Water Quality Evolution and Relationship with the Built Environment

Water systems are crucial to urban life. Since 1972, the US has made progress in water quality management but faces ongoing challenges and criticisms regarding its long-term effectiveness, particularly in highly altered urban rivers. This study evaluates the spatiotemporal relationship between impervious surface extent relates to dissolved oxygen (DO) dynamics at 40 long-term stations over 30 years. Using national datasets, we analyze metrics such as summer DO minima and normalized DO flux to assess ecological resilience across development levels. Unlike previous studies that view urbanization as a linear degradation driver, this research introduces a gradient-based framework that differentiates between low, moderate, mid-, high, and highly urbanized areas. Preliminary findings suggest that mid-range urbanized watersheds with 40–60% impervious cover are vulnerable yet responsive to management, marking key intervention points. This approach advances urban ecological theory by identifying transitional watersheds as resilience tipping points and informs land-use planning, stormwater infrastructure, and policy. Linking water quality changes to built-environment indicators offers a replicable method for identifying vulnerable systems and guiding adaptive watershed governance.