This document discusses a study assessing the impact of anticipated external drivers of change on water resources in the coastal zone of the Ganges basin in Bangladesh. It outlines the following: 1. Key research questions around how drivers will affect hydrology, flooding, salinity, and water availability. 2. The overall methodology which will analyze scenarios involving population growth, land use change, climate change, and transboundary river flows using water flow and salinity modeling. 3. Example scenarios that were developed through stakeholder workshops around the impact of combinations of drivers on water resources by 2030 and 2050. 4. Preliminary results of modeling showing effects of drivers like reduced transboundary flows and climate change on sal

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

2. 1. What are the key drivers of change in the hydrology
and performance of the system?
2. What are the effects of anticipated changes on
flooding, submergence, sedimentation, salinity
intrusion and water availability in the different
polders of the coastal zone?
3. What are the implications of adaptation strategies
for different anticipated changes?
4. What are the implications of policy changes and its
applications to cope with anticipated changes? What
strategies can be put in place to influence policy
makers and stakeholders to adapt to anticipated
changes?
Research Questions

3. Overall Methodology
Assessment of the impact of anticipated external drivers of
change on water resources of the coastal zone
Data, Maps on fresh water availability, Salinity,
Improved drainage and storage plan, storm surge risk
assessment in present & future condition
Up-scaling to LGED, WARPO, BWDB, DoE,,BADC,DAE Planning
Commission and Climate Change Cell Involving G5
Simulation of Scenarios
Population projection
and water requirement
Land use change
Climate change
projection
Trans-boundary flow
analysis
Defining Study Area Field Survey
and Data Collection
Literature Review
Water Flow and Salinity Modelling
(MIKE&SWAT)
Model Development
Calibration Validation
Simulation of
Baseline Condition
Selection of Scenarios
Involving Gs and
Stakeholders
Selection of Drivers of
Change
Involving Gs and other
Stakeholders

4. OutcomeLogicModel
OUTCOMES
Change in KAS Change in Practice/
behavior
Impact
Project outputs
Existing condition:
• Data on WL, Flow, Salinity
•Digital Elevation Model
• Freshwater & salinity zoning map
• Drainage Conditions and
Inundation maps of polders
Use of data, information &
knowledge
Understanding external drivers,
scenarios and their effects
Use of data &
information
Development of
new database
Future condition:
• Climate change projections
• Population projection
• Landuse change projection
• Freshwater & salinity zoning map
• Drainage Conditions and
Inundation maps of polders
•Cyclone induced storm surge level
and embankment crest level
• Improved Drainage plan of the
three polders
Improved and
resilient water
infrastructure and
operation
Improved Polder
management for
maximizing crop &
fish production and
minimizing
inundation risk
Researchers of G1, G2, G3 & other ongoing projects
Acquiring new information
& knowledge
Understanding the benefits
of using new information
and improved plan for
proper drainage and
irrigation
Improved planning,
design and
implementation
BWDB, WARPO, LGED, DOF,BADC,FAO and NGOs
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
Ministry of Water Resources, Ministry ofAgriculture,
Planning Commission
• External drivers
• Scenarios
Outcome
Logic Model

5. Study Area:
Ganges Dependent Area
in Bangladesh
Coastal Divisions:
Barisal: Patuakhali, Barguna
Khulna:
Khulna & Satkhira districts
Project Target Area:
Coastal Zone of the Ganges basin in
Bangladesh except the Sundarbans
Polders:
3 (Satkhira), 30 (Khulna), 43-2F (Patuakhali)

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

7. Data Collection and Analysis
Primary Data
Salinity in the adjacent rivers and in the khals inside the Polders
 Cross section survey of rivers & khals of the three polders
 Water level measurement in the khals & adjacent rivers
 Water flow measurement (tidal) in the adjacent rivers
 Topography & land use survey inside the polders
 Structural information of drainage and flushing regulators
 Salinity measurements at additional 31 stations in southwest region of Bangladesh
 Operation log and flow of the regulators and water level in khals and floodplain
Secondary Data
 Salinity, water flow, rainfall, evaporation data from BWDB
 Water level data from BIWTA
 Climate data from BMD and IMD grid
 Mouza layers, growth center locations from LGED
 Population census data from BBS
 Agriculture and irrigation data from DAE, IRRI
 River cross-sections, land topography, polder, road and such other data from IWM database

8. Digital Elevation Model from Land Level Survey
Polder 3
Polder 30
Polder 43/2F

9. Rabi (Boro)Kharif-2 (T. Aman)Kharif-1 (Aus)
2 PPT
Salinity and Available flow in Payra River
Salinity variation and Flow availability : Polder 43/2F

10. Rabi (Boro)Kharif-2(T. Aman)Kharif-1(Aus)
2 PPT
Salinity and Available flow in Kazibacha River
Salinity variation and Flow availability : Polder 30

11. 2 PPT
Rabi (Boro)Kharif-2 (T. Aman)Kharif-1(Aus)
Salinity in Ichamoti River
Salinity variation : Polder 03

12. Spatial Variation of Salinity in the Coastal Ganges in Bangladesh
May, 2012 Base Year: 2012
KHULNA
BARISAL
Monthly Salinity variation with upstream freshwater flow

13. External Drivers of Change
Final List of Key External Drivers and Their
Ranking

14. Scenario Generation
Scenario Generation Workshop
Combination
of Drivers
Scenarios
• Scenarios developed in a
participatory approach
• Done collectively by experts,
policy makers, service providers,
practitioners, and stakeholders
• Examined different
combinations of external drivers
as likely scenarios
• 14 scenarios selected initially
• Further consolidated into 5
scenarios

15. Scenario: Effect of Transboundary flow and Climate Change
Ganges Basin
Upstream Boundaries (Q, Sal = 0pt)
Minimum and maximum flow in Gorai in dredged condition
Downstream Boundaries (WL, Sal) + Sea Level Rise
Transboundary flow
Best case scenario: maximum flow since GWT
Worst case scenario: minimum flow since GWT
Climate change: A1B condition
(Precipitation, Temperature and Sea
Level Rise)
Scenario : 2030

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

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

18. Scenario: Effect of Multiple Drivers on Water Resources
Ganges Basin
Downstream Boundaries (WL, Sal) + Sea Level Rise
Transboundary flow (best case
scenario: maximum flow since GWT)
Population growth: water extraction
from the river system
Climate change: A1B condition
(Precipitation, Temperature and Sea
Level Rise)
Scenario : 2030
Land-use change
Upstream Boundaries (Q, Sal = 0pt)
Maximum flow in Gorai in dredged condition

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

20. Driver: Transboundary Flow
Transboundary Flow

21. 1. Hisna ~ Mathavanga ~Kobadak ~ Kholpetua
2. Kobadak ~ Sibsa
3. Bhairab ~ Rupsa ~ Pussur
5. Gorai ~ Nabagonga ~ Atai ~ Rupsa ~ Pussur
6. Gorai ~ Madhumati ~ Baleswar
4. Gorai ~ Rupsa ~ sholmari ~ Sibsa
7. Arial Khan ~ Baleswar
8. Arial Khan ~ Biskhali
9. Arial Khan ~ Buriswar
Driver: Infrastructure development (Ganges Barrage)
Ganges Barrage

22. National Land Zoning Map : Ministry of Land

23. May2012, Base condition with maximum Transboundary flow under Ganges Treaty
Effect of Transboundary Flow :South-west Zone of Bangladesh

24. May2012, Base condition with minimum Transboundary flow under Ganges Treaty
Effect of Transboundary Flow :South-west Zone of Bangladesh

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

26. May, 2030 Climate change (A1B) + Transboundary flow with Ganges Barrage
Effect of Infrastructure Development: Ganges Barrage

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

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

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

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

31. 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

32. Base
(2012)
(Sq Km)
Max
TBF
(Sq Km)
Change
(%)
Min TBF
(Sq Km)
Change
(%)
Climate
Change
(SLR)
(Sq Km)
Change
(%)
Min
TBF+SLR
(Sq Km)
Change
(%)
Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
Exposure of area under more than 2ppt
salinity
Barisal
Division
1574 1571 0.2 1588 0.9% 1708 8.5% 1722 9.40%
Khulna
Division
11420 12179 6.6% 13144 15.1% 12094 5.9% 13818 21.00%
Base (2012)
(Sq Km)
Ganges barrage+
SLR Change (%)
(Sq Km)
Khulna Division 11420 11142 (-3%)
Infrastructure development: Ganges Barrage

33. 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
Drainage Performance of Polders at Present and Future
POLDER 30

34. 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
Drainage Performance of Polders at Present and Future
POLDER 30

35. 3 day Depth-Duration Map
(Scenario_2050)
Flood type Area (sqkm) % of Area
Flood Free 13.54 21
F0 (0 - 30 cm) 16.41 25
F1 (30 - 90 cm) 27.86 43
F2 (90 - 180 cm) 6.70 11
Flood type
2030
(Change from present condition)
2050
(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
Drainage Performance of Polders at Present and Future
%
%
%
%
%
%
%
%
POLDER 30

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

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

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

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

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

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

42. Considerations
for Sub-polderization:
 Land level
 Canal system
 Tidal characteristics
of the peripheral
rivers
 Road network
Polder-30: Subpoldering and Community based Water Management
Sub-polder
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 sub-
polders
 High depth of water in aman field reduce production;
thus proper drainage will enhance crop yield
Sub-polder 7 Nos
Community base water management
Unit/ Block 15 Nos

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

44. 0
20
40
60
80
100
0
5
10
15
20
25
30
35
40
45
0 1 2 3 4
Area(Percent)
Area(SqKm)
Elevation (mPWD)
Area Elevation curve (Polder 43/2F)
Level (mPWD) Area below (%)
1.0 9
1.2 23
1.4 52
1.8 92
2.0 98
Kharif-1 Kharif-2 Rabi
Avg WL 1.00m PWD Avg WL 1.20m PWD Avg WL 0.80m PWD
Tidal window 4 hr above 1.40 mPWD: More than 50%
area can be irrigated
Polder-43/2F: Opportunity for Gravity Irrigation

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

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

47.  Land use has changed 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 high-
income aquaculture without
jeopardizing ‘aman’ rice
 Opportunity for crop
diversification
Polder-3: Water Management (Drainage and Flushing)

48. Assessment of risk of polders for cyclonic storm surge
19 Severe Cyclone Track ( 1960-2009)

49. Embankment
damage during
Cyclone SIDR
Assessment of risk of polders for cyclonic storm surge

50. Assessment of risk of polders for cyclonic storm surge

51. Assessment of risk of polders for cyclonic storm surge

52. Polder No: 43/2f
Assessment of risk of polders for cyclonic storm surge

53. 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.
 In polder-30, 3.54 million cubic meters of water can be stored in the drainage canals,
if re-excavated, and an additional 2400 acres area can be brought under irrigation in
the last two months of ‘boro’ season. Storage of freshwater in improved internal
drainage canals can meet irrigation demand of boro rice for 20% area of cultivable
land in Polder-30
 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 and existing formal regulators. These structures can be
used for both drainage and flushing
 Adequate Transboundary flow is required for ensuring flow availability at present
and future

54. Closure Plan
Way Forward to the Project Closure:
Land-use change projections in the study area
Outscaling of the research results:
Workshop presentation in coordination with G5
Institution based workshop: with BWDB, LGED,
DAE ,BADCand DoF
Policy brief on drainage management and water
availability in present and future scenario

55. 55
Thanks for kind
attention