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  Subjects -> WATER RESOURCES (Total: 160 journals)
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Water SA
Journal Prestige (SJR): 0.361
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  This is an Open Access Journal Open Access journal
ISSN (Print) 0378-4738 - ISSN (Online) 1816-7950
Published by SciELO Homepage  [688 journals]
  • South Africa needs a hydrological soil map: a case study from the upper
           uMngeni catchment

    • Abstract: Accurate hydrological modelling to evaluate the impacts of climate and land use change on water resources is pivotal to sustainable management. Soil information is an important input in hydrological models but is often not available at adequate scale with appropriate attributes for direct parameterisation of the models. In this study, conducted in three quaternary catchments in the midlands of KwaZulu-Natal, three different soil information sets were used to configure SWAT+, a revised version of the Soil and Water Assessment Tool (SWAT). The datasets were: (i) the Land Type database (currently the only soil dataset covering the whole of South Africa), (ii) disaggregation of the Land Type database using digital soil mapping techniques (called DSMART), and (iii) a dataset where DSMART were complemented by field observations and interpretations of the hydropedological behaviour of the soils (DSMART+). Simulated streamflow was compared with measured streamflow at three weirs with long-term measurements, and the impact of the soil datasets on water balance simulations was evaluated. In general, the simulations were acceptable when compared to other studies, but could be improved through calibration and including small reservoirs in the model. The DSMART+ dataset yielded more accurate simulations of streamflow in all three catchments with Nash-Sutcliffe efficiencies increasing by between 9% and 67% when compared to the Land Type dataset. The value of the improved soil maps is, however, highlighted through the enhanced spatial detail of streamflow generation mechanisms and water balance components. The internal catchment processes are represented more accurately, and we argue that South Africa needs a detailed hydrological soil map for effective water resource management.
  • Calibration, validation and application of the SWAT model to determine the
           hydrological benefit of wetland rehabilitation in KwaZulu-Natal, South

    • Abstract: In South Africa, with highly variable and intense land-use practices, coupled with limited soil fertility and water resources, there has been a long history of encroachment of arable lands (sugarcane and timber plantations) nto surrounding wetlands. Although wetland delineation within the timber and sugar sectors is well-defined in policy, and existing and proposed legislation, there are significant areas of non-compliance. The spatially-explicit Soil Water Assessment Tool (SWAT) was adopted to investigate the interactions of climate, land-use and soil on the water-use of natural and encroached wetlands. This paper documents the calibration, validation and application of the SWAT model on Quaternary Catchment (QC) U20G, which is a 498 km² catchment that forms part of the uMngeni River basin. The SWAT-CUP parameter sensitivity and optimization model was tested with daily observed streamflow data for this catchment. Parameters were modified using the sequential uncertainty fitting (SUFI-2) analysis routine to calibrate the model. The simulated flow had a close fit to the observed flow with a regression coefficient (r²) of 0.87 and a Nash-Sutcliffe (NS) coefficient of 0.8. Through the buffer scenario analysis, the model showed that if the wetland and a 20-m buffer were to be returned to a natural state, there could be a 16% increase in the annual streamflow contribution, with an upper limit of a 60% increase in some hydrologic response units (HRUs). Thus there would be a hydrological gain if wetlands and sensitive buffer areas were to be cleared of commercial timber species and sugarcane.
  • Impacts of climate change on streamflow and reservoir inflows in the Upper
           Manyame sub-catchment of Zimbabwe

    • Abstract: This study focused on the Upper Manyame sub-catchment which covers an area of approximately 3 786 km² and forms part of the Manyame catchment, one of the seven catchments of Zimbabwe. Manyame catchment has its source in Marondera town and drains into the Zambezi River downstream of the Kariba Dam and upstream of the Cahora Bassa Dam, in the northern part of the country. This study assessed potential climate change impacts on the streamflow and reservoir inflows in the Upper Manyame sub-catchment. Hydrologic simulations for future climate (2030s and 2060s) were carried out using statistically downscaled bias-corrected variables from the HadCM3 (HadCM3A2a and HadCM3B2a scenarios) and CanESM2 (RCP2.6 and RCP8.5) global circulation models. The HEC-HMS hydrological model was set up for two gauged micro-catchments and eight ungauged tributary micro-catchments. Model calibration for gauged micro-catchments of Upper Manyame over the period from 2000-2010 revealed satisfactory model performance of 4.3% (RVE) and 0.1 (bias) for Mukuvisi micro-catchment and 9.5% (RVE) and 0.15 (bias) for Marimba micro-catchment. Model simulations resulted in a projected decrease in streamflow by 7.4-26.4% for HadCM3. For CanESM2, simulations resulted in a projected decrease in streamflow by 2.5-34.7%. Reservoir inflows into Lake Chivero and Lake Manyame, the main water supply sources for Harare, will decrease by 10.5-18% for HadCM3 and by 8-33.6% for CanESM2.
  • Historical and projected climatic trends in KwaZulu-Natal:

    • Abstract: The climate of KwaZulu-Natal, South Africa, is evaluated for historical and projected trends in the period 1950-2100. This region lies next to the warm Indian Ocean and experiences an alternating airflow imposed by subtropical easterly and mid-latitude westerly wind belts. Multi-year wet spells have diminished since 2001 and potential evaporation deficits have spread from the Tugela Valley. Although coastal vegetation is greening and sea temperatures in the Agulhas Current are warming (>0.02-yr-1), there are fewer rain days and less cloud cover. Tropical winds across southern Africa have turned toward Madagascar, re-directing moisture and convection away from KwaZulu-Natal in recent decades. Long-range coupled model projections of monthly rainfall display weak trends over the 21st century (-0.01 mm-day-1-yr-1) which are overshadowed by multi-year fluctuations (r² = 0.04). In contrast, drying trends in potential evaporation are significant (r2 = 0.41). Forecasts of seasonal dry spells could mitigate climate change impacts in south-eastern Africa.
  • Flow patterns and chemical loads in the middle Olifants River, Limpopo
           River System, South Africa

    • Abstract: Historical data (July 1998 - June 2018) for the middle Olifants River, Limpopo River system, were compiled to evaluate the dynamics of selected water physico-chemical parameters with river discharge.The concentration of most water quality parameters increased over time. However, these concentrations are rapidly decreased, or reset, by the rapid filling, or spilling, of Loskop and/or Flag Boshielo Dams during a high-flow event. The flow-duration curves for stations below impoundments in the middle catchment on the Olifants River are typical of highly regulated rivers, although releases from Flag Boshielo Dam were more consistent through :he 20 years. No outflow from Loskop Dam was recorded for 5.4% of the 20 years. The load-duration curves for gauging weirs on the Olifants and Elands rivers immediately upstream of Flag Boshielo Dam showed that the 'tolerable' concentrations were exceeded for total dissolved solids at the 60th and 20th percentiles of the low, respectively. In addition, records for electrical conductivity, sodium, chloride, and alkalinity frequently exceeded the 'tolerable' concentrations at these sites. The results for Loskop and Flag Boshielo dams are generally lower than the tolerable concentrations for the parameters evaluated. Management of the flow regulation of the Olifants River should be aimed at meeting the water quality stipulations for all users in the agricultural, domestic, industrial, and recreational sectors.
  • A preliminary fish survey of the estuaries on the east coast of South
           Africa, Mpande to Mtentwana: a comparative study

    • Abstract: A preliminary ichthyofaunal and physico-chemical survey of estuaries on the east coast of South Africa from the Mpande Estuary to the Mtentwana Estuary was undertaken between November 1997 and January 1998. Sixteen estuaries were surveyed along this stretch of coastline and these were grouped into three estuary types: small (< 10 ha) predominantly closed estuaries, moderate to large (> 10 ha) predominantly closed estuaries and predominantly open estuaries. Multivariate analyses revealed significant differences between the three groups in terms of both their physico-chemical characteristics (small predominantly closed estuaries were different from predominantly open estuaries) and their fish communities (all three estuary types were significantly different). The estuaries in the study area fall within the subtropical/warm-temperate transition-zone and north of the subtropical/warm-temperate biogeographic break; tropical species dominated the fish communities of all the estuaries in terms of numbers of species and biomass. This survey represents one of the few fish surveys undertaken along this little-studied section of the coastline.
  • Environmental regulatory awareness of freshwater recreational bank
           anglers in South Africa

    • Abstract: Freshwater recreational angling is growing in popularity internationally. Due to the potential negative environmental impacts, various regulatory systems exist. In South Africa, freshwater recreational angling is regulated through a complex legal framework, consisting of national and provincial legislation dating back to the 1960s.The legislation also relates to historical and current provincial boundaries, adding to the regulatory complexity. Due to this complexity, the question arises whether freshwater recreational bank anglers in South Africa are aware of the regulatory requirements applicable to them. Low levels of awareness could lead to non-compliance, which would suggest an ineffective regulatory system. The aim of this research was thus to determine the environmental regulatory awareness of freshwater recreational bank anglers in South Africa. This was achieved through a literature review of national and provincial legislation, as well as the rules applicable to organised freshwater recreational bank angling. An online survey was completed by 100 members of the South African Freshwater Bank Angling Federation (SAFBAF). The results of the survey ndicate that the regulatory awareness of the sample of SAFBAF freshwater recreational anglers is low in certain key areas, such as bag and size limits for specific fish species, catch and release requirements, as well as legal definitions for alien and invasive and TOPS species listings. However, the low level of awareness can be ascribed to the complex regulatory system and not unwillingness of anglers to comply per se. It is recommended that (i) a single consolidated and simplified regulatory system for freshwater recreational bank angling be developed, and (ii) that angling organisational and competition rules be aligned with relevant regulatory requirements, to improve overall awareness and promote higher levels of regulatory compliance.
  • Investment models for the water infrastructure value chain in South
           Africa: investment measures, needs and priorities

    • Abstract: South Africa has a serious backlog in investmentfor the development and management of water infrastructure. This study aimed to assess the investment measures, needs and priorities for water infrastructure (engineering realities) through the following objectives: (i) the measurement of water infrastructure investments which demonstrate the budgets required; (ii) understanding the current water infrastructure investment needs and priorities, including benefits and limitations; and (iii) the principles and characteristics for alternative and/or nnovative measures, sources and/or models for water infrastructure investments and the envisaged effects. The range innovative of investment models for water infrastructure needs in South Africa are wide, i.e., 15 nodels were identified depending on the project type and overall transaction costs. The existing public provision model continues to characterise much of the water infrastructure investment in South Africa. The research determined investments in strategic water infrastructure systems over more than 20 years (1998/992019/20). The correlations between the three investment measures (as share of GDP) were generally negative and not significant, except for between GFCF(GG) + PPI and GFCFCE) + PPI, which was highly significant. Total water infrastructure investments constituted only 0.35-0.74% of GDP for the last ca. 20 years and 3.97-14.35% of total infrastructure investments. The results identified under-investment estimated at 54.023 billion ZAR for the medium-term expenditure framework (MTEF) period of 3 years.
  • A review of untreated household greywater quality to inform the water
           saving-risk trade-off in South Africa

    • Abstract: Interest in greywater reuse is increasing in South Africa, because of the potential to supplement scarce freshwater resources in the face of increasing demand and aridity. This paper aims to inform the water saving-risk trade-off associated with residential untreated greywater use, through a statistical analysis of greywater quality results as sourced from prior South African studies. Greywater sources included in this review were the bathroom, kitchen, laundry, mixed and general residential sources. Variability in terms of each of the reported physical, chemical and microbiological constituents by source and between result sets was noted. Statistically significant differences were evident between the pH, conductivity and phosphorus values of certain sources. A risk assessment undertaken for each of the constituents revealed further variability. The constituent with the highest number of high-risk samples was total dissolved solids. The relatively high risk and negative consequences in greywater practices in terms of public health, the environment, and infrastructure, given this variability, provide insight into the trade-off with potential water savings. It is recommended that a more nuanced view of the potential potable savings associated with greywater reuse and also improved risk management is required by the user.
  • Rapid detection of drug-resistant Escherichia coli by Vitek 2
           compact system

    • Abstract: Sewage treatment facilities aim to reduce biological contaminants such as pathogenic bacteria, fungi, protozoa, and viruses in wastewaters before discharging them to the receiving water bodies. However, several studies have shown the persistence of these contaminants throughout the sewage treatment process. In this study, the Vitek 2 compact system was used to detect the presence of Escherichia coli in three sewage treatment facilities located in the Pietermaritzburg urban area (South Africa), and its susceptibility to antimicrobial agents. E. coli has been recognized as an important Gram-negative rod-shaped human pathogen. The effluent and influent samples were analysed to determine the fate of E. coli and its susceptibility to 17 antimicrobial agents. The system identified the presence of drug-resistant E. coli in all of the tested samples, with the highest susceptibility being to ampicillin (33%) and trimethoprim/sulfamethoxazole (27%). The Vitek 2 compact system is a quick and powerful tool to identify antimicrobial-resistant bacteria in effluents and monitoring by this systemcan be used to prevent the outbreak of waterborne diseases.
  • Fabrication and performance evaluation of tannin iron complex
           (TA-FeIII/PES) UF membrane in treatment of BTEX wastewater

    • Abstract: Oil exploration generates produced water that is characterized as hazardous and toxic waste. Produced water contains a mixture of various pollutants, including monoaromatic hydrocarbons BTEX (benzene, toluene, ethylbenzene, and xylene), compounds that are carcinogenic even in small concentrations. In this study, tannin iron complex (TA-FeIII), blended into polyethersulfone (PES) membrane was evaluated for the treatment of BTEX-containing wastewater. The membranes were fabricated using the non-solvent induced phase separation (NIPS) method and loading of the TA-FeIII complex on the membranes varied from 0-0.9 wt%. The fabricated membranes were characterized using various techniques such as scanning electron microscopy (SEM), water contact angle (WCA), Fourier transform infrared (FTIR) spectroscopy, and atomic force microscopy (AFM) to check the surface morphology, hydrophilicity, surface functionality and surface roughness of the fabricated membranes, respectively. The TA-FeIII modified membranes showed increased pure water flux from 100 (PES 0) to ~150 (PES 0.9) L/(m²-h) at 100 kPa. The performance of the fabricated membranes was tested using 70 mg/L synthetic BTEX solution. Overall BTEX rejection > 70% was achieved at increasing TA-FeIII loadings compared to BTEX rejection < 65% for the pure PES membrane. Rejection of the BTEX compounds was mainly through the size exclusion mechanism. These modified TA-FeIII/PES UF membranes proved to be effective in the treatment of BTEX-containing water, and also have the potential to be applied in oily wastewater treatment.
  • Membrane fouling in thermophilic aerobic membrane distillation bioreactor
           treating hospital wastewater

    • Abstract: In the membrane distillation bioreactor (MDBR) process, flux increases with increasing feed temperature, but the presence of microorganisms limits the feed temperature. Also, the accumulation of cells and other substances on the membrane surface can affect the efficiency of MDBR. In this study, hospital wastewater was treated by thermophilic activated sludge MDBR. In the MDBR, the initial flux was 7.87 L-m-2-h-1 and the stable flux was 3.88 L-m-2-h-1. The particle size, zeta potential and hydrophobicity of the activated sludge in MDBR were 2.25 urn, -14 mV and 24%, respectively. In addition, EPS (extracellular polymeric substances) and SMP (soluble microbial products), having a significant effect on membrane fouling, were determined to be 201.50 mg-L-1 and 669.35 mg-L-1 in MDBR, respectively. Contact angle, FTIR (Fourier transform infrared), SEM (scanning electron microscope) and EDX (energy dispersive X-ray spectroscopy) measurements were also made on a virgin membrane and used membrane. Analysis of EDX, SEM and F-TIR showed that the membrane fouling was caused by CaCO3 and EPS.
  • Application of isotherm models to combined filter systems for the
           prediction of iron and lead removal from automobile workshop stormwater

    • Abstract: Langmuir and Freundlich isotherm adsorption models were used to predict iron and lead removal from automobile workshop stormwater runoff. Combined low-cost filter systems consisting of granular activated carbon-rice husk (GAC-RH) and river gravel-granular activated carbon (GR-GAC) were used in this study. The effects of adsorbent dosage and contact time on the adsorption capacity of the adsorbents, as well as the removal efficiencies of the adsorbent systems, were also investigated. The results for the Langmuir model generally showed favourable adsorption processes., with all R L values < 1 (in the range 0.358-0.518). The Langmuir model gave better predictions for iron and lead removal, with high R² values (in the range 0.8420.969), while the root mean square error (RMSE) values ranged from 0.002 to 2.366. The Freundlich model parameters indicated chemisorption processes with all n values < 1 (in the range 0.1296-0.4675). R² values were in the range of 0.634-0.916 while RMSE values ranged from 0.002 to 0.1765. Additionally, the removal efficiencies for iron and lead using GAC-RH filter system (54% and 48%, respectively) were found to be higher than those obtained using GR-GAC filter system (35% and 25%, respectively). The adsorption capacities of the adsorbents decreased with increased dosages of the adsorbent, with optimum adsorbent dosage of 0.5 g and equilibrium contact time of 80 min for the combined filter adsorbents. Further research towards modifying adsorbents for removal of oil and grease from polluted automobile workshop stormwater runoff are warranted.
  • Improving the growth, yield, and quality of ginger (Zingiber officinale
           Rosc.) through irrigation and nutrient management: a study from an
           Ineeptisol of India

    • Abstract: A proper protocol of efficient irrigation and nutrient management for ginger is a necessity for boosting the productivity and quality of the crop in high-intensity cultivated lands. For this, a field experiment for 3 consecutive years was conducted in an Inceptisol of India to optimize irrigation schedule and nutrient management for augmenting rhizome yield and crop water productivity (CWP) of ginger. The trial was laid out in a split plot design with 12 treatment combinations consisting of 4 levels of irrigation schedules viz., rainfed and a ratio of 0.6 (I2), 0.9 (I3) and 1.2 (I4) of irrigation water to cumulative pan evaporation (IW/CPE) and 3 levels of nutrient management: 100% recommended dose of fertilizer (RDF) through inorganic (N1), 75% RDF (inorganic) + 25% RDF through vermicompost (VC) (N2) and 50% RDF (inorganic) + 50% RDF through VC (N3). Mean maximum growth and yield components, quality parameters, green rhizome yield (12.63 Mg-ha-1) and highest nutrient uptake were obtained with I4N2, which was statistically on par with I3N2. The treatment combination I1N2 exhibited maximum CWP. Well-managed irrigation and nutrient scheduling is key to improving ginger production and its marketability for better financial returns.
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