Elucidating coupled natural river-human-engineered systems in urbanized basins: A synthesis of data, model, and fractal theory

In urbanized river basins, sanitary wastewater and urban runoff from urban agglomerations are drained into complex engineered networks, treated at centralized wastewater treatment plants (WWTPs), and then discharged into river water bodies. Discharge from multiple WWTPs induces adverse impairments on the water-quality and aquatic ecosystem integrity of the receiving river bodies. Economic and engineering constraints determine the combination of wastewater treatment technologies used to meet the required environmental regulatory standards for treated wastewater discharged into river networks. Thus, it necessary to understand the coupled natural river-human-engineered systems (CNHES), to characterize their coupled relations, and to diagnose concomitant environmental pollution. My works involve data-model synthesis, which integrates publicly available and simulated data with the approaches of well-established fractal theory, network analysis and modeling. My talk aims to share highlighted findings on (1) the similarities and differences in the scaling and topology of engineered urban drainage networks (UDNs) in two cities, and further how these UDNs have evolved over decades; (2) the scaling and spatial organization of human populations, population equivalents, and WWTPs using geo-referenced data for WWTPs in large urbanized river basins in Germany; and (3) the evaluation of WWTP discharges’ hydrological and water-quality impacts on three large rivers in central Europe; and (4) the simulation of river algal responses to anthropogenic pressures. The quantitative measures and the basin-scale network model presented could be applicable to other large urbanized basins, providing a better understanding of the spatial distribution patterns of the CNHES and the resultant impacts on river water-quality impairment and further algal blooms.