LWU: Lesson - Irrigation Methods (Topic 5.5) 📖

⏳ Estimated Reading/Watching Time: 5 - 7 minutes

Describe the different methods of irrigation.

Irrigation

A pie chart displays the distribution of freshwater usage across three sectors:

Domestic (blue slice): 10%
Industry (light green slice): 20%
Agriculture (dark green slice): 70% — **The largest human use of freshwater is agriculture.**

Water covers 70% of our planet yet water is not easily available in all areas on Earth. Much of this water is saltwater or is locked in frozen form in glaciers and ice caps.

To obtain water from the oceans, desalinization plants must remove the salts and minerals from seawater, a costly process that most countries cannot afford. Utilizing frozen water for consumption is just as difficult because the ice must first be melted and then transported to warmer climates. All of this is expensive, so most communities try to obtain water resources closer to home.

Overall, we use about 27% of accessible freshwater/year. The largest human use of freshwater globally is for irrigation, mostly crop irrigation. Although large-scale, commercial irrigation practices are fairly new, humans have attempted to irrigate crops in various ways for centuries. The availability of water has long been a limiting factor for crop growth even in fertile soil regions such as the Great Plains of North America. The development of irrigation helped remove water as a limiting factor and increase food production.

Early irrigation practices involved dams, dikes, canals, aqueducts, terraces, and even seasonal flooding. Gravity and human or animal power were mostly used to move water from water sources to crops.

As machinery and technology advanced, irrigation techniques advanced accordingly. Today, commercial irrigation is highly advanced although remnants of ancient irrigation techniques are still used in some developing countries.

Essential Knowledge

The largest human use of freshwater is for irrigation (70%).

Irrigation of crops uses trillions of gallons of water per year and that water comes from rivers, lakes, streams, and groundwater. There are four main types of irrigation used in agriculture today: furrow irrigation, flood irrigation, drip irrigation, and spray irrigation. Each of these types of irrigation has its advantages and disadvantages and each can waste water if not carefully controlled. Extraction, application, and runoff of water all play an important role in any type of irrigation.

A main focus of contemporary irrigation is to conserve water, especially in more arid regions.

Essential Knowledge

Types of irrigation include drip irrigation, flood irrigation, furrow irrigation, drip irrigation, and spray irrigation.

Explore the tabs below to learn more about each type of irrigation. Do you use one of these types at your house? At our house, our yard is watered with spray irrigation and our flowerbeds are watered with drip irrigation.

Furrow Irrigation

Rows of green crops stretch toward the horizon.
The setting sun casts an orange glow in the partly cloudy sky.
Puddles of water reflect the sunset. — **A farm using furrow irrigation.**

Furrow irrigation is a method of watering crops by creating long narrow channels or furrows between the rows of plants. Water flows through these furrows by gravity and reaches the roots of the plants. Water is either directed or pumped into furrows between the crops being grown. Using the slope of the land, the water then runs the length of the field and plants are able to access the water via their root systems.

Benefits:

✅ Inexpensive

✅ Uses little energy

✅ Easy to implement

Drawbacks:

❌ About 1/3 of the water is lost due to evaporation and runoff

❌ Soil can become waterlogged, eroded if not carefully managed

❌ Can cause soil salinization if not carefully managed

❌ Runoff can pollute natural water sources

Flood Irrigation

A serene rice paddy scene.

Multiple rectangular plots with young, vibrant green rice plants.
Trees and an electricity pylon in the background add a mix of natural and man-made elements. — **Rice is one of the main grains used to feed the world and rice is typically grown using flood irrigation.**

Flood irrigation involves flooding an agricultural field with water. It is similar to furrow irrigation but rather than having furrows, the entire crop is submerged in water.

Benefits:

✅ Inexpensive

✅ Uses little energy

✅ Easy to implement

✅ Promotes soil fertility and nutrient supply

Drawbacks:

❌ About 20% of the water is lost due to evaporation and runoff

❌ Soil can become waterlogged, eroded if not carefully managed

❌ Can cause soil salinization if not carefully managed

❌ Runoff can pollute natural water sources

❌ Water can pool unevenly, causing some crops to be overwatered and some underwatered

Spray Irrigation

The image showcases efficient irrigation in a cabbage field. Lush green crops are irrigated by evenly spaced sprinklers. — **Spray irrigation is a popular method of irrigating crops.**

Spray irrigation, also known as sprinkler irrigation, is a method of applying water to a controlled manner that is similar to rainfall. The water is distributed through a network that may consist of pumps, valves, pipes, and sprinklers. The sprinklers can be moved by hand but are more often automated to move in a circle or across the entire crop field.

Benefits:

✅ More efficient water use than flood or furrow irrigation

✅ Less water is lost to evaporation and runoff

✅ Easy to implement

✅ Can handle large areas

✅ Can automate on a schedule

Drawbacks:

❌ More expensive than flood or furrow irrigation

❌ Requires more energy to run

❌ Can evaporate before plants absorb the water

❌ Sensitive to wind patterns

❌ Can cause overwatering, waterlogging, and other soil issues if not managed correctly

Drip Irrigation

Drip irrigation uses perforated hoses to release small amounts of water to plant roots. This system is especially useful for smaller-scale operations.

Benefits:

✅ Only about 5% is lost to evaporation

✅ Most efficient method

✅ Prevents soil erosion

✅ Helps prevent leaf diseases

✅ Can automate on a schedule

Drawbacks:

❌ Most expensive irrigation method

❌ Requires more energy to run

❌ System can become clogged

❌ Difficult to check when hoses are covered with mulch

Essential Knowledge

Furrow irrigation involves cutting furrows between crop rows and filling them with water. This system is inexpensive, but about 1/3 of the water is lost to evaporation and runoff.

Flood irrigation involves flooding an agricultural field with water. This system sees about 20% of the water lost to evaporation and runoff. This can also lead to waterlogging of the soil.

Spray irrigation involves pumping ground water into spray nozzles across an agricultural field. This system is more efficient than flood and furrow irrigation, with only 1/4 or less of the water lost to evaporation or runoff. However, spray systems are more expensive than flood and furrow irrigation, and also require energy to run.

Drip irrigation uses perforated hoses to release small amounts of water to plant roots. This system is the most efficient, with only about 5% of water lost to evaporation and runoff. However, this system is expensive and so is not used often.

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