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Water quality indices are commonly used to provide summary information from water quality monitoring programmes to stakeholders. However, declining funding and changing mandates often result in reduced monitoring frequencies which could affect the accuracy of information provided. Thus, this study aimed to assess the effect of water sampling frequency on water quality index reporting using the the upper uMngeni catchment as a study site. A 28-year time series of water quality data from 11 sampling stations was assessed for pH, electrical conductivity, temperature, turbidity, total suspended solids, Escherichia coli counts, NH4-N, NO3-N, PO4-P and total phosphorus. Statistical packages were used to process the data and water quality indices (WQIs) for eutrophication and recreational water were calculated and their sensitivity to input parameters analysed. It was found that the higher the monitoring frequency, the lower the WQI calculated at all sites. This suggests that water quality, due to a declining monitoring frequency, is poorer than reported in the uMngeni catchment. The findings showed that Escherichia coli and turbidity are the most influential variables affecting the recreational and eutrophication WQIs, respectively. Although WQIs are considered a useful tool for monitoring the changes in water quality across space and over time in the uMngeni Catchment, their use should complement, and not substitute for, other, more comprehensive, water quality management tools. [ABSTRACT FROM AUTHOR]

South Africa is a semi-arid country which frequently faces water shortages, and experienced a severe drought in the 2016 and 2017 rainfall seasons. Government is under pressure to continue to deliver clean water to the growing population at a high assurance of supply. Studies now show that the delivery of water may be sustained not only through built infrastructure such as dams and pipelines, but also through investment in ecological infrastructure (EI). Part 1 of this paper in 2 parts concentrated on the role of EI in delivering water-related ecosystem services, as well as the motivation for this study, and the methods used in modelling and mapping the catchment. Part 2 explores and illustrates the current level of delivery of water-related ecosystem services in different parts of the catchment, with potential hydrological benefits of rehabilitation and protection of EI in the uMngeni catchment. The Mpendle, Lions River, Karkloof, Inanda and Durban sub-catchments are important areas for the generation of streamflows which accumulate downstream (i.e. water yield in the catchment) when annual totals are considered. Modelled annual sediment yield (in tonnes) from naturally vegetated areas is most severe in the lower catchment areas with steeper slopes such as Inanda, and in the high-altitude areas which have both steeper slopes and higher rainfall. The central and eastern parts of the uMngeni catchment were found to contribute the greatest yield of sediment from degraded areas with low protective vegetation cover. This combined modelling and mapping exercise highlighted areas of priority ecosystem service delivery, such as higher altitude grassland areas, which could be recommended for formal conservation, or protection under private partnerships. Generally, these areas confirm the intuitive sense of catchment stakeholders, but provide a robust and more defendable analysis through which water volumes are quantifiable, and potential investment into catchment interventions are justified. [ABSTRACT FROM AUTHOR]

South Africa is a semi-arid country which frequently faces water shortages, and experienced a severe drought in the 2016 and 2017 rainfall seasons. Government is under pressure to continue to deliver clean water to the growing population at a high assurance of supply. Studies now show that the delivery of water may be sustained not only through built infrastructure such as dams and pipelines, but also through investment in ecological infrastructure (EI). A daily time-step hydrological model was used to map areas which should be prioritised for protection or rehabilitation to sustain the delivery of water-related ecosystem services within the uMngeni catchment. We focused on three water-related ecosystem services, i.e.: water supply, sustained baseflow, erosion control/avoidance of excessive sediment losses. The two key types of degradation were modelled, namely, overgrazing and the invasion of upland areas by Black Wattle (Acacia mearnsii). This, Part 1 of a paper in 2 parts, provides a discussion on the role of EI in delivering water-related ecosystem services, describes the motivation for the study, and the methods used in modelling and mapping the catchment. The results of this modelling exercise are presented in Part 2, which also explores and illustrates the potential hydrological benefits of rehabilitation and protection of EI in the uMngeni Catchment. [ABSTRACT FROM AUTHOR]

Despite numerous studies, little is known about the quality of rainwater harvested (RWH) from roofs or overland flow by smallholder farmers of Africa. Thus, the main objective of this study was to compare the physical and chemical quality of the rainwater harvested from both dwelling roofs and yards situated in a smallholder community in KwaZulu-Natal (South Africa). Rainwater samples were collected at 51 households during a dry period for assessment of the concentration of specific chemical elements. The water harvested from metallic roofs and yards did not meet the World Health Organization (WHO, 2011) guidelines for drinking water, as it exceeded recommended levels of Se, Al, B and Cd in at least 75% of the roof water samples, and of Al in the case of yard RWH. Compared to yard water, RWH from metallic roofs exhibited higher B, Se, Ni, Pb, Cu, As, Cd, and Cr but lower dissolved organic carbon (DOC), NO3 -, Fe, SO24 2-, Na, Mg, Ca, K, Fe concentrations. The content of nutrients and DOC in the water harvested from the surface correlated with the number of pigs per household (with r = 0.78 for SO24 2-, r = 0.74 for DOC and r = 0.52; NO3 -). These results are expected to inform improved design and implementation of RWH. Further investigations should consider both physicochemical and microbiological aspects of water quality to provide a more holistic understanding of potential health risks. [ABSTRACT FROM AUTHOR]

The spatial representativeness of total evaporation estimates (ET) acquired from conventional approaches is limited, as these techniques generally provide site-specific values. The use of satellite earth observation has shown a great deal of potential in capturing spatially representative hydro-meteorological flux data and therefore represents a practical alternative for estimating ET. However, one of the challenges facing ET estimation using satellite earth observation data is the effect of clouds, which reduce the number of satellite images available for use. The objectives of this paper were firstly to validate satellite-derived ET estimates against estimates acquired from a surface renewal system and, secondly, to assess the feasibility of two infilling techniques to create a daily satellite-derived ET time series. The Surface Energy Balance System (SEBS) model was used to derive daily ET using MODIS imagery. Two infilling approaches, the Kc act approach and a linear interpolation approach, were evaluated by comparing their respective values against in-situ ET measurements, as well as SEBS ET estimates derived using MODIS. The results showed that SEBS ET estimates were approximately 47% higher and produced R² and RMSE values of 0.33 and 2.19 mm·d-1, respectively, compared to in-situ ET values. The ET estimates obtained by applying the Kc act approach and the linear interpolation approach compared favourably with the in-situ ET values, producing RMSE values of 0.9 mm·d-1and 0.6 mm·d-1, respectively. However, comparisons of ET estimates acquired by applying the Kc act approach and the linear interpolation approach against the SEBS ET indicated a poor match, yielding RMSE values of 1.96 mm·d-1and 1.54 mm·d-1, respectively. [ABSTRACT FROM AUTHOR]

Sweet sorghum (Sorghum bicolor (L.) Moench) has been recognized globally as a potential biofuel crop for ethanol production. Sweet sorghum is a drought-tolerant crop that is widely adapted to different environmental growing conditions. The aim of this study was to determine the water use efficiency (utilisable yield per unit amount of water used) of drip-irrigated sweet sorghum (variety Sugargraze) under two different climatic conditions in South Africa. The sweet sorghum trials were conducted at Ukulinga research farm (University of KwaZulu-Natal, Pietermaritzburg) and Hatfield experimental farm (University of Pretoria, Pretoria), South Africa. Field trials were conducted in two successive seasons, viz., 2010/11 and 2011/12. Seasonal water use was estimated using eddy covariance and surface renewal methods. Fresh and dry aboveground biomass yield, stalk yield and stalk Brix % were measured at final harvest. Theoretical ethanol yield was calculated from fresh stalk yield and Brix %. Water use for the two growing seasons was 415 mm at Ukulinga and 398 mm at Hatfield. The ethanol water use efficiency (WUE) values for the sweet sorghum at Ukulinga were 0.27 and 0.60 L.m-3 for 2010/11 and 2011/12 growing seasons, respectively. The ethanol WUE estimate of the sweet sorghum at Hatfield was 0.53 L.m-3 for the 2010/11 season and 0.70 L.m-3 for the 2011/12 growing season. WUE estimates of the sweet sorghum crop were higher for Hatfield compared to Ukulinga research farm. The results from this study showed that the WUE of sweet sorghum was sensitive to plant density. The WUE values confirm that sweet sorghum has high WUE under different climatic conditions. [ABSTRACT FROM AUTHOR]

A combination of measurement and modelling was used to find a pragmatic solution to estimate the annual total evaporation (ET) from the rare and indigenous Nkazana Peat Swamp Forest (PSF) on the east coast of Southern Africa to improve the water balance estimates within the area. Total evaporation was measured during three window periods (between seven and nine days each) using an eddy covariance (EC) system on a telescopic mast above the forest canopy. Sapflow of an understory and an emergent tree was measured using a low maintenance heat pulse velocity system for an entire hydrological year (October 2009 to September 2010). An empirical model was derived, describing the relationship between the observed ET of the Nkazana PSF measured during two of the window periods (R = 0.92 and 0.90) which, overlapped with sapflow measurements, thereby providing hourly estimates of predicted ET of the Nkazana PSF for a year, totalling 1125 mm (while rainfall was 650 mm). In building the empirical model, it was found that including the understory tree sapflow provided no benefit to the model performance. In addition, the observed emergent tree sapflow relationship with observed ET between the two field campaigns was consistent and could be represented by a single empirical model (R = 0.90; RMSE = 0.08 mm). During the window periods of EC measurement, no single meteorological variable was found to describe the Nkazana PSF ET satisfactorily. However, in terms of evaporation models, the hourly FAO56 Penman-Monteith equation best described the observed ET from EC during the August 2009 (R² = 0.75), November 2009 (R² = 0.85) and March 2010 (R = 0.76) field campaigns, compared to the Priestley-Taylor model (R² = 0.54, 0.74 and 0.62 during the respective field campaigns). From the empirical model of ET and the FAO56 Penman-Monteith equation, a monthly crop factor (Kc) was derived for the Nkazana PSF providing a method of estimating long-term swamp forest ET from meteorological data. The monthly crop factor indicated two distinct periods. From February to May, it was between 1.2 and 1.4 compared with June to January, when the crop factor was 0.8 to 1.0. The derived monthly Kc values were verified as [ABSTRACT FROM AUTHOR]

The use of remote sensing technology as a tool to estimate leaf area index (LAI) for use in estimating canopy interception is described in this paper. The establishment of commercial forestry plantations in natural grassland vegetation, results in increased transpiration and interception which in turn, results in a streamflow reduction. Methods to quantify this impact typically require LAI as an input into the various equations and process models that are applied. Remote sensing provides a potential solution to effectively monitor the spatial and temporal variability of LAI. This is illustrated using Hyperion hyperspectral imagery and three vegetation indices, namely the normalized difference vegetation index (NDVI), soil adjusted vegetation index (SAVI) and Vogelmann index 1 to estimate LAI in a catchment afforested with Eucalyptus, Pinus and Acacia genera in the KwaZulu-Natal midlands of South Africa. Of the three vegetation indices used in this study, it was found that the Vogelmann index 1 was the most robust index with an R2 and root mean square error (RMSE) values of 0.7 and 0.3 respectively. However, both NDVI and SAVI could be used to estimate the LAI of 12 year old Pinus patula accurately. If the interception component is to be quantified independently, estimates of maximum storage capacity and canopy interception are required. Thus, the spatial distribution of LAI in the catchment is used to estimate maximum canopy storage capacity in the study area. [ABSTRACT FROM AUTHOR]

Water productivity in smallholder rain-fed agriculture is of key interest for food and livelihood security. A frequently advocated approach to enhance water productivity is to adopt water harvesting and conservation technologies (WH). This study estimates water availability for in situ WH and supplemental water demands (SWD) in smallholder agriculture in the Thukela River Basin, South Africa. It incorporates process dynamics governing runoff generation and crop water demands, an explicit account of the reliability of in situ WH, and uncertainty considerations. The agro-hydrological model SWAT (Soil and Water Assessment Tool) was calibrated and evaluated with the SUFI-2 algorithm against observed crop yield and discharge in the basin. The water availability was based on the generated surface runoff in smallholder areas. The SWD was derived from a scenario where crop water deficits were met from an unlimited external water source. The reliability was calculated as the percentage of years in which the water availability ≥ the SWD. It reflects the risks of failure induced by the temporal variability in these factors. The results show that the smallholder crop water productivity is low in the basin (spatiotemporal median: 0.08-0.22 kgm-3, 95% prediction uncertainty band (95PPU). Water is available for in situ WH (spatiotemporal median: 0-17mmyear-1, 95PPU) which may aid in enhancing the crop water productivity by meeting some of the SWD (spatiotemporal median: 0-113mmyear-1, 95PPU). However, the reliability of in situ WH is highly location specific and overall rather low. Of the 1850 km2 of smallholder lands, 20-28% display a reliability ≥25%, 13-16% a reliability ≥50%, and 4-5% a reliability ≥75% (95PPU). This suggests that the risk of failure of in situ WH is relatively high in many areas of the basin. [ABSTRACT FROM AUTHOR]

Water temperatures, and in particular daily maximum water temperatures, are a critical water quality parameter. An understanding of associated resource management issues, including links between water temperature variability and aquatic diversity values, should be part of any management programme that considers river systems. Simple rule-based models have been shown to be appropriate tools within an adaptive management approach, both because of their heuristic value and in their application for scenario generation. Such a model was developed to simulate changes in the condition factor of Chiloglanis anoterus [Crass, R.S., 1960. Notes on the freshwater fishes of Natal with descriptions of 4 new species. Annals of the Natal Museum 14, 405-458] (Pisces: Mochokidae) in response to annual frequency of exceedance of a threshold temperature under three broad environmental scenarios for part of the Sabie River falling within South Africa's Kruger National Park. This model has potential for application within the adaptive management programme being implemented by the Kruger National Park. Results show that under broad scenarios of a 10% reduction in mean daily flow rates, or a 2 degrees C increase in mean daily air temperatures, system variability is likely to increase relative to reference conditions . It is suggested that so-called "thresholds of probable concern" (TPCs), which are based on current levels of "natural" system variability, are useful as management targets for achieving a "desired future state" for the river system. The model, recognised as a preliminary hypothesis, highlights a lack of knowledge regarding the nature of system variability, and the correspondingly wide confidence limits of the proposed TPC restricts its utility in a short-term management context. Thus, it is now recognised that its value lies more in its use as a long-term modelling tool to reflect water temperature responses to flow variability. This highlights the fact that research outcomes may not always be those intended at the beginning of a project and that opportunities to implement these may be lost as lags in understanding relative to project lifetimes often exist.