Irrigation Water Conveyance and Application Methods
Subtopic: Surface, sprinkler and micro irrigation methods
Question Statement:
In border strip irrigation, when should the inflow stream admitted at the head of the border strip generally be cut off to achieve high application efficiency and prevent excessive tail-water runoff?
Options:
(A) When the advancing water front covers approximately $75\% \text{ to } 80\%$ of the border strip length
(B) Only after water has ponded to a depth of $1\text{ m}$ at the tail end
(C) Immediately after water advances $10\%$ of the strip length
(D) Exactly 24 hours after the start of irrigation
Answer Key:
A
Step-by-Step Solution & Explanation
In border irrigation on non-diked strips, the advancing water front continues to roll forward due to surface storage and inertia after inflow is shut off. Cutting off inflow when advance reaches $75 - 80\%$ of border length allows the receding sheet to cover the remainder of the strip with minimal tail runoff. Option A is correct.