The water strategies of the twentieth century helped to supply drinking water, food, flood control and electricity to a large proportion of the human population. Indeed it is hard to fathom today's world of 6.5 billion people and $55 trillion in annual economic output without the vast network of dams, reservoirs, pumps, canals and other water infrastructure now in place. These projects, however, have dismantled valuable “ecological infrastructure”— the river systems, floodplains, watersheds and wetlands that provide critical services to society. When functioning well, this eco-infrastructure not only supplies water and fish, it captures seasonal floodwaters, recharges groundwater, filters pollutants, purifies drinking water, and delivers nutrients to coastal fisheries. This eco-infrastructure often delivers these services more cost-effectively than technological solutions do. Moreover, with water stress and climate change impacts unfolding more rapidly than scientists had predicted even five years ago, the value of safeguarding the robustness and resilience of nature's way of mitigating floods, droughts and other natural disasters is rising.

Policies and strategies designed to meet human needs while protecting this eco-infrastructure are critical to human well-being. Scientific understanding of the components of aquatic ecosystem health has advanced markedly over the last decade, but the incorporation of this knowledge into water policy and management has lagged. The establishment of a “sustainability boundary” that caps ecological degradation is key to safeguarding ecosystem services and to driving up water productivity—the value derived from each unit of water extracted from the natural environment. Globally, at least a doubling of water productivity will be needed by 2025. Fortunately, a number of nations and regions, including Australia, the European Union, South Africa, and the Great Lakes are pioneering policies that establish such boundaries and begin to reshape water use.