1,501 research outputs found
Monitoring and Modeling Nitrate Persistence in a Shallow Aquifer
No full textA modeling study on fertilizer by-products fate and transport was performed in an unconfined shallow aquifer equipped with a grid of 13 piezometers. The field site was located in a former agricultural field overlying a river paleochannel near Ferrara (Northern Italy), cultivated with cereals rotation until 2004 and then converted to park. Piezometers were installed in June 2007 and were monitored until June 2009 via pressure transducer data loggers to evaluate the temporal and spatial variation of groundwater heads, while an onsite meteorological station provided data for recharge rate calculations via unsaturated zone modeling. The groundwater composition in June 2007 exhibited elevated nitrate (NO 3- ) and chloride (Cl-) concentrations due to fertilizer leaching from the top soil. The spatial distribution of NO 3- and Cl- was heterogeneous and the concentration decreased during the monitoring period, with NO 3- attenuation (below 10 mg/l) after 650 days. A transient groundwater flow and contaminant transport model was calibrated versus observed heads and NO 3- and Cl- concentrations. Cl- was used as environmental tracer to quantify groundwater flow velocity and it was simulated as a conservative species. NO 3- was treated as a reactive species and denitrification was simulated with a first order degradation rate constant. Model calibration gave a low denitrification rate (2.5e-3 mg-NO 3- /l/d) likely because of prevailing oxic conditions and low concentration of dissolved organic carbon. Scenario modeling was implemented with steady state and variable flow time discretization to identify the mechanism of NO 3- attenuation. It was shown that transient piezometric conditions did not exert a strong control on NO 3- clean up time, while transient recharge rate did, because it is the main source of unpolluted water in the domain. © 2010 Springer Science+Business Media B.V
The use of constructed wetlands to ameliorate discharge water from coal mines in the Witbank Coalfield
No full text>Magister Scientiae - MScMining has a lengthy history in South Africa, and subsequent beneficiation processes have been conducted with little regard for the environment, thus leaving the land with un-rehabilitated abandoned mines. Currently, most of these abandoned mine sites are no longer operational and they continuously contaminate soil, air and water resources in various areas where mining took place. This study looks at the treatment of contaminated mine water using the Dispersed Alkaline Substrates (DAS) which is a new South African technology that uses a variety of substrates to neutralize and raise the pH of mine water while lowering the solubility of potentially dangerous metals
Quantification of consumptive water use of full-bearing, high-yielding Japanese Plum trees with the HYDRUS-2D model
No full textIn South Africa, the Japanese plum industry peaked at 87,746 metric tons in 2016 and recently produced 65,258 tons in 2020, with 73% of this output aimed at the export market. Despite its importance, there is a significant lack of data on the water requirements for Japanese plum cultivation, impeding effective water management strategies. This study addresses this gap by analyzing the crop water needs of the 'African Delight' and 'Fortune' cultivars in Robertson and Wellington using the HYDRUS-2D model. Data, including weather conditions, soil properties, and various field measurements, were collected over two seasons. The model's accuracy, with mean absolute errors of 1.45 mm in Wellington and 4.01 mm in Robertson, was evaluated against observed soil water content. Results showed varying water requirements: 'African Delight' in Wellington needed 980 - 1000 mm and in Robertson 1018 - 1030 mm, while 'Fortune' in Robertson required 1017 - 1038 mm. Orchard-specific details include planting densities and yields, with 'African Delight' in Robertson yielding up to 52 t/ha-1, outperforming other sites. Basal crop coefficients (Kcb) ranged from 0.97 to 1.18, and LAI values from 0.54 to 3.19, consistent with international data for high-density plum orchards
Geophysical, technical, and engineering feasibility assessment of solar-powered groundwater abstraction in rural areas of Greater Giyani Municipality, Limpopo
No full textExtreme climate events, such as tropical cyclones, wildfires, and droughts play a role in increased water scarcity. These events may pose severe impacts and effects on communities and ecosystems over many years. Rural communities in Limpopo need more access to energy and water that may be used for agricultural irrigation. Solar-powered irrigation for agriculture is a desirable use of renewable energy. However, for the system to be practical, it must be technically and economically feasible. This study assesses the geophysical, technical, and engineering feasibility of using solar-powered irrigation systems in Greater Giyani Municipality, Limpopo. The geophysical objective is to evaluate the conditions of the site, the yield of the boreholes as well as their characteristics. The technical-engineering objective is to determine the design of the system and how many solar panels and pumps are required, power and capacity of the pump and the pipes and fittings that are required. A toolbox created by GIZ (German Corporation for International Cooperation), and FAO (Food and Agriculture Organization of the United Nations) was used to aid in the design of the solar-powered system. Various toolboxes were used to design, set up, safeguard, and maintain the solar-powered irrigation system. These toolboxes are comprised of modules that contain user-friendly software tools in the form of calculation sheets, checklists and guidelines. Data were collected on climate, soil, geohydrology, land use, borehole characteristics, and farming practices
Preferential flow modelling in a vadose zone using macro 5.0 – Cape flats porous sands and Mpumalanga highveld clays case studies
No full textMagister Scientiae - MScThe objectives of this study were: To review and understand flow and transport processes in unsaturated zones. In this study, particular emphasis is placed on understanding mechanisms that cause non-uniform (preferential) flow for two casestudies, namely the Cape Flats sandy environment and the Mpumalanga Highveld fractured rock environment. To evaluate the adequacy of models, in particular MACRO 5.0, in simulating flow and transport in the vadose zone, by making use of two case study sites (Cape Flats and Mpumalanga Highveld). Of particular importance is the evaluation of transfer coefficients to represent fluid and solute exchange between macropores and matrix. To run a sensitivity analysis with MACRO 5.0 in order determine which input model parameters are the most relevant in describing the effects of preferential flow in water and solute transport
Validation and downscaling of Advanced Scatterometer (ASCAT) soil moisture using ground measurements in the Western Cape, South Africa
No full textSatellite-based remote sensing of soil water content (SWC) is a promising technology for hydrological applications to overcome large spatiotemporal variabilities of SWC. This study investigated the performance of the Advanced Scatterometer (ASCAT) soil moisture product on METOP satellite (~12.5 km and downscaled to ~1 km resolution), against ground measurements of SWC taken with a Hydrosense II probe along transects of 360?820 m on agricultural and natural land at locations in the Western Cape. The ASCAT products estimated fairly accurately seasonal trends of SWC; performance was better on lower slopes (R 2 = 0.66) and uniform vegetation. ASCAT 12.5 km performed better in estimating SWC than the downscaled product (average concordance coefficient = 0.60 and 0.39, and R 2 = 0.84 and 0.74, respectively). ASCAT 12.5 km was more responsive to rainfall events, whilst the downscaled product was more sensitive to vegetation characteristics (normalised difference vegetation index and land surface temperature). In situations with ground measurement networks and data availability constraints, remote sensing could be a feasible alternative to monitor SWC for hydrological applications at the meso-scale (regional scale).Fil: Moller, Jason. University of the Western Cape; SudáfricaFil: Jovanovic, Nebo. CSIR Natural Resources and the Environment; Sudáfrica. University of the Western Cape; SudáfricaFil: García, César Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Católica de Córdoba; ArgentinaFil: Bugan, Richard D. H.. CSIR Natural Resources and the Environment; SudáfricaFil: Mazvimavi, Dominic. University of the Western Cape; Sudáfric
Estimación de la lluvia de diseño mediante información multisatélite de libre disponibilidad
No full textLa amenaza hídrica se cuantifica mediante el empleo de la Creciente de Proyecto. Si ésta no se puede derivar medianteestadística de caudales o niveles históricos, se evalúa partiendo de las relaciones intensidad de lluvia-duración-Recurrencia(i-d-T). Esta metodología es más común pero necesita de extensos registros históricos de lluvias, que en general no estándisponibles o son de difícil acceso. Una posible solución se puede entrever en las nuevas tecnologías satelitales que monitoreanla atmosfera y sus procesos. En este trabajo se desarrolla una metodología para generar una serie histórica de lámina máximadiaria, mediante el empleo de información multisatelital de libre disponibilidad derivada por el algoritmo RFE. Se trabajóen la cuenca experimental del río Sandspruit, Sudáfrica, que cuenta con cuatro series pluviométricas de 25 años de registroen los alrededores y series más cortas (3 años) dentro de la cuenca. La técnica propuesta permitió calcular la i-d-T en la zonade estudio con una resolución de pixel de casi 1km. Los mapas de precipitación resultantes para distintas recurrenciaspermitirán mejorar la exactitud de los cálculos de proyectos y por consiguiente optimizar la inversión en una obra civil.Fil: Catalini, Carlos Gastón. Instituto Nacional del Agua. Gerencia de Programas y Proyectos. Centro de la Region Semiarida.; ArgentinaFil: Garcia Rodriguez, Carlos Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Estudios Avanzados en Ingeniería y Tecnología. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto de Estudios Avanzados en Ingeniería y Tecnología; ArgentinaFil: García, César Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional del Agua. Gerencia de Programas y Proyectos. Centro de la Region Semiarida.; ArgentinaFil: Jovanovic, Nebo. Council for Scientific and Industrial Research. Natural Resources And Environment, Stellenbosch; SudáfricaFil: Bugan, Richard. Council for Scientific and Industrial Research. Natural Resources And Environment, Stellenbosch; Sudáfric
Using multiple-choice questions, short questions and exercises to assess student performance
No full textMultiple-choice questions, short questions and exercises were used to assess the performance of students in environmental and water sciences at the University of the Western Cape (Bellville, South Africa). The objectives were to evaluate and compare these three assessment methods, and to indicate which were particularly appropriate for the various modules and academic years. Altogether 136 test and examination papers were marked. Students generally performed better in multiple-choice questions compared to short questions, while their performance on short exercises was the poorest. No significant difference in performance was found between the academic years. Multiple-choice questions are suitable for large classes, but short questions and exercises are recommended as they facilitate the assessment of conceptual knowledge and practical problem-solving skills
Investigation of water use and trends in South Africa: a case study for the Mzimvubu to Tsitsikamma Water Management Area 7 (WMA7)
No full textThis paper investigated sectoral water use and trends in the Mzimvubu to TsitsikammaWater Management Area 7 (WMA7). The investigation considered the Water Authorisation and Registration Management System (WARMS) database and field surveys as a source of water use information. The study was able to successfully make use of time series statistical analysis to show water use trends for identified priority sectors over a 5-year period by sourcing historical water use data of the study area. Further, the groundwater stress index and streamflow impact were applied to assess water use impacts on the surface and groundwater. The WARMS database and field survey results identified major sectoral water users such as agriculture (irrigation), municipal water services, dam storage, afforestation, power generation, recreation, mining, and industries. Study findings revealed that the agricultural sector is a major water user, with an estimated 60% of the total waterrequirement over a 5-year period (2018 to 2022). The application of the groundwater stress index revealed that the majority of the Quaternary catchments have surplus groundwater available. The application of streamflow impact revealed that the majority of catchments have low flow or no flow. The rise of water use clearly indicates a lack of water use compliance and enforcement. An increase in total water use could put water resources under stress, including an impact on the aquatic ecosystem, reduced water quality, and economic and social consequences. Therefore, the study recommends that a follow-up on compliance of surface water and groundwater use licenses be regularly conducted
The use of treated effluent for agricultural irrigation in the Bottelary River area: Effluent quality, farmers perception and potential extent
No full textMagister Scientiae - MScThe Bottelary River area is located in a Mediterranean climate region, where the agricultural sector plays an important role. During the dry summer season, there is not enough precipitation to meet the agricultural irrigation requirements. Some farmers extract river water which is practically the final treated effluent from the Scottsdene Wastewater Treatment Works to irrigate crops. This research investigated the use of treated effluent for agricultural irrigation in this area, particularly focused on the effluent quality, farmers perception, and the potential extent.South Afric
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