HR: 11:25h
AN: H22A-05 INVITED     [Abstracts]
TI: Review of the Isotope Aided Studies on the Water Balance of the Amazon Basin
AU: * Gat, J R
EM: Joel.Gat@weizmann.ac.il
AF: Weizmann Institute of Science, Dpt Environmental Sciences Weizmann Institute, Rehovot, 76100, Israel
AU: Salati, E
EM: salati@fbds.org.br
AF: Fundacoa Braseileira para Desenvolvimente SUSTENEVEL, Rua Eng.Alvaro Niemeyer 76, Rio deJaneiro, 22610-180, Brazil
AU: Victoria, R L
EM: reyna@cena.usp.br
AF: CENA-USP, Av. Centenario 303, Piracicaba, SP 13416-000, Brazil
AB: Early surveys of the isotope composition of precipitation throughout the Amazonian region, conducted by the GNIP program, revealed the absence of the expected Rayleigh depletion of the heavy isotopomers from the coast inland which would have resulted from the rainout along the trajectory. This was interpreted to be due to the re- introduction of the moisture into the atmosphere by transpiration and thus suggested that the isotope survey could verify the hydrological models, and further monitor any change in the water balance resulting from changes in the ecological structure, in particular deforestation. This required a closer look at the eco-hydrological processes at the lithosphere/ecosphere/atmosphere interface as they affect the isotopic composition of runoff and the evapo-transpiration flux. An observed increase of the d-excess parameter of precipitation from Belem to Manaus and Izobamba further indicated that evaporation from open-surface water also contributed to the moisture recycling in the basin ; the site of this effect, whether from canopy interception or flooded wetlands remains under investigation. The amount of the atmospheric moisture is a direct reflection of the water balance in the atmosphere; the resultant precipitation depends, in addition, on the dynamic structure of the atmospheric boundary layer which is also affected by ecological changes on the surface which affects among others the albedo, surface roughness and convectivity. Due to the limited amount of data on the isotope composition of the atmospheric vapour, one was limited so far in the quantitative interpretation of the isotopic data in terms of the effect of changes in the ecological structure on the water balance and precipitation pattern in Amazonia. The review will outline the new possibilities opening up from the recent advances in direct measurement of the isotopic composition of vapour and the MIBA data set. Suggestions for a continuing monitoring program will then be outlined.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0497 Wetlands (1890)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1818 Evapotranspiration
DE: 1840 Hydrometeorology
SC: Hydrology [H]
MN: 2007 Joint Assembly