Correlation of Land Subsidence with Groundwater Extraction and Urbanization in Hagonoy and Calumpit, Bulacan from 2015 to 2021-Q1

Abstract

This study investigates the spatial relationship between land subsidence and the patterns of groundwater extraction and urbanization in Hagonoy and Calumpit, Bulacan, from 2015 to the first quarter of 2021. Using Persistent Scatterer Interferometry (PSI) from Sentinel-1 InSAR data, zonal proximity analysis, and spatial regression techniques, the research quantifies deformation patterns and their association with anthropogenic stressors. Ordinary Least Squares (OLS) and Geographically Weighted Regression (GWR) models assessed the explanatory power of groundwater level (GWL), population density, and built-up volume. GWR on grid-based PSI sampling outperformed OLS with an adjusted R2 of 0.88, capturing localized subsidence drivers. Results revealed subsidence rates reaching -124.51 mm/year near high-extraction zones. Areas within 500 meters of pumping stations exhibited significantly higher deformation (mean: -70.22 mm/year) than more distant areas (-65.31 mm/year), as confirmed by Welch's t-tests (p < 0.001). Estimates show that Hagonoy's annual extraction volume (∼9 million m3) may contribute -81 mm/year of subsidence. Findings highlight the urgent need for localized monitoring, improved input data from water utilities and Philippine Statistics Authority (PSA), and integration of subsidence risk into land-use planning. The study demonstrates the effectiveness of spatial modeling in understanding land deformation processes in data-limited, flood-prone coastal municipalities.