Surface irrigation is the oldest irrigation system where water is applied to the field through lined or unlined open channels and pipelines, by flooding or furrow method.
Surface irrigation is the simplest and the oldest irrigation system. Farmers use four types of the surface system which differ on how water flows on the field; wild flooding, basin, border, and furrow irrigation. All types are labour intensive but easy to establish and maintenance.
Surface irrigation is the oldest and most used type of irrigation systems. Even ancient farmers in Egypt, India, and China used a surface irrigation system to supply crops with water.
It’s a simple and easy system to manage because it doesn’t require any installation of irrigation mechanism. Water is simply applied to the field through lined or unlined open channels and pipelines. Water then flows across the surface until it covers the entire area provided for irrigation. After water application is stopped, applied water creates ponds on the field’s surface and then either drains or infiltrates into the soil.
Although it’s labour intensive, surface irrigation system has advantages in compare to sprinkler and drip irrigation. The most significant advantages are low initial cost, easy maintenance of the system, and compatibility with all soil types.
Based on the slope, the size and shape of the field, the end conditions, and how water flows into and over the field, surface irrigation is classified into:
- Wild flood irrigation
- Basin irrigation
- Border irrigation
- Furrow irrigation.
Each surface system has unique advantages and disadvantages depending on several factors: initial cost, size and shape of fields, soil characteristics, nature and availability of the water supply, climate, cropping patterns, and influences external to the surface irrigation system.
Wild flood irrigation
In flood irrigation, water is delivered in the field by ditch or pipe and flows over the soil surface through the crops. Despite its simplicity, this irrigation type has negative effects on crop and the soil, using both water and labour inefficiently.
While flooding, only half of applied water is used by the crop. The other half is lost to evaporation, runoff, infiltration of uncultivated areas, and transpiration through the leaves of weeds. For this reason, wild flooding is mainly used on uneven terrains to irrigate pasture, hay, and small grains. which are not affected by sufficient water
An important aspect to consider in wild flooding is that it’s a great solution to irrigate land that cannot be managed by other irrigation methods.
As the most common type of surface irrigation, basin irrigation is the oldest and most simple irrigation type. Basin irrigation requires leveled soil surface and a narrow ridge 15 to 50cm high on all sides of the field which will be the basin. Irrigated field is divided into smaller areas surrounded by small levees. Water is applied into each basin by various pipes and siphons or through the levee. Water is removed from the field with surface drains on the low contour levee.
Basin irrigation is suitable on moderate to slow intake soils and deep-rooted, closely spaced crops such as maize, grains, cotton, orchards. Crops, which do not tolerate flooding and soils subject to crusting can be basin irrigated by furrowing or using raised bed planting.
Despite its effective method of leaching salts from the soil profile into the deeper groundwater, basin irrigation has also some limitations:
- Levelling the field surface may represent the finance and labour issue for a farmer
- Soil tillage is limited due to the small field area
- Levees can be easily destroyed by entering of farm equipment into the field
- Challenging maintenance of narrow ridges (levees) along the field sides.
Basins range in size from those designed to irrigate individual trees or small areas of vegetable crops to rice paddies that occupy several acres.
Border irrigation is the type of flood irrigation which works on the principle of basin irrigation. Water is applied to the field through wide borders. The area between borders is border strip on which crop grows and may range 3-30 m (10-100 feet) in width. To manage a border irrigation, border surface must be levelled across its width so the water can spread uniformly across it.
Sloping borders are suitable for all crops such as grains, alfalfa, and tree fruits, except those that are sensitive to excessive water and too wet soil.
Furrow irrigation is an irrigation method where water is applied from open ditches or pipes through small channels or furrows along the field. As water flows through the channel, it infiltrates into the soil thus irrigating crops. According to furrow direction and level, they can be classified into:
- Level furrow (lengthwise levelled furrows)
- Contour furrow (furrows curved fit to field topography)
- Graded furrow (straight channels down the field slope)
Furrow irrigation is suitable for crops sensitive to too wet soil and excessive water over the stem. Furthermore, crops not suitable for flood irrigation can be irrigated with furrow irrigation method.
Although this method doesn’t require special farm equipment and can minimize irrigation costs, furrow irrigation also has disadvantages. These are:
- Labour intensive
- High accumulation of salts in the furrows
- Difficult passing of farm equipment across the furrows
- Furrow surface needs to be levelled
- Required farmer’s experience to divide water into each furrow and to maintain the correct flow rate
- Difficult to automate the system.
Low Cost or Efficient Surface Irrigation System?
Unlike other surface irrigation types, furrow irrigation is the most efficient one. It can achieve about 60% efficiency in water use. The other 40% is lost by evaporation, by deep percolation in the upper ends of the rows and in the most permeable soils, and run-off from the lower end of the rows. Due to the high potential of water efficiency, farmers increasingly use furrow irrigation system. Additionally, it’s constantly modernizing to become even more efficient. The result is improved water efficiency by reducing the amount of the excess water infiltrating into the upper part of the rows. Another important approach is to improve furrow irrigation efficiency by stabilizing soil structure with certain soil conditioners.
Surface irrigation systems are all low cost because they don’t need additional farm equipment and expensive maintenance. For this reason, this ancient irrigation practice is more favourable among farmers, especially those in developing countries.
Irrigation is an obligated and very important farm practice, so farmers aim to manage it as cheap and simple as possible.
- Tasos on December 8, 2021 @ 18:53:10
This post was created by Filip Gerin on July 19, 2021.