Agriculture
; Catchments
; Decision making
; Evaporation
; Moisture
; Rain
; Soil moisture
; Vegetation
; Eddy covariance towers
; Ground based measurement
; Meteorological measurements
; Meteorological station
; Remotely sensed data
; Sensible and latent heat fluxes
; Temperature variance
; Turbulent flux measurements
; Forestry
英文摘要:
Rain-fed farming is the primary livelihood of semi-arid west Africa. Changes in land cover have the potential to affect precipitation, the critical resource for production. Turbulent flux measurements from two eddy-covariance towers and additional observations from a dense network of small, wireless meteorological stations combine to relate land cover (savanna forest and agriculture) to evaporation in a small (3.5km2) catchment in Burkina Faso, west Africa. We observe larger sensible and latent heat fluxes over the savanna forest in the headwater area relative to the agricultural section of the watershed all year. Higher fluxes above the savanna forest are attributed to the greater number of exposed rocks and trees and the higher productivity of the forest compared to rain-fed, hand-farmed agricultural fields. Vegetation cover and soil moisture are found to be primary controls of the evaporative fraction. Satellite-derived vegetation index (NDVI) and soil moisture are determined to be good predictors of evaporative fraction, as indicators of the physical basis of evaporation. Our measurements provide an estimator that can be used to derive evaporative fraction when only NDVI is available. Such large-scale estimates of evaporative fraction from remotely sensed data are valuable where ground-based measurements are lacking, which is the case across the African continent and many other semi-arid areas. Evaporative fraction estimates can be combined, for example, with sensible heat from measurements of temperature variance, to provide an estimate of evaporation when only minimal meteorological measurements are available in remote regions of the world. These findings reinforce local cultural beliefs of the importance of forest fragments for climate regulation and may provide support to local decision makers and rural farmers in the maintenance of the forest areas.
Department of Civil Engineering, Faculty of Applied Sciences, University of British Columbia, Vancouver, BC, Canada; Laboratory of Environmental Fluid Mechanics and Hydrology, School of Architecture, Civil and Environmental Engineering, Swiss Federal Institute of Technology, Lausanne, Switzerland; Department of Civil Engineering and Geosciences, Delft University of Technology, Delft, Netherlands; Department of Geological Sciences and Engineering, University of Nevada, Reno, NV, United States; Laboratory Hydrology and Resources in Water, International Institute for Water and Environmental Engineering (2iE), Ouagadougou, Burkina Faso
Recommended Citation:
Ceperley N,C,, Mande T,et al. Evaporation from cultivated and semi-wild Sudanian Savanna in west Africa[J]. Hydrology and Earth System Sciences,2017-01-01,21(8)