HR: 0800h
AN: B11A-0130    [Abstracts]
TI: Modeling Hydrological Impact of Land-Use and Climate Change in West and Central Africa
AU: * Li, K Y
EM: kaiyuanli@wisc.edu
AF: The Center for Sustainability and the Global Environment, University of Wisconsin - Madison, 1710 University Ave., Madison, WI 53726 United States
AU: Coe, M T
EM: mtcoe@wisc.edu
AF: The Center for Sustainability and the Global Environment, University of Wisconsin - Madison, 1710 University Ave., Madison, WI 53726 United States
AU: Ramankutty, N
EM: nramanku@wisc.edu
AF: The Center for Sustainability and the Global Environment, University of Wisconsin - Madison, 1710 University Ave., Madison, WI 53726 United States
AU: De Jong, R
EM: dejongr@agr.gc.ca
AF: Ottawa Research Centre, AAFC, Central Experimental Farm, Ottawa, ON K1A 0C6 Canada
AB: Water resources are a particularly important issue in west and central Africa, where large portions of the continent are arid or semiarid and climate is highly variable. In the past 50 years, due to population growth this region has been experiencing land-use changes, including deforestation, overgrazing and reclamation. Meanwhile, there has been persistent drought since the 1960s. These land-use and climate changes have exerted a significant impact on the hydrological regime of this region. Therefore, a quantitative evaluation of the hydrological impacts of land-use and climate change is useful for water resource management. In this study, an investigation is conducted based on numerical simulations with a terrestrial ecosystem model, IBIS, and an aquatic transport model, HYDRA. The results show that deforestation (clearcutting) significantly increases the simulated stream flow by 34% ~ 65%, depending on location, despite the fact that tropical forests represent only a small portion (<5%) of the total basin area. Similarly, overgrazing (100% removal of grasslands) also increases simulated stream flow by 33% to 91%. The cultivation of crops significantly increases the simulated runoff, due primarily to shallow rooting depth, lower canopy cover in the early growing stage and lower transpiration demand. An increase of 10% in precipitation increases the simulated runoff by 26% ~ 48% (depending on the vegetation type); a similar decrease decreases the runoff by 24% ~ 32% (depending on the vegetation type). Changes in temperature by 1.5 øC do not cause any appreciable simulated hydrological changes. The numerical simulations indicate no significant impact on the water yield when deforestation (thinning) is below 50%, or the overgrazing is below 70% for savanna and 80% for grassland; however, the simulated water yield dramatically increases with land cover changes above these thresholds. This threshold effect, which has important implications for water resource management strategies, is reasonably explained by the nonlinearity of the separate response of transpiration and evaporation to the land cover changes.
DE: 3210 Modeling
DE: 1655 Water cycles (1836)
DE: 1803 Anthropogenic effects
DE: 1833 Hydroclimatology
DE: 1860 Runoff and streamflow
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting