decline in the depth to groundwater level. The declining trend is attributed to urbanization and population growth. The increase in impervious surface coverage due to urbanization have extensively reduced the areas of high potential groundwater recharge zones and thereby dropping the level of groundwater in the wells.