Ganges Basin Development Challenge
G4: Assessment of the Impact of Anticipated External
Drivers of Change on Water Resourc...
Outcome
Logic Model
Project outputs
Existing condition:
• Data on WL, Flow, Salinity
•Digital Elevation Model
• Freshwater...
Study Area
Polder-30
Medium Salinity

Polder-43/2F
Low Salinity

Polder-3
High Salinity

Coastal Zone of the Ganges Basin ...
Date

Mar-2014

Jan-2014

Nov-2013

Sep-2013

Jul-2013

Kharif-1

May-2013

Mar-2013

Jan-2013

Nov-2012

Sep-2012

Jul-20...
Temporal variation of Salinity
Salinity at Kazibacha River

Kharif-1
2 PPT

19 Jun 2012

POLDER-30

8 Feb 2012

Rabi

Khar...
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-20...
Spatial and Seasonal Variation of Salinity in the Coastal Ganges in Bangladesh
May, 2012

Base Year: 2012

BARISAL

KHULNA...
Output: External Drivers of Change
External Drivers and Future Scenarios
Scenario Generation Workshop

Final List of Key External Drivers and
Their Ranking

...
Scenario: Effect of Transboundary flow and Climate Change
Upstream Boundaries (Q, Sal = 0pt)
Minimum and maximum flow in G...
Scenario: Transboundary Flow, Land-Use Change and Climate Change
Upstream Boundaries (Q, Sal = 0pt)
Minimum and maximum fl...
Scenarios: Effect of Multiple Drivers on Water Resources
Upstream Boundaries (Q, Sal = 0pt)
Minimum flow in Gorai in dredg...
Scenario: Population Growth
Upstream Boundaries (Q, Sal = 0pt)
Maximum flow in Gorai in dredged condition

Trans-boundary ...
Scenario: Infrastructure Development
Upstream Boundaries (Q, Sal = 0pt)
Minimum flow in Gorai in dredged condition

Popula...
Transboundary Flow
Transboundary Flow
GWT

Farakka Barage

Effect of Transboundary Flow on Salinity
Salinity in the south-west
zone is very much
dependent on up...
Effect of Transboundary Flow :South-west Zone of Bangladesh
May, Base condition with maximum Transboundary flow under Gang...
Effect of Transboundary Flow :South-west Zone of Bangladesh
May, Base condition with minimum Transboundary flow under Gang...
Effect of Climate Change and Transboundary Flow: South-west Zone
May, 2030 climate change (A1B) with minimum Transboundary...
Effect of Infrastructure Development: Ganges Barrage
May, 2030 Climate change (A1B) with Ganges Barrage
Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage

Decrease of Freshwater and mild brackishwater a...
Drainage Condition

Khals within polders vary greatly in size, can store fresh water during the dry season, but
often heav...
Drainage Performance of Polders at Present and Future

3 day Depth-Duration Map
Flood type

Area (sqkm) % of Area

Flood F...
Drainage Performance of Polders at Present and Future

3 day Depth-Duration Map
(Scenario_2030)
Flood type

Area (sqkm) % ...
Drainage Performance of Polders at Present and Future

3 day Depth-Duration Map
(Scenario_2050)
Flood type

Area (sqkm) % ...
Drainage Improvement Measures
• Dredging and Re-excavation
of rivers and khals
• Additional drainage structure
Drainage Improvement Measures

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

25 Year Flood Event : A1B Scenario; 2030
With improvement measures
Polder-30: Case Study- Maitbhanga Village

Discussion with local people of Maitvanga about drainage

Drainage canal has be...
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
...
Polder-30: Subpoldering and Community based Water Management
Considerations
for Sub-polderization:
 Land level
 Canal sy...
Polder-30: Subpoldering and Community based Water Management
Considerations
for Sub-polderization:
 Land level
 Canal sy...
Polder-30: Subpoldering and Community based Water Management
Considerations
for Sub-polderization:
 Land level
 Canal sy...
Polder-30: Subpoldering and Community based Water Management

Sub-polder

Considerations
for Sub-polderization:
 Land lev...
Polder-30: Subpoldering and Community based Water Management

Sub-polder
Community based
water management
Unit/ Block

Con...
Sub-polderization : Community Participation in Water Management
and Governance
Water Management Organization (WMO)
Communi...
Solutions for Drainage Congestion in Polder-30
Message:
 New paradigm shift in water management: Sub-polderization and co...
Polder-30: Opportunity for Gravity Drainage
Kazibacha river
Area (Percent)

Maximum water level 2.4 m

0
4

Average water ...
Area Elevation curve (Polder
Polder-43/2F: Opportunity for Gravity Drainage 43/2F)
45
100

40
35

80

Area (Sq Km)

30
25
...
Polder-3: Water Management (Drainage and Flushing)
Polder-3: Water Management (Drainage and Flushing)
Polder-3: Water Management (Drainage and Flushing)
 Land use has beenchanged over the years
 Shrimp culture has been int...
Trans-Boundary and Food issues
By IWMI
Key Messages
 There is abundant fresh water for irrigation in much of Barisal Division throughout the
dry season. The wat...
Key Messages
 G4 used hydrological, hydrodynamic, salinity and storm-surge models to
assess the impacts of the external d...
Closure Plan
Way Forward to the Project Closure:
Effectiveness of sub-polders
Land-use change projections in the study a...
Closure Plan
Description of Activities
Storm surge modelling for selected 3 polders
Land-use projection
Assessment of the ...
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G4- Assessment of the impact of anticipated external drivers of change on water resources of the coastal zone

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

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G4- Assessment of the impact of anticipated external drivers of change on water resources of the coastal zone

  1. 1. Ganges Basin Development Challenge G4: Assessment of the Impact of Anticipated External Drivers of Change on Water Resources of the Coastal Zone
  2. 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. 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. 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. 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. 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. 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. 8. Output: External Drivers of Change
  9. 9. External Drivers and Future Scenarios Scenario Generation Workshop Final List of Key External Drivers and Their Ranking Combination Scenarios
  10. 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. 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. 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. 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. 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. 15. Transboundary Flow Transboundary Flow
  16. 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. 17. Effect of Transboundary Flow :South-west Zone of Bangladesh May, Base condition with maximum Transboundary flow under Ganges Treaty
  18. 18. Effect of Transboundary Flow :South-west Zone of Bangladesh May, Base condition with minimum Transboundary flow under Ganges Treaty
  19. 19. Effect of Climate Change and Transboundary Flow: South-west Zone May, 2030 climate change (A1B) with minimum Transboundary flow under Ganges Treaty
  20. 20. Effect of Infrastructure Development: Ganges Barrage May, 2030 Climate change (A1B) with Ganges Barrage
  21. 21. Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
  22. 22. Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
  23. 23. Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
  24. 24. Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
  25. 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. 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. 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. 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. 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. 30. Drainage Improvement Measures • Dredging and Re-excavation of rivers and khals • Additional drainage structure
  31. 31. Drainage Improvement Measures 25 Year Flood Event : A1B Scenario; 2030 Inundated Area = 68%
  32. 32. Drainage Improvement Measures 25 Year Flood Event : A1B Scenario; 2030 With improvement measures
  33. 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. 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. 35. Polder-30: Subpoldering and Community based Water Management Considerations for Sub-polderization:  Land level  Canal system
  36. 36. Polder-30: Subpoldering and Community based Water Management Considerations for Sub-polderization:  Land level  Canal system  Tidal characteristics of the peripheral rivers
  37. 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. 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. 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. 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. 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. 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. 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. 44. Polder-3: Water Management (Drainage and Flushing)
  45. 45. Polder-3: Water Management (Drainage and Flushing)
  46. 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. 47. Trans-Boundary and Food issues By IWMI
  48. 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. 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. 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. 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. 52. THANK YOU
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