Salinization is a growing problem in Ethiopian irrigation schemes. The document discusses sources of salinity including geogenic salts from parent materials and anthropogenic salinization from poor irrigation water quality and shallow water tables. Observations from the Middle Awash scheme show increasing salinity levels over time. Management options include leaching, drainage to control water tables, and various cultural practices. Integrated approaches utilizing salt tolerant crops, soil amendments, and improved irrigation management are needed to combat salinization in Ethiopia's irrigation schemes.

1. Practical Experiences in Salinization
Problem : A review
Zeleke Belay
Irrigation Specialist
National SHIDEP Project Team Leader
November 2023, Adama, Ethiopia

2. 2
Outline
1.The what and how of salinity
2.Some observations in Middle Awash
3. Reflections on the management options
4.Concluding remarks

3. 3
I. Why salinity?

4. 4
2. Where is Salinity coming from?
Salinity from where?
a. Geogenic - primary salinity problem
The primary material contains formations that are
highly soluble salts.
Godie –irrigation schemes
Could Tendaho be having the same problem.
In principle, formations that contain highly soluble parent materials should not qualify for
irrigation development, and there is little that can be done to sustainable develop this lands

5. 5
Surface Salinity Maps for Tigray and Amhara Regions

6. 6
Surface Salinity Maps for Oromia and Afar Regions

7. 7
Where is salinity coming from
b. Anthropogenic soil salinity
Secondary salinization or irrigation induced salinization
This is divided into two types:
i. Poor irrigation water quality
Ideally the water for irrigation should be 0.25 – 0.75 dS/m
= 500 -800 mg/l
How much salt is added to the farm if gross irrigation
application is 600 mm = 6000 m3/ha.
(3.6 qt of salt is deposited/ha per year)
Hence, having a good quality water may not be a guarantee to
avoid salinity if the natural drainage systems is bad.

8. 8
Where is salinity coming from?
ii. shallow water table – waterlogging
When valleys are irrigated, the natural hydrologic system is
altered.
The question then is why salinity onset is quick in sme and late
in others.
e.g. Merti and Wonji vs Melka Werer/Amibara irrigation
schemes.
• Egypt has been irrigating for thousands of years – how was it managing
the problem

9. 9
2. Lessons from Middle Awash
The large scale irrigation expansion started ca 1981
Salinity started to be a problem in the late 80s
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7 ECw (dS/m)
Wet Season Dry Season
The water
quality is of
excellent
quality

10. 10
Frew’s paper

11. 11
Frew’s

12. 12
The calcium content is in par with sodium!
The bicarbonate content is unfortunately high

13. 13
The calcium content is in par with sodium
The bicarbonate content is unfortunately high
Bicarbonate is an evil thing in irrigation water –
• It kills calcium
• Creates the opportunity for sodium to prevail

14. 14
Upon irrigation water appraisal, it is important to see both cation and anion composition.

15. 15
Trend in depth to water table (Melka Sedi Farm)
0
5
10
15
20
1980 1985 1990 1995 2000 2005 2010
Depth
to
Water
table
(M)
Water Table Depths
AIP 35 AIP 42 AIP 50 AIP 54 AIP 64

16. 16
Salinity in Godie –
Wabi-Shebelle river

17. 17
What is the problem if the groundwater is closer to the
surface?
Capillary salinization Critical water table depth


 
− +
−
+
−
+
=
n
n
n h
h
n
h
h
z
o
h
h
K
q
dh
h
K
q
dh
h
K
q
dh
dz
1
2
1
1
)
(
1
)
(
1
)
(
1
2
0
1

( )
( ) )
2
(
2
1
1
1
)
( +
−
+





 −
+
= 



m
n
n
m
n
s
h
h
h
K
h
K
Q= 0.1 (arid) -0.5 (humid)
mm/day
( ) 





−


−
=
+
−
= 1
)
(
)
(
z
h
h
K
h
K
dz
dh
h
K
q

18. 18
Recommended subsurface installation depths
0
1 0 0
2 0 0
3 0 0
4 0 0
0 0.1 0.2 0.3 0.4 0.5
 [-]
z
[cm]
1 0
7 .5
5
2 .5
1
0 .5
0 .2 5
0 .1
0 .0 1
0 .0 0 1
mm day
- 1

19. 19
3. What are the management options
The options for comabting salinity problems fall into
three broad categories:
• Leaching – poor irrigation water quality
• Drainage or water table control, and
• Management control mechanisms.

20. 20
iw
e
iw
EC
EC
EC
LR
−
=
5
i. Leaching – poor irrigation water
quality
Can be applied to maintain the salt balance in the root
zone
Often irrigation is in efficient – hence it will be unlikely that we take this inot
account
Moreover this could only be possible
if depth to water table is large deep enough
and
soil is well drained naturally or artificially.
Take it out of the
equation of gross
irrigation requirement
unless you use drip
irrigation

21. 21
ii. Water table control – drainage (Amibara Farm)

22. 22
iii - Management Options
• Improvements in water management
• Cultural practices:
•Irrigation practice –
keep the root zone wet
•Seed bed arrangements
•Soil or water
•amendments – gypsum
for sodicity problem
•Salt tolerant crop
planation

23. 23
Integrated Management Practices/Reclamation

24. 24
Management Strategies

25. 25
Forage Demonstration visited by ICBA staffs at Dubti Site
Demonstration of Promising Salt Tolerant Forage Grass…

26. 26
Field Day Event at Dubti District
2.Demonstration of Promising Salt Tolerant Forage Grass…

27. 27
Farmer’s Field day Event at Kewet District
2. Demonstration of Promising Salt Tolerant Forage Grass…

28. 28
Plot trials on Forage crop Genotypes
Dolichos lablab
Sesbania sesban
Chlorous gayana
Evaluation of Some Selected Locally Available Forage Grass and
Legume Crop Species for Their Salt Tolerance

29. 29
Dolichos lablab
Rhodes
Grass
Sesbania Sesban
Dolichos lablab

30. 30
Using Magnetic Water Application

31. 31

32. 32
Magnetic Forces –application Principle

33. 33
Advantages

34. 34
Additional Challenges Encountered in
Ethiopia

35. 35
Jema (geren) irrigation scheme
Belbelit irrigation scheme

36. 36
Wanza irrigation scheme

37. 37
Dengora irrigation scheme

38. 38
Salt-affected soil photos in Somali Region
Sodium incident Abandoned land for sodicity Poor water management
Crop affected by salinity Compacted soil by sodium Salt concentration

39. 39
Shallow water table (60-80 cm)
Tewelde

40. 40
▪ Trampled due to Na effect
Arategna

41. 41
Golina-Beregu-Melie

42. 42
Ambo

43. 43
Upper-Tuloabajibo
White salt crust & water logging

44. 44
Middle-Tuloabajibo
Water logging
Salt abandoned

45. 45
Koba: The land changed into grazing land

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