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While natural floods play a crucial role in shaping the composition of aquatic communities, the most rivers worldwide are regulated or dammed for anthropogenic purposes, resulting in alterations to the biological and chemical composition of these ecosystems. Studies have demonstrated various negative effects of river regulation on aquatic invertebrate communities globally. However, there is a scarcity of research in Africa, despite its vulnerability to anthropogenic impacts. This study aimed to compare aquatic invertebrate communities in the Phongolo River, an impacted regulated river, and the Usuthu River, a less impacted unregulated river, in South Africa. It further aimed to ascertain whether Lake Nyamithi, a naturally saline lake receiving water from both of the aforementioned systems, exhibited a stronger similarity to one of the two rivers in terms of its aquatic invertebrate composition. Aquatic invertebrate and water samples were collected from 2012 to 2018 over several surveys. The Usuthu River demonstrated a diverse and sensitive aquatic invertebrate community, emphasising its high conservation value. The Phongolo River demonstrated effects of anthropogenic impact, with taxa more resilient to changes in water quality and flow compared to the Usuthu River. Mismanagement and excessive water use may lead to the loss of any remaining sensitive aquatic invertebrate communities in this river. The presence of invasive molluscan in the Phongolo River and Lake Nyamithi also poses a threat to the native aquatic invertebrate communities. These invasive species are currently absent from the Usuthu River although other invasive species, such as the Australian redclaw crayfish, are found in both river systems. Lake Nyamithi displayed a unique aquatic invertebrate community, distinct from both rivers and their floodplains. This study provides important baseline information on the Usuthu River's aquatic invertebrates and emphasises the need to maintain adequate water flow in rivers and floodplains to protect biodiversity and sensitive species. [ABSTRACT FROM AUTHOR]

Vegetation cover in catchments in semi-arid environments with distinct rain seasons is important in influencing water quality and availability through its effect on runoff and groundwater recharge. This study assessed catchment-scale vegetation cover and condition, indicated by land degradation and vegetation vigour, using recent rain season Landsat TM/ETM+ images supplemented by dry season images for comparison. Image classification into vegetation density categories was used in mapping land degradation, the bare land category used as indicator. Vegetation vigour indicates vegetation productivity levels, and has been shown to correlate with the NDVI in similar previous studies. The 30 savanna biome vegetation types in the catchment were used as strata for assessing relative vigour using NDVI values. The NDVI frequency distributions per vegetation stratum were normal (Gaussian), the location of whose peaks enabled comparisons. Land degradation could be mapped with certainty mainly in the vicinity of settlements. Rivers draining through degraded areas had elevated colour and turbidity values. As the NDVI profiles per vegetation type could be explained by the land use and landscape position context of the vegetation types, NDVI profiling proved useful for assessing vegetation condition. NDVI profiling of vegetation types is potentially useful in monitoring savanna vegetation condition using remotely sensed images. [ABSTRACT FROM AUTHOR]

The concept of water neutrality, based on its carbon equivalent, was first coined during the World Summit on Sustainable Development in 2002. Since then the term has been loosely used, with little quantitative validation. Here we present a first quantitative framework for a water-neutral scheme that allows a private water user to balance its water account through both demand- and supply-side interventions. Such innovative voluntary mechanisms can provide benefits in a chronically water stressed and developing country, such as South Africa. This scheme seeks to harness private sector investment in water security, by allowing investors to balance quantitatively their water account based on sound scientific rationale. Investors are required to engage in a three-step process of: reviewing their water usage, implementing a reduction strategy, and replenishment of water to hydrological systems through the investment in watershed services, equivalent to their water usage. Initially, the scheme allows participants to replenish quantitatively their water usage through investment in the clearing of water-intensive invasive alien plants. The project, however, encourages the innovation and development of further quantitative mechanisms for investing in watershed services, and proposes an operational model for the promotion of a water-neutral market in South Africa. [ABSTRACT FROM AUTHOR]

Water is considered an essential nutrient because the body cannot produce enough water itself, by metabolism of food, to fulfil its need. When the quantity or quality of water is inadequate, health problems result, most notably dehydration and diarrhoea. As a result of contaminated water and poor hygiene, related infections are still a serious problem. Indeed, in the South African setting water availability and sanitation are critical issues because of the prevalence of childhood diarrhoea and also the HIV/AIDS crisis. Though considerable efforts have been made to improve the water and sanitation problems in South Africa – especially with regard to water supply infrastructure – there is still room for much improvement. Water is a healthy alternative to calorie-dense, non-nutritive beverages, such as artificial fruit drinks and soda. The latter should be avoided as they contribute little other than energy and may contribute to overweight and obesity. Also, they displace more nutritious foods from the child's diet. Consumption of fruit juice should also be limited. These issues highlight the need for a specific guideline relating to water intake in the paediatric food-based dietary guidelines. [ABSTRACT FROM AUTHOR]

The invasion of fynbos shrublands by woody weed species can reduce the water yield from catchment areas dramatically. We modelled the consequences of uncontrolled invasion on water yield using a geographical information system (Arc/info). Five important processes were recognized: the occurrence of fire; the spread and establishment of alien plants after fire; rainfall-to-run-off ratios; growth and changes in biomass between fires; and effects of these changes on streamflow. The simulations of water yield were modelled with the Arc/Info GRID module using a 200 × 200-m grid. It was assumed that the interval between fires was 15 years and that proliferation and dispersal of alien plants took place only after fires. Between fires, the model simulated the growth of the vegetation and its effects on streamflow, using relationships between rainfall and run-off, and run-off and aboveground biomass. Results for the Kogelberg area in the Western Cape Province showed that alien plants invaded about 40% of the grid cells within 50 years. Cover of alien plants increased from an initial estimate of 2.4% to 62.4% after 100 years. Invasion of catchment areas would result in an average decrease of 347 m3 of water per hectare per year over 100 years, resulting in average losses of more than 30% of the water supply to the city of Cape Town. In individual years, where large areas would be covered by mature trees, losses would be much greater. In addition, invasion of fynbos by alien plants will cause the extinction of many plant species, increase the intensity of fires, destabilize catchment areas with resultant erosion and diminished water quality, and decrease the aesthetic appeal of mountain areas. Control of alien weed species is necessary to avert the above impacts, and the costs of control operations could be justified by the savings achieved in maintaining adequate water run-off from stable catchments in the long term. [ABSTRACT FROM AUTHOR]