Scielo RSS <![CDATA[Water SA]]> vol. 43 num. 3 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>Design and implementation of a citizen technician-based suspended sediment monitoring network: Lessons from the Tsitsa River catchment, South Africa</b>]]> Locally resident citizen technicians using basic equipment and Open Data Kit-enabled smartphones have collected flood-focused suspended sediment (SS) samples from 11 sites on the Tsitsa River and its tributaries, in the Eastern Cape Province of South Africa. In the highly degraded and gullied Tsitsa River catchment, existing modelled SS data were unverified and at odds with the results of studies based on dam sedimentation rates. Suspended sediment concentration (SSC), flux and yield data were required at subcatchment scale to support the prioritisation of community-based land rehabilitation initiatives in rural communal areas and to determine the relative contributions of subcatchments to SS yield at the site of the proposed Ntabelanga Dam. Approaches relying on researcher presence and/or installed instrumentation were precluded by cost, study area size, and the risk of equipment theft, vandalism and damage during high flows. Analysis of the quantitative data collected by the citizen technicians allows high-resolution SSC, flux, and yield data to be produced at subcatchment scale, which will be benchmarked by an acoustic SSC probe at a downstream Department of Water and Sanitation gauging weir. Qualitative descriptive and photographic data allows distant researchers to gain a real-time, catchment-wide overview of river and SS levels. This paper outlines the method, benefits and challenges of a direct-sampling approach that has the potential to address spatial and temporal challenges commonly experienced during SS sampling campaigns. <![CDATA[<b>Experimental evaluation of helically coiled tube flocculators for turbidity removal in drinking water treatment units</b>]]> The constant need to improve water treatment techniques allows for the emergence of new technologies for obtaining adequate water, both in terms of quality and quantity. In order to obtain an efficient, rapid and low-cost clarification system, this study proposes the use of helically coiled tubes (HCTs) as a coagulation-flocculation reactor coupled with a conventional decanter system. Eighty-four (84) turbidity removal tests were performed to evaluate the proposed clarification system, while varying hydraulic and geometrical parameters in HCTs. Removal efficiency values higher than 80% were obtained (with a maximum removal efficiency of 86.2%), presenting better results than systems using baffled tanks, which are traditionally applied for water treatment purposes in developing countries. In addition, significantly lower processing times (lower than 2 min, about 10% of baffled tank processing times) were observed for high efficiency process values, indicating that this clarification system can be useful in rational design of coagulation-flocculation units. It should be noted that the turbidity removal efficiency results obtained (with a rising-then-decreasing behaviour over time) differ significantly from those obtained by the commonly used models for flocculation evaluation (with asymptotic behaviour over time), presenting a maximum absolute percentage deviation of 48.9%, and indicating caution in the use of such models for alternative flocculation unit evaluation. <![CDATA[<b>Genetic characterization of <i>Salmonella</i> and <i>Shigella</i> spp. isolates recovered from water and riverbed sediment of the Apies River, South Africa</b>]]> Riverbed sediment is a vital component of river ecosystems and plays an important role in many geomorphological and ecological processes. However, when re-suspension occurs, pathogenic bacteria associated with sediment particles may be released into the water column, thus creating a health risk to those who use such water for drinking, household and recreational purposes. The aim of this study was to investigate the presence of bacterial pathogens Salmonella spp. and Shigella spp. in the Apies River and to ascertain whether there was any level of genetic relatedness between river water and riverbed sediment isolates of these pathogenic bacteria. A total of 124 water and sediment samples were collected from a site located on the Apies Rivers upstream of the Daspoort Wastewater Treatment Works, Pretoria, Gauteng, South Africa, between August and November 2014. In order to detect and identify the target bacteria, samples were analysed by culture-dependent and culture-independent techniques (quantitative real-time PCR). Genetic relatedness was established using Sanger sequencing of the invA gene of Salmonella spp. and ipaH of Shigella spp. Results of this study displayed the presence of the target bacteria both in the water and sediment of the river. The phylogenetic tree of Salmonella spp. revealed a ≥ 99% and 99% genetic relatedness between river water and riverbed sediment isolates for Salmonella spp. and Shigella spp., respectively. The degree of genetic relatedness between sediment and water pathogen isolates suggests that these organisms could possibly have a common origin and that there could be possible movement of microorganisms between the water column and the sediments. <![CDATA[<b>Water service delivery challenges in a small South African municipality: Identifying and exploring key elements and relationships in a complex social-ecological system</b>]]> South Africa is a developing country undergoing social and ecological transformation. Water service delivery (i) exemplifies the challenge of improvement and transformation towards a more socially and ecologically just situation, and (ii) can usefully be viewed as a complex social-ecological system (C-SES) in the search for 'just transitions'. Household water security problems associated with water service delivery in South Africa are recognisably intractable, multi-scaled, comprising many actors and elements and having no single solution. There is a global and South African trend towards systemic approaches to addressing such complex water challenges. However, the steps required to take a systemic approach are seldom explicit. This paper presents the analytical process of defining boundaries, identifying elements and exploring relationships between elements as the foundational step in a study of the Makana Local Municipality water service delivery C-SES in the Eastern Cape Province of South Africa. The resulting narrative and heuristics provide a clear systemic basis from which to research the emergence, practice and social learning process of a civil society organisation (Water for Dignity) seeking to confront water service delivery issues in the Makana Local Municipality. <![CDATA[<b>The use of two microbiotests to evaluate the toxicity of sediment from Mpumalanga, South Africa</b>]]> Rapid urbanisation throughout the world has resulted in numerous ecological and environmental problems. The release of contaminants into the aquatic environment and the subsequent accumulation in sediment is a specific area of concern due to the potential re-release of the contaminants into solution. The responses of two microbiotests designed to evaluate sediment toxicity (the Ostracodtoxkit F and Phytotoxkit test) were compared once exposed to three samples collected in the vicinity of a power station in Mpumalanga, South Africa. Sediment characterisation and chemical analyses were conducted in order to determine possible correlations with the expressed results. Where possible, the concentration of chemicals in the sediment was compared to available sediment guidelines. The study showed that whilst the Phytotoxkit test results did not indicate any acute toxicity (< 50% inhibition), the Ostracodtoxkit F test indicated 100% mortality at the upstream site, with increased growth inhibition at the remaining two sites. The concentration of chrome at all three sites exceeded the interim sediment quality guidelines (37 mg/kg), with the sample collected at the upstream site exceeding the probable effect level (90 mg/kg). The findings from this study indicated that the Phytotoxkit and Ostracodtoxkit F test kits are sensitive enough to evaluate sediment toxicity. <![CDATA[<b>Spatial analysis of fluoride concentrations in drinking water and population at risk in Namibia</b>]]> Namibia, the driest country in sub-Saharan Africa, is largely reliant on groundwater for its potable water demand and groundwater is a major source of naturally-occurring fluoride. This study assessed the spatial distribution of fluoride in potable water and appraised the population at risk for high fluoride intake. Analysis of fluoride levels used existing databases that include 28 000 borehole locations across the country, while the population data were based on the 2011 Census. Spatial analysis and spatial statistics methods employed included Moran's I, local indicators of spatial association (LISA), basic Euclidian distance, analysis of variance (ANOVA) and spatial overlay in a GIS environment. Fluoride concentrations above the recommended limit of 1.5 mg/L occur in a fifth of the boreholes and as much as 8% of the population across the country is at risk. Although the number of people in Namibia who are exposed to high fluoride is relatively small at a global scale, it is significant at a national level. Preventative measures against high fluoride intake are thus necessary in the country. <![CDATA[<b>Jumping the water queue: changing waterscapes under water reform processes in rural Zimbabwe</b>]]> This paper contributes to the ongoing discussion on the implementation of water reforms in rural African waterscapes and explores how farmers in a tertiary catchment in Zimbabwe react to these reforms. It shows how privileged farmers have jumped the water queue by moving their agricultural activities upstream where they illegally divert water straight from the river, while downstream, in the smallholder irrigation scheme, farmers resort to rainfed farming. This unforeseen consequence of the 1998 water reform process, implemented during the economically unstable decade that followed, is explained by adopting a socio-nature approach. Empirical field data as well as processed satellite images are presented and the politicized implications of water reform processes in the Zimbabwean context are discussed. Besides the need to critically examine the content of water reform processes, more attention is needed for understanding what happens to the water that escapes stipulated plans, prescribed rules of control and visible decision-making arenas. <![CDATA[<b>Discharge coefficient of semi-circular labyrinth side weir in subcritical flow</b>]]> Side weirs are flow diversion or intake devices that are widely used in irrigation and drainage networks and urban sewage systems. Labyrinth weirs have a proven hydraulic advantage due to their increased discharge rate at the same head for a given design condition. A labyrinth weir is defined as a weir crest that is not straight in plan-form. The increased sill length provided by labyrinth weirs effectively reduces upstream head to the particular discharge. In this study, a comprehensive laboratory study was conducted in a physical model of a semi-circular labyrinth side weir and the model is evaluated for three heights and three radii. In this particular study, the hydraulic effects of this shape of side weir in increasing discharge capacity was investigated. The discharge coefficient of semi-circular labyrinth side weirs was determined and the results were analysed to find the influence of the dimensionless parameters of weir height (w/b), weir length (r/b), nape height ((y1−w)/r), and upstream Froude number (Fr1) on discharge coefficient (Cd), based on the experimental conditions and previous studies. It was found that the discharge coefficient of the semi-circular labyrinth side weir gives a relatively high discharge coefficient value compared to other types of classic side weir positioned on a straight channel. Additionally, reliable equations for calculating the discharge coefficient (Cd) of semi-circular labyrinth side weirs are proposed. According to the proposed equation, Cd depends on dimensionless parameters, which are the ratios of r/b, r/w, (y1−w)/r, (y2−w)/r and Fr1. <![CDATA[<b>An assessment of recreational bank angling in the Free State Province, South Africa, using licence sale and tournament data</b>]]> Recreational angling is an important form of utilisation of inland fisheries in South Africa but there is little information on this sector. The objective of this study was to provide an assessment of recreational bank angling in the Free State Province using licence sale and tournament data. During 2013 and 2014, 8 256 and 7 710 angling licences were sold, respectively. This represents a decline of 76% compared to the total licence sales in the Province in 1971. Tournament catch and effort data were obtained for 4 796 tournaments that were held on 17 dams from 1974 to 2014. Reported tournament effort decreased by 67% from 8 548 tournament days in 1998 to 2 828 days in 2014. Tournament catch composition was dominated by alien common carp Cyprinus carpio. Overall, this species comprised 81% of the weight and 77% of the number of fish landed during tournaments making it the most important angling species. The recent observed increase in subsistence angling could not be included in the analysis as participants are mostly not licensed. Alternative methods are therefore required if total catch and effort are to be estimated. <![CDATA[<b>Impacts of DEM resolution and area threshold value uncertainty on the drainage network derived using SWAT</b>]]> Many hydrological algorithms have been developed to automatically extract drainage networks from DEM, and the D8 algorithm is widely used worldwide to delineate drainage networks and catchments. The simulation accuracy of the SWAT model depends on characteristics of the watershed, and previous studies of DEM resolution and its impacts on drainage network extraction have not generally considered the effects of resolution and threshold value on uncertainty. In order to assess the influence of different DEM resolutions and drainage threshold values on drainage network extraction using the SWAT model, 10 basic watershed regions in China were chosen as case studies to analyse the relationship between extracted watershed parameters and the threshold value. SRTM DEM data at 3 different resolutions were used in this study, and regression analysis for DEM resolution, threshold value and extraction effects was done. The results show that DEM resolution influences the selected flow accumulation threshold value; the suitable flow accumulation threshold value increases as the DEM resolution increases, and shows greater variability for basins with lower drainage densities. The link between drainage area threshold value and stream network extraction results was also examined, and showed a variation trend of power function y = axb between the sub-basin counts and threshold value, i.e., the maximum reach length increases while the threshold value increases, and the minimum reach length shows no relation with the threshold value. The stream network extraction resulting from a 250 m DEM resolution and a 50 000 ha threshold value was similar to the real stream network. The drainage network density and the threshold value also shows a trend of power function y = axb; the value of b is usually 0.5. <![CDATA[<b>Gill net catch composition and catch per unit effort in Flag Boshielo Dam, Limpopo Province, South Africa</b>]]> Gill net surveys were conducted in 2013 to determine species composition and fisheries potential of Flag Boshielo Dam. Species contributing the most towards total biomass were Labeo rosae (40%), Oreochromis mossambicus (15%), Schilbe intermedius (10%) and Labeobarbus marequensis (9.8%). Catch per unit effort for gill nets set at night (4.4 ± 0.6 kg·100 m-net−1·hr−1) was significantly higher (P < 0.05) than for those set during the day (0.9 ± 0.1 kg·100 m-net−1·hr−1). Total fish biomass captured in 30, 50, 70, 90 and 110 mm mesh sized nets was 3.1, 31.5, 43.5, 23.5 and 16.1 kg, respectively. Catch in gillnets with mesh sizes ≥ 70 mm was dominated by L. rosae comprising 60% of the catch in the 70 mm mesh; L. rosae (40%) and O. mossambicus (36%) in the 90 mm mesh; and O. mossambicus (40%) and Clarias gariepinus (40%) in the 110 mm mesh. If a small-scale fishery were to be initiated, it is recommended that mesh sizes should exceed 70 mm and that further research on the biology and ecology of the main target species and of the current utilisation of the fishery be conducted to guide sustainable utilisation. <![CDATA[<b>COD and colour removal from molasses spent wash using activated carbon produced from bagasse fly ash of Matahara sugar factory, Oromiya region, Ethiopia</b>]]> The aim of this study was to investigate the removal of chemical oxygen demand (COD) and colour from a melanoidin solution using activated carbon produced from bagasse fly ash (BFA). Melanoidins are heterogeneous polymers and major contributors to the dark brown colour of molasses spent wash, which is an extensive cause of environment pollution. The surface area of the BFA was determined as 160.9 ± 2.8m²/g with 90% of particle less than 156.8 µm in size. Characterization of the BFA by Fourier transform infrared spectroscopy (FTIR) showed the presence of hydroxyl and carbonyl functional groups, whereas X-ray diffraction analysis indicated its amorphous nature. Moreover, scanning electron microscopy analysis showed a heterogeneous and irregular shape of pores. Among the adsorption isotherm models analysed, the Freundlich model fitted best to the experimental data, indicating a maximum adsorptive capacity of 124.80 mg/g. The removal of COD and colour from a melanoidin solution with this activated carbon was carried out using an experimental design taking 4 factors into account. These were adsorbent dose, contact time, pH and initial COD concentration, with removal of COD and colour as response variables. COD reduction was influenced by initial COD concentration whereas colour removal was dominated by contact time, which was in line with the findings of principal component analysis . The maximum COD removal recorded was 61.6% at the optimum condition of adsorbent dose of 4 g in 100 mL, contact time of 4 h, pH 8 and initial COD concentration 6 000 mg/L, whereas the decolourization of melanoidin solution was 64% at adsorbent dose of 4 g, contact time 4 h, pH 3 and initial COD concentration 6 000 mg/L. Hence, activated BFA is a promising option for simultaneous removal of COD and colour from molasses spent wash under the stated conditions. <![CDATA[<b>Modelling and water yield assessment of Lake Sibhayi</b>]]> This study has been undertaken to establish the probable causes of the almost 4 m drop in the level of Lake Sibhayi between 2001 and 2014, to assess the impact of abstractions for domestic water consumption and by commercial plantations on lake levels, and to determine what sustainable yield can be abstracted from Lake Sibhayi. From the analysis and simulations undertaken, it is concluded that the major cause of the drop in the level of Lake Sibhayi was the below-average rainfall over the period 2001 to 2011. However, while the simulation results show that the effect on lake levels of abstractions for domestic usage over this period has been negligible, they do indicate that nearly 1.4 m of the drop in lake level can be attributed to the impact of the afforestation which began in the catchment in the 1990s. A yield analysis of simulated results with historical developments in the catchment for the 65-year period of observed climate record was undertaken using both a fixed minimum allowable lake level or a maximum drop from a reference lake level as criteria for system failure. Results from simulating lake levels using the historical climate record with the area afforested and abstractions levels fixed at 2014 values indicate that no sustainable additional yield is possible because of the sustained decline in both the simulated lake levels and conceptual groundwater store, which would be environmentally, socially and ecologically unacceptable. Preliminary simulated results indicate that the removal of approximately 5 km² of forestry is required to release 1 MCM/yr for domestic abstractions. However, these preliminary results require improved verification of input data and a review of the modelling for increased confidence in the results. <![CDATA[<b>A modified version of the SMAR model for estimating root-zone soil moisture from time-series of surface soil moisture</b>]]> Root-zone soil moisture at the regional scale has always been a missing element of the hydrological cycle. Knowing its value could be a great help in estimating evapotranspiration, erosion, runoff, permeability, irrigation needs, etc. The recently developed Soil Moisture Analytical Relationship (SMAR) can relate the surface soil moisture to the moisture content of deeper layers using a physically-based formulation. Previous studies have proved the effectiveness of SMAR in estimating root-zone soil moisture, yet there is still room for improvement in its application. For example, the soil water loss function (i.e. deep percolation and evapotranspiration), assumed to be a linear function in the SMAR model, may produce approximations in the estimation of water losses in the second soil layer. This problem becomes more critical in soils with finer textures. In this regard, the soil moisture profile data from two research sites (AMMA and SCAN) were investigated. The results showed that after a rainfall event, soil water losses decrease following a power pattern until they reach a minimum steady state. This knowledge was used to modify SMAR. In particular, SMAR was modified (MSMAR) by introducing a non-linear soil water loss function that allowed for improved estimates of root zone soil moisture. <![CDATA[<b>Land cover models to predict non-point nutrient inputs for selected biomes in South Africa</b>]]> WQSAM is a practical water quality model for use in guiding southern African water quality management. However, the estimation of non-point nutrient inputs within WQSAM is uncertain, as it is achieved through a combination of calibration and expert knowledge. Non-point source loads can be correlated to particular land cover types. Although observed water quality data through which non-point source loads can be estimated are scarce, land cover databases exist covering the entire area of South Africa. To reduce the uncertainty associated with estimating non-point source loads, this study describes a formal model to link the nutrient signatures of incremental flow to land cover. Study catchments incorporating the fynbos, grassland, savanna and thicket biomes were identified. Instream nutrients of 25 sites were modelled using WQSAM and calibrated against observed data. Multiple regression was used to investigate the relationships between the calibrated nutrient signatures of incremental flow from WQSAM and land cover within study sites. The regression models reflected greater non-point loads from cultivation- and urban-related land cover categories. The nutrient signatures of incremental flow obtained through the multiple regressions were consistent with those obtained through calibration of the WQSAM model at higher signature values, whereas discrepancies were evident at lower values. It is argued that this formal modelling approach for linking land cover to nutrient signatures of incremental flow can be implemented for situations where it is known that there are strong non-point inputs of nutrients into a river reach. The statistical model presented in the current study could potentially be applied as an alternative to the water quality model as a relatively simple method to estimate non-point source loads of nutrients from tributary catchments in South Africa. <![CDATA[<b>Hydraulic head and groundwater <sup>111</sup>Cd content interpolations using empirical Bayesian kriging (EBK) and geo-adaptive neuro-fuzzy inference system (geo-ANFIS)</b>]]> In this study, hydraulic head and 111Cd interpolations based on the geo-adaptive neuro-fuzzy inference system (Geo-ANFIS) and empirical Bayesian kriging (EBK) were performed for the alluvium unit of Karabağlar Polje in Muğla, Turkey. Hydraulic head measurements and 111Cd analyses were done for 42 water wells during a snapshot campaign in April 2013. The main objective of this study was to compare Geo-ANFIS and EBK to interpolate hydraulic head and 111Cd content of groundwater. Both models were applied on the same case study: alluvium of Karabağlar Polje, which covers an area of 25 km² in Muğla basin, in the southwest of Turkey. The ANFIS method (called ANFIS XY) uses two reduced centred pre-processed inputs, which are cartesian coordinates (XY). Geo-ANFIS is tested on a 100-random-data subset of 8 data among 42, with the remaining data used to train and validate the models. ANFIS XY and EBK were then used to interpolate hydraulic head and heavy metal distribution, on a 50 m² grid covering the study area for ANFIS XY, while a 100 m² grid was used for EBK. Both EBK- and ANFIS XY-simulated hydraulic head and 111Cd distributions exhibit realistic patterns, with RMSE < 9 m and RMSE < 8 µg/L, respectively. In conclusion, EBK can be considered as a better interpolation method than ANFIS XY for both parameters. <![CDATA[<b>Comparison of UV and ELS detectors in HSPEC analysis of natural organic matter in dam water</b>]]> This project arose out the need for a simple method to analyse natural organic matter (NOM) on a routine basis. Water samples were obtained from the Vaal Dam. Analysis was preceded by separating the NOM into the humic and non-humic fractions. The humic portion was separated further into two fractions by employing a non-ionic DAX-8 resin to separate humic acid from fulvic acid. High-performance size-exclusion chromatography (HPSEC), equipped with a UV detector and an evaporative light scattering detector (ELSD) was used to obtain information on the molecular weight distribution and concentration levels of the two acids. Mixed standards of polyethylene oxide/glycol were employed for calibration. The molecular weight distributions (MWDs) of the isolated fractions of humic and fulvic acids were determined with ELSD detection as weight-average (Mw), number-average (Mn) and polydispersity (ρ) of individual NOM fractions. The Mw/Mn ratio was found to be less than 1.5 in all fractions, indicating that they have a low and narrow size fraction. It is noted that the ELSD detector proved to be far more capable than the UV detector. A finding of interest is that 40% of the total organic carbon in the dam water samples could be attributed to humic substances. The developed method successfully separated the humic substances from water and further separated the humic substances into the component acids, namely, humic and fulvic acids. Molecular weight distribution of these compounds is a powerful indication of how much DOM was present in the dam water. Even though the UV method was useful in characterizing these substances, the ELS detector is recommended because it detects all the organic species present.