Waterlogging

1. Engr. Muhammad Waqas Muneer
Department of Civil Engineering and Technology,
Institute of Southern Punjab (ISP), Multan.
CE-416
Irrigation Engineering

2. Lecture – 8
Water Logging & Salinity

3. Learning Objectives
1. Water Logging and Salinity
2. Adverse Effect of Water-logging
3. Causes of Water-logging
4. Sources of Inflow & Outflow in/from Water-Table
5. Anti-Water Logging Measures
6. Optimum Depletion of Water-Table Depth

4. Water Logging and Salinity
 A land is said to be water-logged, when the soil pores within the root zones of
the crops are effectively saturated due to lack of aeration of soil.
 The depth of water table at which such conditions arise depends upon:
 Type of crop grown i.e. whether shallow or deep rooted
 Type of soil i.e. capillary fringe
 Admissible water table depths in different soils at which water-logging will not
occur are:
Clay soil : 1.5 m or more Loamy Soil
: 1.2 m or more
Sandy Soil : 0.8 m or more
Therefore, higher water-table can be tolerated in sandy soils than in loamy or
clay soils.

5. Adverse Effect of Water-logging
 Lack of aeration
 Creation of salinization
 Growth of natural weeds
 Difficulty in carrying out cultivation operations
 Reduction in nitrification process
 Reduction in soil temperature
 Maturity period of crop reduced
 Reaction of plant nutrients in soil and fertilizers is affected
 Soil warms up slowly which decreases both seed germination and growth
 Soil pH value is increased

6. Causes of Water-logging
 It is the rise in water-table which is responsible for water-logging
 All the factors which tend to raise the water- table can be called as Sources
of Inflow
 All the factors which tend to lower water-table are called Sources of
Outflow
 For water-table remain in equilibrium, the inflow and outflow should
balance each other

7. Sources of Inflow in Water-Table
a) In Pre-Canal Period
 Percolation of rainfall in saturated phase
 Poor water management in irrigated areas
 Sub-soil flow from upper reaches
 Infiltration or occasional flooding from rivers
 Geological formations
b) In Post-Canal Period
 Seepage from canal Irrigation System i.e. Main Canals, Minors,
Distributaries, Water Courses, and Field Courses

8. Sources of Outflow from Water-Table
 Sub-soil flow towards neighboring region
 Soil evaporation from water-table surface
 Transpiration by the plants

9. Anti-Water Logging Measures
 Anti-waterlogging measures can be classified in two main categories,
namely:
I. Preventive Measures
II. Curative Measures
 Land Reclamation

10. Anti-Water Logging Measures (cont…)
I. Preventive Measures
 Economic use of irrigation water
 Restricted supply of irrigation water or lowering the water level in canals
 By providing intercepting seepage drains parallel to canal
 Adopting proper cropping pattern
 Lining of canal irrigation system (i.e. main canals, minors, distributaries,
and water courses) to arrest contribution by seepage losses
 Better management of canal supplies
 Educating the cultivators for optimum utilization, controlled intensity, etc
of canal water
 Reducing percolation losses from rainfall
 Adopting modern irrigation practices like sprinkling and drip irrigation

11. Anti-Water Logging Measures (cont…)
II. Curative Measures
 Extraction of excess water from root-zone of crops to restore the
conductive conditions for normal crop growth
 Outflow from water-table can be increased by an efficient sub-surface or
vertical drainage system
 Providing deep seepage drains
 Puncturing of under ground barriers to lower water level of perched water-
table
 Construction of local reservoirs or sumps

12. Optimum Depletion of Water-Table Depth
The optimum depth of depletion of water table is that which ensure overall
efficient crop growth and at the same time it should not be able to rise again
under given conditions of recharge and drainage
The benefits embodied by optimum depletion of water table depth are:
 Minimum irrigation water requirement
 Elimination of menace of waterlogging and salinization
 Maximum water storage in root zone of crops
 Healthy sanitary conditions
 Higher crop yield
Optimum depth to which watertable may be depressed is governed by depth of
root zone of crops, nature of soil, etc
Higher depletion shall mean higher requirement of irrigation water for normal
crop growth, while less lowering of watertable shall restrict aeration and crop
growth