Application of SWAT+ model to assess the hydrology of irrigated agricultural catchments in Western Cape, South Africa
- Authors: Mabohlo, Sakikhaya
- Date: 2024-10-11
- Subjects: Soil and Water Assessment Tool , Agricultural hydrology , Hydrologic models , Irrigation , Reservoirs , Water-supply, Agricultural South Africa Western Cape
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464986 , vital:76563
- Description: Agricultural activities can modify hydrological processes in catchments. An in-depth investigation of the impact of agriculture on hydrological processes is thus crucial for sustainable water management and utilisation planning in agricultural catchments. Hydrological models are widely used as practical tools to estimate and understand hydrological processes at various scales in catchments. However, it is often challenging to represent hydrological processes accurately in agriculture-dominated areas due to their complexity and the structural inadequacy of models. Complexities driven by agricultural developments such as reservoirs, cultivation irrigation, and water transfers are often intricate and difficult to represent in detail. The current study applied the SWAT+ hydrological model to the agriculture-dominated Twee and Leeu catchments in the Western Cape Province of South Africa. The SWAT+ model was preferred because it is versatile in representing multiple reservoirs and irrigation from multiple sources. The model application aimed to enhance the understanding of hydrological processes and the impact of agricultural water use on catchment hydrology, explore the capabilities and performance of this relatively new version of the SWAT in a complex catchment and provide baseline hydrology input for systems models that were used to formulate a water management plan for the catchment. The SWAT+ model was able to represent the significant number of reservoirs in the catchment. In some cases, small farm dams had to be lumped together to deal with the model's structural inadequacy. The model performed well in terms of observed and simulated streamflow comparison. NSE and R2 values above the standard of 0.5 were obtained for both catchments. Moreover, an NSE of 0.7 at a daily time-step simulation was obtained for the Leeu Catchment validation period, indicating a generally impressive SWAT+ performance. The model indicated that hydrological processes in the area were largely dominated by evapotranspiration, which is expected of semi-arid regions. 55% of the total water input into the Twee quaternary catchment is lost through evapotranspiration, while 22% is converted into surface runoff. Interflow and groundwater flow account for 9% and 9% of the catchment water, respectively. The remaining 5% is distributed to soil moisture and groundwater storage. For the Leeu, the model simulated a loss of 67% of the precipitation through evapotranspiration. Interflow and surface runoff were estimated to be 25% and 24%, respectively. Groundwater contribution to the stream accounts for 7%. Therefore, evapotranspiration and surface runoff are the dominant processes from a water balance perspective, whereas groundwater flow is also significant. Agricultural activities impacted the hydrological system significantly, and this is mainly attributed to the construction of numerous reservoirs and the subsequent intensive irrigation in the dry summer periods. The model simulation revealed that the reservoir and irrigation reduced the annual average streamflow by 71% in the Twee Catchment. In the Leeu Catchment, reservoirs and irrigation resulted in an annual average streamflow reduction of 77%. Therefore, agriculture has significantly altered flow patterns in the catchment, particularly downstream areas, during drier years. In conclusion, understanding of hydrological processes, reservoir and irrigation impact on catchment flow dynamics are the key outcomes that support decision-making regarding sustainable water management and utilisation planning. The broader outcomes, including spatially distributed flows and irrigation demand for different crop types, were used as baseline inputs for systems models that explored various water management options. SWAT+ thus played a crucial role in developing a water management plan for the area. Although the model exhibited some structural deficiencies in representing some catchment complexities, it fairly represented and enhanced our understanding of the hydrological dynamics of the Twee and Leeu Catchments. Additionally, the model has proven to be a versatile tool that can be applied for practical catchment water management in the agriculture-dominated catchments of South Africa. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Date Issued: 2024-10-11
- Authors: Mabohlo, Sakikhaya
- Date: 2024-10-11
- Subjects: Soil and Water Assessment Tool , Agricultural hydrology , Hydrologic models , Irrigation , Reservoirs , Water-supply, Agricultural South Africa Western Cape
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/464986 , vital:76563
- Description: Agricultural activities can modify hydrological processes in catchments. An in-depth investigation of the impact of agriculture on hydrological processes is thus crucial for sustainable water management and utilisation planning in agricultural catchments. Hydrological models are widely used as practical tools to estimate and understand hydrological processes at various scales in catchments. However, it is often challenging to represent hydrological processes accurately in agriculture-dominated areas due to their complexity and the structural inadequacy of models. Complexities driven by agricultural developments such as reservoirs, cultivation irrigation, and water transfers are often intricate and difficult to represent in detail. The current study applied the SWAT+ hydrological model to the agriculture-dominated Twee and Leeu catchments in the Western Cape Province of South Africa. The SWAT+ model was preferred because it is versatile in representing multiple reservoirs and irrigation from multiple sources. The model application aimed to enhance the understanding of hydrological processes and the impact of agricultural water use on catchment hydrology, explore the capabilities and performance of this relatively new version of the SWAT in a complex catchment and provide baseline hydrology input for systems models that were used to formulate a water management plan for the catchment. The SWAT+ model was able to represent the significant number of reservoirs in the catchment. In some cases, small farm dams had to be lumped together to deal with the model's structural inadequacy. The model performed well in terms of observed and simulated streamflow comparison. NSE and R2 values above the standard of 0.5 were obtained for both catchments. Moreover, an NSE of 0.7 at a daily time-step simulation was obtained for the Leeu Catchment validation period, indicating a generally impressive SWAT+ performance. The model indicated that hydrological processes in the area were largely dominated by evapotranspiration, which is expected of semi-arid regions. 55% of the total water input into the Twee quaternary catchment is lost through evapotranspiration, while 22% is converted into surface runoff. Interflow and groundwater flow account for 9% and 9% of the catchment water, respectively. The remaining 5% is distributed to soil moisture and groundwater storage. For the Leeu, the model simulated a loss of 67% of the precipitation through evapotranspiration. Interflow and surface runoff were estimated to be 25% and 24%, respectively. Groundwater contribution to the stream accounts for 7%. Therefore, evapotranspiration and surface runoff are the dominant processes from a water balance perspective, whereas groundwater flow is also significant. Agricultural activities impacted the hydrological system significantly, and this is mainly attributed to the construction of numerous reservoirs and the subsequent intensive irrigation in the dry summer periods. The model simulation revealed that the reservoir and irrigation reduced the annual average streamflow by 71% in the Twee Catchment. In the Leeu Catchment, reservoirs and irrigation resulted in an annual average streamflow reduction of 77%. Therefore, agriculture has significantly altered flow patterns in the catchment, particularly downstream areas, during drier years. In conclusion, understanding of hydrological processes, reservoir and irrigation impact on catchment flow dynamics are the key outcomes that support decision-making regarding sustainable water management and utilisation planning. The broader outcomes, including spatially distributed flows and irrigation demand for different crop types, were used as baseline inputs for systems models that explored various water management options. SWAT+ thus played a crucial role in developing a water management plan for the area. Although the model exhibited some structural deficiencies in representing some catchment complexities, it fairly represented and enhanced our understanding of the hydrological dynamics of the Twee and Leeu Catchments. Additionally, the model has proven to be a versatile tool that can be applied for practical catchment water management in the agriculture-dominated catchments of South Africa. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2024
- Full Text:
- Date Issued: 2024-10-11
Impact of human dimensions on smallholder farming in the Eastern Cape Province of South Africa
- Authors: Kibirige, Douglas
- Date: 2013
- Subjects: Farms, Small -- South Africa -- Eastern Cape , Agriculture -- Economic aspects -- South Africa , Rural development -- South Africa -- Eastern Cape , Community development -- South Africa -- Eastern Cape , Entrepreneurship -- South Africa -- Eastern Cape , South Africa -- Social conditions , South Africa -- Economic conditions , DEA approach , Stochastic production frontier , Production efficiency , Human dimensions , Irrigation
- Language: English
- Type: Thesis , Doctoral , PhD (Agricultural Economics)
- Identifier: vital:11201 , http://hdl.handle.net/10353/d1007532 , Farms, Small -- South Africa -- Eastern Cape , Agriculture -- Economic aspects -- South Africa , Rural development -- South Africa -- Eastern Cape , Community development -- South Africa -- Eastern Cape , Entrepreneurship -- South Africa -- Eastern Cape , South Africa -- Social conditions , South Africa -- Economic conditions , DEA approach , Stochastic production frontier , Production efficiency , Human dimensions , Irrigation
- Description: Considering the backward and forward linkages, the agro-industrial sector contributes about 12 percent of South Africa‘s GDP, and employs approximately 8.5 million people. In the Eastern Cape Province, the sector contributes about 1.9 percent of the Provincial GDP, and over 3 million people derive their livelihoods from subsistence smallholder farming. Despite its importance, agricultural productivity has stagnated for several years across the Eastern Cape rural communities. There have been several attempts by the government to improve the agricultural productivity on smallholder farms since the end of apartheid, especially through the establishment of small-scale irrigation schemes, subsidization of farm inputs, and provision of credit facilities and enacting a number of land reform policies. In spite of the government support, most rural communities like Qamata and Tyefu are still faced with high levels of poverty affecting 76 percent and 91 percent of the population, respectively. This research evaluated the current smallholders‘ production efficiency, and the link between smallholder farmers‘ human dimensions (entrepreneurial spirit and positive psychological capital, goals and social capital, and other efficiency related variables) with production efficiency and household commercialisation index/level. The study used participatory approaches for site selection, sample selection and data collection. The analysis was based on both information from informal interviews and formal primary data collection. The Data Envelopment Analysis and Stochastic Production Frontier techniques were used to determine the relative efficiencies of individual farmers and to identify the major factors that influence the efficiency of production. Overall, 158 farmers were interviewed both at Qamata and Tyefu irrigation schemes. Descriptive statistics of this study indicated that most of the farmers were men with an average age of 61 years, and mean household size of 4 persons with the household head having at least obtained some primary school education. Farming is the major source of livelihood for smallholders with an average income of R4527.49 per crop season. Smallholders use improved seeds, fertilizers and tractor for ploughing with less use of pesticides and herbicides. Although smallholder irrigators generate more gross margins from maize and cabbage enterprises, generally both categories of farmers exhibited a low average household commercialization index for maize and cabbage at 0.41 and 0.22, respectively. Both Data Envelopment Analysis and Stochastic Production Frontier results indicate that farmers are about 98 percent technically efficient in maize and cabbage enterprises, respectively. However, farmers were allocatively inefficient as they were under-utilizing seed and pesticides while over-utilizing inorganic fertilizers. Factors that are positively associated with technical efficiency in maize production included household size, farming experience, off-farm income, use of agro-chemical; gross margins and commercialisation level of maize output. Determinants of technical efficiency in cabbage enterprise included farming experience, amount of land owned, use of agro-chemicals, group membership and gross margins accrued to cabbage sales. Farmers‘ human dimensions that could be more positively and significantly associated with production, efficiency and household commercialisation level included risk taking (hope), innovativeness (confidence) and optimism for entrepreneurial/positive psychological capital. Farmers‘ goals included self-esteem and independence, and only external social capital which were identified to be more positively and significantly associated with farmers‘ production efficiency and commercialization level. The transition from homestead subsistence to commercial oriented small-scale irrigation farming is inevitable since smallholder irrigators earn more incomes from maize and cabbage and are relatively food secure. However, the key policy options that must be considered to address inefficiencies and improved commercialization level to aid the transition include: agricultural policies geared toward attracting youth in farming, improved quality of extension services, speeding up the land reform process, and formation of cooperatives and participatory policy formulation that takes full cognizance of the farmers‘ human dimensions. Since farmers‘ human dimensions as defined in the literature and this study are not things that are amenable to direct policy intervention, they can only be modified indirectly through policy actions that affect their determinants. This means that a number of the demographic and socio-economic characteristics such as age, sex and education level of household head, farming experience, size of land owned, crop incomes, source of water for irrigation and location of the irrigation scheme that govern the way people perceive reality and respond to them must be the focus of concerted policy actions over the medium to long term.
- Full Text:
- Date Issued: 2013
- Authors: Kibirige, Douglas
- Date: 2013
- Subjects: Farms, Small -- South Africa -- Eastern Cape , Agriculture -- Economic aspects -- South Africa , Rural development -- South Africa -- Eastern Cape , Community development -- South Africa -- Eastern Cape , Entrepreneurship -- South Africa -- Eastern Cape , South Africa -- Social conditions , South Africa -- Economic conditions , DEA approach , Stochastic production frontier , Production efficiency , Human dimensions , Irrigation
- Language: English
- Type: Thesis , Doctoral , PhD (Agricultural Economics)
- Identifier: vital:11201 , http://hdl.handle.net/10353/d1007532 , Farms, Small -- South Africa -- Eastern Cape , Agriculture -- Economic aspects -- South Africa , Rural development -- South Africa -- Eastern Cape , Community development -- South Africa -- Eastern Cape , Entrepreneurship -- South Africa -- Eastern Cape , South Africa -- Social conditions , South Africa -- Economic conditions , DEA approach , Stochastic production frontier , Production efficiency , Human dimensions , Irrigation
- Description: Considering the backward and forward linkages, the agro-industrial sector contributes about 12 percent of South Africa‘s GDP, and employs approximately 8.5 million people. In the Eastern Cape Province, the sector contributes about 1.9 percent of the Provincial GDP, and over 3 million people derive their livelihoods from subsistence smallholder farming. Despite its importance, agricultural productivity has stagnated for several years across the Eastern Cape rural communities. There have been several attempts by the government to improve the agricultural productivity on smallholder farms since the end of apartheid, especially through the establishment of small-scale irrigation schemes, subsidization of farm inputs, and provision of credit facilities and enacting a number of land reform policies. In spite of the government support, most rural communities like Qamata and Tyefu are still faced with high levels of poverty affecting 76 percent and 91 percent of the population, respectively. This research evaluated the current smallholders‘ production efficiency, and the link between smallholder farmers‘ human dimensions (entrepreneurial spirit and positive psychological capital, goals and social capital, and other efficiency related variables) with production efficiency and household commercialisation index/level. The study used participatory approaches for site selection, sample selection and data collection. The analysis was based on both information from informal interviews and formal primary data collection. The Data Envelopment Analysis and Stochastic Production Frontier techniques were used to determine the relative efficiencies of individual farmers and to identify the major factors that influence the efficiency of production. Overall, 158 farmers were interviewed both at Qamata and Tyefu irrigation schemes. Descriptive statistics of this study indicated that most of the farmers were men with an average age of 61 years, and mean household size of 4 persons with the household head having at least obtained some primary school education. Farming is the major source of livelihood for smallholders with an average income of R4527.49 per crop season. Smallholders use improved seeds, fertilizers and tractor for ploughing with less use of pesticides and herbicides. Although smallholder irrigators generate more gross margins from maize and cabbage enterprises, generally both categories of farmers exhibited a low average household commercialization index for maize and cabbage at 0.41 and 0.22, respectively. Both Data Envelopment Analysis and Stochastic Production Frontier results indicate that farmers are about 98 percent technically efficient in maize and cabbage enterprises, respectively. However, farmers were allocatively inefficient as they were under-utilizing seed and pesticides while over-utilizing inorganic fertilizers. Factors that are positively associated with technical efficiency in maize production included household size, farming experience, off-farm income, use of agro-chemical; gross margins and commercialisation level of maize output. Determinants of technical efficiency in cabbage enterprise included farming experience, amount of land owned, use of agro-chemicals, group membership and gross margins accrued to cabbage sales. Farmers‘ human dimensions that could be more positively and significantly associated with production, efficiency and household commercialisation level included risk taking (hope), innovativeness (confidence) and optimism for entrepreneurial/positive psychological capital. Farmers‘ goals included self-esteem and independence, and only external social capital which were identified to be more positively and significantly associated with farmers‘ production efficiency and commercialization level. The transition from homestead subsistence to commercial oriented small-scale irrigation farming is inevitable since smallholder irrigators earn more incomes from maize and cabbage and are relatively food secure. However, the key policy options that must be considered to address inefficiencies and improved commercialization level to aid the transition include: agricultural policies geared toward attracting youth in farming, improved quality of extension services, speeding up the land reform process, and formation of cooperatives and participatory policy formulation that takes full cognizance of the farmers‘ human dimensions. Since farmers‘ human dimensions as defined in the literature and this study are not things that are amenable to direct policy intervention, they can only be modified indirectly through policy actions that affect their determinants. This means that a number of the demographic and socio-economic characteristics such as age, sex and education level of household head, farming experience, size of land owned, crop incomes, source of water for irrigation and location of the irrigation scheme that govern the way people perceive reality and respond to them must be the focus of concerted policy actions over the medium to long term.
- Full Text:
- Date Issued: 2013
Principles of Irrigation: AGC 321
- Authors: Meikle, G. J , Chiduza, C
- Date: 2010-02
- Subjects: Irrigation
- Language: English
- Type: Examination paper
- Identifier: vital:17564 , http://hdl.handle.net/10353/d1009900
- Description: Principles of Irrigation: AGC 321, supplementary examination February 2010.
- Full Text: false
- Date Issued: 2010-02
- Authors: Meikle, G. J , Chiduza, C
- Date: 2010-02
- Subjects: Irrigation
- Language: English
- Type: Examination paper
- Identifier: vital:17564 , http://hdl.handle.net/10353/d1009900
- Description: Principles of Irrigation: AGC 321, supplementary examination February 2010.
- Full Text: false
- Date Issued: 2010-02
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