IRRIGATION SYSTEM

Our vision is to make efficient use of water in farming

WHAT IS IRRIGATION?

Irrigation is the process of applying water to soil, primarily to meet the water needs of growing plants. Water from rivers, reservoirs, lakes, or aquifers is pumped or flows by gravity through pipes, canals, ditches or even natural streams. Applying water to fields enhances the magnitude, quality and reliability of crop production. According to the Food and Agriculture Organization of the United Nations, irrigation contributes to about 40% of the world’s food production on 20% of the world’s crop production land. Various irrigation methods have been developed over time to meet the irrigation needs of certain crops in specific areas. The three main methods of irrigation are surface, sprinkler and drip/micro. Water flows over the soil by gravity for surface irrigation. Sprinkler irrigation applies water to the soil by sprinkling or spraying water droplets from fixed or moving systems. Microirrigation applies frequent, small applications by dripping, bubbling or spraying, and usually only wets a portion of the soil surface in the field. A fourth, and minor, irrigation method is subirrigation where the water table is raised to or held near the plant root zone using ditches or subsurface drains to supply the water

 

SURFACE IRRIGATION

Surface irrigation entails water flowing by gravity over soil. Water is usually supplied by gravity from the water source through canals, pipes or ditches to the field. In some locations, however, water may need to be pumped from the source to a field at a higher elevation. Types of surface irrigation systems include furrow, basin and border irrigation. Surface irrigation systems are typically used for field crops, pastures and orchards. Efficiency of surface irrigation systems vary tremendously because of variations in soil type, field uniformity, crop type and management. Surface irrigation is often considered less efficient than sprinkler irrigation or microirrigation because soil, not a pipe, conveys the water within surface irrigated fields. However, a well managed surface irrigation system on a uniform soil with a runoff reuse system can approach 90% application efficiency.

 

surface irrigation

FURROW IRRIGATION

When furrow irrigating, water flows in evenly spaced furrows or corrugates that are typically 0.1–0.3 m wide on fields with slopes of 0.1–3%. Water commonly flows in furrows for 12–24 hours during irrigation, but shorter or longer durations may be used depending on furrow length, soil properties, and water management considerations. Inflow rates for individual furrows can vary from about 10 to 100 L min-1 , again depending on soil, slope, field length and management considerations. Ideally, water should advance across the field in about 25% of the total irrigation time to uniformly irrigate the field. Since soil erosion increases as field slope and inflow rate increase, the flow rate must be carefully managed on fields with steeper slopes (>1%). Low inflow rates and long irrigation durations may be needed to apply the desired amount of water during irrigation on soils with low infiltration rate.

Conversely, higher inflow rates are often needed on fields with low slopes and/or high infiltration rate soils in order for the water to flow across the field and uniformly irrigate the upper and lower portions of the field. Inflow to irrigation furrows may be supplied from gated pipe or ditches (earthen or concrete). Siphon tubes are frequently used to convey and regulate water flow from ditches to individual furrows. By creating a siphon, water flows through the tube, over the ditch bank, and into the furrow as long as the tube outlet is lower than the water elevation in the ditch. Furrow inflow rate is controlled by tube diameter and the elevation difference between the ditch water level and tube outlet. Gated pipe distributes water to furrows through evenly spaced outlets on the pipe. Furrow inflow rate is controlled by outlet opening and water pressure within the gated pipe. With earthen ditches, water flows through a breach or other opening in the ditch bank to individual furrows or a smaller feed ditch that distributes water to several furrows.

It is much more difficult to regulate flow through a breach in an earthen ditch than through siphon tubes or pipe gates. Furrow irrigation requires lower capital investment, less technical knowledge and greater labor than most other irrigation systems. Fields can be irrigated without leveling or grading because the water flows in furrows. Furrow irrigation is not well suited to automation because water flow rate must be adjusted for each furrow for each irrigation.

FURROW IRRIGATION

OTHER IRRIGATION SYSTEM

Surface irrigation. Water is distributed over and across the land by gravity, no mechanical pump involved.

1. Localized irrigation

2. Drip irrigation

3. Sprinkler irrigation

4. Center pivot irrigation

5. Lateral move irrigation

6. Sub-irrigation

7. Manual irrigation

SUBIRRIGATION

Subirrigation applies water below the soil surface to raise the watertable into or near the plant root zone. Subirrigation is not often used in arid or semi-arid irrigated areas where irrigation is often needed to germinate crops. It is typically used in conjunction with subsurface drainage, or controlled drainage. Subsurface drainage lowers the watertable and removes excess water through open ditches or perforated pipe. Watertable depth can be controlled by installing a weir on the drainage system. During wet periods, the watertable is lowered so the root zone remains unsaturated. During dry periods, water is pumped into the drainage system to raise the watertable and provide additional water for plant growth. In some situations, drained water can be stored for use when irrigating

 

Choosing an irrigation system

Choosing an irrigation system is a difficult task. Irrigation systems are as varied as the people who use them. The right selection for a user depends on soil, water and climatic conditions as well as crop types, user knowledge and preference, capital and operating costs, and infastructure availability. No system is best for all situations. Some typical advantages and disadvantages of irrigationsystems are shown in . Sprinkler and microirrigation are often better choices than surface irrigation on sandy soil where excessive percolation is a problem. Surface irrigation may be better in arid, windy areas where wind and evaporation losses can be significant. Surface irrigation offers less control of application depth so small, frequent irrigations are not practical for water sensitive crops, which are better suited to microirrigation, solid-set or center pivot systems