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Global water balance – can we refine it?

IWRA World Water Congress 2008 Montpellier France
2. Towards the Future: Water Resources and Global Changes

Keyword(s): global water balance, hydrological cycle, water on Earth

AbstractGlobal water balance – can we refine it? Vincent Kotwicki Kuwait Institute for Scientific Research Water Resources Division, Hydrology Department P.O. Box 24885 Kuwait Safat 13109 Tel: (+965) 4 98 98 86 Fax: (00985) 4 98 98 19 Email address: vkotwicki@safat.kisr.edu.kw Preferred mode of presentation: Oral Suggested sub-theme: 1 – Water availability, use and management Abstract The paper reviews new developments in geophysics and planetary disciplines on water accumulation and presence in the interior of the Earth and its hydrosphere and presents a compact picture of the occurrence of water on Earth, including the temporal development of water resources of the planet, current water balance, and the future of water on Earth. In examining of numerous standard hydrological references and new developments in quantification of the water resources of planet Earth, several corrections are proposed to the hydrological water balance of Earth. While most of considerations of water resources is concerned with volumes, it is the surface area of open waters which dictates water exchange between the surface of Earth and its atmosphere. The paper demonstrates that the area of open water surfaces on land is at least 10% higher than quoted by recent hydrological references, which has obvious implications for climatic models and a range of other applications. The paper stresses the need for improvements in our understanding of the hydrological cycle and presents several conclusions on the ways of improving the monitoring of long-term changes of these variables to get a coherent picture of effects of climatic changes and global warming. Water on Earth is in a state of constant flux and this fact will be reflected in future versions of water balances of Earth. The static version of the water balance, such as presented in standard references and encyclopedias may serve as an illustration at an introductory level, but the accelerating development in sciences and the ever increasing need to account for quickly dwindling water resources per capita will soon result in much more sophisticated solutions. Nobody would question the practicality of having exact figures on global water storages month after month and year after year, so the real question is: how quickly we can convince ourselves that we can do it?
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