<p>The Sapanca Lake Basin has experienced significant population growth, industrialization, and urbanization over the past two decades, attributed to its strategic location, its function as a drinking water source, and its natural attractiveness. These developments have resulted in substantial alterations in land use. As both a drinking and utility water source for the Sakarya and Kocaeli provinces, the lake has experienced a decline in water quality as a result of these detrimental environmental impacts. This study’s primary objective is to assess the pollution sensitivity risk of the Sapanca Lake Basin. Land use alterations and changes in the lake area were identified as potential contributors to pollution risk. This analysis was based on Landsat 5 TM (1987) and Landsat 8 OLI/TIRS satellite images from 1985, 1995, 2005, and 2020, processed with ArcGIS Pro 2.5. The analysis identified a 7.2% reduction in natural vegetation from 1985 to 2020. To assess the sensitivity arising from these pressures and impacts related to land use, the study employed the WRASTIC index, a recognized environmental risk analysis method. Detailed analyses were conducted on the direction and magnitude of land use changes in the basin due to escalating human influence, utilizing the WRASTIC index and a newly developed WRASTIC-PW (P = Precipitation, W = Water withdrawal) index that incorporates additional modules. The sensitivity levels of the basin derived from these indices were assessed. The WRASTIC index demonstrated a progression from high sensitivity to moderate sensitivity in the basin from 1985 to 2020, an improvement attributable to advancements in wastewater management and favorable developments in industrial impacts. The assessment with the WRASTIC-PW index revealed that the basin's sensitivity bordered between sensitive and moderately sensitive throughout the period from 1985 to 2020. This underscores the necessity of considering not only wastewater and industrial discharges but also land use changes, water withdrawals, and the implications of climate change in sensitivity determination studies of the basin using the proposed new index. The findings of this study have critical implications for watershed management and regional policy-making. They demonstrate that effective water resource protection goes beyond improvements in wastewater treatment, requiring the integration of sustainable water withdrawal strategies, land-use planning, and adaptation to changing precipitation patterns at the basin scale. By incorporating these factors into sensitivity assessments, the enhanced WRASTIC-PW index enables authorities to develop more resilient and targeted water management policies, prioritize protective zoning, and ensure long-term drinking water security for growing urban populations. Additionally, its comprehensive methodology provides planners and decision-makers with a robust and adaptable tool that can guide sustainable watershed management in other regions facing similar environmental pressures.</p>