Drainage SYSTEMS

Drainage

Drainage is the removal of excess water from the land. This is often necessary in areas of high rainfall, which causes the soils to be waterlogged.

Waterlogging leads to retardation in plant development and the growth of micro-organisms in the soil. Waterlogging is the accumulation of excess water in the root zone of the soil.

Drainage is also necessary where salinization of the soil occurs. Salinization is the accumulation of soluble salts at the soil surface, or at some point below the soil surface, to levels that have negative effects on plant growth and/or on soils.

Benefits of Drainage

The benefits of proper drainage are that it:

• Allows for easier exchange of gases

• Enhances the activities of soil micro-organisms

• Prevents leaching

• Prevents the accumulation of toxic chemicals and salts

• Provides room for crops to root more deeply.

• Allows the production of crops in areas that were waterlogged.

• Increases the bearing capacity of the land.

• Improves the workability and tilth of soil.

• Improves the soil structure and impermeability.

• Raises soil temperatures allowing crops and grasses to be grown earlier.

Types of Drains

1. Surface Drainage

This is used mainly on agricultural lands. The purpose is to release some of the water from the soil surface, draining it through the soil into depressions or ditches which channel it to larger and deeper collector drains. The field must be given an artificial slope by means of land grading in order to facilitate this flow.

2. Sub-surface Drainage System

Sub-surface drainage is the removal of water from the root zone. It is accomplished by:

1. Deep open drains

2. Underground drains

Deep open drains extend all the way to the water table.

Deep open drains are advantageous in that:

• They have low construction costs

They are disadvantageous in that they:

• use land that otherwise could be used for crops,

• restrict the use of machines

• Require a large number of bridges for road crossings and access to the fields.

• Require frequent maintenance

Underground drains are pipe lines (either clay, plastic or concrete) prepared and placed beneath the soil level for the purpose of draining the entire area. It is basically used for draining cricket and recreational grounds.

Underground drains are advantageous in that:

-they cause no loss of cultivable land

-maintenance requirements are limited

However they:

• Have a high installation cost, requiring materials, equipment and skilled manpower.

• Are difficult to repair if broken due to their being buried in the soil

Subsurface drainage systems are often employed to deal with salinization.

Extra irrigation water is applied to the field. This infiltrates into the soil dissolving the salts within it and washing them into subsurface drains which carry them away. This is a process called leaching.

If you remember clearly, leaching is the removal of soluble salts by water percolating into the soil.

Constructing and Establishing of Drains and Canals

Drains must be constructed so that superfluous water is removed from the soil surface and the upper sub-soil while at the same time retaining adequate reserves to carry crops through dry weathers.

Drains may be constructed using hand-tools or machines.

Drainage in Guyana

Within Guyana, a combination of surface and deep open drains, originally constructed by the dutch, are used to control waterlogging on farms and fields.

Since the coastal plains are below sea-level, the sea-walls are used to prevent the coastal areas from flooding during high tides.

A network of drains have been laid down within and around residential, commercial and agricultural areas in order to control the flow of rainfall runoff.

These drains lead to canals which lead to kokers that empty them into the nearby rivers and ocean. As such, drainage is heavily affected by the tide.

To the author's knowledge, not much is done to control salinization.

Drainage Quiz

1. The removal of excess water from the land is referred to as:

a. Leaching

b. Waterlogging

c. Salinization

d. Drainage

2. The accumulation of excess water in the root zone is referred to as:

1. Leaching

2. Waterlogging

3. Salinization

4. Drainage

3. The accumulation of soluble salts below the soil surface is referred to as:

1. Leaching

2. Waterlogging

3. Salinization

4. Drainage

4. Which of the following influences drainage the MOST:

1. Soil type

2. Depth of water table

3. Depth of permeable soil layer

4. Crop type

5. The removal of soluble salts by water percolating into the soil is referred to as:

1. Leaching

2. Waterlogging

3. Salinization

4. Drainage

6. Salinization is controlled by the use of

1. u-shaped drains

2. v-shaped drains

3. Deep open drains

4. Underground drains

7. V-shaped drains are constructed mainly by

1. Shovels

2. Tractor implements

3. Both of the above

4. None of the above

8. U-shaped drains are constructed by

1. Shovels

2. Tractor implements

3. Draglines

4. Hoes

9. Which of the following is NOT a benefit of drainage:

1. Provides room for crops to root more deeply

2. Improves workability and tilth of the soil

3. Dissolves nutrients allowing them to infiltrate through the soil

4. Prevents leaching

10. Which of the following is NOT a type of drain?

1. Surface drain

2. Deep-open drain

3. L-shaped drain

4. V-shaped drain

11. Which of the following are constructed MAINLY in order to release water from the soil surface?

1. Surface drain

2. Deep-open drain

3. L-shaped drain

4. V-shaped drain

12. Which of the following is constructed MAINLY in order to remove water from the root zone?

1. Surface drain

2. Deep-open drain

3. L-shaped drain

4. V-shaped drain

13. Which of the following is an advantage of the deep-open drain?

1. Has low construction costs.

2. Causes no loss of cultivable land.

3. Requires limited maintenance

4. Restricts the use of machines

14. Which of the following is an advantage of the underground drain?

1. Has low construction costs.

2. Causes no loss of cultivable land.

3. Requires a lot of maintenance

4. Restricts the use of machines

15. Which of the following is NOT a disadvantage of the deep open drain?

1. use land that otherwise could be used for crops,

2. restrict the use of machines

3. Require a large number of bridges for road crossings and access to the fields.

4. Require limited maintenance.

16. Which of the following is a disadvantage of underground drains?

1. use land that otherwise could be used for crops,

2. Have a high installation cost, requiring materials, equipment and skilled manpower.

3. Causes no loss of cultivable land.

4. Restricts the use of machines

True or False

Write T if the statement is True or F is the statement is false.

17. Artificial drainage becomes necessary when natural drainage is inadequate to remove extra salts or water.

18. An artificial slope is necessary in order to facilitate proper drainage in a field.

19. V-shaped drains are constructed basically on sandy soils.

20. Drains must be constructed so that excess water is removed but not so much as to deplete soil reserves.

21. Underground drains are usually made of clay, plastic or concrete.

22. Guyana uses a combination of surface and underground drains to control waterlogging.

23. Kokers are used to control the flow of runoff into rivers and oceans.

24.The drainage system in Guyana was originally built by the British.

25. Underground drains are usually used in cricket or recreational grounds.

Click here for a Practical Activity on the Impacts of Irrigation and Drainage Systems

Discussion

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References

• Grade 9 Curriculum Guide for Crops and Soils

• Food and Agricultural Organization. Drainage Systems. Irrigation Water Management: Training Manual No. 1 - Introduction to Irrigation <http://www.fao.org/3/r4082e/r4082e07.htm>

• Drainage Effects on Water Table Image <https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcTKFUYFPkJED_HFiuNBNmawps1YQ4CAaaRqoQ&usqp=CAU>

• Surface Drains Image <https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcRRSIWLnlJtfOZJH2AKXRm5SH4qcJJsVFKOdw&usqp=CAU>

• Subsurface Drains Image <https://www.schneiderconstructioninc.com/drainage/photos-drainage/detail-FrenchDrain-02_700.jpg>

• Types of Drains Image <https://encrypted-tbn0.gstatic.com/images?q=tbn%3AANd9GcSQG1LhHmG8yfsoF_ocWBuQ8TYv2WE0Dvcs8A&usqp=CAU>