Global and regional water availability and demand: Prospects for the future

One of the most pressing global issues currently facing mankind is the increase in world population and its impact on the availability of freshwater. Recent estimates of water stocks and flows through the world's hydrologic cycle and their spatiotemporal variability illustrate the nature of current and projected water disparities throughout the world. As all such problems manifest themselves at smaller scales, a major challenge in freshwater assessments is how to handle this on different geographical scales. Increasing use of water is creating water shortages in many countries that are projected to have significant population increases in the next 25 years. Humankind is projected to appropriate from 70% to 90% of all accessible freshwater by 2025. Agriculture is the dominant component of human water use, accounting for almost 70% of all water withdrawals. Hence, many of the solutions to water-related food and environmental security come from within agriculture by increasing the efficiency and productivity of water use. Many factors significantly impact the increasing water demand, including population growth, economic growth, technological development, land use and urbanization, rate of environmental degradation, government programs, climate change, and others. Demand management, not increasing supply availability, is the realistic way forward. Although, thanks to market forces, the threatened exhaustion of nonrenewable resources has not happened, renewable resources, such as freshwater, remain problematic because they are vulnerable to human overuse and pollution. Climate change adds further risks and uncertainties to the global picture requiring the adoption of adaptive management in water resources based on monitoring and reevaluation. Although climate change may be perceived as a long-term problem, it needs to be addressed now because decisions today will affect society's ability to adapt to increasing variability in tomorrow's climate. If we are to balance freshwater supply with demand, and also protect the integrity of aquatic ecosystems, a fundamental change in current wasteful patterns of production and consumption is needed. Recognition of the links between rapidly growing populations and shrinking freshwater supplies is the essential first step in making water use sustainable. © 2004 International Association for Mathematical Geology.