Reports by the United Nations indicate that agriculture takes about 70% of freshwater worldwide. Furthermore, more and more people install sprinkler systems in their yards to combat the increasingly common drought conditions due to climate change. But are irrigation systems sustainable?
Irrigation systems like drip irrigation are sustainable because it allows water to drip slowly into the roots reducing water wastage. Others like surface irrigation aren’t sustainable because they lead to water wastage.
In this article, I’ll discuss sustainable and unsustainable irrigation systems. Also, I’ll highlight the importance of sustainable irrigation systems.
Sustainable Irrigation Systems
Sustainable irrigation systems include the ones which account for water wastage. In most irrigation systems, the rate of water wastage is higher than its replenishment rate, creating a disaster for future users. A lot of water is usually lost through runoff and evaporation, which takes time to recover. Droughts all over the US are getting more and more serious.
Therefore, the irrigation system must account for this water loss to be sustainable.
Let’s look at some of the most sustainable irrigation systems:
Drip Irrigation System
Drip irrigation, also called trickle, is the most sustainable irrigation system. It’s a widely used irrigation system in drier parts of the world, such as Israel, where surface water isn’t readily available. Hence, farmers must maximize water usage by conserving as much as possible.
As the name suggests, the system involves dripping water directly on the roots at very low pressure. For this reason, the system uses thin pipes with small holes known as emitters, which must be situated close to the roots. Thus, only the soil in contact with the roots gets wet.
Drip Irrigation System Layout
This irrigation system comprises the following elements :
- Pump unit.
- Control head.
- Main and sub-main lines.
- Laterals.
- Emitters or drippers.
The pump unit pumps water from the source to the control head with valves controlling the system’s pressure. Also, it has filters that remove any material present in the water. In some plans, the control head can include a nutrient/fertilizer tank to ensure the water has nutrients before it’s dispatched.
The water leaves the control head through the mains, sub-mains, and laterals, depending on the complexity of the systems. These pipes can be on the ground or slightly below the surface to protect them from direct sunlight. However, the mainlines and sub-mains are usually missing in small-scale systems.
The emitter spacing depends on the crop spacing. Therefore, it’s essential to consider your spacing before you install the system.
The emitters discharge water at a controlled rate. Ideally, you should increase the rate at the beginning to ensure the water wets a wider area, allowing the lateral roots to get enough water. Then you can reduce the rates after some time, providing the water goes deeper into the tap roots to meet the plant’s water needs.
Drip irrigation saves water lost through runoff and evaporation. However, you must control the system effectively. For instance, you should consider watering at night when temperatures are low to reduce evaporation.
Water Sources for Drip Irrigation
Your system might vary depending on your water source. Mostly, these systems are more economical in arid and semi-arid areas that use groundwater or wells. However, you can use surface water from rivers, lakes, or dams.
Also, tap water can be sustainable if you live in areas with plenty of water. But, it helps to invest in a storage tank to avoid inconveniences when water isn’t available.
In addition, ensure the water you use is clean. Thus, you should have filters within the system to avoid blocking the emitters. The openings range between 0.2 and 2.0 mm and can block easily from soil or suspended material.
Disadvantages of the Drip Irrigation System
- The system is expensive to install and maintain.
- Blockages are common and can result from unfilterable materials such as fertilizer, requiring the services of an engineer and increasing the maintenance cost.
- It’s not economical for small-scale farming where surface water is readily available.
Sprinkler Irrigation System
Sprinkler irrigation is a reasonably sustainable system, as it works like rainfall. Like drip irrigation, the water goes through a series of pipes. However, the water ends up in sprinklers that break it into tiny rain-like drops.
Sprinkler Irrigation System Layout
This irrigation system comprises the following elements:
- Pump unit.
- Mainlines and sub-main lines (depending on system complexity).
- Laterals.
- Sprinklers.
The pump unit pumps water through the main lines, the laterals, and the sprinklers. Unlike drip irrigation, the water must be under high pressure. But it also depends on the distance you want to cover.
Moreover, it helps to control the nozzle to avoid big drops that can cause erosion and increased runoff.
For large-scale systems, the mainlines and sub-main lines are permanent. The laterals are usually mobile, making moving from one farm location to another easier. Additionally, the system can include several sets of sprinklers about 9 meters (29.5 feet) apart.
The system has various designs, and you can choose between a solid fixed layout and a set-move design. The fixed design has numerous nozzles to ensure you don’t move the laterals to water the desired part. However, it’s more expensive.
With the set-move design, you need to move the laterals to cover the areas you need to water.
There’s also a self-propelled center pivot system since it rotates around the pivot point. The pivot is adjustable; hence, you can adjust it depending on the plant’s height.
Water Sources for Sprinkler Irrigation
Although a sprinkler can be sustainable, it requires more water than drip irrigation. Therefore, the best water sources include surface water, such as dams, lakes, and rivers. Underground water and wells are also ideal sources for the sprinkler system.
On the other hand, it’s impractical to run a sprinkler system using tap water. Although you can use it for small-scale applications such as watering a lawn, it’s not sustainable, especially where tap water is scarce.
The Cons of the Sprinkler Irrigation
- It’s expensive to install and maintain.
- It’s not as sustainable as drip irrigation since it requires more water. Also, unlike drip irrigation, the sprinkler loses water through evaporation, especially when it’s windy.
- It can spread pathogens within the crops due to the splashes. Other crop diseases thrive in wet plants and can therefore worsen an infection.
- Some systems, such as the set-move design, are labor intensive.
Unsustainable Irrigation Systems
Most farmers in rural areas across America and the world rely on surface water for irrigation. Therefore, they use cheap unsustainable systems leading to high levels of water wastage.
Here are several systems that fall under surface irrigation:
Furrow Irrigation
Furrow irrigation, also called flood irrigation, is a popular irrigation system. It replaces the bucket method, which requires a lot of labor. Therefore, people have embraced the system because it’s cheaper and easier to manage.
It involves small trenches that move water from the source to the farm. The crops are planted in rows/ridges, and the furrows are in the middle. The furrows are also interconnected like pipes from the water source.
Water Sources for Furrow Irrigation
Furrows will generally work with streams or small rivers because the size of the stream determines the water pressure. This system doesn’t work well with water under high pressure since it can cause erosion in the furrows. Also, the water can destroy the ridges, damaging the crops’ root system.
The furrows can be long or short, depending on the size of the stream. If the stream is larger, the furrows can be longer and vice versa.
Groundwater and wells are unsuitable for this system because it relies on gravity to drive the water through the furrows.
The Cons on Furrow Irrigation
- It’s only applicable where there’s stream water. Big rivers aren’t suitable because water can cause erosion.
- It’s unreliable for sloped areas because it relies on gravity to drive the water.
- It leads to high levels of water wastage through deep percolation and evaporation.
- It’s only ideal for row crops such as maize and sunflower.
Basin Irrigation
Basin irrigation works more like furrow irrigation. It involves enclosing water in a wide section of land using a bund, which is a wall or ridge about 50-100 cm (3.5 to 7 in) high and 100-150 cm (7 to 10.5 in) wide. Therefore, it’s most suitable for submerged crops that thrive in waterlogged soil, such as paddy rice.
The system involves draining the water from the source through furrows or canals that may be large or small, depending on the size of the land you want to farm. You can divide the land into small portions to ensure it’s well leveled. Otherwise, the water may not reach all corners.
Water Sources for Basin Irrigation
Basin irrigation is more applicable in flat areas with readily available surface water. You can irrigate directly from a river or stream by channeling the water to the basin through a furrow. Where gravity doesn’t work, you can use a pump and a horse pipe to drive the water from the source.
You can also irrigate from a lake or artificial dam.
The Cons of Basin Irrigation
- High water wastage levels since it involves waterlogging the soil.
- Works well in flat areas only since it relies on gravity.
- It’s labor intensive, especially when irrigating large areas or when you have to pump the water.
- The bunds can be affected by erosion during rainfall, flooding, or when used as a footpath.
The Importance of Sustainable Irrigation Systems
According to the United Nations, over 1.7 billion of the world’s population live near rivers. For this reason, there are high levels of water wastage, which could cause a water crisis in the future. Since most of the world’s water goes to agriculture, rethinking irrigation systems is one way to avert this crisis.
Here are the reasons why sustainable irrigation practices are vital:
Sustainable Irrigation Saves Water
As I mentioned earlier, most irrigation systems use water faster than it’s replenished. Therefore, it is essential to use water sparingly to ensure it lasts longer. Sustainable irrigation systems are convenient because they include localized watering.
So, they water as close to the root system as possible to ensure the plant gets enough water while minimizing wastage.
In addition, you can monitor and manipulate them to avoid overwatering. Also, with these systems, you can water crops when it’s most convenient such as during the night when the temperatures are lower and when it’s not windy, to avoid evaporation.
Thus, you use the water where you need it most to ensure it’s available for other uses such as cooking and general sanitation.
Sustainable Farming Ensures Consistent Food Production
If you’re using groundwater or a well, using a sustainable irrigation method could mean production all year round. However, with the current climatic changes, water sources will likely be scarce in a few years.
Additionally, the increasing population will need more food and farming land. Hence, this leads to further destruction of catchment areas. Therefore, the only way to ensure you have water for future farming is through conserving what you have.
The Systems Require Little or No Labor
With sustainable irrigation systems, the work comes during the installation process. But labor may be intense depending on the complexity of the system and the land size. However, once you install the system, you only need to monitor and operate it, which is easy.
Additionally, you might require regular checkups with the help of an expert to avoid blockages, which might be costly to repair.
They Enhance the Uptake of Nutrients
Sustainable irrigation systems are not only beneficial in protecting the environment. They also enhance crop production since crops take up most of the nutrients from the soil. In addition, these irrigation systems involve localized wetting of the soil. This ensures that nutrients such as fertilizer remain within the root system allowing the plants to maximize uptake.
Contrastingly, unsustainable systems involve runoff and deep percolation, sweeping away most nutrients. Consequently, this can lead to low yields or overuse of nutrients, which can be costly.
Final Thoughts
Irrigation contributes to more than half of the food consumed worldwide. However, water overuse is threatening this mode of farming, hence the need to adopt sustainable irrigation methods.
Drip irrigation and sprinklers are some of the most sustainable methods. Although they may be expensive to install, they are far more economical and practical than other irrigation systems.
Additionally, they can use surface or groundwater. So, you can use these systems in flat and sloped areas. Most importantly, they enhance water conservation while maximizing yields.