Irrigation Association Certified Irrigation Designer — Agriculture (CID) · USA · Irrigation Association
Original practice questions written to the published syllabus · not past papersDesigning and evaluating sprinkler and drip systems, from emitter hydraulics to pump selection.
In the exams: GATE AG Section 5 (sprinkler in 4 of 8, drip in 3 of 8 papers 2019–26); ICAR AICE subject 43 Unit 4; NCEES PE irrigation; IA CID (General Ag, Drip/Micro and Sprinkler exams)
How our questions for Irrigation Association Certified Irrigation Designer spread across the units of Sprinkler & Micro-Irrigation Systems. Difficulty: 3 easy, 24 medium, 10 hard.
| Filtration | 5 | |
| Fertigation | 5 | |
| System layout and pump selection | 4 | |
| Emitter hydraulics: exponent and coefficient of variation | 3 | |
| Emission uniformity | 3 | |
| Automation | 3 | |
| Sprinkler spacing and application rate | 2 | |
| Christiansen's uniformity coefficient | 2 | |
| Sprinkler lateral and main design | 2 | |
| Drip system components | 2 | |
| Drip lateral and sub-main design | 2 | |
| Economics of pressurised irrigation | 2 | |
| Sprinkler types and components | 1 | |
| Allowable pressure variation and the friction factor F | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Runoff appears only near the outer end of a centre pivot on a loam, although the depth per revolution matches crop need. Which change addresses the cause most directly?
B. Spread the application over a wider wetted width (booms or wider-throw heads) or add surface storage by tillage
At the outer end the instantaneous application rate is highest because the same wetted width must deliver the largest discharge. Speeding up reduces depth per pass but not the instantaneous rate; reducing outer discharge under-irrigates the largest area. Widening the wetted pattern or storing surface water attacks the rate problem.
Further reading: Keller and Bliesner, Sprinkle and Trickle Irrigation
A sprinkler lateral is laid down a uniform gentle slope from its inlet. Compared with the same lateral on level ground, what does the slope do?
C. Elevation gain offsets friction, so a longer lateral or smaller pipe can meet the same pressure limit
Going downhill, each metre of fall adds pressure that offsets friction loss; on gentle slopes the profile flattens and the allowable length grows. On steep slopes the gain can exceed friction and the end pressure rises, which again needs checking.
Further reading: Keller and Bliesner, Sprinkle and Trickle Irrigation
What distinguishes an in-line emitter from an on-line emitter?
A. In-line emitters are built into the tubing during manufacture; on-line emitters are punched into it later
The distinction is physical: in-line emitters are inserted or formed inside the tube at the factory at fixed spacing (as in dripline and tape); on-line emitters are inserted into punched holes in the field at chosen spacings. Either type can be pressure-compensating.
Further reading: Lamm, Ayars and Nakayama, Microirrigation for Crop Production
A drip system draws from an open farm pond with heavy algae growth in summer. Which primary filter is most appropriate?
A. Media (sand/gravel) filter, backflushable
Media filters trap organic material in the depth of the bed and are backflushed; they are the standard primary filter for surface water with algae. A screen alone clogs quickly with algae; a hydrocyclone does not remove organic matter; chlorination complements, but does not replace, filtration.
Further reading: Lamm, Ayars and Nakayama, Microirrigation for Crop Production
A grower chlorinates drip water from a well with pH 8.3 to control bacterial slime, but results are poor. Which change most improves chlorine's effectiveness?
D. Inject acid to lower pH, since hypochlorous acid predominates at lower pH
Chlorine in water is present as hypochlorous acid (a strong biocide) and hypochlorite ion (weak); the balance shifts towards hypochlorous acid as pH falls, so acid improves effectiveness. Mixing chlorine with fertilisers can cause reactions and is avoided.
Further reading: Lamm, Ayars and Nakayama, Microirrigation for Crop Production
5 kg N/ha is to be applied to 4 ha as urea (46 % N) dissolved at 0.3 kg urea per litre of stock solution and injected over 2 hours. What is the injection rate?
B. 72.5 L/h
N = 5 × 4 = 20 kg; urea = 20/0.46 = 43.5 kg; stock volume = 43.5/0.3 = 145 L; injection rate = 145/2 = 72.5 L/h. Forgetting to convert N to urea gives 33.3 L/h; forgetting the injection time gives 145 L/h. 66.7 L/h forgets both the urea conversion and the 2-hour injection time (20/0.3).
Further reading: Lamm, Ayars and Nakayama, Microirrigation for Crop Production
In chemigation safety equipment, where is the main check valve placed?
B. In the irrigation line between the water source/pump and the injection point
The irrigation-line check valve prevents water containing chemicals from flowing back to the well or source; it sits between the pump and the injection point, with a vacuum-relief valve and low-pressure drain upstream of it. The injection line has its own check valve as well.
Further reading: US EPA chemigation label requirements; ASABE EP409
A drip system has static lift 20 m, well drawdown 3 m, mainline friction 4 m, filter loss 5 m (dirty limit), injector loss 2 m, required sub-main inlet pressure 15 m and a 2 m rise to the critical block. What is the total dynamic head?
A. 51 m
TDH = 20 + 3 + 4 + 5 + 2 + 15 + 2 = 51 m. Omitting drawdown gives 48 m, omitting the elevation rise gives 49 m, and omitting the required operating pressure gives 36 m, all of which would leave the critical block under-pressured.
Further reading: Keller and Bliesner, Sprinkle and Trickle Irrigation
How is the operating point of a centrifugal pump in an irrigation system found?
A. At the intersection of the pump head–flow curve and the system head curve
The pump delivers the flow at which the head it produces equals the head the system requires. The designer then checks that this point is close to best efficiency; if it is not, the pump or impeller is changed.
Further reading: Keller and Bliesner, Sprinkle and Trickle Irrigation
Ten here, 37 in the app. The Laisha app has every practice question we have written to Irrigation Association Certified Irrigation Designer in this subject, marked as you go, with timed papers, a jump-to-unanswered list and a certificate when you pass at 70 per cent.
Free for ten days, then one subscription of US$10 a month. We would rather say so here than have you find it later.
An AI operating system for agriculture: free guides, manuals and tools written for every country.