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Water issues are rarely simple. At the global scale, water is at the focus of a powerful multifaceted challenge. Demands for both consumptive and nonconsumptive uses are growing, while climate change is at the same time decreasing availability in some places and increasing risks of heavy precipitation in many others. Through diverse mechanisms that interact with natural processes, human activities impact not only the quantity of water available but also its quality.

Water in its various forms–as salty ocean water, as sweet river water, or as rain–has played a major role in human myths, from the hypothetical, reconstructed stories of our ancestral “African Eve” to those recorded some five thousand years ago by the early civilizations to the myriad myths told by major and smaller religions today.

This essay defines the concept of water security and explores the implications of the eternal pursuit of it. Briscoe describes how water security is perceived by wealthy and by poorer nations, the tensions that arise from these differing views, and how these tensions are being resolved in a world in which the geography of economics and power is changing rapidly.

Nonpoint source pollution is the runoff of pollutants (including soil and nutrients) from agricultural, urban, and other lands (as opposed to point source pollution, which comes directly from one outlet). Many efforts have been made to combat both types of pollution, so why are we making so little progress in improving water quality by reducing runoff of soil and nutrients into lakes and rivers?

Water is a vital renewable resource that is increasingly stressed by multiple and competing demands from people, industry, and agriculture. When water becomes unavailable or unusable, life itself cannot be sustained. Changes in supply and demand for water are driven by population growth, climate change, and our energy and land use choices. Poverty frequently precludes the ability of many people to respond and adapt to water insecurity.

Water management activities involve a complex and interconnected web of science, infrastructure considerations, societal expectations, and institutional limitations that has evolved over time. Much of the water management system's current complexity developed in response to the interests of local water users and land owners, historical water supply and demand issues, political demands, and water quality and environmental considerations. Climate change poses a new set of questions for water managers and may require more flexible solutions than those that have evolved historically.

Geographical realities, population growth, and favorable economic conditions can create the impetus for investments in new technologies, while support by activist groups and NGOs can encourage more sustainable approaches using locally sourced water. New approaches–whether desalination, stormwater use, water recycling, or potable reuse–share a common path to mass adoption.

Static models used in economics and ecology ignore dynamic processes at work in both human and natural systems. In the case of water management, whether for quantity or quality, static models fail to connect changing human demands on water systems with changing supplies due to short-run climate variations and long-run climate change.

Water is an essential building block of the Earth system and a nonsubstitutable resource upon which humankind must depend. But a growing body of evidence shows that freshwater faces a pandemic array of challenges. Today we can observe a globally significant but collectively unorganized approach to addressing them. Under modern water management schemes, impairment accumulates with increasing wealth but is then remedied by costly, after-the-fact technological investments.