HR: 17:27h
AN: B14A-06    [Abstracts]
TI: Land Cover Change Effects on Hydrological and Biogeochemical Functions in the Mekong River Basin: Insights From Macro-Scale Hydrologic and Biogeochemical Models.
AU: * Costa-Cabral, M C
EM: cabral@hydro.washington.edu
AF: Department of Civil and Environmental Engineering, University of Washington, Seattle, USA., Box 352700, Seattle, WA 98195-2700 United States
AU: Richey, J E
EM: jrichey@u.washington.edu
AF: Department of Chemical Oceanography, University of Washington, Box 357940, Seattle, WA 98195-7940 United States
AU: Goteti, G
EM: ggoteti@uci.edu
AF: Department of Civil and Environmental Engineering, University of Washington, Seattle, USA., Box 352700, Seattle, WA 98195-2700 United States
AU: Goteti, G
EM: ggoteti@uci.edu
AF: Department of Earth System Science, University of California, Croul Hall, Irvine, CA 92697-3100 United States
AU: Lettenmaier, D P
EM: lettenma@hydro.washington.edu
AF: Department of Civil and Environmental Engineering, University of Washington, Seattle, USA., Box 352700, Seattle, WA 98195-2700 United States
AU: Snidvongs, A
EM: anond@start.or.th
AF: Southeast Asia START Regional Center, SWU Pathumwan Building Number 5, Henri Dunant Road, Bangkok, 10330 Thailand
AB: Concerns with the high rates of deforestation in the tropics include the possible impacts on species diversity, hydrologic response, biogeochemical cycles and water quality, topsoil erosion, atmosphere chemistry, and land surface-atmosphere interactions affecting climate. Our work is concerned with hydrologic response and stream biogeochemistry under the monsoonal climate of Southeast Asia. How are the different components of the terrestrial hydrological cycle affected by changes in land cover, such as conversion of forest to agricultural land? Field observations have confirmed local hydrologic effects; but how do localized changes in land cover affect the streamflow at a distance downstream? How does land cover affect the flow response to rainstorms? How does it affect dry season flows? What are the main implications for stream biogeochemistry? Finally, how might each of these effects turn out under altered climate conditions, such as higher average temperature and modified precipitation patterns? We apply the macro-scale Variable Infiltration Capacity (VIC) model to the Mekong basin (795,000 sq.km) in Southeast Asia at a resolution of 5 arc-minutes (roughly, 9 km), using climate forcing from 1979-2004, long-term stream-flow records, historical land cover, and hypothetical land cover and climate scenarios. We consider not only the replacement of forest cover with permanent agriculture, but also the often prevalent but little studied deforestation for swidden cultivation, succeeded by secondary regrowth. Field studies and a simple model attempt to capture effects on stream biogeochemistry. While soil-vegetation-atmosphere transfer schemes (SVATS) have recently been incorporated into GCMs, use of such models to study the impacts on the hydrologic response of river basins has been limited, particularly in the humid tropics.
DE: 1655 Water cycles (1836)
DE: 1812 Drought
DE: 1821 Floods
DE: 1866 Soil moisture
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting