Mapping anthropogenic pressure in the Brahmani-Baitarani River Basin: a PCA-based approach

This study presents a robust objective methodology for assessing and mapping anthropogenic pressure in the Brahmani-Baitarani River Basin (BBRB) through an objective principal component analysis (PCA)-based approach. Nine key stressors-Aerosol Trend (AERT), Degree of Urbanization Change (DUC), Land Use/Land Cover Change (LULCC), Normalized Difference Moisture Index Trend (NDMIT), Normalized Difference Vegetation Index Trend (NDVIT), Observed Minus Reanalysis Temperature (OMR), Nightlights Change (NLC), Population Count Change (PPC), and Water Balance Trend (WBT)-were used to construct a composite pressure index. These stressors were selected based on their direct link to human-induced environmental modifications. The datasets, spanning from 2000 to 2023, were preprocessed and normalized to ensure comparability. The suitability of the dataset for PCA was confirmed through the Kaiser-Meyer-Olkin (KMO = 0.61) and a significant Bartlett test (χ² = 378037, p < 0.01). PCA was applied to determine variable weightings, reducing redundancy and highlighting dominant stressors, with OMR, DUC, and LULCC contributing the highest weights. The final composite anthropogenic pressure raster (CAPR) was generated with index ranging from 9 to 78%. Spatial analysis reveals significant variations in anthropogenic pressure, with towns such as Byasanagar and Lohardaga experiencing very high mean anthropogenic pressures (~ 50%). Conversely, regions like Deogarh, Gua, and Kiriburu exhibit relatively very low anthropogenic pressures (~ 20%). Further, the CAPR was grouped into 7 categories based upon natural breaks in the data and pseudo-F-statistics-based elbow test, providing a clear representation of the spatial distribution of anthropogenic impacts, serving as a critical tool for sustainable management and policy formulation.