Question

If a tile drainage system is laid along a length of 400 m with laterals spaced 24 m apart, and the outflow through one lateral is 8 m³/h, then the drainage coefficient will be

• A. 2 mm/day
• B. 2 cm/day
• C. 1 cm/day
• D. 1 mm/day

Hint:

Drainage coefficient (DC) = Outflow rate Drainage area.
Units: cm/day or mm/day.
Typical DC for agricultural drainage: 1-2 cm/day.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Drainage coefficient is the rate at which water is removed by the drainage system, expressed as a depth of water per day.

Step 2: Key Formula or Approach:
Drainage coefficient = \(\frac{\text{Outflow}}{\text{Drainage area}}\)
Area drained = Length × Lateral spacing

Step 3: Detailed Explanation:
Given:
Length = 400 m
Lateral spacing = 24 m
Area drained = \(400 \times 24 = 9600 \mathrm{m^2}\)
Outflow through one lateral = 8 m³/h
Total outflow = 8 m³/h
Drainage coefficient = \(\frac{8 \mathrm{m^3/h}}{9600 \mathrm{m^2}} = \frac{8}{9600} \mathrm{m/h} = 0.000833 \mathrm{m/h}\)
Convert to m/day: \(0.000833 \times 24 = 0.02 \mathrm{m/day} = 2 \mathrm{cm/day}\)
Thus, the drainage coefficient is 2 cm/day.

Step 4: Final Answer:
Thus, the drainage coefficient is 2 cm/day.
[0.5cm]