The United Nations World Water Development Report 2009

Volume I - Water in a Changing World; Volume II - Facing the Challenges

image of The United Nations World Water Development Report 2009

The Third edition of the United Nations World Water Development Report (WWDR3), “Water in a Changing World” was officially launched on March 16, 2009 at the 5th World Water Forum in Istanbul, Turkey. The WWDR3 builds on the work of previous studies, including the two previous WWDRs, “Water for People, Water for Life” (WWDR1), presented at the 3rd World Water Forum in Japan in 2003, and “Water: A Shared Responsibility” (WWDR2), presented in 2006 at the 4th World Water Forum in Mexico. However, the third edition of the Report presents several changes from the previous two editions. Unlike the earlier Reports which were structured along UN agency lines, the third Report has a new, holistic format. A number of themes are addressed through out the report, including climate change, the Millennium Development Goals (MDGs), groundwater, biodiversity, water and migration, water and infrastructure, biofuels, etc.



Changes in the global water cycle

Water is essential to life, sustainable economic growth and the functioning of ecosystems. These are all affected by variations in water storage and fluxes at the land surface – storage in soil moisture and groundwater, snow, and surface water in lakes, wetlands and reservoirs – and precipitation, runoff and evaporative fluxes to and from the land surface. Water planners have generally seen these key elements in the land surface water cycle as at least approximately statistically stationary, their challenge being to characterize and buffer against natural variability. Over the last several decades, however, studies of changes in streamflow, snowpack and evapotranspiration have made it increasingly clear that the assumption of statistical stationarity is no longer defensible. Arguing that ‘stationarity is dead’, at least for water planning, some researchers are making the case for a new initiative in water management to deal with nonstationarity problems.1 Meeting this challenge requires understanding the nature of observed changes in the land surface water cycle – the objective of this chapter.


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