15. Water Logging and Salinity Part-1.pdf

Water logging and salinity Part-1

1. Water Logging & Salinity

CE-402: Irrigation Engineering
(CH-03)

Edited by
Dr. Muhammad Ajmal
Lecturer Agri. Engg. UET

Peshawar

4. Water Logging

nN O grain is ever dass without water, but too

5. Water Logging

Q An agricultural land is said to be water logged when its
productivity or fertility is affected by high water table.

U Nutrients like nitrates are required by the plants which are

produced by bacteria, and they require oxygen for
survival. Water logging kills these bacteria.

U Productivity gets affected when root zone of plants gets
flooded with water for long time.

Soil water / root zone

Aeration
zone

Intermediate zone

Lithosphere
Capillary zone

6. Water Logging (contd.)

+ The adverse effects of high water table upon the yield of
crops also depend upon the nature of crop grown.
« Plants with longer roots going deeper are more susceptible
to high water table.
“ The depth of water table which adversely affects the
growth of different crops are as follows.
Y” Wheat crop 0.90-1.20 m
Y” Cotton 1.50 -1.80 m

Y” Sugarcane 0.30 m

7. Water Logging (contd.)

" WATER LOGGED AREA
- ROOT ZONE

CAPILLARY FRINGE

SATURATED ZONE —
IMPERVIOUS LAYER

Fig Definition of waterlogged area

Q As per WAPDA's criterion
+ For the land depth to water table < 3 m (water logged area).

Q Further Categories:
(1) Severely Water Logged Area (D = 0 — 1.50 m)
(2) Less Severely Water LoggedArea (D=1.50-3.0m)

8. Water Logging (contd.)
Properties of waterlogged soil

Physical Electro-chemical
i. Oxygen depletion i, Soil-pH .
ii. CO2 accumulation ii. Increase specific
iii. Compaction conductance
iv. Massive structure iii, Decrease redox
. Lowering diffusion potential (Eh)

coefficient of gases

Chemical
. Soil reduction

Biological
Reduced aerobic

ii. Micronutrient

microbial activity toxicity (cationic)

ii. Mineralization
iii. Immobilization

Das (2002)

9. Types of Water Logging (contd.)

(1) Riverine flood water-logging

= Inthe rainy season, flood may come to the nearby land from the
river having excess flood water.

(2) Oceanic flood water-logging

=" Ocean water spreads in the nearby land and causes water-
logging.

(3) Seasonal water-logging

= Run off water accumulates in the lowlands and depressions in

the rainy season.

10. Types of Water Logging (contd.)

(4) Perennial water-logging

=" Deep water, swamp etc., get rain water, run off water and
seepage water from canal causing perennial water-logging.

(5) Sub-soil water-logging

= High water table in the rainy reason is normally unsuitable for

root growth.

11. Water logging (contd.)
World Population and Cereal Crops Production

WORLD POPULATION source UNDESA

10bn
Least developed 0
= countries P predicted
8bn 2 7
= Most developed
countries
6bn

an

1950 1975 2007 2050

CEREAL CROP PRODUCTION (tonnes) source:raosrar
Sbn

M Oceania
4bn MM Europe
ME Asia
3bn I Latin America
= M North America

W Africa

predicted -

2bn

1bn

196170 80 90 2000 09 2050

12. Causes of Water-Logging

“ The following are the main cause of water logging:
(1) Over Irrigation

= In inundation irrigation since there is no controlling
system of water supply it may cause over irrigation.

= The excess water percolates and remains stored within the
root zone of the crops.

= Again, in perennial irrigation system if water is applied
more than what is required than this excess of water is
responsible for water logging.

13. Causes of Water-Logging

(2) Seepage from Canals:

= In Unlined canal systems, the water percolates through the
bank of the canal and gets collected in the low lying areas
along the course of the canal and thus the water table gets
raised.

= This seepage is more in case of canal in banking.

14. Causes of Water-Logging

(3) Inadequate Surface Drainage

+ When the rainfall is heavy and there is no proper provision for
surface drainage the water gets collected and submerges vast
area. When the condition continuous for a long period, the water
table is raised.

(4) Obstruction in Natural Water Course

» If the bridges or culverts are constructed across with the opening
with insufficient discharges capacity, the upstream area gets
flooded and this causes water logging.

15. Causes of Water-Logging

+ Obstruction in Sub-Soil Drainage:

* If some impermeable stratum exists at a lower depth
below the ground surface, then the movement of the
subsoil water gets obstructed and this cause water
logging in the area.

+ Nature of Soil:

» The soil having low permeability, like black cotton soil,
does not allow the water to percolate through it. So, in
case of over irrigation or flood, the water retains in this
type of land and cause water logging.

16. Causes of Water-Logging

Incorrect method of Cultivation

If the agriculture land is not levelled properly and there is no
arrangement for the surplus water to flow out, then it will
create pools of stagnant water leading to water logging.

Seepage from Reservoir

If the reservoir basin consists of permeable zones, cracks
and fissures which were not detected during the construction
of dam, these may cause seepage of water. This sub-soil
water will move forward toward the low lying area and
cause water logging.

17. Causes of Water-Logging

» Poor Irrigation Management:

* If the main canal is kept open for a long period

unnecessarily without computing the total water
requirement of the crops, then this leads to over
irrigation, which shall result in water logging.

+ Excessive Rainfall:

» If the rainfall is excessive and the water gets no time to
get drained off completely, then a pool of stagnant water
is formed which might lead to water logging.

18. Causes of Water-Logging

+ Topography of the land:

» If the agricultural land is flat, i.e. with no country slope
and consists of depression or undulations, then this
leads to water logging.

» Occasional Flood:

» If an area gets affected by flood every year and there is
no proper drainage system, the water table gets affected
and this cause water logging.

19. cc oo 0.0010

D

Effect of Water Logging

Normal cultivation operations cannot be carried out easily in wet soil
(makes cultivation operation difficult due to standing water).

Certain water loving plants like grasses, weeds etc grow fastly in water
logged land and affects the growth of the crops.

Kills the bacteria which produces nutrients.

Causes the loss in crop yield.

Spread of mosquitoes and malaria.

Destruction of roads due to reduced bearing capacity.
Water logging leads salinity.

Causes dampness in buildings, appearance of salts on surface,
weakens the plaster and produces ugly spots.

If salty soil is used to make bricks, salts appear on the wall surface.

20. Remedial Measures of Water Logging

. Lining of canals and water courses

. Reducing the intensity of irrigation

. By introducing crop rotation

. Optimum use of water

. Providing intercepting drains

. Provision of efficient drainage system
. Improving natural drainage of area

. Introducing to lift irrigation

21. 1. Lining of canals and water courses
+ Lining of canal system reduces seepages of water.

2. Reducing the intensity of irrigation
+ In area where there is possibility of water logging, Intensity
of irrigation should be reduced.

3. By introducing crop rotation
* Certain crops require more water and others requires less
water so by rotation of crops avoid high water table.

4. Optimum use of water
+ Certain fixed amount of irrigation gives best results.

+ Less than and more than that reduces yield.

22. 5. Providing intercepting drains
= Intercepting drains along canals should be provided which
prevent seeping canal water from reaching the water logged
area.

6. Provision of efficient drainage system
" A good horizontal drainage system provided for rainstorm
water (surface and sub-surface).

7. Improving natural drainage of area

= To reduce percolation of water the water should not stand for
longer period.

8. Introducing to lift irrigation
= It helps in lowering the water table through tube wells
(vertical drainage).

23. Pumping from waterlogged area

24. Pumping from waterlogged area

25. Thank You