Agrohydrological sensitivity analyses with regard to projected climate change in Southern Africa.
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Date
1997
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Abstract
Climate change resulting from the augmented "greenhouse effect" is likely to have significant
effects on the terrestrial hydrological system and the social and ecological systems linked to
it. Climate change could potentially affect inputs to the agrohydrological system such as
rainfall, temperature and potential evaporation; processes within the system such as vegetation
dynamics and crop production; and hydrological responses such as runoff, recharge of soil
water into the vadose zone and net irrigation demand. This study outlines the use of a daily
water budget model, ACRU, and SCENGEN, a climate change scenario generator, to assess
potential impacts of global climate change on agricultural production and hydrological
responses in southern Africa. This study also considers potential impacts of climate change on
plant response which may determine the extent of potential impacts of climate change on
agricultural production and hydrological response. Two approaches to climate change impact
studies are adopted for use in this study. The first, and more conventional approach considers
the impact of a specified climate change scenario, in this case developed with the use of
SCENGEN, on the terrestrial hydrological system. The second approach considers the degree
of climate change, in this case precipitation change, required to perturb the hydrological system
significantly in the various climate regimes found in southern Africa. A comparative analysis
of the sensitivity of selected hydrological responses to climate change produced the following
results, in ascending order of sensitivity: net irrigation demand < stormflow response < runoff
< recharge into the vadose zone. The impacts of a specific climate scenario change on
hydrological responses produced unexpected results. A general decrease in mean annual
precipitation over southern Africa is predicted for the future with SCENGEN. However,
widespread simulated increases in runoff, soil moisture content in the A- and B-horizon and
recharge into the vadose zone are obtained. These increases are a product of the CO2
"fertilisation" feedback, which is incorporated as a maximum transpiration suppression routine,
in the ACRU model. Net irrigation demand, which is not linked to this routine, is simulated to
increase in the future.
Description
Thesis (M.Env.Dev.)-University of Natal, Pietermaritzburg, 1997.
Keywords
Climatic changes., Crops and climate., Agriculture--Environmental aspects., Greenhouse effect, Atmospheric., Theses--Environmental Science.