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ECONOMIC DEVELOPMENT AND WATERImage: Tony H. F. WongGreen corridors and constructed wetlands are multifunctional green infrastructure, providing ecosystem services including water quality improvement,micro-climate enhancement, flood conveyance and increasing biodiversityto reduce their dependency on externally sourced water, includingdesalination of seawater, by accessing locally derived waterin a portfolio of water sources. A serious departure from nineteenthand twentieth century thinking? Yes. The old plans andprecepts are unworkable, as even the current state of cities makesclear. Traditional mechanisms of governance yield fragmentedinfrastructure and compartmentalized service provision. Thesereductive ‘either/or’ approaches have had their day and new, holistic,integrated solutions are called for. We need more sophisticatedperceptions of system boundaries, whereby a city may be seen asboth a generator and a consumer of essential resources. Embracingthe concept of diverse water supplies and mixed infrastructureswill give cities enormous flexibility, freeing them to access a wealthof sources at minimal cost. Each of the alternative water sourceswill have its own level of reliability and its own environmentalcost-and-risk profile. In a future water sensitive city, each sourcecan be optimized through diversified and parallel infrastructures– for water harvesting, water treatment and new ways of storageand delivery. Depending on a city’s particular conformation andneeds, the mix might include both centralized and decentralizedelements – from a simple rainwater tank for non-potable use tolarge-scale schemes for redirecting or reusing water.The second pillar supporting water sensitive cities, cities providingecosystem services, has a place close to the first. Like it, thispillar stands against traditional ways that have outworn their usefulness;but now the principle is broader. We may consider it under theheading ‘water sensitive urban design’ (WSUD). The water sensitivecity must provide green infrastructure more generally,not just a sustainable water catchment for itself – theimperative upheld by the first pillar.Landscapes are the product of both natural andhuman forces, interacting in regional ecosystemsand beyond. Public spaces are essential to publicamenity – or putting it differently, to the materialconditions that enable human flourishing. However,urban landscapes must be functional beyond providingamenity. Our conception of the value inherent inopen space needs to be enlarged, by consideration ofthe ecological functioning of urban landscapes. Thisexpanded view encompasses great diversity: sustainablewater management, microclimate influences,facilitation of carbon sinks, use of ‘low-mileage’ foodproduction, environments for wildlife and more.Excluding the urban environment from this interwovenfabric is yet another reductive, binary-thinkingnotion that has outstayed its welcome. Three broadthemes characterize the ecological design objectivesfor urban landscapes: nature conservation (buildingand conserving biodiversity, in terrestrial and aquaticenvironments of the city); urban-rural interfacemanagement (protecting and rehabilitating highconservationareas regardless of where they are found,and mitigating the environmental impacts of urbanization);and urban ecology (urban design incorporating[ 276 ]