Journal of Water Supply: Research and Technology - Aqua
Irrigation consumes approximately 70% of total freshwater use worldwide. This necessitates the us... more Irrigation consumes approximately 70% of total freshwater use worldwide. This necessitates the use of efficient irrigation methods such as micro-irrigation. Moistube irrigation (MI) is a new subsurface irrigation technology where the water emits from a semi-permeable membrane of the Moistube at a slow rate depending on the applied pressure and soil water potential. There is currently limited information on the performance of Moistube tapes with respect to discharge as a function of pressure or water quality. The aim of this study was to determine the flow characteristics of Moistube tapes as a function of pressure and the effect of suspended and dissolved solids on the emission characteristics. The pressure–discharge relationship was determined within a range of 20 kPa and 100 kPa. The clogging of the Moistube was determined using water containing low, moderate and high concentrations of suspended and dissolved solids at 20 kPa and 30 kPa. The results indicated that the Moistube discharge follows a power function with the applied pressure. The discharge decreased linearly over time because of clogging. Suspended solids had a more severe clogging effect on Moistube than dissolved solids. The results of this study should help in the design, operation and maintenance of MI systems. doi: 10.2166/aqua.2018.166 om https://iwaponline.com/aqua/article-pdf/67/5/438/481710/jws0670438.pdf er 2019 Edwin Kimutai Kanda (corresponding author) Aidan Senzanje School of Engineering, University of KwaZulu-Natal, P. Bag X01, Scottsville, 3209, Pietermaritzburg, South Africa E-mail: [email protected] Tafadzwanashe Mabhaudhi School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, P. Bag X01, Scottsville, 3209, Pietermaritzburg, South Africa
Abstract The water-energy-food (WEF) nexus facilitates understanding of the intricate and dynamic... more Abstract The water-energy-food (WEF) nexus facilitates understanding of the intricate and dynamic interlinkages among the three resources. Its implementation can enhance resource securities and sustainable development. Despite its potential, full adoption of the approach has been hindered by a lack of actionable strategies to guide its practical application. This is attributed to (i) poor data (ii) lack of empirical evidence, (iii) inadequate analytical tools, and (iv) lack of clarity on applicable spatial scale. This study undertook a literature review, coupled with systemic analyses of a WEF nexus analytical model, whose outputs were used as a basis to develop a Theory of Change, an iterative outline for operationalising the approach in the context of southern Africa. The consultative and iterative Theory of Change culminated with the formulation of pathways to (i) overcome the barriers impeding WEF nexus operationalisation, (ii) mitigation of trade-offs while enhancing synergies towards attaining simultaneous resource securities, (iii) poverty alleviation and reduction of inequalities, and (iv) reconciling policy with implementation scale. The WEF nexus operationalisation outcomes are linked to Sustainable Development Goals 2 (zero hunger), 6 (clean water and sanitation), and 7 (affordable and clean energy), with synergies to SDGs 1 (no poverty), 5 (gender equality), 8 (decent work and economic growth), 12 (responsible consumption and production), 13 (climate action), 14 (life below water), and 15 (life on land). Operationalising the WEF nexus through an interactive process can inform sustainable pathways towards resource security, job and wealth creation, improved livelihoods and well-being, and regional integration.
Kanda, E.K., T. Mabhaudhi and A. Senzanje, 2018. Coupling hydrological and crop models for improv... more Kanda, E.K., T. Mabhaudhi and A. Senzanje, 2018. Coupling hydrological and crop models for improved agricultural water management – A review. Bulg. J. Agric. Sci., 24 (3): 380–390 Understanding the relationships among plant, soil, and water is important in agricultural water management practices. Simulation of the soil water balance is central to improving crop water productivity. Individual crop or hydrological models have shortcomings due to the simplifi cation of the surface or subsurface processes. Coupling of crop and hydrological models helps in understanding the complex processes involved in crop production. This review highlights the application of coupled crop and hydrological models in simulation of crop response to water availability. The hydrological models considered are CHAIN-2D, HYDRUS-1D, HYDRUS 2D/3D, and MODFLOW. The crop growth models considered are the water-driven model (AquaCrop), solar-radiation driven model (EPIC), and the carbon-driven models (WOFOST and DSS...
Limited understanding of the complex interactions of factors that influence the sustainability of... more Limited understanding of the complex interactions of factors that influence the sustainability of access to improved water services poses a threat to rural livelihoods. The study assessed the complex interactions of the factors using a network approach. The assessment was to understand the complex interaction of the factors resulting from their cause-effect relationship that influence the sustainability of access to improved water services in a rural municipality of South Africa. The results highlighted that limited budget, limited or no water supply and improper operation and maintenance were critical factors resulting from the cause-effect relationship of other factors that influenced the sustainability of access to improved water services in the study area. We conclude that critical factors with a cause-effect relationship can influence the sustainability of access to improved water services. As a result, this deprives rural communities of the benefits derived from accessing impr...
There is a need to mainstream traditional crops in sub-Saharan Africa, in order to tackle food an... more There is a need to mainstream traditional crops in sub-Saharan Africa, in order to tackle food and nutritional insecurity through incorporating nutritional quality into crop water productivity, in the wider context of the water–food–nutrition–health nexus. The objective of the study was to determine the effect of irrigation water regimes on the nutritional yield (NY) and nutritional water productivity (NWP) of cowpea under Moistube irrigation (MTI) and subsurface drip irrigation (SDI). We hypothesized that NY and NWP of cowpea were not different under MTI and SDI and that deficit irrigation improved NWP. The experiment was laid as a split-plot design arranged in randomized complete blocks, replicated 3 times, with 3 irrigation water regimes: 100% of crop evapotranspiration (ETc), 70% of ETc, and 40% of ETc. Irrigation type and water regime did not significantly (p > 0.05) affect the nutritional quality of cowpea. Similarly, NWP of crude fat (28.20–39.20 g∙m-3), ash (47.20–50.70...
Highlights Very few sediment yield events contribute to annual sediment yield. Any rainfall, runo... more Highlights Very few sediment yield events contribute to annual sediment yield. Any rainfall, runoff, and peak discharge event has the potential to generate the most extreme sediment yield event. Twenty year return period recommended for design of conservation structures. . Design of conservation structures includes both hydrologic and hydraulic designs. Hydrologic design involves estimation of design floods which are required for the sizing of the hydraulic structures. The minimum recommended return period for the design of conservation structures is 10 years but due to the projected levels of risk, and the fact that a few large events are likely to be responsible for the majority of the erosion, the 10-year return period currently recommended may be inadequate. This study investigated system design criteria and the capital cost of varying design return periods for soil and water conservation structures in the sugar industry of South Africa. Observed rainfall data and results of run...
Moistube irrigation (MTI) is a type of technology which uses a semipermeable membrane to emit wat... more Moistube irrigation (MTI) is a type of technology which uses a semipermeable membrane to emit water continuously in response to soil water potential and applied pressure. Soil water dynamics under MTI incorporating plant water uptake have not been studied. Therefore, this study aimed at determining the soil water distribution under MTI, using cowpea as a reference crop. The effect of Moistube placement depth on the soil water dynamics under MTI was also determined. The experiment was carried out in tunnels with MTI and subsurface drip irrigation (SDI) as a control. The HYDRUS 2D/3D model was calibrated and thereafter used to simulate soil water dynamics for different placement depths. The soil water content above the Moistube/drip lateral was higher under SDI than MTI, while the lateral movement of water was similar for both irrigation types. The simulated soil water contents closely matched (coefficient of determination [R2] ≥ 0.57, root mean square error [RMSE] ≤ 0.029 cm3 cm−3, n...
We investigated the conceptual capability of Moistube irrigation to discharge under zero applied ... more We investigated the conceptual capability of Moistube irrigation to discharge under zero applied positive pressure under varied climatic conditions by inducing an artificial evaporative demand (Ed) or negative pressure around moistube tubing. This was premised on the null hypothesis that an artificially induced Ed or negative pressure does not impact moistube discharge. Moistube tubing was enclosed in a 1 m long PVC conduit. A 20 l water reservoir placed on an electronic balance provided a continuous supply of water whilst a three-speed hot air blower facilitated the radiative factor and advection process. The procedure was conducted under varied climatic conditions of air velocities (ua) 1.2 m.s−1, 2.5 m.s−1, and 3.0 m.s−1 and the experiment run times were 159 h, 134 h and 10 h, respectively. The average temperature (Tave) and relative humidity (RH) data for ua = 1.2 m.s−1 were 53°C and 7.31%, whilst for ua = 2.5 m.s−1, Tave was 56°C and RH = 7.19%, and for ua = 3.0 m.s−1, Tave was...
ObjectiveThe analytical study systematically reviewed the evidence about the IWRM water strategy ... more ObjectiveThe analytical study systematically reviewed the evidence about the IWRM water strategy model. The study analysed the IWRM strategy advances and practical implications it had, since inception on effective water management in East, West and Southern Africa.MethodsThe study adopted the Preferred Reporting Items for Systematic Review and Meta-analysis Protocols (PRISMA-P) and the scoping literature review approach. The study searched selected databases for peer-reviewed articles, books, and grey literature. DistillerSR software was used for article screening. A constructionist thematic analysis was employed to extract recurring themes amongst the regions.ResultsThe systematic literature review detailed the adoption, policy revisions and growing/emerging policy trends and issues (or considerations) on IWRM in East, West and Southern Africa. Thematic analysis derived four cross-cutting themes that contributed to IWRM strategy implementation and adoption. The identified four them...
Moistube irrigation (MTI) is a new subsurface irrigation technology where the water emits from a ... more Moistube irrigation (MTI) is a new subsurface irrigation technology where the water emits from a semi-permeable membrane at a slow rate depending on applied pressure and soil water potential. There is lack of information on how various crops respond to MTI. This study determined growth, yield and water use efficiency (WUE) of cowpea (Vigna unguiculata (L.) Walp) under varying water regimes under MTI and subsurface drip irrigation (SDI), using field and glasshouse experiments in summer and winter of 2018, respectively. A split-plot design arranged in randomized complete blocks, replicated 3 times, with SDI as the control experiment was used. The main plot was irrigation type while the sub-plots were the water regimes. The water treatments consisted of full irrigation (100% of crop water requirement (ETc)), and deficit irrigation (DI) of 70% ETc and 40% ETc. Water deficit had a significant effect (p < 0.05) on time to flowering; plants under 40% ETc flowered 14 days earlier than pl...
The Agricultural Catchments Research Unit (ACRU) model is a daily time step physical-conceptual a... more The Agricultural Catchments Research Unit (ACRU) model is a daily time step physical-conceptual agrohydrological model with various applications, design hydrology being one of them. Model verification is a measure of model performance and streamflow, soil water content and sediment yield simulated by the ACRU model have been extensively verified against observed data in southern Africa and internationally. The primary objective of this study was to verify simulated runoff volume, peak discharge and sediment yield against observed data from small catchments, under both bare fallow conditions and sugarcane production, which were located at La Mercy in South Africa. The study area comprised 4 research catchments, 101, 102, 103 and 104, monitored both under bare fallow conditions and sugarcane production, with different management practices per catchment. Observed data comprised: daily rainfall, maximum and minimum temperature, A-pan evaporation and runoff for the period 1978–1995, and...
Irrigated agriculture is under pressure to increase water use efficiency and crop water productiv... more Irrigated agriculture is under pressure to increase water use efficiency and crop water productivity because of inter-sectoral competition for scarce water resources. The shift to micro-irrigation has improved crop quality, yield and water use efficiency. Subsurface drip irrigation significantly reduces non-beneficial water balance components such as runoff and soil evaporation. However, the problem of water loss by deep percolation still exists in this method. Moistube irrigation is a relatively new type of irrigation method where water flows out of the Moistube nanopores as a function of soil water potential and operating pressure. It supplies water continuously to the crop at 80-90% of the field capacity. Therefore, it is a form of deficit irrigation. Based on the previous studies, this paper reviews Moistube irrigation technology by highlighting its hydraulic characteristics, crop growth and yield response, water use efficiency, clogging characteristics and the soil water dynamics. Areas which need further research are also described which can provide a reference for further studies in the relevant area.
The need to cultivate effluent-irrigated rice is paramount and synonymous with treated wastewater... more The need to cultivate effluent-irrigated rice is paramount and synonymous with treated wastewater reuse, recycling and water resources management. A trial in a peri-urban set-up with a low-cost decentralized wastewater treatment system (DEWATS) was carried out in the 2017 and 2018 cropping seasons to assess the effect of irrigation water reuse management techniques on the yield and water productivity of rice. It was hypothesized that anaerobic baffled reactor (ABR) irrigation water management does not have an effect on the yield of peri-urban grown rice. The impacts of irrigation water management techniques were very significant (P < 0.001) on the number of irrigation events, amount of irrigation and daily water balance. The impact was not significant (P > 0.05) on the tiller numbers per plant; it was however significant (P < 0.05) on the panicle numbers per plant. The effects were not significant (P > 0.05) on the plant height but significant (P < 0.05) on the yield ...
This paper contains a critical review of the norms employed in the design of soil and water conse... more This paper contains a critical review of the norms employed in the design of soil and water conservation structures in the South African sugar industry and highlights research needs in order to update them. Sugarcane in South Africa is grown on wide-ranging soils, sometimes in non-ideal climates and on steep topographies where soils are vulnerable to erosion. A consequence of unsustainable soil loss is reduction in field production capacity. Sugarcane fields are protected against erosion through, inter alia, the use of engineered waterways, contour banks and spill-over roads. The South African Sugarcane Research Institute (SASRI), previously known as the South African Sugar Experiment Station (SASEX), developed a nomograph to easily compute the maximum width of field panels based on soil type, tillage method, replant method, surface structures to control runoff, surface cover and slope. This was followed by guidelines and norms for the design of soil and water conservation structure...
Physics and Chemistry of the Earth, Parts A/B/C, 2018
Water control infrastructure in smallholder irrigation schemes (SISs) is supposed to be engineere... more Water control infrastructure in smallholder irrigation schemes (SISs) is supposed to be engineered for resilience. Resilience can be defined as the ability of the water control infrastructure to absorb natural and man-made disturbances while retaining functionality. Infrastructure remains constant in the face of scheme dynamic social changes and changes in self-organization and the capacity to adapt to stress. Irrigation schemes are an indispensable component of economic growth, poverty reduction, in smallholder irrigation schemes across Africa (Tortajada, 2016). Although infrastructure in SIS is critical for water conveyance, it needs to closely relate to policies, institutions (both formal and informal), laws, regulations, management practices, and participation models for the efficient management of water
Aquaponic system is a productive, innovative and sustainable fish and vegetable production system... more Aquaponic system is a productive, innovative and sustainable fish and vegetable production system that could contribute to the needed innovation in agriculture in the face of drought, soil pollution and climate change. Aquaponics are still an emerging practice worldwide, but particularly in South Africa. This study was conducted in 2016 using an online survey questionnaire to collect information about the types of systems used, the management and distribution of aquaponics in South Africa. A total of 44 responses were captured within three months. The most commonly raised fish was tilapia (82%). The most commonly raised plants were leafy vegetables (75%). Since aquaponics is still not practiced by many and aquaponics systems are mostly small, aquaponics in South Africa can be considered an emerging practice. Most of the current aquaponics practitioners have limited aquaponics production knowledge. We therefore conclude that attention should be paid to raising the awareness about the potential of aquaponics, and raising the technological knowledge of aquaponics operators to increase the number of aquaponics operations and to increase the total amount of food produced in and with aquaponics.
The Limpopo Basin is prone to frequent droughts and short season rainfall making agricultural pro... more The Limpopo Basin is prone to frequent droughts and short season rainfall making agricultural production a very risky enterprise. The need assist to farmers and rural communities to optimize the utilization of low rainwater and existing SWI to boost agricultural productivity, standard of living and reduce poverty. A multi-level participatory approach shall be used to assess the causes of the SWIs failure in all the four basin countries. Rehabilitation guidelines which shall consider governance, institutional issues, technical, environmental compliance issues and multiple use systems (MUS) shall be produced by a team of multi-disciplinary experts. Additionally, the study shall explore alternative design approaches of new SWIs that will support multiple use systems (small-scale cash crop irrigation schemes, domestic use, livestock watering, aquaculture, rural industries, etc), improve livelihood of the rural community, improved food security and nutritional requirements for children and women. Field trials and demonstrations of rain water harvesting (RWH) techniques shall be done with the utmost cooperation of the farming community as a way of empowering them, fostering ownership and ultimate adoption of the recommended technologie
The potential benefits from smallholder irrigation schemes are rarely realised due to unsatisfact... more The potential benefits from smallholder irrigation schemes are rarely realised due to unsatisfactory performance of their water delivery systems. A study was conducted to quantify and evaluate water delivery performance indicators of adequacy (Ad), equity (Eq) and dependability (Dp) in three sub-blocks of Nyanyadzi smallholder irrigation scheme using water requirement analysis and a questionnaire survey. The water delivery performance evaluation was carried out between October 1996 and January 1997 for two maize crops under supplementary irrigation and for two consecutive irrigation cycles. Water supply adequacy (ratio of supply to demand) in the first cycle was good (Ad>1.21) and became marginally good (0.96 to 1.01) and poor (Ad<0.74) in the second cycle. Adequacy of water supply to the sub-blocks decreased with increase in water requirement (r=-0.87). Water distribution equity (a spatial indicator) was poor in both cycles and Eq values ranged from 0.33 to 1.14. The manageme...
Journal of Water Supply: Research and Technology - Aqua
Irrigation consumes approximately 70% of total freshwater use worldwide. This necessitates the us... more Irrigation consumes approximately 70% of total freshwater use worldwide. This necessitates the use of efficient irrigation methods such as micro-irrigation. Moistube irrigation (MI) is a new subsurface irrigation technology where the water emits from a semi-permeable membrane of the Moistube at a slow rate depending on the applied pressure and soil water potential. There is currently limited information on the performance of Moistube tapes with respect to discharge as a function of pressure or water quality. The aim of this study was to determine the flow characteristics of Moistube tapes as a function of pressure and the effect of suspended and dissolved solids on the emission characteristics. The pressure–discharge relationship was determined within a range of 20 kPa and 100 kPa. The clogging of the Moistube was determined using water containing low, moderate and high concentrations of suspended and dissolved solids at 20 kPa and 30 kPa. The results indicated that the Moistube discharge follows a power function with the applied pressure. The discharge decreased linearly over time because of clogging. Suspended solids had a more severe clogging effect on Moistube than dissolved solids. The results of this study should help in the design, operation and maintenance of MI systems. doi: 10.2166/aqua.2018.166 om https://iwaponline.com/aqua/article-pdf/67/5/438/481710/jws0670438.pdf er 2019 Edwin Kimutai Kanda (corresponding author) Aidan Senzanje School of Engineering, University of KwaZulu-Natal, P. Bag X01, Scottsville, 3209, Pietermaritzburg, South Africa E-mail: [email protected] Tafadzwanashe Mabhaudhi School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, P. Bag X01, Scottsville, 3209, Pietermaritzburg, South Africa
Abstract The water-energy-food (WEF) nexus facilitates understanding of the intricate and dynamic... more Abstract The water-energy-food (WEF) nexus facilitates understanding of the intricate and dynamic interlinkages among the three resources. Its implementation can enhance resource securities and sustainable development. Despite its potential, full adoption of the approach has been hindered by a lack of actionable strategies to guide its practical application. This is attributed to (i) poor data (ii) lack of empirical evidence, (iii) inadequate analytical tools, and (iv) lack of clarity on applicable spatial scale. This study undertook a literature review, coupled with systemic analyses of a WEF nexus analytical model, whose outputs were used as a basis to develop a Theory of Change, an iterative outline for operationalising the approach in the context of southern Africa. The consultative and iterative Theory of Change culminated with the formulation of pathways to (i) overcome the barriers impeding WEF nexus operationalisation, (ii) mitigation of trade-offs while enhancing synergies towards attaining simultaneous resource securities, (iii) poverty alleviation and reduction of inequalities, and (iv) reconciling policy with implementation scale. The WEF nexus operationalisation outcomes are linked to Sustainable Development Goals 2 (zero hunger), 6 (clean water and sanitation), and 7 (affordable and clean energy), with synergies to SDGs 1 (no poverty), 5 (gender equality), 8 (decent work and economic growth), 12 (responsible consumption and production), 13 (climate action), 14 (life below water), and 15 (life on land). Operationalising the WEF nexus through an interactive process can inform sustainable pathways towards resource security, job and wealth creation, improved livelihoods and well-being, and regional integration.
Kanda, E.K., T. Mabhaudhi and A. Senzanje, 2018. Coupling hydrological and crop models for improv... more Kanda, E.K., T. Mabhaudhi and A. Senzanje, 2018. Coupling hydrological and crop models for improved agricultural water management – A review. Bulg. J. Agric. Sci., 24 (3): 380–390 Understanding the relationships among plant, soil, and water is important in agricultural water management practices. Simulation of the soil water balance is central to improving crop water productivity. Individual crop or hydrological models have shortcomings due to the simplifi cation of the surface or subsurface processes. Coupling of crop and hydrological models helps in understanding the complex processes involved in crop production. This review highlights the application of coupled crop and hydrological models in simulation of crop response to water availability. The hydrological models considered are CHAIN-2D, HYDRUS-1D, HYDRUS 2D/3D, and MODFLOW. The crop growth models considered are the water-driven model (AquaCrop), solar-radiation driven model (EPIC), and the carbon-driven models (WOFOST and DSS...
Limited understanding of the complex interactions of factors that influence the sustainability of... more Limited understanding of the complex interactions of factors that influence the sustainability of access to improved water services poses a threat to rural livelihoods. The study assessed the complex interactions of the factors using a network approach. The assessment was to understand the complex interaction of the factors resulting from their cause-effect relationship that influence the sustainability of access to improved water services in a rural municipality of South Africa. The results highlighted that limited budget, limited or no water supply and improper operation and maintenance were critical factors resulting from the cause-effect relationship of other factors that influenced the sustainability of access to improved water services in the study area. We conclude that critical factors with a cause-effect relationship can influence the sustainability of access to improved water services. As a result, this deprives rural communities of the benefits derived from accessing impr...
There is a need to mainstream traditional crops in sub-Saharan Africa, in order to tackle food an... more There is a need to mainstream traditional crops in sub-Saharan Africa, in order to tackle food and nutritional insecurity through incorporating nutritional quality into crop water productivity, in the wider context of the water–food–nutrition–health nexus. The objective of the study was to determine the effect of irrigation water regimes on the nutritional yield (NY) and nutritional water productivity (NWP) of cowpea under Moistube irrigation (MTI) and subsurface drip irrigation (SDI). We hypothesized that NY and NWP of cowpea were not different under MTI and SDI and that deficit irrigation improved NWP. The experiment was laid as a split-plot design arranged in randomized complete blocks, replicated 3 times, with 3 irrigation water regimes: 100% of crop evapotranspiration (ETc), 70% of ETc, and 40% of ETc. Irrigation type and water regime did not significantly (p > 0.05) affect the nutritional quality of cowpea. Similarly, NWP of crude fat (28.20–39.20 g∙m-3), ash (47.20–50.70...
Highlights Very few sediment yield events contribute to annual sediment yield. Any rainfall, runo... more Highlights Very few sediment yield events contribute to annual sediment yield. Any rainfall, runoff, and peak discharge event has the potential to generate the most extreme sediment yield event. Twenty year return period recommended for design of conservation structures. . Design of conservation structures includes both hydrologic and hydraulic designs. Hydrologic design involves estimation of design floods which are required for the sizing of the hydraulic structures. The minimum recommended return period for the design of conservation structures is 10 years but due to the projected levels of risk, and the fact that a few large events are likely to be responsible for the majority of the erosion, the 10-year return period currently recommended may be inadequate. This study investigated system design criteria and the capital cost of varying design return periods for soil and water conservation structures in the sugar industry of South Africa. Observed rainfall data and results of run...
Moistube irrigation (MTI) is a type of technology which uses a semipermeable membrane to emit wat... more Moistube irrigation (MTI) is a type of technology which uses a semipermeable membrane to emit water continuously in response to soil water potential and applied pressure. Soil water dynamics under MTI incorporating plant water uptake have not been studied. Therefore, this study aimed at determining the soil water distribution under MTI, using cowpea as a reference crop. The effect of Moistube placement depth on the soil water dynamics under MTI was also determined. The experiment was carried out in tunnels with MTI and subsurface drip irrigation (SDI) as a control. The HYDRUS 2D/3D model was calibrated and thereafter used to simulate soil water dynamics for different placement depths. The soil water content above the Moistube/drip lateral was higher under SDI than MTI, while the lateral movement of water was similar for both irrigation types. The simulated soil water contents closely matched (coefficient of determination [R2] ≥ 0.57, root mean square error [RMSE] ≤ 0.029 cm3 cm−3, n...
We investigated the conceptual capability of Moistube irrigation to discharge under zero applied ... more We investigated the conceptual capability of Moistube irrigation to discharge under zero applied positive pressure under varied climatic conditions by inducing an artificial evaporative demand (Ed) or negative pressure around moistube tubing. This was premised on the null hypothesis that an artificially induced Ed or negative pressure does not impact moistube discharge. Moistube tubing was enclosed in a 1 m long PVC conduit. A 20 l water reservoir placed on an electronic balance provided a continuous supply of water whilst a three-speed hot air blower facilitated the radiative factor and advection process. The procedure was conducted under varied climatic conditions of air velocities (ua) 1.2 m.s−1, 2.5 m.s−1, and 3.0 m.s−1 and the experiment run times were 159 h, 134 h and 10 h, respectively. The average temperature (Tave) and relative humidity (RH) data for ua = 1.2 m.s−1 were 53°C and 7.31%, whilst for ua = 2.5 m.s−1, Tave was 56°C and RH = 7.19%, and for ua = 3.0 m.s−1, Tave was...
ObjectiveThe analytical study systematically reviewed the evidence about the IWRM water strategy ... more ObjectiveThe analytical study systematically reviewed the evidence about the IWRM water strategy model. The study analysed the IWRM strategy advances and practical implications it had, since inception on effective water management in East, West and Southern Africa.MethodsThe study adopted the Preferred Reporting Items for Systematic Review and Meta-analysis Protocols (PRISMA-P) and the scoping literature review approach. The study searched selected databases for peer-reviewed articles, books, and grey literature. DistillerSR software was used for article screening. A constructionist thematic analysis was employed to extract recurring themes amongst the regions.ResultsThe systematic literature review detailed the adoption, policy revisions and growing/emerging policy trends and issues (or considerations) on IWRM in East, West and Southern Africa. Thematic analysis derived four cross-cutting themes that contributed to IWRM strategy implementation and adoption. The identified four them...
Moistube irrigation (MTI) is a new subsurface irrigation technology where the water emits from a ... more Moistube irrigation (MTI) is a new subsurface irrigation technology where the water emits from a semi-permeable membrane at a slow rate depending on applied pressure and soil water potential. There is lack of information on how various crops respond to MTI. This study determined growth, yield and water use efficiency (WUE) of cowpea (Vigna unguiculata (L.) Walp) under varying water regimes under MTI and subsurface drip irrigation (SDI), using field and glasshouse experiments in summer and winter of 2018, respectively. A split-plot design arranged in randomized complete blocks, replicated 3 times, with SDI as the control experiment was used. The main plot was irrigation type while the sub-plots were the water regimes. The water treatments consisted of full irrigation (100% of crop water requirement (ETc)), and deficit irrigation (DI) of 70% ETc and 40% ETc. Water deficit had a significant effect (p < 0.05) on time to flowering; plants under 40% ETc flowered 14 days earlier than pl...
The Agricultural Catchments Research Unit (ACRU) model is a daily time step physical-conceptual a... more The Agricultural Catchments Research Unit (ACRU) model is a daily time step physical-conceptual agrohydrological model with various applications, design hydrology being one of them. Model verification is a measure of model performance and streamflow, soil water content and sediment yield simulated by the ACRU model have been extensively verified against observed data in southern Africa and internationally. The primary objective of this study was to verify simulated runoff volume, peak discharge and sediment yield against observed data from small catchments, under both bare fallow conditions and sugarcane production, which were located at La Mercy in South Africa. The study area comprised 4 research catchments, 101, 102, 103 and 104, monitored both under bare fallow conditions and sugarcane production, with different management practices per catchment. Observed data comprised: daily rainfall, maximum and minimum temperature, A-pan evaporation and runoff for the period 1978–1995, and...
Irrigated agriculture is under pressure to increase water use efficiency and crop water productiv... more Irrigated agriculture is under pressure to increase water use efficiency and crop water productivity because of inter-sectoral competition for scarce water resources. The shift to micro-irrigation has improved crop quality, yield and water use efficiency. Subsurface drip irrigation significantly reduces non-beneficial water balance components such as runoff and soil evaporation. However, the problem of water loss by deep percolation still exists in this method. Moistube irrigation is a relatively new type of irrigation method where water flows out of the Moistube nanopores as a function of soil water potential and operating pressure. It supplies water continuously to the crop at 80-90% of the field capacity. Therefore, it is a form of deficit irrigation. Based on the previous studies, this paper reviews Moistube irrigation technology by highlighting its hydraulic characteristics, crop growth and yield response, water use efficiency, clogging characteristics and the soil water dynamics. Areas which need further research are also described which can provide a reference for further studies in the relevant area.
The need to cultivate effluent-irrigated rice is paramount and synonymous with treated wastewater... more The need to cultivate effluent-irrigated rice is paramount and synonymous with treated wastewater reuse, recycling and water resources management. A trial in a peri-urban set-up with a low-cost decentralized wastewater treatment system (DEWATS) was carried out in the 2017 and 2018 cropping seasons to assess the effect of irrigation water reuse management techniques on the yield and water productivity of rice. It was hypothesized that anaerobic baffled reactor (ABR) irrigation water management does not have an effect on the yield of peri-urban grown rice. The impacts of irrigation water management techniques were very significant (P < 0.001) on the number of irrigation events, amount of irrigation and daily water balance. The impact was not significant (P > 0.05) on the tiller numbers per plant; it was however significant (P < 0.05) on the panicle numbers per plant. The effects were not significant (P > 0.05) on the plant height but significant (P < 0.05) on the yield ...
This paper contains a critical review of the norms employed in the design of soil and water conse... more This paper contains a critical review of the norms employed in the design of soil and water conservation structures in the South African sugar industry and highlights research needs in order to update them. Sugarcane in South Africa is grown on wide-ranging soils, sometimes in non-ideal climates and on steep topographies where soils are vulnerable to erosion. A consequence of unsustainable soil loss is reduction in field production capacity. Sugarcane fields are protected against erosion through, inter alia, the use of engineered waterways, contour banks and spill-over roads. The South African Sugarcane Research Institute (SASRI), previously known as the South African Sugar Experiment Station (SASEX), developed a nomograph to easily compute the maximum width of field panels based on soil type, tillage method, replant method, surface structures to control runoff, surface cover and slope. This was followed by guidelines and norms for the design of soil and water conservation structure...
Physics and Chemistry of the Earth, Parts A/B/C, 2018
Water control infrastructure in smallholder irrigation schemes (SISs) is supposed to be engineere... more Water control infrastructure in smallholder irrigation schemes (SISs) is supposed to be engineered for resilience. Resilience can be defined as the ability of the water control infrastructure to absorb natural and man-made disturbances while retaining functionality. Infrastructure remains constant in the face of scheme dynamic social changes and changes in self-organization and the capacity to adapt to stress. Irrigation schemes are an indispensable component of economic growth, poverty reduction, in smallholder irrigation schemes across Africa (Tortajada, 2016). Although infrastructure in SIS is critical for water conveyance, it needs to closely relate to policies, institutions (both formal and informal), laws, regulations, management practices, and participation models for the efficient management of water
Aquaponic system is a productive, innovative and sustainable fish and vegetable production system... more Aquaponic system is a productive, innovative and sustainable fish and vegetable production system that could contribute to the needed innovation in agriculture in the face of drought, soil pollution and climate change. Aquaponics are still an emerging practice worldwide, but particularly in South Africa. This study was conducted in 2016 using an online survey questionnaire to collect information about the types of systems used, the management and distribution of aquaponics in South Africa. A total of 44 responses were captured within three months. The most commonly raised fish was tilapia (82%). The most commonly raised plants were leafy vegetables (75%). Since aquaponics is still not practiced by many and aquaponics systems are mostly small, aquaponics in South Africa can be considered an emerging practice. Most of the current aquaponics practitioners have limited aquaponics production knowledge. We therefore conclude that attention should be paid to raising the awareness about the potential of aquaponics, and raising the technological knowledge of aquaponics operators to increase the number of aquaponics operations and to increase the total amount of food produced in and with aquaponics.
The Limpopo Basin is prone to frequent droughts and short season rainfall making agricultural pro... more The Limpopo Basin is prone to frequent droughts and short season rainfall making agricultural production a very risky enterprise. The need assist to farmers and rural communities to optimize the utilization of low rainwater and existing SWI to boost agricultural productivity, standard of living and reduce poverty. A multi-level participatory approach shall be used to assess the causes of the SWIs failure in all the four basin countries. Rehabilitation guidelines which shall consider governance, institutional issues, technical, environmental compliance issues and multiple use systems (MUS) shall be produced by a team of multi-disciplinary experts. Additionally, the study shall explore alternative design approaches of new SWIs that will support multiple use systems (small-scale cash crop irrigation schemes, domestic use, livestock watering, aquaculture, rural industries, etc), improve livelihood of the rural community, improved food security and nutritional requirements for children and women. Field trials and demonstrations of rain water harvesting (RWH) techniques shall be done with the utmost cooperation of the farming community as a way of empowering them, fostering ownership and ultimate adoption of the recommended technologie
The potential benefits from smallholder irrigation schemes are rarely realised due to unsatisfact... more The potential benefits from smallholder irrigation schemes are rarely realised due to unsatisfactory performance of their water delivery systems. A study was conducted to quantify and evaluate water delivery performance indicators of adequacy (Ad), equity (Eq) and dependability (Dp) in three sub-blocks of Nyanyadzi smallholder irrigation scheme using water requirement analysis and a questionnaire survey. The water delivery performance evaluation was carried out between October 1996 and January 1997 for two maize crops under supplementary irrigation and for two consecutive irrigation cycles. Water supply adequacy (ratio of supply to demand) in the first cycle was good (Ad>1.21) and became marginally good (0.96 to 1.01) and poor (Ad<0.74) in the second cycle. Adequacy of water supply to the sub-blocks decreased with increase in water requirement (r=-0.87). Water distribution equity (a spatial indicator) was poor in both cycles and Eq values ranged from 0.33 to 1.14. The manageme...
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Papers by Aidan Senzanje