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Schachtschneider K.,South African Council for Scientific and Industrial Research | Schachtschneider K.,University of Cape Town | Reinecke K.,Southern Waters Ecological Research and Consulting cc
Water SA | Year: 2014

Riparian tree species, growing under different conditions of water availability, can adapt their physiology to maximise their survival chances. Rivers in South Africa may flow perennially, seasonally or ephemerally (episodically). Different riparian species are adapted to survive under each of these different flow regimes by making use of surface, ground, soil, rainwater, or some combination of these. These water sources are available to varying degrees, depending on local climatic, hydrological, geohydrological and geomorphological conditions. This paper tests physiological differences among trees along rivers with varying flow regimes. In this study 3 parameters were selected and tested, namely wood density, specific leaf area and water use efficiency through stable carbon isotope measurements. All three parameters are quick, simple and cheap to determine and as such their value for standard-procedure river monitoring programmes or environmental flow requirement procedures was tested. Acacia erioloba is an arid-adapted riparian tree along the ephemeral Kuiseb (Namibia) and Kuruman (South Africa) Rivers that shows decreasing specific leaf area and increasing wood density correlating with deeper groundwater levels. Intraspecific changes for specific leaf area and carbon isotope values were demonstrated for Acacia mellifera and Croton gratissimus at varying distances from the active channel of the seasonal Mokolo River (South Africa). No significant differences in physiology were noted for Salix mucronata, Brabejum stellatifolium and Metrosideros angustifolia, growing along the perennial Molenaars and Sanddrifskloof Rivers (South Africa) under reduced flow conditions. Only the measurement of specific leaf area recurrently showed that significant physiological differences for trees occurred along rivers of the drier flow regime spectrum (seasonal and ephemeral). As such, this physiological measurement may be a valuable indicator for water stress, while the other measurements might provide more conclusive results if a larger sampling size were used. Specific leaf area, in conjunction with other carefully picked water stress measurement methods, could be considered for monitoring programmes during environmental flow assessments, river health monitoring exercises and restoration projects. This would be particularly valuable in rivers without permanent flow, where there is little species-specific knowledge and where current monitoring methods are unsuited. Source


Reinecke M.K.,Southern Waters Ecological Research and Consulting cc | Reinecke M.K.,Stellenbosch University | Brown C.A.,Southern Waters Ecological Research and Consulting cc | Brown C.A.,University of the Western Cape | And 4 more authors.
Wetlands | Year: 2015

Plant species are known to be distributed on river banks in a sequence of community zones from the water’s edge to the outer riparian area. The interplay between flow and landscape is thought to drive the existence of these zones, and specifically, between a lower zone that is inundated most years and an upper zone that is inundated less frequently. There remains no consensus on the number of zones present, what their links to flow might be or whether the same zones occur in different basins. This paper reports on the number and nature of vegetation zones along South African rivers in different geographical areas and their relationship to the flow regime. River bank sites in four climatic areas of South Africa were found to support four vegetation zones (in two groups) despite major differences in vegetation community types, climate and patterns of river flow. The Wet bank and Dry Bank zones were separated at an elevation that correlated well with the 1:2 year flood line. If vegetation zones along rivers can be linked in this generic way to the flow regime of a river, it will strengthen our ability to predict vegetation changes likely to occur with flow modifications. © 2015, Society of Wetland Scientists. Source


Dollar E.S.J.,MWH Global | Nicolson C.R.,University of Massachusetts Amherst | Brown C.A.,Southern Waters Ecological Research and Consulting cc | Turpie J.K.,University of Cape Town | And 6 more authors.
Water Policy | Year: 2010

Despite the transition to democracy in 1994, South Africa still had apartheid legislation on the statute books and the allocation ofwater was regulated by the 1956 Water Act. Accordingly, post-apartheid South Africa underwent a water sector reform process culminating in the new National Water Act (No. 36) of 1998. One component of theAct is the requirement for a classification system to determine different classes of water resources. The classification system providesa definition of the classes that are to be used and a seven-step procedure to be followed in order to recommend a class. The class outlines those attributes society requires of different water resources. The economic, social and ecological implications of choosing a classare established and communicated to all interested and affected parties during the classification process. This paper outlines the socioeconomic and political context in which the WRCS was developed and outlines the seven-step procedure. © IWA Publishing 2010. Source

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