Water Logging and Reclamation MCQ Quiz - Objective Question with Answer for Water Logging and Reclamation - Download Free PDF

Explanation:

• The cross-section of shallow surface drains is normally trapezoidal in shape.

• These drains are primarily used to dispose of run-off water, helping reduce the percolation of stormwater.

• They are especially useful in areas with local depressions, where water tends to accumulate.

• The trapezoidal shape provides greater hydraulic efficiency and is easier to construct and maintain compared to other shapes.

Explanation

Sodium-ion in small amounts is good for plants. But excess sodium ion creates the problem for both plant and soil. Excess sodium contributes to salinity and is toxic for some sensitive crops.

Soil with high sodium content becomes very plastic in nature in the wet stage, which shows low permeability and poor aeration.

This excessiveness of sodium ion is measured in terms of sodium absorption ratio (SAR).

\({\rm{SAR}} = \frac{{\left[ {{\rm{N}}{{\rm{a}}^ + }} \right]}}{{\sqrt {\frac{{\left[ {{\rm{C}}{{\rm{a}}^{2 + }}} \right] + \left[ {{\rm{M}}{{\rm{g}}^{2 + }}} \right]}}{2}} }}\)

Where,

[Na+] = concentration of sodium ion in milli-equivalent per liter

[Ca2+] = concentration of calcium ion in milli-equivalent per liter

[Mg2+] = concentration of magnesium ion in milli-equivalent per liter

SAR = \(\frac{{{\rm{Na}^{+}}}}{{\sqrt {\frac{{{\rm{Ca}^{++}} + {\rm{Mg}^{++}}}}{2}} }}\) = \(\frac{{28}}{{\sqrt {\frac{{12 + 20}}{2}} }} = 7\)

Important Points

SAR - [0 - 10] (Type of water is Low sodium)

Concept:

Water Logging: An agricultural land is said to be water logged when the root zone of the crops gets flooded with high water table and become ill-aerated. The productivity gets affected by water logging problem.

Water logging & Salinity: When water table has risen up substantially it comes within the root zone of the crops and the soluble salts present in the water also rise up towards the surface. So, when water is evaporated the salts gets deposited in the root zone, resulting in increased salinity. Therefore, it affects the process of osmosis which in turn results in reduction in water extraction capacity of the roots. Thus, water logging reduces the productivity or yield of the crops.

∴ Statement 1 is correct.

Control of water logging: Water logging can be controlled by provision of efficient drainage to drain away the storm water and excess irrigation water by use of surface and sub-surface drainage. These drainage will check and reduce the water percolating in the soil mass, thus reducing the chances of water logging. But it cannot be eliminated completely as there will be always some water percolation into the soil mass.

Explanation:

Water logging occurs when excess water accumulates in the root zone of crops, reducing oxygen availability and affecting plant growth. Preventive measures aim to reduce water stagnation and improve drainage.

Analysis of Each Option:

1. Efficient surface drainage (Correct Preventive Measure)

   • Surface drainage helps remove excess water from fields, preventing waterlogging.

2. Lining of canals (Correct Preventive Measure)

   • Unlined canals lead to seepage, increasing water table levels and causing water logging.

   • Lining canals reduces seepage, minimizing waterlogging risks.

3. Stopping the practice of sprinkler irrigation (Incorrect Preventive Measure)

   • Sprinkler irrigation is actually a water-efficient method that prevents excess water application.

   • Stopping it would lead to inefficient water use, potentially increasing waterlogging issues.

4. Economic use of water (Correct Preventive Measure)

   • Using water judiciously prevents excess water accumulation, reducing chances of waterlogging.

Concept:

Sodium-ion in small amounts is good for plants. But excess sodium ion creates the problem for both plant and soil. Excess sodium contributes to salinity and it is toxic for some sensitive crops.

Soil with high sodium content becomes very plastic in nature in the wet stage, which shows low permeability and poor aeration.

This excessiveness of sodium ion is measured in terms of sodium absorption ratio (SAR).

\({\rm{SAR}} = \frac{{\left[ {{\rm{N}}{{\rm{a}}^ + }} \right]}}{{\sqrt {\frac{{\left[ {{\rm{C}}{{\rm{a}}^{2 + }}} \right] + \left[ {{\rm{M}}{{\rm{g}}^{2 + }}} \right]}}{2}} }}\)

Where,

[Na⁺] = concentration of sodium ion in milli-equivalent per liter

[Ca²⁺] = concentration of calcium ion in milli-equivalent per liter

[Mg²⁺] = concentration of magnesium ion in milli-equivalent per liter

Concept:-

When, pH = 7 to 8.5 normal yields. (Best suited pH for maximum yields)

When, pH = 8.0 to 9.0 yield decreases and partially infertile

When, pH = 11 soil becomes more alkaline and infertile

Note: -

Water logging may be defined as the increase in water-table which lead to decreased productivity of the land. Whenever there is water-logging, there will always be salinity. And hence soil becomes alkaline.

Causes of water logging: -

1. Over and intensive irrigation
2. Seepage of water from adjoining high lands
3. Seepage of water through canals.
4. Inadequate natural drainage.
5. Excessive rainfall
6. Submergence due to floods.

Concept:-

When pH = 7 to 8.5 normal yields. (Best suited pH for maximum yields)

When pH = 8.0 to 9.0 yield decreases and partially infertile

When pH = 11 soil becomes more alkaline and infertile

Note: -

Waterlogging may be defined as the increase in water-table which leads to decreased productivity of the land. Whenever there is water-logging, there will always be salinity. And hence soil becomes alkaline.

Causes of waterlogging: -

1. Over and intensive irrigation
2. Seepage of water from adjoining high lands
3. Seepage of water through canals.
4. Inadequate natural drainage.
5. Excessive rainfall
6. Submergence due to floods.

Effects of Waterlogging

1. Poor aeration - The pores of soil are filled with water and hence there is no effective circulation of air 
2. Reduced soil temperature - A waterlogged soil warms up slowly and due to low temperature action of soil bacteria is inhibited and plant food available is less. It lowers the rate of nitrogen fixation.
3. Alters pH
4. Retard cultivation.
5. Affects soil nutrients.
6. Affects human health due to mosquito breeding and disease vectors.
7. Inhibiting activity of soil bacteria
8. Decrease in available capillary water

Explanation:

Acidic Soil Formation: In regions of high rainfall soluble basic salts such as, Ca, Mg, K, Na, are leached away by drainage water and insoluble acidic residue accumulates such as silicates of iron, silicon, and aluminium which increases acidity in the soil.

Some other reasons for the formation of acidic soil are rainfall, decomposition of organic matter, etc.

Different liming materials such as CaO, Ca (OH)₂, CaCO₃ are added to the soil for its reclamation.

For acidic soil - The use of limestone as a soil amendment can prove to be the best method of reclamation of soil.

For alkaline soil - The use of gypsum as a soil amendment can prove to be the best method of reclamation of soil.

Explanation:

It is a phenomenon in which the productivity of land gets affected due to the high water table leading to flooding of the root zone of the plants and making the root zones of the plants ill-aerated.

1. Over and intensive irrigation
2. Seepage of water from the adjoining lands
3. Impervious obstruction
4. Inadequate surface drainage
5. Inadequate natural drainage
6. Heavy rains
7. Submergence due to floods High water table

Lift irrigation:

• Irrigation with which water is supplied to the system by water-lifting devices is called pumping/mechanical/lift irrigation (by means of mechanical water-lifting devices).
• It has high operating costs. 
• It has fewer problems with waterlogging.

Extensive irrigation:

• These systems are more costly to build and to maintain.
• Irrigation service provided to end-users is often limited to only two to three irrigations per season.
• These systems often have fewer problems with waterlogging and salinity and provide incentives for the conjunctive use of ground and surface water.

Intensive irrigation

• This system uses a large amount of water, labour, and resources for a small area in order to increase production and yield.
• More prone to waterlogging as no limit to the amount of irrigation water.

Concept:

The drainage coefficient is defined as the depth of water to be removed in 24 hours from the entire drainage area.

• It is used for the design of drainage systems for agricultural lands.
• In agricultural lands, open ditches or drains are the most commonly used surface drainage structures.
• The rate at which the open drains should remove water from a drainage area depends on:
  • Rainfall
  • Size of the drainage area
  • Characteristics of the drainage area
  • Nature of the crops grown
  • The degree of protection required for them from waterlogging

​Calculation:

Given:

Drainage coefficient = 1.25 cm ( i.e Depth of water removed per day)

Area = 12 ha = 120000 m2

(1 ha = 10000 m2)

Water removal period = 2 days

The volume of water removed = Drainage coefficient × Area × Time = (1.25/100) × 120000 × 2 = 3000 m3

Explanation:

Water logging:

• Water logging of the land occurs when the water table rises and the soil in the root zone of the plants gets saturated and the air circulation is stopped.
• Water logging generally occurs because of intensive irrigation and inadequate drainage of the irrigated land.
• Waterlogging affects the productivity and fertility of the land and causes a reduction in crop yield.

Causes of waterlogging -

• Over-Irrigation
• Inadequate surface drainage
• Obstruction of natural surface drainage
• Obliteration of a natural drainage
• Obstruction of natural subsurface drainage
• Impervious top layer
• Seepage from canals
• Construction of a reservoir
• Defective methods of cultivation
• Defective irrigation practice

Effect of waterlogging -

• Reduction in the growth of plants
• Difficulty in cultivation
• Accumulation of salts
• Weed growth
• Increase in plant diseases
• Lowering of soil temperature
• Increase in incidence of malaria

Hence statements B and D are incorrect.

Explanation:

Waterlogging is simply the saturation of soil with water when the capillary fringe reaches the root zone of plants.

Causes of Waterlogging

1. Excessive irrigation and poor drainage system by farmers.
2. Natural causes such as prolonged rainfall or flood.
3. Interflows and seepage from nearby water bodies like lakes, shallow aquifers, etc.
4. Soil type like clay holds water due to low permeability.
5. An impervious stratum below the topsoil, obstructs the infiltration of rainfall, causing a false water table or perched water table.

Effects of Waterlogging

1. Poor aeration.
2. Alters pH.
3. Changes in soil temperature.
4. Retard cultivation.
5. Affects soil nutrients.
6. Affects human health due to mosquito breeding and disease vectors.​​

Concept:

Tile drainage is a type of drainage system that removes excess water from soil below the surface. Plants need air as well as moisture in their root zones for their survival, excess irrigation farm water is free to move into the underground tile drains, this water, if not removed, retards the plant growth because It fills the soil voids and restricts proper aeration, Therefore there is a need for Sub-surface drainage or tile drainage.

The spacing of the drains is given by the Hooghoudt equation:

\(S = \frac{{4k}}{q}\left( {{b^2} - {a^2}} \right)\)

Where,

k = Coefficient of permeability

q = discharge per unit length in the drain

a = depth of the impervious strata below the drain

b = maximum height of the drained water table above the impervious layer

Concept:

Leaching Requirement:

leaching requirement (LR) is a fraction of the amount of irrigation water and the fraction is the ratio of the salinity of the irrigation water to the salinity of the deep percolated (drained) water.

\(LR={D_d\over D_i}={C_i\over C_d}={EC_{(i)}\over EC_{(d)}}={EC_{(i)}\over 2EC_{(e)}}\)

Where D_d = Depth of water drained out per unit area

D_i = Total irrigation water depth applied

C_i = Salt concentration of irrigation water

C_d = Salt content of drained or leached water.

EC_(i) = Electrical conductivity of irrigation water

EC_(d) = Electrical conductivity of drained water

EC(d) = Value is twice the value of saturation soil extract EC_(e).

Calculation:

Given

Electrical conductivity saturated soil Extract (EC_(e))= 10 m mho/cm 

Electrical conductivity of irrigation water (EC_(i)) = 1.5 m mho/cm

\(LR={EC_{(i)}\over 2EC_{(e)}}\)

\(LR = {1.5\over 2\times 10}=0.075\)

Leaching requirement (LR) = 7.5%