Irrigation Water Conveyance and Application Methods
Subtopic: Surface, sprinkler and micro irrigation methods
Question Statement:
Referring to the sprinkler overlapping precipitation profile illustrated in the accompanying diagram, which of the following statements regarding the Christiansen Uniformity Coefficient ($C_u$) are CORRECT?
Options:
(A) $C_u = 100 \left( 1 - \frac{\sum |x_i - \bar{x}|}{n \bar{x}} \right)$, where $x_i$ is individual catch can depth and $\bar{x}$ is mean application depth
(B) A triangular precipitation distribution from individual overlapping sprinklers produces a nearly uniform composite depth profile
(C) $C_u \ge 85\%$ is widely accepted as the minimum standard for field crop sprinkler installations
(D) Sprinkler spacing equal to $100\%$ of the wetted diameter yields the highest possible $C_u$
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
1. Formula for Christiansen coefficient is $C_u = 100 (1 - \frac{\sum |x_i - \bar{x}|}{n \bar{x}})$. (Statement A True)
2. Individual triangular overlap with spacing $50-65\%$ of diameter sums to a flat horizontal depth. (Statement B True)
3. Industry design standard mandates $C_u \ge 85\%$. (Statement C True)
4. At $100\%$ diameter spacing, overlap is zero at boundaries, resulting in severe dry spots and very low $C_u$. (Statement D False)