Masters Degrees (Environmental Hydrology)

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The design, construction and testing of a mobile essential oil distillation unit.
(2005) Talanda, Colin Erlo.; Ascough, Gregory William.
Steam distillation is the most widely accepted process for the large scale production of volatile essential oils from herbaceous material and is also regarded as the standard practice throughout the flavour and fragrance industry. A mobile essential oil distillation unit for the extraction of oils from herbaceous materials would be extremely valuable to the essential oil industry in South Africa. Using a mobile platform, the extraction technology could be taken to rural areas where essential oil crops are grown in order to extract and then analyse the oils produced. Existing systems in South Africa are static distillation units which are usually owned by commercial growers that are generally positioned large distances away from the rural areas. The objective of this project was to design, construct and test a prototype mobile distillation unit for the extraction of essential oils from herbaceous materials. The unit was to have a charge vessel capacity of approximately 250 kg of plant material and should be able to perform in-field distillations in areas where electricity is not available. A literature review on all the essential oil extraction methods, the theory behind steam distillation and oil isolation and the effect that each of the distillation components have on the distillation process was performed. A small test distillation unit was set up in a laboratory in order to investigate the effects of varying steam flow . rates on the distillation time, oil yield and oil quality. A double charge vessel unit was designed, constructed and mounted onto a frame which in turn was fixed onto a trailer to be hauled by a light delivery vehicle (LDV). The steam generator with all its ancillary equipment was fixed onto a separate trailer. The unit could thus be easily transported and in-field distillations on various crops could be conducted. Field distillations were conducted with two crop types, namely rose geranium and lemon grass. Satisfactory results were obtained as the oil yields were within the expected oil yield range.
Procedures for estimating gross irrigation water requirement from crop water requirement.
(2001) Ascough, Gregory William.; Kiker, Gregory Alan.
The goal of irrigation is to supply sufficient water for crop growth to all areas within a field. Therefore, the uniformity of application of irrigation water is of great importance. The objectives of this study were to quantify the performance of irrigation systems under field conditions using standard evaluation techniques and to investigate the use of spatial statistics to characterise the spatial variability of application. The main objective was to develop techniques to estimate gross irrigation water requirement that incorporates the uniformity of application. Different practitioners have given different definitions to the criteria used to evaluate the performance of an irrigation system. A literature review was conducted to determine the current definitions used and the factors that affect these performance criteria. The theory and application of spatial statistics was investigated in order to charaterise spatial distribution of irrigation water. The spatial distribution of irrigation water under centre pivots was determined using field measurements. A number of centre pivot, sprinkler, floppy, drip and micro-irrigation systems were evaluated using standard techniques. The results from the evaluation of spatial data show that this approach is useful to determine a map of the distribution of applied irrigation water. Due to the smoothing characteristic of the spatial statistical method employed, the maps have a uniformity that is greater than in reality. The results from the standard evaluation techniques show that quick and representative results for the performance of an irrigation system can be obtained. The distribution uniformity has an affect on the efficiency of a system and should therefore be included in the calculation of the gross irrigation water requirement. The methods for these calculations are discussed. Further research needs to be conducted to determine actual distribution uniformities and application efficiencies for irrigation systems under various field conditions. This will provide useful standards to include in the calculation of gross irrigation water requirements.
Quantifying and benchmarking irrigation scheme performance with water balances and performance indicators.
(2007) Greaves, Kevin Robert.; Lecler, Neil Louis.; Smithers, Jeffrey Colin.; Ascough, Gregory William.
South Africa is a water scarce country. As pressure on available water resources increases, irrigation, the largest consumer of water, has to find ways of improving water use efficiency. Benchmarking in the irrigation sector has been identified as a suitable technique to implement this improvement. Benchmarking can be broadly defined as the identification and application of organisation specific best practices with the goal of improving competitiveness, performance and efficiency. A South African sugarcane irrigation scheme was identified to investigate a proposed benchmarking methodology. The scheme was unique in that electromagnetic flow meters were utilised and monitored on a daily basis. This facilitated an in depth study into irrigation water use at the scheme. The project focused on three different objectives. The first objective was to determine the losses, and consequently the efficiency, with which the irrigation scheme was able to deliver irrigation water from the water source to the farm boundary during the years 2004 and 2005. This was achieved by completing the water balance for the scheme with specified geographic and temporal boundaries. Results indicated that the scheme was very efficient with a delivery efficiency of 83.4 and 94.0 % for 2004 and 2005 respectively. These efficiencies were above the accepted South African Department of Water Affairs and Forestry (DWAF) standard of 80 %. The temporal distribution of the delivery efficiency was also investigated to identify periods within each year when inefficiencies occurred, and to better understand the nature of potential losses. It was concluded that the investigations into the temporal distributions be utilised together with the water balance approach in future studies into the performance of irrigation water delivery infrastructure at other South African irrigation schemes. The second objective was to calculate a set of internationally applied external irrigation benchmarking indicators. External indicators from the International Water Management Institute (1WMI), the International Program for Training and Research in Irrigation and Drainage (IPTRID) and the Irrigation Training and Research Center (ITRC) were reviewed for application in a South African context. The external indicator analysis highlighted that at a scheme level, insufficient irrigation was occurring to effectively meet the irrigation demand. It was also found that the scheme infrastructure was not the limiting cause of this observation. The external indicator results highlighted the need for additional schemes for comparison purposes. The results from this component of the study also emphasized the importance of stakeholder confidentiality concerns when attempting to implement a benchmarking initiative. The third objective was to rank individual farm performance of all the farms in the scheme, in terms of total farm sugarcane yield and seasonal irrigation water use. Farm yield and irrigated area were obtained to investigate the relationships between yield and irrigation water application. There were substantial variations in total farm yield and water use for both the 2004 and 2005 seasons, indicating much potential for improvement by many farmers relative to each other. The individual seasonal farm water use was also compared to a simulated irrigation demand, as determined with the SAsched irrigation systems and crop yield model. Simulation results with the SAsched model, using representative soils and climate data for the scheme, showed that the majority of farms were under irrigating relative to the simulated demands, especially in the late spring/early summer period. From on-farm irrigation system evaluations that were performed, it was found that irrigation system capacity constraints were not limiting irrigation applications in the majority of farms. Further research in the form of selected soil water monitoring is required to investigate these observations further.

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Browsing Masters Degrees (Environmental Hydrology) by Author "Ascough, Gregory William."