by: Dr. Zahir Haque Khan & Team Presented at the GBDC Reflection Workshop,November 2013

1. Ganges Basin Development Challenge
G4: Assessment of the Impact of Anticipated External
Drivers of Change on Water Resources of the Coastal Zone

2. Outcome
Logic Model
Project outputs
Existing condition:
• Data on WL, Flow, Salinity
•Digital Elevation Model
• Freshwater & salinity
zoning map
• Drainage Conditions and
Inundation maps of polders
• External drivers
• Scenarios
Future condition:
Outcome Logic Model
• Climate change projections
• Population projection
• Landuse change projection
OUTCOMES
Change in KAS
Change in Practice/
behavior
Planning
Commission, minis
Farmers and fishers of polder 3, 30 and 43/2F
tries of water
resources,
Encouraged to
Awareness building
environment &
participate in discussions
Knowledge enhancement
forests, agriculture
to contribute in planning
and fisheries in
Bangladesh –
Researchers of G1, G2, G3 & other ongoing projects
Scaling up
Acquiring data, information & Use of data & information
knowledge
Extrapolation Domain,
Understanding of the
Understanding external
drivers, scenarios and their
effects
new database,
Planning of cropping
system
LGI, BWDB, WARPO, LGED, DOF and NGOs
Acquiring new
information & knowledge
Understanding the
benefits of using new
information and improved
plan for proper drainage
and irrigation
Use in Improving
planning, design and
implementation
• Freshwater & salinity
zoning map
• Drainage Conditions and
Inundation maps of polders
• Improved Drainage plan
of the three polders
Ministry of Water Resources, Planning Commission
Understanding of effects of
external drivers
Motivated and encouraged
to use the new information
Assimilation of new
knowledge and
information in project
planning and approval
and policy change
effects of external
drivers & anticipated
change of water
resources and the
benefits of
adaptation measures
will encourage these
policymakers to be
motivated to
formulate new
policies.
Impact
Improved and
resilient water
infrastructure
and operation
Improved
Polder
management
for
maximizing
crop & fish
production

3. Study Area
Polder-30
Medium Salinity
Polder-43/2F
Low Salinity
Polder-3
High Salinity
Coastal Zone of the Ganges Basin in Bangladesh

4. Date
Mar-2014
Jan-2014
Nov-2013
Sep-2013
Jul-2013
Kharif-1
May-2013
Mar-2013
Jan-2013
Nov-2012
Sep-2012
Jul-2012
May-2012
0.5
Mar-2012
Rabi
Jan-2012
11-May
1-Apr
2.0
Nov-2011
12.0
Sep-2011
Jul-2011
21-Feb
12-Jan
Salinity (ppt)
0.0
May-2011
POLDER-43/2f
Date
3-Dec
8.0
Mar-2011
24-Oct
14-Sep
5-Aug
Salinity (ppt)
24.0
Polder 43-2f (Station-2 (In Side),Para River)
Data:Temporal variation of Salinity
20.0
16.0
Polder 43-2f (Paira River)
2 PPT
4.0
1.5
1.0
Kharif-2
0.0

5. Temporal variation of Salinity
Salinity at Kazibacha River
Kharif-1
2 PPT
19 Jun 2012
POLDER-30
8 Feb 2012
Rabi
Kharif-2

6. 12.0
8.0
4.0
0.0
Apr-2012
Date
2 PPT
Aug-2013
Jun-2013
Apr-2013
14 Sep 2012
Feb-2013
Kharif-1
Dec-2012
Oct-2012
Aug-2012
Jun-2012
Rabi
Feb-2012
Dec-2011
Oct-2011
Aug-2011
Jun-2011
16.0
17 Dec 2011
20.0
Apr-2011
POLDER-3
Salinity (ppt)
Data:Temporal variation of Salinity
24.0
Polder 3 (Ichamoti River)
Kharif-2

7. Spatial and Seasonal Variation of Salinity in the Coastal Ganges in Bangladesh
May, 2012
Base Year: 2012
BARISAL
KHULNA
Fresh and Brackish water zone

8. Output: External Drivers of Change

9. External Drivers and Future Scenarios
Scenario Generation Workshop
Final List of Key External Drivers and
Their Ranking
Combination
Scenarios

10. Scenario: Effect of Transboundary flow and Climate Change
Upstream Boundaries (Q, Sal = 0pt)
Minimum and maximum flow in Gorai in dredged condition
Trans-boundary flow
Best case scenario: maximum flow since GWT
worst case scenario: minimum flow since GWT
Ganges Basin
Climate change: A1B condition
(Precipitation, Temperature and Sea
level rise)
Scenario : 2050
Downstream Boundaries (WL, Sal) + Sea Level Rise

11. Scenario: Transboundary Flow, Land-Use Change and Climate Change
Upstream Boundaries (Q, Sal = 0pt)
Minimum and maximum flow in Gorai in dredged condition
Trans-boundary flow
Best case scenario: maximum flow since GWT
Land-use change
Ganges Basin
Climate change: A1B and A2 condition
(Precipitation, Temperature and Sea
level rise)
Scenario : 2030 and 2050
Downstream Boundaries (WL, Sal) + Sea Level Rise

12. Scenarios: Effect of Multiple Drivers on Water Resources
Upstream Boundaries (Q, Sal = 0pt)
Minimum flow in Gorai in dredged condition
Trans-boundary flow (worst case
scenario: minimum flow since GWT)
Population growth: water extraction
from the river system
Ganges Basin
Land-use change
Climate change: A1B condition
(Precipitation, Temperature and Sea
level rise)
Scenario : 2030
Downstream Boundaries (WL, Sal) + Sea Level Rise

13. Scenario: Population Growth
Upstream Boundaries (Q, Sal = 0pt)
Maximum flow in Gorai in dredged condition
Trans-boundary flow (best case
scenario: maximum flow since GWT)
Population growth: water extraction
from the river system
Land-use change
Ganges Basin
Climate change: A1B condition
(Precipitation, Temperature and Sea
level rise)
Scenario : 2030
Downstream Boundaries (WL, Sal) + Sea Level Rise

14. Scenario: Infrastructure Development
Upstream Boundaries (Q, Sal = 0pt)
Minimum flow in Gorai in dredged condition
Population growth: water extraction
from the river system
Trans-boundary flow (best case
scenario: maximum flow since GWT
Land-use change
Change in water
management practices
Water infrastructure development
Ganges Basin
Change in water governance and institutions
(including policy change)
Climate change: A1B condition
(Precipitation, Temperature & Sea level rise)
Scenario : 2030
Downstream Boundaries (WL, Sal) + Sea Level Rise

15. Transboundary Flow
Transboundary Flow

16. GWT
Farakka Barage
Effect of Transboundary Flow on Salinity
Salinity in the south-west
zone is very much
dependent on upstream
freshwater flow
Salinity variation with upstream freshwater flow
during dry season (Salinity Data Source: BWDB)
Ganges Water Treaty is very
important for salinity control in the
south-west zone of Bangladesh
Salinity variation with upstream freshwater flow
during dry season (Salinity Data Source: IWM)

17. Effect of Transboundary Flow :South-west Zone of Bangladesh
May, Base condition with maximum Transboundary flow under Ganges Treaty

18. Effect of Transboundary Flow :South-west Zone of Bangladesh
May, Base condition with minimum Transboundary flow under Ganges Treaty

19. Effect of Climate Change and Transboundary Flow: South-west Zone
May, 2030 climate change (A1B) with minimum Transboundary flow under Ganges Treaty

20. Effect of Infrastructure Development: Ganges Barrage
May, 2030 Climate change (A1B) with Ganges Barrage

21. Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage

22. Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage

23. Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage

24. Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage

25. Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
Decrease of Freshwater and mild brackishwater area (0-2ppt):
Transboundary flow: 1100 sq. km
Climate Change: 800 sq. km

26. Drainage Condition
Khals within polders vary greatly in size, can store fresh water during the dry season, but
often heavily silted up (some no longer exist), blocked…
26

27. Drainage Performance of Polders at Present and Future
3 day Depth-Duration Map
Flood type
Area (sqkm) % of Area
Flood Free
25.48
40
F0 (0 - 30 cm)
21.01
33
F1 (30 - 90 cm)
13.42
20
F2 (90 - 180 cm)
4.32
7

28. Drainage Performance of Polders at Present and Future
3 day Depth-Duration Map
(Scenario_2030)
Flood type
Area (sqkm) % of Area
Flood Free
21.97
34
F0 (0 - 30 cm)
22.24
34
F1 (30 - 90 cm)
15.26
24
F2 (90 - 180 cm)
5.03
8

29. Drainage Performance of Polders at Present and Future
3 day Depth-Duration Map
(Scenario_2050)
Flood type
Area (sqkm) % of Area
Flood Free
16.41
25
F1 (30 - 90 cm)
27.86
43
F2 (90 - 180 cm)
Flood type
21
F0 (0 - 30 cm)
2030
13.54
6.70
11
2050
(Change from present condition) (Change from present condition)
Flood Free
-6
%
-19 %
F0 (0 - 30 cm)
1
%
-8
F1 (30 - 90 cm)
4
%
23 %
F2 (90 - 180 cm)
1
%
4
%
%

30. Drainage Improvement Measures
• Dredging and Re-excavation
of rivers and khals
• Additional drainage structure

31. Drainage Improvement Measures
25 Year Flood Event : A1B Scenario; 2030
Inundated Area = 68%

32. Drainage Improvement Measures
25 Year Flood Event : A1B Scenario; 2030
With improvement measures

33. Polder-30: Case Study- Maitbhanga Village
Discussion with local people of Maitvanga about drainage
Drainage canal has been silted up
and the bottom level has been
same as the surrounding land
Drainage canal blocked by
human intervention
The high depth of water in Aman
field of Maitvanga beel
UP road crosses the canal
without any culvert blocking
cross-drainage

34. 2
1.5
Considerations
for Sub-polderization:
 Land level
1
0.5
0
0
2000
4000
Distance (m)
2
1.5
1
0.5
0
-0.5
0
2000
4000
Distance (m)
Land Level (mPWD)
Land Level (mPWD)
Land Level (mPWD)
Polder-30: Subpoldering and Community based Water Management
2
1.5
1
0.5
0
-0.5
0
2000
4000
Distance (m)

35. Polder-30: Subpoldering and Community based Water Management
Considerations
for Sub-polderization:
 Land level
 Canal system

36. Polder-30: Subpoldering and Community based Water Management
Considerations
for Sub-polderization:
 Land level
 Canal system
 Tidal characteristics
of the peripheral
rivers

37. Polder-30: Subpoldering and Community based Water Management
Considerations
for Sub-polderization:
 Land level
 Canal system
 Tidal characteristics
of the peripheral
rivers
 Road network

38. Polder-30: Subpoldering and Community based Water Management
Sub-polder
Considerations
for Sub-polderization:
 Land level
 Canal system
 Tidal characteristics
of the peripheral
rivers
 Road network

39. Polder-30: Subpoldering and Community based Water Management
Sub-polder
Community based
water management
Unit/ Block
Considerations
for Sub-polderization:
 Land level
 Canal system
 Tidal characteristics
of the peripheral
rivers
 Road network
Benefits of Sub-polderization:
 Better water management, i.e., drainage and flushing of
irrigation water
 Conflict management between high and low land
 Involvement of local community in water management
 Easy and timely maintenance over the years for subpolders
 High depth of water in aman field reduce production;
thus proper drainage will enhance crop yield

40. Sub-polderization : Community Participation in Water Management
and Governance
Water Management Organization (WMO)
Community Based Water
management Unit/Block
Water management Group (WMG)
Sub-polder
Water management Association (WMA)
Polder
Water management Federation (WMF)

41. Solutions for Drainage Congestion in Polder-30
Message:
 New paradigm shift in water management: Sub-polderization and community based
water management
Outscaling Opprotunity:
 Blue Gold
 Costal Embankment Improvement Project (CEIP)

42. Polder-30: Opportunity for Gravity Drainage
Kazibacha river
Area (Percent)
Maximum water level 2.4 m
0
4
Average water level 1.3 m
40
60
80
100
Area-Elevation curve
3.5
Land level (mPWD)
Minimum water level 0.0 m
20
3
2.5
2
1.5
1
0.5
0
0
Lower-Shalta river
10
20
30
40
50
60
Area (sqkm)
Level (mPWD) Area below %
Average water level 1.0 m
Digital Elevation Model
0.60
1.00
1.20
1.60
1.80
2.00
15
61
80
95
98
99

43. Area Elevation curve (Polder
Polder-43/2F: Opportunity for Gravity Drainage 43/2F)
45
100
40
35
80
Area (Sq Km)
30
25
60
20
Level (mPWD)
1.0
1.2
1.4
1.8
2.0
15
10
5
Area below (%)
9
23
52
92
98
40
20
0
0
0
Kharif-1
Avg WL 1.00m PWD
0.5
1
1.5
2
2.5
Elevation (mPWD)
Kharif-2
Avg WL 1.20m PWD
3
Rabi
3.5
Avg WL 0.80m PWD
4
Area (Percent)
Tidal window above 1.40 mPWD

44. Polder-3: Water Management (Drainage and Flushing)

45. Polder-3: Water Management (Drainage and Flushing)

46. Polder-3: Water Management (Drainage and Flushing)
 Land use has beenchanged over the years
 Shrimp culture has been introduced
 Huge number (133 pipes and 27 private regulators)
of informal structures have been built for flushing
brackish water into the polder
 Present drainage system needs to be revisited to
meet the demand of flushing brackish water
 18 new formal structures and improved canal
system can meet the demand of flushing brackish
water
Benefits:
 If properly managed, brackish
water can be considered as a
resource, can be used for highincome aquaculture
 Opportunity for crop
diversification

47. Trans-Boundary and Food issues
By IWMI

48. Key Messages
 There is abundant fresh water for irrigation in much of Barisal Division throughout the
dry season. The water will remain suitable for irrigation all over the year in the
changing climate in 2030.
 Polder 30:Storage of freshwater in improved internal drainage canals can meet
irrigation demand of boro rice for 20% area of cultivable land
 In high saline areas, brackish water can be considered as a resource that, if properly
managed, can be used for high-income aquaculture.
In polder-3, existing huge number of informal pipes (133 Nos) and structures (27 Nos)
can be replaced by a smaller number of formal structures (18) and improved
canal
system.

49. Key Messages
 G4 used hydrological, hydrodynamic, salinity and storm-surge models to
assess the impacts of the external drivers of change on the water
resources in the Ganges dependent coastal area in Bangladesh
 To predict future climate, population growth and land-use scenario G4
used model results (PRECIS, SDSM and SWAT) provided by partner
organizations: IWFM-BUET and IWMI

50. Closure Plan
Way Forward to the Project Closure:
Effectiveness of sub-polders
Land-use change projections in the study area
Storm surge risk assessment in the thee selected polders
(Polder-3, 30 & 43/2F)
Out scaling of the research results:
Workshop presentation in coordination with G5
Institution based workshop: with
BWDB, LGED, DAE and DoF
Policy brief on drainage management and water
availability in present and future scenario

51. Closure Plan
Description of Activities
Storm surge modelling for selected 3 polders
Land-use projection
Assessment of the effect of Land-use and
Population growth of Sub-polder in Polder-30
Water management
Outscaling
Policy Brief
Drainage Management
Water Availability
Transboundary flow
Infrastructure Development
Final Closure Report
2013
2014
Dec
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

52. THANK YOU