Dr Calvin Sambo, Dr Khumbulani Dhavu and Sandisiwe Mahlamvu, researchers at the Agricultural Research Council’s natural resources and engineering division of the agricultural engineering campus, share generalised steps for a well-designed irrigation system to ensure high water use efficiency and food security.
South Africa is a country riddled with water scarcity because of unreliable rainfall patterns, low rainfall (below the global average), and high temperatures that increase evaporation and chances of frequent droughts. Consequently, there is a need to conserve the available water resources by promoting higher water use efficiency in sectors known to be high water consumers.
Agriculture is estimated to consume 62% of the available water in South Africa. This is a sector that is responsible for producing food to ensure food security and alleviation of poverty.
Irrigation provides water to crop fields to meet the crop water requirements for growth. The use of irrigation is to supplement water where the seasonal rainfall is not adequate to meet the water demand for the crop.
In South Africa, the water used for irrigation is sourced from already constrained water sources such as boreholes or rivers. To ensure high water use efficiency there is a need for well-designed irrigation systems because well-designed irrigation systems are crucial to ensuring optimal water distribution, maximising crop yields while conserving water resources.
To achieve this, factors such as soil type, crop water requirements, topography, and available water sources in the design process are considered. This results in an enhanced agricultural productivity contributing to food security, economic development, and environmental sustainability through the reduction of water wastage, reduced soil erosion, and application of water use efficient approaches.
Steps for a well-designed irrigation system
Generalised steps for a well-designed irrigation system to ensure high water use efficiency and food security are:
Site assessment
- Evaluate the land to be irrigated, considering its size, topography, and soil characteristics. This involves conducting soil tests to determine soil texture, fertility, and drainage capacity.
- Assess the water source(s) available for irrigation, such as rivers, wells, reservoirs, or groundwater.
Determine crop water requirements
- Identify the types of crops to be grown and their specific water needs, which depend on factors such as crop type, growth stage, and climate.
- Determine the crop water requirements based on factors such as evapotranspiration rates, crop coefficients, and local climate data.
Select irrigation method
- Choose an appropriate irrigation method based on factors such as soil type, crop type, water availability, and local conditions.
- Common irrigation methods include surface irrigation (furrow, flood), sprinkler irrigation, drip irrigation, and subsurface irrigation. Sprinkler and drip irrigation systems are generally more efficient than the surface irrigation systems.
Design water delivery system
- Design the layout of the irrigation system, including pipes, pumps, valves, and emitters (if applicable), to ensure efficient water distribution.
- Calculate pipe sizes, flow rates, and pressure requirements based on water source capacity, elevation changes, and friction losses.
Hydraulic analysis
- Perform hydraulic calculations to ensure adequate water pressure and flow rates throughout the irrigation system.
- Consider factors such as pipe sizing, pump capacity, head losses, and pressure variations along the distribution network.
Automation and control
- Determine the level of automation and control needed for the irrigation system, such as timers, sensors, and control valves.
- Incorporate technologies like soil moisture sensors, weather stations, and remote monitoring systems to optimise water use efficiency and manage irrigation scheduling.
Environmental considerations
- Assess potential negative environmental impacts of the irrigation scheme, such as waterlogging, soil erosion, and runoff.
- Implement measures to mitigate environmental risks, such as proper drainage systems, soil conservation practices, and water reuse/recycling.
Cost-benefit analysis
- Evaluate the costs associated with implementing and operating the irrigation scheme, including infrastructure, equipment, energy, and maintenance.
- Estimate the potential benefits in terms of increased crop yield, water savings, and economic returns.
Permitting and regulatory compliance
- Obtain necessary permits and approvals from regulatory authorities, such as water rights permits, environmental permits, and land use permits.
- Ensure compliance with relevant laws, regulations, and codes governing water use, land use, and environmental protection.
Implementation and monitoring
- Construct the irrigation system according to the design specifications and standards.
- Implement a monitoring and maintenance programme to regularly assess system performance, detect problems, and adjust as needed.
- Monitor water use, crop growth, and soil moisture levels to optimise irrigation scheduling and water management practices.
Training and capacity building
- Provide training to farmers and operators on proper operation and maintenance of the irrigation system.
- Build local capacity for sustainable water management practices and efficient irrigation techniques.
Adaptation and improvement
Following these steps and considering various factors, an irrigation system that meets the crop water requirements ensuring increased agricultural production with reduced water losses can be operationalised. As a result, this helps to conserve the limited water resources and improve food security in South Africa.
- Calvin Sambo, Dr Khumbulani Dhavu, Macdex Mutema and Sandisiwe Mahlamvu are researchers at the Agricultural Research Council’s natural resources and engineering division of the agricultural engineering campus. The views and opinions expressed in this article are those of the author and do not necessarily reflect the views or positions of Food For Mzansi.
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