Agricultural/Bioengineering Irrigation and Drainage Engineering 2 — Questions and Answers
Question 1: The Penman-Monteith equation is used in irrigation planning to calculate:
- Soil hydraulic conductivity
- Reference evapotranspiration (ETo) (Correct answer)
- Drainage pipe spacing
- Pump discharge rate
Correct answer: Reference evapotranspiration (ETo)
The FAO Penman-Monteith equation is the standard method for estimating reference evapotranspiration (ETo) from meteorological data for irrigation scheduling.
Question 2: A center-pivot irrigation system rotates around a central point, covering a field shaped like a:
- Rectangle
- Triangle
- Circle (Correct answer)
- Hexagon
Correct answer: Circle
Center-pivot systems irrigate a circular area as the lateral arm rotates 360° around the pivot point, leaving corners of square fields unirrigated.
Question 3: Waterlogging in agricultural fields occurs when:
- Soil is too dry for plant growth
- The water table rises to or near the root zone, limiting aeration (Correct answer)
- Excess nitrogen accumulates in the soil
- Irrigation water is too saline
Correct answer: The water table rises to or near the root zone, limiting aeration
Waterlogging occurs when the water table rises into or near the crop root zone, displacing air and causing anaerobic conditions harmful to plants.
Question 4: The hydraulic gradient in a drainage system is best defined as:
- The total soil water content
- The change in hydraulic head per unit distance in flow direction (Correct answer)
- The porosity of the drain pipe
- The crop water demand
Correct answer: The change in hydraulic head per unit distance in flow direction
Hydraulic gradient is the ratio of the difference in water pressure head to the flow distance, driving water movement toward drain pipes.
Question 5: Sprinkler irrigation is generally preferred over surface irrigation on:
- Flat, heavy clay soils
- Steep or irregular topography where surface methods would cause erosion (Correct answer)
- Fields with extremely high infiltration rates only
- Level fields with uniform sandy loam soils
Correct answer: Steep or irregular topography where surface methods would cause erosion
Sprinkler systems can apply water uniformly on irregular terrain where surface irrigation would cause runoff, erosion, or uneven distribution.
Question 6: Net irrigation requirement is calculated as:
- Gross water applied minus losses
- Crop evapotranspiration minus effective rainfall (Correct answer)
- Field capacity minus wilting point
- Total drainage minus seepage
Correct answer: Crop evapotranspiration minus effective rainfall
Net irrigation requirement equals the crop's ET demand minus effective rainfall, representing the irrigation water needed to meet the deficit.
Agricultural/Bioengineering Irrigation and Drainage Engineering 2
The Penman-Monteith equation is used in irrigation planning to calculate: