The Future of Global Water Scarcity: Policy and Management Challenges and Opportunities

Article excerpt

Water is a ubiquitous natural resource covering approximately three-quarters of the Earth's surface. However, almost all of the water on the planet (over 97 percent) is saline ocean water, unusable by most terrestrial organisms. Of the remaining three percent, more than two-thirds is sequestered as ice and snow at high elevations or latitudes and is functionally unavailable, leaving less than one percent of global water as both fresh and potentially available for meeting human needs (Figure I).1 While this fraction of available fresh water is small compared to the overall volume of water on the planet, this supply has been sufficient to meet historic needs. During the past century, water availability has become a prominent global concern, particularly as demands for fresh water have grown beyond our capacity to meet them.

Inefficient or non-existent water management regulations and policies, often combined with a lack of financial capital and a poor understanding of how local systems function, have perpetuated unsustainable water management practices. As a result, over-allocation and inefficient use of water resources have significantly diminished supplies in many areas.2 Groundwater mining - where resources are removed at rates exceeding that at which they are recharged - has led to dramatic drops in water table levels in India, the United States, and Mexico threatening water supplies, the health local ecosystems, and future food security.3 Water quality degradation exacerbates these problems as pollution, poor sanitation, industrial waste, and salinization render available water sources unusable.

In response to these problems, more governments are discarding old water management practices that ignore the socio-economic and environmental aspects of water use, and instead are adopting a new management framework that re-envisions water from a more holistic perspective. This paradigm shift on water resource use and development is designed to promote sustainability by accounting for the full range of water needs (social, economic, environmental) across sectors (agriculture, urban, industrial, ecosystem) through institutional coordination (local, regional, national, international). While the new framework seeks to integrate multiple facets of water resource development, this additional complexity makes implementation more difficult. This commentary highlights the extensive differences between the new framework and past management practices, and argues that future policies must actively support sustainable water management practices in order for these practices to succeed.

DEFINING WATER SCARCITY

Water scarcity is determined to occur when there is not enough clean water to meet human needs; however, more complex assessments may take into consideration environmental needs, individuals' capacity to access local resources, and multiple spatial or temporal scales.4·5 Since there is no universal standard for how water scarcity should be analyzed, several measures currently exist for assessing global water scarcity. The Falkenmark Water Stress Index (1989) is one of the earliest assessments and measures water availability as a function of population, accounting for differences between "genuine" water scarcity- a lack of water due to climate or drought, and "human-induced" water scarcity - a reduction in water availability due to poor management or overpopulation.6 Based on this definition, "degrees of scarcity" ranging from "limited water stress" (>1,700 m^sup 3^/person/year) to "absolute water scarcity" (<500 m^sup 3^/person/year) were developed based on a per capita minimum of 100 liters per day. While scientists have used this simple measure frequently over the past two decades to assess global water scarcity, others have developed alternative indices and assessments of varying complexity. Rijsberman4 provides a useful review of the most commonly referenced global water scarcity indexes, including the Water Poverty Index and the Water Scarcity Index. …