Irrigation Water Conveyance and Application Methods
Subtopic: Design of irrigation channels and underground pipelines
Question Statement:
Irrigation Water Conveyance and Application Methods: Design of irrigation channels and underground pipelines; irrigation scheduling; surface, sprinkler and micro irrigation methods, design and evaluation of irrigation methods; irrigation efficiencies.
An irrigation stream of 27 L/s is diverted to a check basin of size 12 m × 12 m. Water holding capacity of the soil is 15% and average soil moisture content in the crop root zone before irrigation is 7.5%. Depth of crop root zone is 1.2 m, apparent specific gravity of soil is 1.5. Assuming no deep percolation loss, the irrigation time (minutes) required to replenish the root zone moisture to field capacity is ______.
Official Answer Key:
12 to 12
Step-by-Step Solution & Explanation
Net depth of water to be applied, dnet = (WHC − current moisture) × apparent specific gravity × root zone depth
= (0.15 − 0.075) × 1.5 × 1.2 m = 0.075 × 1.5 × 1.2 = 0.135 m.
Volume of water required = dnet × basin area = 0.135 m × (12×12) m² = 0.135 × 144 = 19.44 m³.
Stream size = 27 L/s = 0.027 m³/s.
Time = Volume/Flow = 19.44/0.027 = 720 s = 12.0 minutes. Answer: exactly 12.
Section 6 — Agricultural Process Engineering
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