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Large-scale water projects to improve economic well-being or the environment often entail substantial uncertainty relating to gestation periods, cost, resettlement issues, adverse environmental impacts, and the potential for poor planning and execution as well as corruption. Because of widespread water scarcity, India has already invested a large amount of money in harnessing water resource projects. The government often uses cost-benefit analysis to assess large-scale projects, and, as knowledge of the technique grows, application of economic principles to small water projects has become more widespread. From small-scale projects like gray-water recycling at residential schools to analysis of the economic value of avoiding water-borne diseases, cost-benefit analysis can be used to inform decisions about how best to manage this precious commodity.

Themes that characterise urban wetlands in this century are: an association with human activities, especially development, education, and culture; invasive species management; migratory species feeding and breeding grounds; recognition by international environmental agreements; restored or constructed wetlands; and a role in providing for a focus of sustainability in the urban system. The chapter sets those themes in the context of the emerging paradigm of ecohydrology and the application of the ecosystem approach of the convention on biological diversity. For wetlands, especially in an urban context, understanding the linkage between ecology and hydrology — ecohydrology — is an important new way of thinking. Four key points that define ecohydrology are: understanding that ecosystem change is inevitable, and the role of people in managing change; integrating water and biodiversity science at management relevant spatial and temporal scales; understanding the role of ecosystem services; and defining and understanding the links between green and blue water. The role of blue and green water in an urban setting is also linked with human generated grey and black water, and linkages between these waters result in a range of semi-natural and artificial (or constructed) wetland ecosystems in urban landscapes. Human health in urban areas also depends on having well-functioning and well-managed ecosystems to provide a range of ecosystem services that support both human health, but also the health (functioning) of other ecosystems and their components. The chapter also identifies ten urgently needed research directions.