Human appropriation of renewable fresh water

Science

Volumn 271, Issue 5250, 1996, Pages 785-788

  Postel, Sandra L ^a   Daily, Gretchen C ^b   Ehrlich, Paul R ^b  

^a Global Water Policy Project   (United States)

^b STANFORD UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

FRESH WATER; RUNOFF;

AGRICULTURE; ARTICLE; ECOLOGY; EVAPORATION; LAND USE; POPULATION GROWTH; PRIORITY JOURNAL; RESERVOIR; WATER SUPPLY;

DAM CONSTRUCTION; FRESHWATER RESOURCES; RESOURCES USE; WATER MANAGEMENT;

EID: 0029667904     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.271.5250.785     Document Type: Article

References (36)

1. A relatively small volume of fresh water is transported longer distances by tanker to supply drinking water to water-scarce areas.
2. S. Postel, Last Oasis: Facing Water Scarcity (Norton, New York, 1992)
3. P. H. Gleick, Int. Secur. 18, 79 (summer 1993); N Myers, Ultimate Security: The Environmental Basis of Political Stability (Norton, New York, 1993) .
4. P. H. Gleick, Int. Secur. 18, 79 (summer 1993); N Myers, Ultimate Security: The Environmental Basis of Political Stability (Norton, New York, 1993) .
5. I. A. Shiklomanov, in Water in Crisis: A Guide to the World's Fresh Water Resources, P. H Gleick, Ed. (Oxford Univ. Press. New York, 1993), pp. 13-24
6. P H Gleick, Ed , Water in Crisis: A Guide to the World's Fresh Water Resources (Oxford Univ. Press, New York, 1993).
7. I. L'Vovich et al., in The Earth as Transformed by Human Action, B L Turner et al , Eds (Cambridge Univ Press, Cambridge, 1990), pp. 235-252.
8. P. M. Vitousek, P R. Ehrlich, A H Ehrlich, P A. Matson, Bioscience 36, 368 (1986).
9. G. L. Ajtay, P. Ketner, P Duvigneaud, in The Global Carbon Cycle, B. Bolin, E. T. Degens, S. Kempe, P. Ketner, Eds. (Wiley, New York, 1979), pp 129-182.
10. Our global estimate conforms well to values derived from small-scale field studies with crops [B. A. Stewart, J. T. Musick, D. A Dusek, Agron. J 75, 629 (1983); Yield Response to Water (U.N. Food and Agriculture Organization, Rome, 1979); Z Zixi, B A Stewart, F. Xiangjun, Field Crops Res. 36, 175 (1994)].
11. Our global estimate conforms well to values derived from small-scale field studies with crops [B. A. Stewart, J. T. Musick, D. A Dusek, Agron. J 75, 629 (1983); Yield Response to Water (U.N. Food and Agriculture Organization, Rome, 1979); Z Zixi, B A Stewart, F. Xiangjun, Field Crops Res. 36, 175 (1994)].
12. Our global estimate conforms well to values derived from small-scale field studies with crops [B. A. Stewart, J. T. Musick, D. A Dusek, Agron. J 75, 629 (1983); Yield Response to Water (U.N. Food and Agriculture Organization, Rome, 1979); Z Zixi, B A Stewart, F. Xiangjun, Field Crops Res. 36, 175 (1994)].
13. 1990 Production Yearbook (U N Food and Agriculture Organization, Rome, 1991), with adjustments for United States and Taiwan based on data from U.S. Department of Agriculture.
14. E. Czaya, Rivers of the World (Van Nostrand Reinhold, New York, 1981).
15. Population estimates from C Haub and M. Yanagishita, Population Reference Bureau (personal communication, Washington, DC, January 1995).
16. M. Dynesius and C Nilsson, Science 266, 753 (1994).
17. 3 annually, just under 5% of the combined average annual flow of the Copper and Stikine rivers, leaving 95% of their flow still remote [Alaskan Water for California? The Subsea Pipeline Option - Background Paper (U.S Office of Technology Assessment, Washington, DC, 1992)].
18. Uncaptured flood runoff provides a variety of human benefits, including support of flood-recession farming, fisheries, and generation of hydroelectricity; however, in these capacities, its use is either insignificant globally or does not involve actual appropriation.
19. 3 of capacity usable for runoff storage on an average annual basis
20. 3/ha is closer to the actual global average application rate. Moreover, the California figures account only for on-farm water applications and do not include the portion of diversions lost to seepage or evaporation between reservoirs and farmers' fields
21. 3/year, which is equal to 12% of the Nile's average annual flow [J A Allan, in The Nile: Sharing A Scarce Resource, P. P. Howell and J. A. Allan, Eds (Cambridge Univ Press, Cambridge, 1994), pp 313-320]
22. H. E Schwarz, J Emel, W. J. Dickens, P Rogers, J. Thompson, in The Earth as Transformed by Human Action, B. L. Turner et al., Eds. (Cambridge Univ Press, Cambridge, 1990), pp 253-269.
23. Even in the countries of the Organization for Economic Cooperation and Development, domestic wastewater treatment is estimated to cover only ∼60% of the population [A. K. Biswas, Water Int. 17, 68 (February 1992)]. Information for developing countries is sparse, but treatment coverage is certainly far lower Moreover, few regions control for farm runoff and other dispersed pollution sources that add substantial quantities of sediment, pesticides, and fertilizers to water bodies
24. Even if wastewater treatment coverage should become nearly universal, substantial instream flows would still be required to maintain fisheries, support recreational demands, and satisfy other instream needs. For example, California's instream environmental water requirements (after omission of the north coast hydrologic region, which contains several wild and scenic rivers and thus may not be indicative of instream needs more narrowly defined) equal 22% of average annual runoff [California Water Plan Update (California Department of Water Resources, Sacramento, CA, 1994).
25. We did not consider it feasible to estimate accessible ET in a manner comparable to our estimate of AR. To be conservative, we therefore assumed all terrestrial ET to be accessible.
26. Wangnick Consulting, 1990 IDA Worldwide Desalting Plants Inventory (International Desalination Association, Englewood, NJ, 1990)
27. P. H. Gleick, Annu. Rev. Energy Environ. 19, 267 (1994)
28. J A. Veltrop, in Water for Sustainable Development in the Twenty-first Century, A. K Biswas, M. Jellali, G. E. Stout, Eds. (Oxford Univ. Press, Oxford, 1992), pp. 102-115.
29. Status of Dam Construction. 1991 (International Commission on Large Dams, Paris, 1992). suggests that ∼300 dams are now commissioned each year, but these data include only 64 countries
30. A. P Covich [in (5), pp. 40-55] indicates that large dams are currently being completed at an average rate of 500 per year, or 56% of the rate of the period from 1950 to 1986.
31. 3 would be live storage for water supply.
32. Even as dam construction is adding to the total stable runoff, other human activities are reducing it Deforestation and the paving over of aquifer recharge areas often reduce rainwater infiltration, thereby reducing base flow and increasing surface flood runoff. More important globally, many reservoirs are tosing active storage capacity faster than originally estimated because of rapid siltation from deforestation, soil erosion, and generally poor watershed management The Nizamsagar reservoir in India, for instance, lost more than 60% of its capacity over 40 years [M. Newson, Land, Water and Development: River Basin Systems and Their Sustainable Management (Routledge London, 1992]. Lacking global estimates, we make no subtraction for these losses.
33. P. E Waggoner, Ed , Climate Change and U S. Water Resources (Wiley, New York, 1990).
34. National Research Council, Restoration of Aquatic Ecosystems (National Academy Press, Washington, DC, 1992).
35. 1994 World Population Data Sheet (Population Reference Bureau, Washington, DC, 1994).
36. We gratefully acknowledge comments from W Falcon, P. Gleick, R. Naylor, A. Vickers, P. Vitousek, and two anonymous reviewers. Supported by a grant from Charles and Nancy Munger, the Winslow and Heinz foundations, and an anonymous donor.