Methods Of Irrigation
In this method of surface irrigation, water is applied to the field by furrow which are small canales having a continuous our nearly uniform slope in the direction of irrigation. Water flowing in the furrow into the soil spreads laterally to irrigate the area between furrows.
The rate of lateral spread of water in the soil depends on soil type.i.e. For a given time, water will infiltrate more vertically and less laterally in relatively sandy soils than in clay soil.
Where the land grade is less than 1% in the direction of furrow, striate graded furrows may be adapted. The grade can be as much as 2 to 3% depending on the soil type and the rainfall intensity, which affects erosion. When field sloped is too steep to align the furrows down the slope, control furrows which run along curved routed may be used. Spacing of furrows depends on the crop type and the type of machinery used for cultivation and planting.
Length of furrows depends largely on permeability of the soil, the available labor and skill, and experiences of the irrigation.
Flow rates are related to the infiltration to the rate of the soil.
Longitudinal slope of furrow depends up on the soil type, especially its errodiability and the velocity of flow. slope may be related to discharge as follows.
slope % 0.25 0.5 0.75 1.0 1.5 2.0
Qmax ( m3/hr) 9.0 4.5 3.0 2.2 1.5 1.1
Furrows are small channels, which carry water down the land slope between the crop rows. Water infiltrates into the soil as it moves along the slope. The crop is usually grown on the ridges between the furrows. This method is suitable for all row crops and for crops that cannot stand in water for long periods (e.g. 12-24 hours).
Boarder – strip Irrigation
The farms are divided into number of strips of 5 to 20 meters wide and 100 to 400 meters long. Parallel earth bunds or levees are provided in order to guide the advancing sheet of water.
Recommended safe limits of longitudinal slope also depends on the soil texture:
Sandy loam to sandy soils 0.25 – 0.6%
Medium loam soils 0.2 – 0.4%
Clay to clay loam soils 0.05 – 0.2%
Borders are long, sloping strips of land separated by bunds. They are sometimes called border strips.
Irrigation water can be fed to the border in several ways: opening up the channel bank, using small outlets or gates or by means of siphons or spiles. A sheet of water flows down the slope of the border, guided by the bunds on either side.
Large stream of water is applied to almost level and smaller unit of fields which are surrounded by levees or bunds. The applied water is retained in the basin until it filtrates.
Soil type, stream size and irrigation depth are the important factors indeterming the basin area.
Method of irrigation Type of Crop suited
Border strip method Wheat, Leafy vegetables, Fodders
Furrow method Cotton, Sugarcane, Potatoes
Basin method Orchard trees
Basins are flat areas of land, surrounded by low bunds (see section 2.2.2). The bunds prevent the water from flowing to the adjacent fields. Basin irrigation is commonly used for rice grown on flat lands or in terraces on hillsides (see Figure 2a). Trees can also be grown in basins, where one tree is usually located in the middle of a small basin In general, the basin method is suitable for crops that are unaffected by standing in water for long periods
It is mostly used for young growth, to humid the atmosphere, for soil compaction( specially for sandy loam soils before planting, for land having up and down slope and used to wash out plant leaves especially in dusty area.
Sprinkler irrigation offers a means of irrigating areas which are so irregular that they prevent use of any surface irrigation methods. By using a low supply rate, deep percolation or surface runoff and erosion can be minimized. Offsetting these advantages is the relatively high cost of the sprinkling equipment and the permanent installations necessary to supply water to the sprinkler lines.
Very low delivery rates may also result in fairly high evaporation from the spray and the wetted vegetation. It is impossible to get completely uniform distribution of water around a sprinkler head and spacing of the heads must be planned to overlap spray areas so that distribution is essentially uniform
Economical to labour & uniform distribution.
Sprinkler irrigation is similar to natural rainfall. Water is pumped through a pipe system and then sprayed onto the crops through rotating sprinkler heads.
Sprinkler irrigation is a method of irrigation in which water is sprayed, or sprinkled through the air in rain like drops. The spray and sprinkling devices can be permanently set in place (solid set), temporarily set and then moved after a given amount of water has been applied (portable set or intermittent mechanical move), or they can be mounted on booms and pipelines that continuously travel across the land surface (wheel roll, linear move, center pivot).
Methods Of Irrigation