1. Concept Explanation (Exam-Focused)
Water Logging
Water logging is a condition in which the water table rises and reaches the root zone of crops, causing saturation of soil pores and lack of oxygen for plant roots.
In simple words:
When soil contains more water and less air → water logging.
Why Water Logging is Dangerous
Plants need oxygen for respiration. In water logged soil, air spaces are filled with water, so oxygen supply reduces and root activity stops.
Causes of Water Logging (Most Asked)
• Excessive irrigation
• Seepage from canals and reservoirs
• Poor natural drainage
• Heavy rainfall
• Flat topography
• Impervious subsoil layer
Effects of Water Logging
• Reduced crop yield
• Poor root growth
• Development of saline soil
• Rise in water table
• Mosquito breeding
• Damage to soil structure
Drainage
Drainage is the artificial removal of excess water from soil surface or root zone to maintain optimum moisture for crops.
Main objectives:
• Lower water table
• Improve soil aeration
• Prevent salinity
• Increase crop productivity
Types of Drainage (Highly Repeated)
1. Surface Drainage
Removes excess water from the land surface.
Examples:
• Open field drains
• Shallow ditches
Used when:
• Heavy rainfall
• Low soil permeability
2. Subsurface Drainage
Removes excess water below the ground surface.
Examples:
• Tile drains
• Perforated pipes
Used when:
• High water table
• Seepage problem
Subsurface drainage is most effective permanent solution.
2. Important Formulas
Drainage Coefficient
DC=Total depth of water to be removedTimeDC = \frac{Total\ depth\ of\ water\ to\ be\ removed}{Time}DC=TimeTotal depth of water to be removed
Unit: mm/day
Discharge Required for Drainage
Q=A×DC86.4Q = \frac{A \times DC}{86.4}Q=86.4A×DC
Where:
Q = discharge (m³/s)
A = area (hectares)
DC = drainage coefficient (mm/day)
🔥 Most repeated numerical formula
3. Short Notes / One-Liners
• Water logging occurs when water table enters root zone.
• Major cause: over irrigation + canal seepage.
• Drainage improves soil aeration.
• Subsurface drainage is best for water logged areas.
• Water logging leads to salinity and alkalinity.
• Surface drainage is cheaper but temporary.
• Tile drainage is most common subsurface method.
• Water logging reduces soil fertility.
4. PYQ Patterns
Common Trends:
Definition of water logging
Causes and effects
Surface vs subsurface drainage
Drainage coefficient numericals
Typical Traps:
• Confusing water logging with flooding
• Choosing evaporation as major cause
• Forgetting 86.4 in discharge formula
• Using area in m² instead of hectares
5. Solved Examples
Example 1 (Conceptual)
Why does water logging reduce crop yield?
Because oxygen supply to roots decreases.
Example 2 (Numerical)
Area = 200 ha
Drainage coefficient = 20 mm/day
Q=200×2086.4=46.3 m³/sQ = \frac{200 \times 20}{86.4} = 46.3 \text{ m³/s}Q=86.4200×20=46.3 m³/s
6. MCQs (50 Exam-Level)
Q1. Water logging occurs when:
A) Soil becomes dry
B) Water table falls
C) Root zone is saturated
D) Rainfall stops
✅ Answer: C
Q2. Major cause of water logging:
A) Evaporation
B) Over irrigation
C) Wind
D) High temperature
✅ Answer: B
Q3. The main effect of water logging is:
A) Increased fertility
B) Better yield
C) Lack of oxygen to roots
D) Increased rainfall
✅ Answer: C
Q4. Drainage is required to:
A) Increase seepage
B) Raise water table
C) Remove excess water
D) Increase evaporation
✅ Answer: C
Q5. Subsurface drainage is best when:
A) Rainfall is low
B) Soil is sandy
C) Water table is high
D) Land is sloping
✅ Answer: C
Q6. Which is a permanent solution for water logging?
A) Flood irrigation
B) Surface drainage
C) Subsurface drainage
D) Stop irrigation
✅ Answer: C
Q7. Water logging mainly affects:
A) Leaves
B) Stem
C) Roots
D) Fruits
✅ Answer: C
Q8. Drainage coefficient is expressed in:
A) m³/s
B) mm/day
C) ha
D) m
✅ Answer: B
Q9. Tile drains are used in:
A) Surface drainage
B) Subsurface drainage
C) Canal irrigation
D) Flood control
✅ Answer: B
Q10. Which leads to salinity?
A) Proper drainage
B) Water logging
C) Sprinkler irrigation
D) Drip irrigation
✅ Answer: B
Q11. Which is not a cause of water logging?
A) Over irrigation
B) Seepage
C) Flat land
D) Proper drainage
✅ Answer: D
Q12. Which drainage system is cheapest?
A) Subsurface
B) Tile
C) Surface
D) Pipe
✅ Answer: C
Q13. Which crop is most affected by water logging?
A) Rice
B) Wheat
C) Sugarcane
D) Cotton
✅ Answer: B
Q14. Drainage improves crop yield by:
A) Increasing rainfall
B) Increasing evaporation
C) Improving aeration
D) Increasing salinity
✅ Answer: C
Q15. Drainage coefficient represents:
A) Discharge
B) Area
C) Depth of water removed per day
D) Velocity
✅ Answer: C
Q16. Water logging occurs mainly due to:
A) Low rainfall
B) Excess irrigation
C) High evaporation
D) Wind action
✅ Answer: B
📝 Explanation: Over-irrigation raises water table.
Q17. Which layer is responsible for water logging?
A) Permeable layer
B) Impervious layer
C) Sandy layer
D) Gravel layer
✅ Answer: B
Q18. Which drainage system is best for heavy rainfall areas?
A) Subsurface drainage
B) Tile drainage
C) Surface drainage
D) Pipe drainage
✅ Answer: C
Q19. The main objective of drainage is to:
A) Increase groundwater
B) Raise water table
C) Lower water table
D) Increase seepage
✅ Answer: C
Q20. Which of the following is not an effect of water logging?
A) Reduced yield
B) Salinity
C) Improved aeration
D) Root damage
✅ Answer: C
Q21. Drainage coefficient of 25 mm/day means:
A) 25 mm water removed in one day
B) 25 mm rainfall
C) 25 m water removed
D) 25 mm seepage
✅ Answer: A
Q22. Which crop is least affected by water logging?
A) Wheat
B) Cotton
C) Rice
D) Barley
✅ Answer: C
Q23. The main loss in water logged soil is:
A) Fertility
B) Oxygen
C) Nitrogen
D) Moisture
✅ Answer: B
Q24. Tile drains are generally placed:
A) On surface
B) At shallow depth
C) Below root zone
D) Above ground
✅ Answer: C
Q25. Which condition leads to permanent water logging?
A) Temporary rainfall
B) Seasonal irrigation
C) Poor drainage system
D) Short-term flooding
✅ Answer: C
Q26. Water logging increases:
A) Soil permeability
B) Crop yield
C) Salinity of soil
D) Root respiration
✅ Answer: C
Q27. Which is not a method of drainage?
A) Open drains
B) Tile drains
C) Pipe drains
D) Canal lining
✅ Answer: D
Q28. Which drainage is suitable for flat land?
A) Vertical drainage
B) Horizontal drainage
C) Surface drainage
D) Subsurface drainage
✅ Answer: C
Q29. Which is a numerical trap in drainage problems?
A) Using area in hectares
B) Forgetting factor 86.4
C) Using mm/day
D) Using discharge
✅ Answer: B
Q30. Vertical drainage is done by:
A) Open channels
B) Tile drains
C) Pumping wells
D) Surface ditches
✅ Answer: C
Q31. Which drainage system uses wells?
A) Surface
B) Subsurface
C) Horizontal
D) Vertical
✅ Answer: D
Q32. Which condition indicates water logging?
A) Water table > root depth
B) Water table < root depth
C) Dry soil
D) High rainfall only
✅ Answer: A
Q33. Drainage coefficient mainly depends on:
A) Soil type
B) Crop type
C) Rainfall
D) All of the above
✅ Answer: D
Q34. Which one is false?
A) Water logging reduces aeration
B) Drainage improves yield
C) Subsurface drainage is temporary
D) Water logging causes salinity
✅ Answer: C
Q35. Which drainage is costly but permanent?
A) Surface
B) Subsurface
C) Open drain
D) Shallow drain
✅ Answer: B
Q36. Which soil is most prone to water logging?
A) Sandy soil
B) Gravel soil
C) Clay soil
D) Loamy soil
✅ Answer: C
Q37. Which is the main benefit of drainage?
A) More irrigation
B) Reduced rainfall
C) Improved aeration
D) Increased seepage
✅ Answer: C
Q38. Water logging leads to:
A) Drought
B) Flood
C) Alkaline soil
D) Fertile soil
✅ Answer: C
Q39. Which drainage removes water below ground?
A) Surface drainage
B) Subsurface drainage
C) Vertical drainage
D) Both B and C
✅ Answer: D
Q40. Which is a cause of temporary water logging?
A) Impervious layer
B) Poor drainage
C) Heavy rainfall
D) Seepage
✅ Answer: C
Q41. The depth of drains in subsurface drainage is usually:
A) 0.2–0.3 m
B) 0.5–1.0 m
C) 2–3 m
D) Above ground
✅ Answer: B
Q42. Which method controls water logging in delta areas?
A) Flooding
B) Sprinkler
C) Drainage
D) Drip
✅ Answer: C
Q43. Which drainage method uses gravity only?
A) Vertical drainage
B) Surface drainage
C) Pump drainage
D) Well drainage
✅ Answer: B
Q44. Which is not an objective of drainage?
A) Lower water table
B) Improve soil aeration
C) Increase crop yield
D) Increase soil saturation
✅ Answer: D
Q45. Water logging is most harmful during:
A) Germination stage
B) Flowering stage
C) Harvesting stage
D) Maturity stage
✅ Answer: A
Q46. The best indicator of water logging is:
A) High rainfall
B) Presence of weeds
C) Rise in water table
D) Soil cracks
✅ Answer: C
Q47. Which one is true?
A) Drainage increases salinity
B) Drainage reduces crop yield
C) Drainage improves aeration
D) Drainage causes water logging
✅ Answer: C
Q48. Subsurface drainage mainly removes:
A) Surface runoff
B) Rainfall
C) Seepage water
D) Canal water
✅ Answer: C
Q49. Which is a sign of water logging?
A) Yellowing of leaves
B) High yield
C) Dry roots
D) Soil cracks
✅ Answer: A
Q50. Water logging problem can be solved by:
A) More irrigation
B) Lining canals
C) Stopping crops
D) Removing drains
✅ Answer: B