Quantifying Mass Fluxes from Urban Drainage Systems to the Urban Soil-Aquifer System (11 pp)

• Published in: Journal of soils and sediments 2007-06, Vol.7 (2), p.85-95
• Main Authors: Wolf, Leif, Klinger, Jochen, Hoetzl, Heinz, Mohrlok, Ulf
• Format: Article
• Language: English
• Subjects: Aeration zone; AISUWRS (Assessing and Improving the Sustainability of Urban Water Resources and Systems); Aquifer systems; Aquifers; Boron; Case studies; Cities; Contaminants; contamination; Decision support systems; Drainage systems; Emissions; Fertilizer application; Groundwater; Groundwater recharge; Hydrologic cycle; infiltration; leakages; mass balance; Moisture content; Monte Carlo simulation; Risk assessment; scenarios; Sensitivity analysis; Sewer systems; sewers; Soil water; Studies; Sustainability; Urban areas; Urban drainage; urban soil and aquifer system; vulnerability concepts; Water flow; Water pollution; Water resources; Water sampling; Water shortages; Water supply; Water use
• ISSN: 1439-0108; 1614-7480
• DOI: 10.1065/jss2007.02.207

Background, Aim and Scope The urban soil and aquifer system is subject to contamination not only by event-based accidents and spillages but also by the constant emissions from urban drainage systems. Leaky sewer systems, decentralized stormwater infiltration measures or fertilizer application to gardens are omnipresent in the urban soil-water system. Due to the spatial variability and complexity of the input, only few attempts have been undertaken to balance the mass fluxes to the urban soil-groundwater system by using integrated modeling of urban water supply and drainage systems. However, considering the protective function of the soil for the groundwater system, planning authorities are in need of a decision support system, especially regarding the impact of leaky sewer systems. The European Union funded project AISUWRS (Assessing and Improving the Sustainability of Urban Water Resources and Systems) was completed at the end of the year 2005. The overall scope of the initiative was to assess and improve the sustainability of urban water resources and systems with the help of computer tools. Materials and Methods This was achieved by the development of a chain of different models to describe and link urban water supply, urban drainage, including sewer leakage, the unsaturated zone, and urban groundwater systems. The uppermost model applied in the AISUWRS system is the Urban Volume and Quantity model (UVQ), developed by CSIRO, Australia. Its main input parameters are climate records, water consumption characteristics (e.g. water use for laundry or typical contaminant loads through toilets) and urban sealing coefficients. The model calculates water flows and contaminant loads through the wastewater and stormwater systems and assesses direct recharge to groundwater. This information is fed into the specially developed Network Exfiltration and Infiltration Model (NEIMO), which estimates the amount of wastewater exfiltration from or the groundwater infiltration into sewers. The results of the AISUWRS model chain are compared with a Monte Carlo simulation approach which explicitly addresses the uncertainties included in estimations of sewer leakage. Results A holistic description of the urban water cycle was derived. All major water fluxes were quantified together with loadings of marker substances (e.g. chloride, potassium, boron, sulphate, zinc). Extensive groundwater sampling programs constrained the results of the forward modeling exercises. This paper con