Manu Magombeyi - Academia.edu (original) (raw)
Papers by Manu Magombeyi
Physics and Chemistry of the Earth, Parts A/B/C, 2011
Computerised integrated models from science contribute to better informed and holistic assessment... more Computerised integrated models from science contribute to better informed and holistic assessments of multifaceted policies and technologies than individual models. This view has led to considerable effort being devoted to developing integrated models to support decision-making under integrated water resources management (IWRM). Nevertheless, an appraisal of previous and ongoing efforts to develop such decision support systems shows considerable deficiencies in attempts to address the hydro-socioeconomic effects on livelihoods. To date, no universal standard integration method or framework is in use. For the existing integrated models, their application failures have pointed to the lack of stakeholder participation. In an endeavour to close this gap, development and application of a seasonal time-step integrated model with prediction capability is presented in this paper. This model couples existing hydrology, agronomy and socioeconomic models with feedbacks to link livelihoods of resource-constrained smallholder farmers to water resources at catchment level in the semi-arid Olifants subbasin in South Africa. These three models, prior to coupling, were calibrated and validated using observed data and participation of local stakeholders. All the models gave good representation of the study conditions, as indicated by the statistical indicators. The integrated model is of general applicability, hence can be extended to other catchments. The impacts of untied ridges, planting basins and supplemental irrigation were compared to conventional rainfed tillage under maize crop production and for different farm typologies. Over the 20 years of simulation, the predicted benefit of untied ridges and planting basins versus conventional rainfed tillage on surface runoff (Mm 3 /year) reduction was 14.3% and 19.8%, respectively, and about 41-46% sediment yield (t/year) reduction in the catchment. Under supplemental irrigation, maize yield improved by up to 500% from the long-term average yield of 0.5 t/ha. At 90% confidence interval, family savings improved from between US$ 4 and US$ 270 under conventional rainfed to between US$ 233 and US$ 1140 under supplemental irrigation. These results highlight the economic and environmental benefits that could be achieved by adopting these improved crop management practices. However, the application of various crop management practices is site-specific and depends on both physical and socioeconomic characteristics of the farmers.
The Challenge Program on Water and Food (CPWF) Phase II for the Limpopo Basin Development Challen... more The Challenge Program on Water and Food (CPWF) Phase II for the Limpopo Basin Development Challenge (LBDC) project aims to develop methods, processes, and technologies to help resource- constrained smallholder farmers mitigate poverty and food insecurity through improved agricultural water management (AWM) strategies. The purposes of this paper are to: 1) Identify areas in the Limpopo River Basin with high levels of rural poverty and food insecurity; 2) Identify areas where AWM interventions are taking place; and 3) Check whether current activities of the CPWF in the Limpopo Basin are located in areas of need as per poverty profiles and geographical location of smallholder farms. The generated poverty and food insecurity maps were based on food security surveys and estimates of consumption or income-based welfare outcomes at the district level from 2003–2013. Based on existing district level poverty and other relevant data in the basin, the study shows that the LBDC study sites are ...
Physics and Chemistry of the Earth, Parts A/B/C, 2016
Abstract The mappings of poverty and food insecurity were carried out for the rural districts of ... more Abstract The mappings of poverty and food insecurity were carried out for the rural districts of the four riparian countries (Botswana, Mozambique, South Africa and Zimbabwe) of the Limpopo river basin using the results of national surveys that were conducted between 2003 and 2013. The analysis shows lower range of food insecure persons (0–40%) than poverty stricken persons (0–95%) that is attributable to enhanced government and non-government food safety networks in the basin countries, the dynamic and transitory nature of food insecurity which depends on the timings of the surveys in relation to harvests, markets and food prices, and the limited dimension of food insecurity in relation to poverty which tends to be a more structural and pervasive socio-economic condition. The usefulness of this study in influencing policies and strategies targeted at alleviating poverty and improving rural livelihoods lies with using food insecurity mappings to address short-term socio-economic conditions and poverty mappings to address more structural and long-term deprivations. Using the poverty line of $1.25/day per person (2008–2013) in the basin, Zimbabwe had the highest percentage of 68.7% of its rural population classified as poor, followed by Mozambique with 68.2%, South Africa with 56.1% and Botswana with 20%. While average poverty reduction of 6.4% was observed between 2003 and 2009 in Botswana, its population growth of 20.1% indicated no real poverty reduction. Similar observations are made about Mozambique and Zimbabwe where population growth outstripped poverty reductions. In contrast, both average poverty levels and population increased by 4.3% and 11%, respectively, in South Africa from 2007 to 2010. While areas of high food insecurity and poverty consistently coincide with low water availability, it does not indicate a simple cause–effect relationship between water, poverty and food insecurity. With limited water resources, rural folks in the basin require stronger institutions, increased investments and support to enable them generate sufficient income from their rain-fed farming livelihood to break out of the poverty cycle.
Physics and Chemistry of the Earth, Parts A/B/C, 2019
Declining water resources in dry regions requires sustainable groundwater management as trends in... more Declining water resources in dry regions requires sustainable groundwater management as trends indicate increasing groundwater use, but without accountability. The sustainability of groundwater is uncertain, as little is known about its extent and availability, a challenge that requires a quantitative assessment of its current use. This study assessed groundwater use for irrigated agriculture in the Venda-Gazankulu area of Limpopo Province in South Africa using crop evapotranspiration and irrigated crop area derived from the normalised difference vegetation index (NDVI). Evapotranspiration data was derived from the Water Productivity through Open access of Remotely sensed Actual Evapotranspiration and Interception (WaPOR) dataset (250 m resolution), and irrigated areas were characterised using dry season NDVI data derived from Landsat 8. Field surveys were conducted for four years to assess accuracy and for post-classification correction. Daily ET for the dry season (May to September) was developed from the actual ET for the irrigated areas. The irrigated areas were overlaid on the ET map to calculate ET for only irrigated land parcels. Groundwater use during the 2015 dry period was 3627.49 billion m 3 and the irrigated area during the same period was 26% of cultivated land. About 82 435 ha of cultivated area was irrigated using 44 million m 3 /ha of water, compared to 186.93 million m 3 /ha on a rainfed area of 237 847 ha. Groundwater management is essential for enhancing resilience in arid regions in the advent of water scarcity.
Physics and Chemistry of the Earth, Parts A/B/C, 2008
Efficiency for Access Coalition, Aug 1, 2021
This study was undertaken under the Low Energy Inclusive Appliances (LEIA) programme and delivers... more This study was undertaken under the Low Energy Inclusive Appliances (LEIA) programme and delivers on the project titled: 'Environmental sustainability of solar water pumping in Sub-Saharan Africa'. It also contributes to the CGIAR Research Program on Water, Land and Ecosystems (WLE) .
Physics and Chemistry of the Earth, Parts A/B/C, 2011
Computerised integrated models from science contribute to better informed and holistic assessment... more Computerised integrated models from science contribute to better informed and holistic assessments of multifaceted policies and technologies than individual models. This view has led to considerable effort being devoted to developing integrated models to support decision-making under integrated water resources management (IWRM). Nevertheless, an appraisal of previous and ongoing efforts to develop such decision support systems shows considerable deficiencies in attempts to address the hydro-socioeconomic effects on livelihoods. To date, no universal standard integration method or framework is in use. For the existing integrated models, their application failures have pointed to the lack of stakeholder participation. In an endeavour to close this gap, development and application of a seasonal time-step integrated model with prediction capability is presented in this paper. This model couples existing hydrology, agronomy and socioeconomic models with feedbacks to link livelihoods of resource-constrained smallholder farmers to water resources at catchment level in the semi-arid Olifants subbasin in South Africa. These three models, prior to coupling, were calibrated and validated using observed data and participation of local stakeholders. All the models gave good representation of the study conditions, as indicated by the statistical indicators. The integrated model is of general applicability, hence can be extended to other catchments. The impacts of untied ridges, planting basins and supplemental irrigation were compared to conventional rainfed tillage under maize crop production and for different farm typologies. Over the 20 years of simulation, the predicted benefit of untied ridges and planting basins versus conventional rainfed tillage on surface runoff (Mm 3 /year) reduction was 14.3% and 19.8%, respectively, and about 41-46% sediment yield (t/year) reduction in the catchment. Under supplemental irrigation, maize yield improved by up to 500% from the long-term average yield of 0.5 t/ha. At 90% confidence interval, family savings improved from between US$ 4 and US$ 270 under conventional rainfed to between US$ 233 and US$ 1140 under supplemental irrigation. These results highlight the economic and environmental benefits that could be achieved by adopting these improved crop management practices. However, the application of various crop management practices is site-specific and depends on both physical and socioeconomic characteristics of the farmers.
The Challenge Program on Water and Food (CPWF) Phase II for the Limpopo Basin Development Challen... more The Challenge Program on Water and Food (CPWF) Phase II for the Limpopo Basin Development Challenge (LBDC) project aims to develop methods, processes, and technologies to help resource- constrained smallholder farmers mitigate poverty and food insecurity through improved agricultural water management (AWM) strategies. The purposes of this paper are to: 1) Identify areas in the Limpopo River Basin with high levels of rural poverty and food insecurity; 2) Identify areas where AWM interventions are taking place; and 3) Check whether current activities of the CPWF in the Limpopo Basin are located in areas of need as per poverty profiles and geographical location of smallholder farms. The generated poverty and food insecurity maps were based on food security surveys and estimates of consumption or income-based welfare outcomes at the district level from 2003–2013. Based on existing district level poverty and other relevant data in the basin, the study shows that the LBDC study sites are ...
Physics and Chemistry of the Earth, Parts A/B/C, 2016
Abstract The mappings of poverty and food insecurity were carried out for the rural districts of ... more Abstract The mappings of poverty and food insecurity were carried out for the rural districts of the four riparian countries (Botswana, Mozambique, South Africa and Zimbabwe) of the Limpopo river basin using the results of national surveys that were conducted between 2003 and 2013. The analysis shows lower range of food insecure persons (0–40%) than poverty stricken persons (0–95%) that is attributable to enhanced government and non-government food safety networks in the basin countries, the dynamic and transitory nature of food insecurity which depends on the timings of the surveys in relation to harvests, markets and food prices, and the limited dimension of food insecurity in relation to poverty which tends to be a more structural and pervasive socio-economic condition. The usefulness of this study in influencing policies and strategies targeted at alleviating poverty and improving rural livelihoods lies with using food insecurity mappings to address short-term socio-economic conditions and poverty mappings to address more structural and long-term deprivations. Using the poverty line of $1.25/day per person (2008–2013) in the basin, Zimbabwe had the highest percentage of 68.7% of its rural population classified as poor, followed by Mozambique with 68.2%, South Africa with 56.1% and Botswana with 20%. While average poverty reduction of 6.4% was observed between 2003 and 2009 in Botswana, its population growth of 20.1% indicated no real poverty reduction. Similar observations are made about Mozambique and Zimbabwe where population growth outstripped poverty reductions. In contrast, both average poverty levels and population increased by 4.3% and 11%, respectively, in South Africa from 2007 to 2010. While areas of high food insecurity and poverty consistently coincide with low water availability, it does not indicate a simple cause–effect relationship between water, poverty and food insecurity. With limited water resources, rural folks in the basin require stronger institutions, increased investments and support to enable them generate sufficient income from their rain-fed farming livelihood to break out of the poverty cycle.
Physics and Chemistry of the Earth, Parts A/B/C, 2019
Declining water resources in dry regions requires sustainable groundwater management as trends in... more Declining water resources in dry regions requires sustainable groundwater management as trends indicate increasing groundwater use, but without accountability. The sustainability of groundwater is uncertain, as little is known about its extent and availability, a challenge that requires a quantitative assessment of its current use. This study assessed groundwater use for irrigated agriculture in the Venda-Gazankulu area of Limpopo Province in South Africa using crop evapotranspiration and irrigated crop area derived from the normalised difference vegetation index (NDVI). Evapotranspiration data was derived from the Water Productivity through Open access of Remotely sensed Actual Evapotranspiration and Interception (WaPOR) dataset (250 m resolution), and irrigated areas were characterised using dry season NDVI data derived from Landsat 8. Field surveys were conducted for four years to assess accuracy and for post-classification correction. Daily ET for the dry season (May to September) was developed from the actual ET for the irrigated areas. The irrigated areas were overlaid on the ET map to calculate ET for only irrigated land parcels. Groundwater use during the 2015 dry period was 3627.49 billion m 3 and the irrigated area during the same period was 26% of cultivated land. About 82 435 ha of cultivated area was irrigated using 44 million m 3 /ha of water, compared to 186.93 million m 3 /ha on a rainfed area of 237 847 ha. Groundwater management is essential for enhancing resilience in arid regions in the advent of water scarcity.
Physics and Chemistry of the Earth, Parts A/B/C, 2008
Efficiency for Access Coalition, Aug 1, 2021
This study was undertaken under the Low Energy Inclusive Appliances (LEIA) programme and delivers... more This study was undertaken under the Low Energy Inclusive Appliances (LEIA) programme and delivers on the project titled: 'Environmental sustainability of solar water pumping in Sub-Saharan Africa'. It also contributes to the CGIAR Research Program on Water, Land and Ecosystems (WLE) .