Assessment of land use land cover changes and its impact on groundwater resources of Kamrup along the banks of the River Brahmaputra

Urbanisation induced land use land cover changes (LULC) are irreversible and is an intensifying worldwide phenomenon. The unprecedented urban growth rate affects the hydrological system and its associated ecosystem services. This has led to a situation where even regions with huge water potential such as the Ganga-Brahmaputra basins of India, are experiencing potable water scarce conditions. Hence, this study is an effort to evaluate the role of LULC on the groundwater resources of Kamrup district, along the banks of River Brahmaputra in Assam. The study entails a quantitative analysis using GIS applications, whereas the statistical significance is evaluated using Man Kendall trend analysis. Satellite images of Landsat and Sentinel are clustered and segmented to classify six different classes. The cloud-based platform of Google Earth Engine (GEE) is utilised for the object oriented (OO) classification. A combination of Simple Non-Iterative Clustering (SNIC) and Random Forest Classifier is utilised to obtain an accuracy >85% for all the images. It is observed that the area under agriculture and wetlands has reduced by 58.99% and 44.7% between 1990 to 2020, respectively. On the other hand, the area under urban impervious cover has increased from 1.875% in 1990 to 17.05% in 2020. The Mann Kendall trend analysis of the groundwater levels shows that 69% of the well locations demonstrate a declining trend at 95% confidence interval. The maximum decline rate is of 0.13 m year−1 and minimum decline rate is 0.03 m year−1. Comparative investigation of the groundwater decline and urban growth shows that 47% of the groundwater wells with declining water levels are located in regions urbanised from 1990 to 2020. The decline in the groundwater levels can be attributed to increased impervious surfaces with the urbanisation. Further, the reduced chances of infiltration have led to amplified runoff and floods with reduced groundwater level in the wells. The results from this study indicate that the depletion in groundwater across the study area can be strongly linked to anthropogenic interferences. Such monitoring of LULC changes along with the dynamics in water levels across the study area, provide a necessary database for the protection, decision-making and sustainable management of the existing freshwater resources.