Change in land cover and water abstraction : modelling runoff effects in the Bot River Catchment

[摘要] River basins have long been attracting human settlement and development, promising water andfertile lands (Newson 1992). The Bot River Catchment on the southern coast of South Africa isno exception. However, much of the development in this catchment has not been controlled andits land and water resources are being abused. This is affecting the water quality and quantity ofthe river system and estuary at an alarming rate.In this thesis, the 'reference' land cover in the Bot River Catchment is recreated. This term isused to describe 'the hydrological state of the catchment as it was when completely covered innatural vegetation, thus before it was impacted by humans (Jacobs & Bruwer 2002:12). Arainfall-runoff model is employed to investigate the effects of various land covers on thecatchment's runoff quantity, by comparing the simulation results of the catchment's referenceand current state.The results of the model point to a large reduction in runoff since the reference state of thecatchment. As the rainfall-runoff model applied did not allow for modelling of the annualagriculture that dominates the catchment, the runoff reduction was attributed to the smaller areasof perennial agriculture, forestry and alien vegetation infestation. The simulation resultsconfirmed the threat of current land use practices on the environmental integrity of the Bot RiverCatchment. A transition to agricultural practices that are more suited to the climate is suggestedand the eradication of alien vegetation should be seen as a priority. Most importantly, a holisticapproach should be taken towards the management of the Bot River Catchment.The altered hydrodynamic regime of the Bot River Estuary is symptomatic of misuse of theentire catchment. As ongoing demographic and land use pressures create a new generation ofwater management problems (Department of Water Affairs & Forestry 1993), a deeperunderstanding of the relationships between the different components in the Bot River Catchmentbecomes increasingly urgent.

[发布机构] Stellenbosch University