Global climate change is a naturally occurring phenomenon, influencing weather and climate
patterns. However, the greatest cause for concern at present is the rate at which climate
change is currently occurring. Natural shifts in climate take place over a period of many
thousands of years, not in a matter of decades, which is what is occurring at present. In South
Africa, climate change is projected to have different regional effects, which in turn could
impact on the components of the terrestrial hydrological system, such as land use. The
alteration of the catchment upstream of the estuaries could affect the quantity and quality of
streamflows entering estuaries. This could impact negatively upon estuaries, thereby
reducing the considerable biodiversity in estuaries and the ecosystems goods and services
provided by estuaries which would reduce the significant revenue provided by these systems.
The research undertaken in this project investigates the possible effects of climate change,
and changes in upstream land use on freshwater inflows into estuarine ecosystems using a
daily hydrological model. Owing to the regionality of climate change in South Africa 10
estuaries in different climatic regions were selected for this investigation. Climate output
from five GCMs under the SRES A2 climate scenario for the present (1971 – 1990),
intermediate (2046 – 2065) and distant future (2081 – 2100) periods was used as input for the
selected climate input. Results of these simulations show that the eastern regions of South
Africa may experience considerable increases in the occurrence of high intensity rainfall
events into the future. This could influence the abiotic factors of the system which may
impact upon the biotic components of estuaries, as these systems are physically controlled.
In the western regions the difference of the magnitude of flows between present and projected
future is minimal. However, projected increases in temperature could influence evaporation,
thereby decreasing future flows into estuaries. This, in some instances, may result in systems
turning hyper-saline, which could have far reaching implications, both ecologically and
economically.
Additionally, an investigation, as to the possible effects of irrigation and climate change
combined on flows entering and breaching events of the Klein estuary, was undertaken.
Hence, simulations including and excluding irrigation routines have been completed. Results
from these simulations illustrate the detrimental effects of irrigation into the future periods,
especially during 1 in 10 low flow years, when flows into the Klein estuary cease completely.
Breaching event results illustrate that climate change could have a negative impact on this
estuarine system as the number of events decreases into distant future period. The addition of
agricultural abstractions decreases the number of breaching events markedly. Therefore, the
link between the marine and terrestrial hydrological systems is lost which could, if this
estuary is isolated from the ocean for an extended period of time, become extremely
detrimental to the ecological integrity of the Klein estuary. This highlights the value and
vulnerabilities of estuarine ecosystems in South Africa to future climate and upstream land
use changes. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/8571 |
| Date | January 2012 |
| Creators | Davis, Nicholas Savile. |
| Contributors | Schulze, Roland E., Kunz, Richard P., Stuart-Hill, Sabine I. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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