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1 van der Kwast, J.; Yalew, S.; Dickens, C.; Quayle, L.; Reinhardt, J.; Liersch, S.; Mul, Marloes; Hamdard, M.; Douven, W. 2013. A framework for coupling land use and hydrological modelling for management of ecosystem services. International Journal of Environmental Monitoring and Analysis, 1(5):230-236. [doi: https://doi.org/10.11648/j.ijema.20130105.18]

Land use ; Hydrology ; Simulation models ; Ecosystem services ; Water management ; Water resources ; Indicators / South Africa / KwaZulu-Natal Province / uThukela Catchment

(Location: IWMI HQ Call no: e-copy only Record No: H046237)

http://article.sciencepublishinggroup.com/pdf/10.11648.j.ijema.20130105.18.pdf
https://vlibrary.iwmi.org/pdf/H046237.pdf

(0.51 MB) (525.01KB)

It is well known that land-use changes influence the hydrological cycle and that those changes in the hydrological cycle influence land use. The sophisticated spatial dynamic planning tools that have been developed in the last decades to support policy makers in the decision making process do not take into account the mutual feedbacks between land use and hydrology. In this study a framework for an integrated spatial decision support system is presented where the feedbacks between land use and hydrology are taken into account by coupling the SITE (Simulation of Terrestrial Environments) land-use model to the SWIM hydrological model. This framework enables policy makers to assess the impact of their planning scenarios on ecosystem services using a web-based tool that interactively presents trends in space and time of spatial indicators derived from both models. This approach is tested for the uThukela area, which is located along the northern areas of the Drakensberg Mountains which form the border between Lesotho and South Africa. The region is extremely important for its catchment-services as water derived from it is pumped into the Vaal River supplying water to the city of Johannesburg. Because of poor management of ecosystem services, less water is produced by the catchment more erratically, siltation levels are increasing and less carbon is retained in the soil. Biodiversity is threatened by grazing livestock, alien plants and other poor land management practices. In addition, overstocking, frequent burning and lack of soil protection measures have caused rill and gully erosion in areas of communal ownership where an overall management policy is lacking. The presented framework for a spatial integrated decision support system is currently being implemented and will be used by policy makers to assess policies developed for an Environmental Management Framework (EMF). Scenarios will be defined during stakeholder workshops. A prototype of the decision support system has been developed, but not all data necessary for modelling and calibration is yet available. From the analysis of land-use maps of 2005 and 2008 it was observed that forest and bush decreased, while settlements, subsistence farming, commercial farming and grassland increased.

2 Yalew, S.; Pilz, T.; Schweitzer, C.; Liersch, S.; van der Kwast, J.; Mul, Marloes L.; van Griensven, A.; van der Zaag, P. 2014. Dynamic feedback between land-use and hydrology for ecosystem services assessment. In Ames, D.P., Quinn, N.W.T., Rizzoli, A.E. (Eds.). Proceedings of the 7th International Congress on Environmental Modelling and Software, San Diego, California, USA, 15-19 June 2014. Manno, Switzerland: International Environmental Modelling and Software Society (iEMSs). 8p.

Hydrology ; Ecosystem services ; Land use ; Catchment areas ; Grasslands ; Biomass ; Soils ; Case studies / South Africa / uThukela Catchment

(Location: IWMI HQ Call no: e-copy only Record No: H046491)

http://www.iemss.org/sites/iemss2014/papers/iemss2014_submission_255.pdf
https://vlibrary.iwmi.org/pdf/H046491.pdf

(0.48 MB) (495.82 KB)

Ecosystem services assessment requires an integrated approach, as it is influenced by elements such as climate, hydrology and socio-economics, which in turn influence each other. However, there are few studies that integrate these elements in order to assess ecosystem services. Absence of integrated approach to modelling hydrological and land-use changes, for instance, often oversights the dynamic feedback between the two processes. Dynamic changes in land-use should be fed into hydrological models and vice-versa at each time-step for a more realistic representation. In this study, this approach is demonstrated with a case study of the uThukela catchment, South Africa. There is an increasing pressure on grasslands in the catchment. The grassland supports livestock grazing, one of the main economic and social service for the communal farmers. High livestock population causes degradation of the grasslands, and increasing demand for agricultural lands decreases the extent of the grazing lands. In addition, this is further influenced by changes in climate, and has multiple impacts, such as increased erosion and changing flow regime. The SITE (SImulation of Terrestrial Environments) land-use change model and the SWIM (Soil and Water Integrated Model) hydrological model were coupled at code level to account for these processes. The two models exchange land-use maps (from SITE) and biomass production (from SWIM). SWIM was modified to produce biomass output. Grassland capacity for grazing service is determined through biomass coming from SWIM. Likewise, the simulated land-use change is passed back to the hydrological model to determine effects of land-use change on hydrological components. Preliminary result of the interactions between the two models and its use for estimating grazing capacity show that through the coupled models, sustainable level of grassland grazing locations were easily identifiable.