1. Comments on the role of a surface water mission in the context of global water issues Dennis P. Lettenmaier Department of Civil and Environmental Engineering University of Washington Seattle, WA CNES/NASA Surface Water Working Group Meeting Toulouse November 16, 2004

3. Domestic consumptive use (U.S.) is ~200-250 liters/day Compare with drinking water requirement (about 5 l/day). U.S. domestic consumption has declined slightly over the last two decades. Much of difference between potable water requirement and use is sanitation, laundry, etc. Industrial requirement in developed world is of same order as domestic Total water withdrawals are about 6000 km 3 /yr Compare with global (land) precip ~150,000 km 3 /yr (or global runoff ~0.4 x runoff)

4. Table courtesy Peter Gleick

6. Figure courtesy of world soil information, Wageningen University

8. (Oki, et. al, 2002, IHE-UNESCO) Caribbean North America Central America South America South America WestAfrica Oceania East & South East Asia SouthAsia USSR North West Africa WesternEurope MiddleEast 1~55~10 10~15 15~20 20~30 30~50 50< Importer based, over 5 km 3 /y km 3 /y (Based on Statistics from FAO etc., for 2000) 78.5 33.5 46.2 57.5 38.8 36.4 An Adaptation Strategy to Cope with Scarcity? “Virtual Water” flow in 2000 (cereals only)

9. Global Reservoir Database Location (lat./lon.), Storage capacity, Area of water surface, Purpose of dam, Year of construction, … 13,382dams,

10. Global Water System Project IGBP – IHDP – WCRP - Diversitas

11. Global Water System Project IGBP – IHDP – WCRP - Diversitas Human modification of hydrological systems

12. Reservoir construction has slowed. All reservoirs larger than 0.1 km 3

13. Visual from Palmieri, NAS Sackler symposium, 2004

14. The Global Picture ● Water resource issues will have large effects on many of the world’s major decisions in the next 50 years. ● 1 billion people live on less than $1/day. ● More than 1.2 billion have inadequate drinking water (poor quality, insufficient quantity, but still priced beyond the means of the poorest), and twice that many (2.5 billion) lack sanitation facilities. ● Poorly handled: could result in wars and will result in premature deaths, poor quality of life for many, and widespread degradation of aquatic ecosystems. ● Well handled: opportunities for scientific and political creativity, international collaboration, promoting cooperation rather than discord.

15. Unmet Basic Human Needs for Water 1.1 billion people lack access to adequate drinking water (mostly in Africa and Asia). 2.4 billion people lack access to adequate sanitation services. 2.2 to 5 million die annually from preventable water-related diseases.

16. Gleick 2001 The link between water use and economic growth can be broken

17. Widespread efficiency improvements are possible, in all sectors 1930s: 200 tons of water per ton of steel 1980s: 20-30 tons of water per ton of steel 2002: 2-3 tons of water per ton of steel (and we are changing the structure of our economy…) Agricultural water use can drop and yields can increase with better irrigation technology.

18. Possible role and implications of a global surface water mission Free and open exchange of global hydrologic data (which presently does not exist) Understanding how reservoirs are operated (presently there is no coherent data base for reservoir storage) Water and human health (2 billion incidences of waterborne diseases per year globally!)