Sustainable urban water management

Great advances in the development of compact and highly efficient water and energy reclamation plants from wastewater; landscape designs based on the efficient best management practices to control and buffer diffuse pollution; and water conservation call for a fundamental change in the way water, stormwater, and wastewater are managed. A paradigm of integrated water management has been emerging over the last ten years. This new paradigm of sustainable urban waters and watersheds is based on the premise that urban waters are the lifeline of cities and the focus of the movement towards more sustainable and emerging “green” cities (Novotny and Brown, 2007). The concepts of the new sustainable urban water management system and the criteria by which their performance will be judged include:

• integration of water conservation, stormwater management and wastewater disposal into a one system managed on a principle of a closed loop hydrologic balance concept (Novotny, 2007a; Heaney, 2007);

• consideration of designs that reduce risks of failure and catastrophes due to the effects of extreme events and are adaptable to future anticipated increases of temperature and associated weather and sea level changes (IPCC, 2002);

• decentralisation of water conservation, stormwater management and wastewater treatment into drainage and water/wastewater management clusters to minimise or eliminate long distance transfers, enabling water reclamation and energy recovery near the point of use (Heaney, 2007; Lucey and Barraclough, 2007). Decentralised management clusters with a simple water reclamation facility (e.g., a primary treatment followed by a wetland and/or a pond) are especially suitable for megacities in developing countries;

• incorporation of green LEED certified buildings (USGBC, 2005;2007) that reduce water use through conservation, with best management practices (BMP’s), including green roofs, rain gardens and infiltration;

• recovery of heat and cooling energy, biogas and fertilising nutrients (phosphorus) from sewage in the cluster water reclamation and energy recovery facilities (Engle, 2007; Barnard, 2007);

• implementation of new innovative and integrated infrastructure for reclamation, and reuse of highly treated effluents and urban stormwater for various purposes including landscape irrigation and aquifer replenishment (Hill, 2007; Ahern 2007; Novotny, 2007a; LEED criteria (USGBC, 2005, 2007) that

would also control and remove emerging harmful pollutants such as endocrine disruptors, THM precursors and pharmaceutical (drug) residues;

• minimisation or even elimination of long distance subsurface transfers of stormwater and wastewater and their mixtures (Heaney, 2007; Lucey and Barraclough, 2007);

• practicing environmental flow enhancement of effluent-dominated and flow-deprived streams (Novotny, 2007b); and ultimately providing a source for safe water supply (Lucey and Barraclough; 2007);

• implementation of surface stormwater drainage and hydrologically and ecologically functioning landscapes, making the combined structural and natural drainage infrastructure and the landscape far more resilient to the extreme meteorological events than the current underground infrastructure. The landscape design will emphasise interconnected ecotones (areas of transition between two or more ecosystems) connecting ecologically with viable interconnected surface water systems. Surface stormwater drainage is also less costly than subsurface systems and enhances aesthetic and recreational amenities of the area (Hill, 2007; Ahern, 2007);

• consideration of residual pollution loading capacity of the receiving waters as the limit for residual pollution loads (Rees, 1992, 2007; Novotny, 2007b), as defined in the Total Maximum Daily Load (TMDL) guidelines (US EPA, 2007), and striving for zero pollution load systems (Metcalf and Eddy, 2007);

• adoption and development of new green urban designs through new or reengineered resilient drainage infrastructure and retrofitted old underground systems interlinked with the daylighted or existing surface streams (Novotny 2007);

• reclamation and restoration of floodplains as ecotones buffering the diffuse (nonpoint) pollution loads from the surrounding human habitats and incorporation of best management practices that increase attenuation of pollution such as ponds and wetlands (Novotny, 2007a);

• connecting green cities, their transportation needs and infrastructure with drainage and receiving waters that would be ecologically based, protect the aquatic life, provide recreation and, by doing so, be acceptable to and desired by the public;

• consideration and promotion of changes in transportation in the future cities, relying more on clean fuels (hydrogen, electricity) and public transpiration by electric street cars, buses and trains;

• development of surface and underground drainage infrastructure and landscape that will 1. store and convey water for reuse, providing eco-

logical flow to urban flow deprived rivers, and allowing for safe downstream uses;

2. treat and reclaim polluted flows; and 3. integrate the urban hydrologic cycle with mul-

tiple urban uses and functions to make it more sustainable.