Nature provides essential services to humans, including climate regulation, water provisioning and regulation. These so-called ecosystem services have economical, societal and environmental value. This research aims at improving the knowledge on the linkages between selected hydrological ecosystem services and current and proposed land uses within the water-limited Mpushini/Mkhondeni Catchments in South Africa. The research contributes to the recognition of feedback and linkages within the complex ecological-human system, so that informed land use decisions can be made. The research aim is achieved by first reviewing the literature on hydrological ecosystem services, land use in an ecosystem services context and the links between the two. The study area is then sub-delineated into land use determined hydrological response units for baseline natural land cover, as well as for current and proposed land use scenarios. Using an appropriate model, selected hydrological processes are simulated in order to isolate the effects of individual land uses on hydrological responses, both on a local and a more catchment-wide scale. Various land uses were found to affect hydrological responses, such as runoff and its components of stormflows and baseflows, as well as transpiration and sediment yields, differently. These responses were found to be suitable indicators of selected ecosystem services such as water provisioning or flow regulation. Irrigation and high biomass crops, such as sugarcane and wattle plantations were found to reduce downstream water provisioning services. Degraded lands were found to reduce physical water quality through increased sediment yield, to reduce water provisioning during low flow periods, while the degraded lands increased stormflows, thereby reducing regulation of high flows. Urban land uses were found to significantly increase runoff, with increased impervious areas causing a shift from evaporation and transpiration towards runoff. Stormflows increased, with high flow regulation being reduced. Baseflows increased as well, as a result of a spill-over of runoff from impervious to pervious urban areas, which led to increased low flow regulation. In addition, in this study area urban return flows are generated from externally sourced water, further increasing streamflows and especially low flows. While urban areas showed an increase in downstream water quantity provision, the water quality was reduced. The combined effects of the current land use mosaic on the annual streamflows partially cancel each other out, while the proposed urbanisation dominated hydrological responses. Influences of various land uses on hydrological ecosystem services were thereby shown, which contributes to a better understanding of the linkages between the two. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2014.

Natural vegetation has been converted to land uses, such as agriculture, commercial forestry and urban use, to meet increasing human demands for food, fuel and shelter. These land use changes modify the surface conditions of an area, resulting in changes in hydrological responses. Urban land use, in particular, has a significant impact on catchment hydrology as a result of the increased impervious areas such as concrete, tar and roofs. To assess the future hydrological impacts of urban land use, the scale and location of future urban areas must be considered. The objective of this study was to assess the hydrological responses to future urban growth in the Mgeni catchment, South Africa. An urban growth model was used to generate scenarios of plausible future urban growth and these scenarios were modelled using a hydrological model to determine the hydrological responses to urban growth. The plausible future urban growth in the Mgeni catchment was modelled using the SLEUTH Urban Growth model (SLEUTH). The SLEUTH acronym stands for the input layers required for the model viz. Slope, Land use, Excluded areas, Urban Extent, Transport routes and Hillshade. SLEUTH is able to provide the scale and location of future urban growth required to assess the hydrological impacts of future urban growth. The data requirements and modelling procedure for SLEUTH is relatively simply and therefore it is well suited to a South African context. SLEUTH was calibrated and applied to the Mgeni catchment to project future urban land use. When assessing the 95-100% probability class, the results revealed that the Henley, Pietermaritzburg and Durban areas would experience the highest urban growth in the Mgeni catchment by the year 2050. The outputs of the SLEUTH Model for the Mgeni catchment showed a number of similarities to another application of SLEUTH in Cape Town. These similarities indicate the SLEUTH performs in a similar way for the two South African cities. Therefore, it was concluded that the SLEUTH Model is suitable to account for urban growth in the Mgeni catchment, as required for use in hydrological impact studies. The hydrological responses to urban growth in the Mgeni catchment were assessed using the ACRU model. The scenarios of plausible future urban growth generated by SLEUTH were overlaid with current land cover layers to generate maps of plausible future urban land use. The results showed extensive urban growth of >95% probability occurring in the Midmar, Albert Falls, Henley, Pietermaritzburg, Table Mountain, Inanda and Durban Water Management Areas (WMAs) by 2050. Increases in mean annual streamflows were observed in many of these areas; however the Henley, Pietermaritzburg and Table Mountain WMAs were shown to have greater increases in mean annual streamflow than the other areas that showed similar increases in urban growth, thus indicating that these WMAs could be particularly responsive to urban growth in the future. Furthermore, the results showed that the type of urban land use is important in determining the hydrological responses of urban land use, as the imperviousness differs between the different urban land uses. Streamflow responses were shown to be influenced by the scale and location of urban growth in the Mgeni catchment and specific areas, such as the WMAs along the Msunduzi River, were identified as potentially responsive to urban growth. Summer streamflows were indicated as being more responsive to urban land use changes than winter streamflows and increases in streamflows due to urban growth start to over-ride the impacts of other land uses which have substantial impacts on hydrological responses such as commercial forestry, and commercial sugarcane by 2050, whereas in other areas increases were mitigated by the presence of major dams. Lastly, it was shown that the type of urban land use, such as built up urban areas when compared to informal urban areas for example, have a significant impact on streamflow responses. These results are useful as they can be used to inform both water resources planning as well as urban planning to ensure that South Africa’s valuable water resources are protected. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.