Sprinkler Irrigation Design & Distribution Uniformity
Subtopic: Sprinkler allowable pressure variation
Question Statement:
In the hydraulic design of sprinkler laterals, which of the following criteria is/are standard engineering practice?
Options:
(A) Total pressure variation along a lateral should not exceed $20\%$ of the nominal operating pressure
(B) Discharge variation between the first and last sprinkler on a lateral should not exceed $10\%$
(C) The Christiansen $F$-factor accounts for multi-outlet friction head loss reduction compared to pipe flow with total discharge at inlet
(D) Application rate must strictly exceed the steady infiltration rate of the soil to guarantee surface ponding
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
1. Pressure variation $\Delta P \le 20\%$ of design pressure ensures discharge variation within $\Delta q \le 10\%$ since $q \propto P^{0.5}$ (A and B are true).
2. Multi-outlet friction factor $F$ ($F \approx 0.35$ for large $N$) reduces total friction loss compared to plain pipe (C is true).
3. Application rate must NEVER exceed soil infiltration capacity to prevent surface runoff and erosion (D is false).