摘要：The World Commission for Water in the 21st Century estimated the annual cost of meeting future infrastructural needs for water at US$180 billion by 2025, including supply, sanitation, waste-water treatment, agriculture, and environmental protection. These estimates assume that future global demand for water-related services will mimic those of industrialised nations that rely on centralised water supply and treatment infrastructural systems. This large annual expenditure excludes an estimated US$40 billion that will be invested annually on new hydropower dams and other large-scale water transfer systems. These estimates exclude the environmental and social cost from improperly designed dams, and the true long-term cost to society will be many times greater. Many hydropower schemes are at risk from irregular flow regimes resulting from drought and climate change, while increased land-use intensity leads to sedimentation rates that diminish reservoir storage capacity. Methane emissions from rotting vegetation can be higher than displaced fossil-fuel power plants, while fragmented aquatic habitats and altered flow regimes threaten biodiversity and inland fisheries – a primary protein source for millions of poor people. We present evidence that a value-adding and risk-minimising water planning process can be achieved by shifting from the conventional focus on supply expansion to one that concentrates on efficiently delivering services at and near the point of use. The State of California has two decades of experience with this approach, demonstrating that market-based policy and regulatory innovations can unleash efficiency gains resulting in more utility water services and energy services delivered with less supply expansion at lower costs, while minimising climate-change risk, pollution and the social cost that accompany large infrastructural projects. Efficiency in delivered water services could be accomplished with investments in the range of US$10-25 billion annually, while obviating the need for spending hundreds of billions of dollars on more expensive hydropower and related infrastructural expansion projects. The shift to a regulatory system that encompasses cost-effective end-use efficiency improvements in delivering water and energy services could eliminate the need for an estimated half of all proposed dams globally, thus allowing for the maintenance of other ecosystem service benefits and offer the best hopes of meeting basic human needs for water at a more achievable level of investment.
