Introduction of the Sprinkler irrigation system:
Today, let us talk Sprinkler Irrigation Design, Layout, Components, Cost and Types of Sprinkler irrigation systems and their advantages, disadvantages.
Sprinkler irrigation is the process of irrigation by which water is sprayed on the land surface in the form of artificial rain. Water is distributed through a system of pipes generally by pumping. It is then sprayed into the air through sprinklers so that it breaks up into very small water drops which fall to the ground. The pump supply system, sprinklers & operating conditions must be designed to enable a uniform application of water. To make the precipitation, water under pressure is ejected through the nozzle of a device called a sprinkler. Sprinkle irrigation systems are available in various designs & irrigation capacities.
There are two basic categories of sprinkler heads, small & large. Compared to “large” sprinklers, “small” type sprinklers have a moderately small radius of throw and can work at low pressures and flow conditions. As the precipitation charge of “small” sprinklers is relatively light, the possibility of soil erosion is negligible. Thus, “small” type sprinklers are useful when irrigating a small piece of uneven land with narrow terraces.
Importance of Sprinkler System:
- Sprinkler irrigation maintains moisture in the soil. Moisture is essential for the germination of seeds.
- Water supplies two essential elements, hydrogen & oxygen to the crop.
- Irrigation is essential for the absorption of mineral nutrients by the plants from the soil.
- It is important for the growth of the roots of the crop plants.
Different types of Sprinkler irrigation systems:
Traditional spray systems:
This is one of the sprinkler irrigation systems that probably come to mind when you consider watering your lawn. The traditional spray method uses a pop-up head to spray water in the area surrounding it. It can normally be set to spray in a full circle, half circle or quarter circle. Although homeowners do understand the widespread water coverage that these sprinkler irrigation methods provide, they are not as capable as other types and therefore not as popular. These systems really spray too much water, so much in fact, that the ground cannot absorb it fast enough, leading to wasted water. If you do prefer this system, be sure that each sprinkler head is installed at a distance that allows it to cover the area that the next closest head does not.
Industrial spray system:
Higher pressure sprinklers that themselves shift in a circle are driven by a ball drive, gear drive, or impact mechanism (impact sprinklers). These can be designed to turn into a full or partial circle.
Rain guns are related to impact sprinkler, except that they generally operate at very high pressures of 40 – 130 lbf/in² (275 to 900 kPa) and flows of 50 – 1200 US gal/min (3 to 76 L/s), generally with nozzle diameters in the range of 0.5 – 1.9 inches (10 to 50 mm). In addition to irrigation, guns are used for industrial purposes, such as dust suppression and logging.
Many irrigation sprinklers are buried in the ground along with their supporting plumbing, though above ground & moving sprinklers are also common. Most irrigation sprinklers work through electric & hydraulic technology. That can be cooperatively turned on and turned off by actuating a solenoid-controlled valve.
Although soaker hoses are not theoretically sprinklers, they are a type of irrigation system & should be considered by homeowners before making a final decision. Soaker hoses are laid throughout, landscaping & emit water throughout the entire length of the hose, as opposed to just through the nozzle. Soaker hoses are a wise option for homeowners who have dense landscaping that is complex with water using one of the traditional sprinkler irrigation systems.
Between rotor & spray sprinkler irrigation systems, rotors are more efficient & are capable of covering a wider area in the yard. Like the drip systems, rotors also discharge water at a slower rate & are therefore more energy efficient. This system to be used solely on larger yards; however, newer models have been planned to accommodate a smaller area. Most rotor sprays agree with you to adjust the nozzle to change how far the water sprays & how much water is released, so you have complete manage as your landscaping situation changes throughout the year.
Fixed Systems contain a solid set (portable or permanent pipeline). There are enough laterals & sprinklers that none have to be moved to complete irrigation. In New Jersey, this method is used predominantly on blueberries & cranberries for both irrigation and frost control.
Periodic Move Systems:
Periodic Move Systems include hand move, side roll, end tow laterals, hose fed laterals or pull laterals, gun type sprinklers, boom sprinklers, & perforated pipe. In New Jersey, the hand move, stationary gun, & some side roll/wheel roll systems are used primarily on vegetable crops.
Continuous Move/Self Move Systems:
Continuous Move or Self Move Systems contain center pivots, linear move laterals, & traveling gun sprinklers.
Main features and application of the sprinkler system:
- A whole set of technology is preassembled for easy use
- It is very easy to install
- It creates light precipitation & more irrigation coverage, creation, soil erosion nearly negligible
- Land leveling is not essential to use
- It is low-cost & durable equipment
Due to these above features, sprinkle irrigation works well on rolling land with porous soil. Its optimal use is for irrigation of close developed crops of low height; it is not convenient to irrigate tall crops with sprinklers. Additionally, application uniformity can be influenced by heavy winds & water pressure. Hence, the sprinkler method should be operated during non-windy periods & water pressure must be regulated by valves.
Components of the sprinkler irrigation system:
- A pump unit
- Tubings- main/submains and laterals
- Sprinkler head
- Other accessories such as valves, bends, plugs & risers
- Pumping Unit: Sprinkler irrigation method distributes water by spraying it over the fields. The pressure forces the water through sprinklers or through perforations or nozzles in pipelines & then forms a spray. A high speed centrifugal or turbine pump used for operating sprinkler irrigation for individual fields. A centrifugal pump is used when the distance from the pump inlet to the water surface is less than 8 meters. For pumping water from deep wells or more than 8 meters, a turbine pump is suggested. The driving part may be either an electric motor or an internal combustion engine.
- Tubings: Mains or submains and laterals: The tubings consist of mainline, submains & laterals. The main line conveys water from the source & distributes it to the submains. The submains convey water to the laterals which in turn provide water to the sprinklers. Aluminum or PVC pipes are normally used for portable systems, while steel pipes are generally used for center-pivot laterals. Asbestos, cement, PVC & wrapped steel are generally used for buried laterals and main lines.
- Couplers: Couplers are used for connecting two pipes & uncoupling quickly and easily. Basically, a coupler should provide
(a) Reuse and flexible relation
(b) Not leak at the point of the joint
(c) Be simple and easy to couple & uncouple
(d) Be light, non-corrosive, durable.
- Sprinkler Head: Sprinkler head distributes water evenly over the field without runoff or excessive loss due to deep percolation. Different types of sprinklers are obtainable. They are either rotating type or fixed type. The rotating type can be adapted for a wide range of application rates & spacing. They are effective with a pressure of about 10 m – 70 m head at the sprinkler. Pressures ranging from 16 m to 40 m head are considered the most practical for most farmers.
Fixed head sprinklers are normally used to irrigate small lawns and gardens. Perforated lateral lines are used as sprinklers. They need less pressure than rotating sprinklers. They discharge more water per unit area than rotating sprinklers. Hence, fixed head sprinklers are flexible for soils with a high intake rate.
- Fittings and accessories: The following are some of the main fittings & accessories used in the sprinkler system.
(a) Water meters: It is used to determine the volume of water delivered. This is required to operate the system to give the required quantity of water.
(b) Flange, couplings, and nipple used for proper connection to the pump, suction & delivery.
(c) Pressure gauge: It is essential to know whether the sprinkler system is working with the desired pressure to ensure application uniformity.
(d) Bend, tees, reducers, elbows, hydrants, butterfly valve & plugs.
(e) Fertilizer applicator: Soluble chemical fertilizers can be injected into the sprinkler system & applied to the crop. The equipment for fertilizer application is relatively cheap, simple and can be fabricated locally. The fertilizer applicator consists of a sealed fertilizer tank with essential tubings & connections. A venturi injector can be arranged in the main line, which creates the differential pressure suction & allows the fertilizer solution to flow in the main water line.
Climate conditions for the Sprinkler irrigation system:
Climatic conditions such as temperature, humidity, wind velocity of a place have a huge influence on the consumptive use of a crop. The sprinkler irrigation system should be designed for the peak rate for consumptive use of crops to be irrigated by it. In areas where wind velocities & temperatures are high, heavy evaporation losses from the sprinkler sprays considerably reduces the saving of water. The wind influences the spacing of sprinklers. Therefore, it is essential to recognize the velocity of wind and its direction. For wind velocities over 16 km/hour, the sprinkler method becomes unsuitable.
Suitable crops for the Sprinkler irrigation system:
Sprinkler irrigation is suited for the most row, field and tree crops & water can be sprayed over or under the crop canopy. Large sprinklers are not optional for irrigation of delicate crops such as lettuce since the large water drops produced by the sprinklers may damage the crop.
Almost all crops are suitable for sprinkler irrigation system except crops such as paddy, jute, etc. The dry crops, flowering crops, orchards, plantation crops such as tea, coffee are all suitable & can be irrigated through sprinklers.
Suitable soils for the Sprinkler irrigation system:
Sprinklers are best suitable to sandy soils with high infiltration rates, although they are adaptable to most soils. The average application rate from the sprinklers (in mm/hour) is always selected to be less than the basic infiltration rate of the soil so that surface ponding & runoff can be avoided.
Sprinklers are not fit for soils which easily form a crust. If the sprinkler irrigation system is the only method available, then light fine sprays should be used. The larger sprinklers generate larger water droplets are to be avoided.
General rules for sprinkler irrigation system design:
- Main should be laid up & downhill.
- Lateral should be laid across the slope or almost on the contour.
- For multiple lateral operations, lateral pipe sizes should not be more than 2 diameters.
- Water providing source should be nearest to the center of the area.
- The layout should facilitate & minimize lateral movement during the season.
- Booster pump should be considered where a small portion of the field would need high pressure at the pump.
- The layout should be modified to apply different rates & amounts of water where soils are greatly different in the design area.
Operation and maintenance of Sprinkler irrigation systems:
Proper planning of a sprinkler system does not in itself ensure success. The structure should be operated in keeping with good irrigation practices. It should be ensured that the prime mover & the pump are in alignment. For these, the drive shaft, as well as the pump shaft, should lie at practically the same height to prevent too great an angle on the universal shaft. Service & installation procedures in respect of the pump and power units should be strictly observed.
While laying the main pipes, and lateral pipes, always begin lying at the pump. This essentially gives the correct connection of all quick coupling pipes. While joining couplings, it is ensured that both the couplings & the rubber seal rings are clean.
In starting the sprinkler irrigation system, the motor or engine is started with the valves closed. The pump attains the pressure stated on type-plate or otherwise there is a fault on the suction line. After the pump reaches the regulator pressure, the delivery tap is opened slowly. Likewise, the delivery valve is closed after stopping the power unit.
A sprinkler irrigation system, like any other farm equipment, needs maintenance to keep it operating at peak efficiency. Parts of the structure subject to the most wear are the rotating sprinkler heads, the pumping set, the couplers, and the pipeline. General principles regarding the maintenance of the pipes, fittings, and sprinkler heads are given below:
- Pipes and fittings:
The pipes & fittings require virtually no maintenance, but attention must be given to the following procedures:
(a) Occasionally fresh any dirt or sand out of the groove in the coupler in which the rubber sealing ring fits. Any accumulation of dirt or sand will change the performance of the rubber sealing ring.
(b) Keep all nuts & bolts tight.
(c) Do not lay pipes on fresh damp concrete or on piles of fertilizer. Do not arrange fertilizer sacks on the pipe.
- Sprinkler heads:
The sprinkler heads should be the following attention:
(a) When moving the sprinkler lines, make sure that the sprinklers are not damaged and pushed into the soil.
(b) Do not apply oil, grease to the sprinklers. They are water lubricated & using oil, grease or any other lubricant may stop them from working.
(c) Sprinklers generally have a sealed bearing and at the bottom of the bearing, there are washers. Generally, it is the washers that wear & not the more expensive metal parts. Check the washers for wear once a season or every 6 months this is especially very important where water is sandy. Change the washers if worn.
(d) After several season’s operations, the swing arm spring needs tightening. This is done by pulling out the spring end at the top & rebending it. This will raise spring tension.
Cleaning of the line filter:
The line filter needs to be cleaned every week to two weeks depending on water quality. Accumulation of impurities inside the filter can basis the sprinklers to malfunction. To fresh the filter, unscrew the outer case and rinse the slotted portion with clean water.
Checking the pipelines:
It is important to securely attach the pipe and fittings in order to have an optimal sprinkler function. Any leaks in the pipeline will reason a drop in pressure & discharge which will result in poor sprinkler head rotation. If leaks are found, check every connection to make sure they are secure. If the leaks persist, repair them with tape.
Selecting the most appropriate sprinkler systems:
While selecting a sprinkler system, the important physical parameters to be considered are:
- The crops to be cultivated.
- The shape & size (acres) of the field.
- The topography of the system field.
- The amount of time & labor required to operate the system.
During the rainy time when irrigation is not required, the sprinkler set should be stored in a safe place, preferably indoors to reduce wear and tear.
The following points are to be observed while storing the sprinkler set during the offseason:
(a) Remove the sprinklers & store in a cool, dry place.
(b) Remove the rubber sealing rings from the couplers and fittings & store them in a cool, dark place.
(c) The pipes can be stored outdoors in which they should be placed in racks with one end higher than the other. Do not store pipes along with the fertilizer.
(d) Disconnect the suction and delivery pipework from the pump & pour in a small amount of medium grade oil. Rotate the drive for a few minutes. Blank off the suction & delivery branches. This will stop the pump from rusting. Grease the shaft.
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(e) Protect the electric motor from the ingress of dust, dampness & rodents.
Advantages of Sprinkler irrigation systems:
- Eliminates water conveyance channels, thereby dropping conveyance loss.
- Suitable in every type of soil except heavy clay.
- Suitable for irrigation where the plant residents per unit area are very high.
- Reduce soil compaction.
- Crops germinated with the sprinkler irrigation system may later be surface irrigated with deeper applications.
- Labor is used for a short period daily in each field.
- Mechanization & automation are practical to reduce labor.
- Soluble fertilizers & chemical use are possible.
Cost Sprinkler Irrigation kit:
Sprinkler irrigation kit cost for one-acre land is about Rs 19,000/Acre
Per head Sprinkler cost is Rs. 3,500/-. The per acre installation cost is Rs. 15,000/-, inclusive of the installation of three inches PVC main pipeline & riser pipe. It can irrigate one acre in about one and a half hour time.
Area irrigated by the Sprinkler system in India:
In India, the area irrigated by the sprinkler system is about 3.59 million ha, which is less than 2.5% of the total area under irrigation.
Disadvantages of the Sprinkler irrigation system:
- Water will drift when there is a group of wind.
- Water must be free from sand, debris and the large quantity of salt.
- Stable water supply is needed.
- Excessive seepage & leakage of water create marshes and ponds all along the channels. The marshes and the ponds in some time the colonies of the mosquito, which gives rise to a disease like malaria.
- It lowers the temperature & makes the locality damp due to the presence of irrigation water.
- Excessive seepage into the ground raises the water, thus causing water logging in the area.