Estimated impacts of soil degradation on the African water balance and climate
Issue Date
1998Author
Feddema, Johannes J.
Publisher
Inter Research
Type
Article
Article Version
Scholarly/refereed, publisher version
Published Version
http://www.int-res.com/articles/cr/10/c010p127.pdfMetadata
Show full item recordAbstract
This study uses a well-established water balance methodology, the Thornthwaite-Mather
approach, to evaluate the effects of soil water holding capacity assumptions on estimates of African
evapotranspiration rates, moisture deficit, and moisture surplus conditions. Under constant climate
conditions, the model tests the impact of using a constant 150 mm soil water holding capacity compared
to using a newly derived soil water holding capacity data set (the Dunne-Willmott data set). The study
also uses a worldwide survey of soil degradation between 1950 and 1980 (GLASOD: Global Assessment
of Soil Degradation) to evaluate the impacts of human-induced soil degradation on local water
balances. The GLASOD data are used to alter local soil water holding capacities based on the Dunne-
Willmott data to simulate human soil degradation patterns in Africa. Results indicate that the use of
simplified soil water holding capacities can lead to significant errors in estimated evapotranspiration
rates and water surplus and deficit conditions in Africa. Regions most affected are those with seasonal
wet and dry climates, which are also those locations with the greatest climate variability. Because these
are often the climates most studied to detect and model environmental change, it is important that
accurate soil moisture estimates be used to simulate climate conditions in these regions. Results also
indicate that soil degradation occurring over a 30 yr period (1950 to 1980) has had a significant impact
on local water resources. The greatest impacts of these changes are in some of the more productive
agricultural areas in the wetter sub-humid climates. Changes include increased runoff during wet
seasons and an extended drought period during the dry seasons. Given that these agricultural systems
have less flexibility to respond to long-term desiccation as compared to pastoral systems, this could lead
to significant changes in local growing seasons and perhaps overall productivity in the future.
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Citation
Feddema, J.J. (1998): Estimated Impacts of Soil Degradation on the African Water Balance and Climate. Climate Research, 10(2): 127-141.
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