Operation of the Drip Irrigation System
The proper operation of a drip irrigation system involves the following steps for the owner/operator:
- (i) Acquiring complete information and instructions from the designer and dealer,
- (ii) Determining when and how long to irrigate.
- (iii) Checking the water meter readings and recording the figures,
- (iv) Accurately setting the hydraulic metering valve,
- (v) Operating the head valve to begin irrigation,
- (vi) Checking the system along all components for proper operation, beginning with pressure readings at the header,
- (vii) Checking the emitters, at least on a random basis,
- (viii) Setting the chemical and fertilizer injection equipment. (US Soil Cons. Service, 1984).
Maintenance of Drip Irrigation Systems
Reliable performance of a drip irrigation system depends on preventive maintenance that includes proper filtration, pipe flushing, field check of leakage in any component of the system, and monitoring the effective functioning of mechanical devices. General maintenance includes periodic checking of drippers, including their discharge, wetting zone, and leakage of pipes and filter gaskets in the lids, flushing valves and fittings. The placement of drippers should be periodically inspected. In case the placement is disturbed, they should be put at the proper location. Filter is the heart of the drip irrigation system. Filter failure will lead to clogging of the entire system. Various.
Flushing of sub-mains and laterals: After installation/repairs, the system should be flushed systematically, beginning with the main line and proceeding to the sub-mains, manifolds, and laterals. The main lines and then the sub-mains should be flushed one at a time with the manifold or riser valves turned off. Closing the valves on all lines, except the one being flushed, allows a large flow of water. The manifolds should be flushed with all the lateral riser valves turned off. Finally, the lateral hoses should be connected and flushed for about an hour at each operating station.
Sometimes silt escapes through the filters and settles in sub-mains and laterals. Further, some algae and bacteria lead to the formation of slimes/pastes in the pipe and laterals. To remove these silts and slimes, opening the flush valve should flush the sub-mains.
Removing the end stops flushes the lateral lines. By flushing, even the traces of accumulated salts will also be removed. Stop the flushing once the water going out is clean.
Fine sand, silt and clay tend to settle in the low-velocity section of the system, at the ends of manifolds and laterals. Emitters' receiving high concentrations of fine contaminants are susceptible to clogging; therefore, periodic flushing is a recommended part of a good maintenance program. Annual flushing is enough for many systems, but some water and emitter combinations require more frequent flushing to control clogging.
(o) Chemical treatment. Clogging or plugging of drippers will be due to precipitation and accumulation of certain dissolved salts like carbonate, bicarbonate, iron, calcium and manganese salts. Clogging is also due to the presence of microorganisms and the related iron and sulphur slimes due to algae and bacteria. Clogging or plugging is usually avoided/cleared by chemical treatment of water. Chemical treatments commonly used in drip irrigation systems include addition of chloride and/or acid to the water supply.
Acid treatment: Hydrochloric acid (HC1) is injected into drip systems, at the rate suggested. The acid treatment is performed till a pH of 4 is observed and the system is shut for 24 hours. Next day the system is flushed by opening the flush valve and lateral ends.
Chlorine treatment. Chlorine treatment in the form of bleaching powder is performed to inhibit the growth of organisms like algae and bacteria. The bleaching powder is dissolved in water and this solution is injected into the system for about 30 minutes. Then the system is shut off for 24 hours. After 24 hours, the lateral ends and flush valves are opened to flush out the water with impurities. Bleaching powder is directly added into the source at a rate of 2 mg/ litre.