G4: Assessment of the Impact of Anticipated External
Drivers of Change on Water Resources of the Coastal Zone
Ganges Basin...
1. What are the key drivers of change in the hydrology
and performance of the system?
2. What are the effects of anticipat...
Overall Methodology
Assessment of the impact of anticipated external drivers of
change on water resources of the coastal z...
OutcomeLogicModel
OUTCOMES
Change in KAS Change in Practice/
behavior
Impact
Project outputs
Existing condition:
• Data on...
Study Area:
Ganges Dependent Area
in Bangladesh
Coastal Divisions:
Barisal: Patuakhali, Barguna
Khulna:
Khulna & Satkhira ...
Polder-3
High Salinity
Polder-30
Medium Salinity
Polder-43/2F
Low Salinity
Coastal Zone of the Ganges Basin in Bangladesh
...
Data Collection and Analysis
Primary Data
Salinity in the adjacent rivers and in the khals inside the Polders
 Cross sec...
Digital Elevation Model from Land Level Survey
Polder 3
Polder 30
Polder 43/2F
Rabi (Boro)Kharif-2 (T. Aman)Kharif-1 (Aus)
2 PPT
Salinity and Available flow in Payra River
Salinity variation and Flow a...
Rabi (Boro)Kharif-2(T. Aman)Kharif-1(Aus)
2 PPT
Salinity and Available flow in Kazibacha River
Salinity variation and Flow...
2 PPT
Rabi (Boro)Kharif-2 (T. Aman)Kharif-1(Aus)
Salinity in Ichamoti River
Salinity variation : Polder 03
Spatial Variation of Salinity in the Coastal Ganges in Bangladesh
May, 2012 Base Year: 2012
KHULNA
BARISAL
Monthly Salinit...
External Drivers of Change
Final List of Key External Drivers and Their
Ranking
Scenario Generation
Scenario Generation Workshop
Combination
of Drivers
Scenarios
• Scenarios developed in a
participatory...
Scenario: Effect of Transboundary flow and Climate Change
Ganges Basin
Upstream Boundaries (Q, Sal = 0pt)
Minimum and maxi...
Scenario: Transboundary Flow, Land-Use Change and Climate Change
Ganges Basin
Land-use change
Climate change: A1B and A2 c...
Scenario: Effect of Multiple Drivers on Water Resources
Ganges Basin
Transboundary flow (worst case
scenario: minimum flow...
Scenario: Effect of Multiple Drivers on Water Resources
Ganges Basin
Downstream Boundaries (WL, Sal) + Sea Level Rise
Tran...
Scenario: Infrastructure Development
Ganges Basin
Land-use change
Transboundary flow (best case
scenario: maximum flow sin...
Driver: Transboundary Flow
Transboundary Flow
1. Hisna ~ Mathavanga ~Kobadak ~ Kholpetua
2. Kobadak ~ Sibsa
3. Bhairab ~ Rupsa ~ Pussur
5. Gorai ~ Nabagonga ~ Atai ~ Ru...
National Land Zoning Map : Ministry of Land
May2012, Base condition with maximum Transboundary flow under Ganges Treaty
Effect of Transboundary Flow :South-west Zone ...
May2012, Base condition with minimum Transboundary flow under Ganges Treaty
Effect of Transboundary Flow :South-west Zone ...
May, 2030 climate change (A1B) with minimum Transboundary flow under Ganges Treaty
Effect of Climate Change and Transbound...
May, 2030 Climate change (A1B) + Transboundary flow with Ganges Barrage
Effect of Infrastructure Development: Ganges Barra...
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 ar...
Base
(2012)
(Sq Km)
Max
TBF
(Sq Km)
Change
(%)
Min TBF
(Sq Km)
Change
(%)
Climate
Change
(SLR)
(Sq Km)
Change
(%)
Min
TBF+...
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) 13.4...
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 (...
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 (...
• Dredging and Re-excavation
of rivers and khals
• Additional drainage structure
Drainage Improvement Measures
Polder-30: Case Study- Maitbhanga Village
Discussion with local people of Maitvanga about drainage The high depth of water...
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...
Considerations
for Sub-polderization:
 Land level
 Canal system
Polder-30: Subpoldering and Community based Water Manage...
Considerations
for Sub-polderization:
 Land level
 Canal system
 Tidal characteristics
of the peripheral
rivers
Polder-...
Considerations
for Sub-polderization:
 Land level
 Canal system
 Tidal characteristics
of the peripheral
rivers
 Road ...
Considerations
for Sub-polderization:
 Land level
 Canal system
 Tidal characteristics
of the peripheral
rivers
 Road ...
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 ...
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 (Po...
Polder-3: Water Management (Drainage and Flushing)
Polder-3: Water Management (Drainage and Flushing)
 Land use has changed over the years
 Shrimp culture has been introduced
 Huge number (133 pipes and 27 private regulat...
Assessment of risk of polders for cyclonic storm surge
19 Severe Cyclone Track ( 1960-2009)
Embankment
damage during
Cyclone SIDR
Assessment of risk of polders for cyclonic storm surge
Assessment of risk of polders for cyclonic storm surge
Assessment of risk of polders for cyclonic storm surge
Polder No: 43/2f
Assessment of risk of polders for cyclonic storm surge
Key Messages
 There is abundant fresh water for irrigation in much of Barisal Division throughout the
dry season. The wat...
Closure Plan
Way Forward to the Project Closure:
Land-use change projections in the study area
Outscaling of the researc...
55
Thanks for kind
attention
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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 Zahirul Haque Khan. At Ganges Regional Research Workshop of the Challenge Program on Water and Food/Water Land and Ecosystems (CPWF/WLE), May 2014

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G4- Assessment of the Impact of Anticipated External Drivers of Change on Water Resources of the Coastal Zone

  1. 1. G4: Assessment of the Impact of Anticipated External Drivers of Change on Water Resources of the Coastal Zone Ganges Basin Development Challenge
  2. 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. 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. 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. 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. 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. 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. 8. Digital Elevation Model from Land Level Survey Polder 3 Polder 30 Polder 43/2F
  9. 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. 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. 11. 2 PPT Rabi (Boro)Kharif-2 (T. Aman)Kharif-1(Aus) Salinity in Ichamoti River Salinity variation : Polder 03
  12. 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. 13. External Drivers of Change Final List of Key External Drivers and Their Ranking
  14. 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. 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. 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. 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. 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. 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. 20. Driver: Transboundary Flow Transboundary Flow
  21. 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. 22. National Land Zoning Map : Ministry of Land
  23. 23. May2012, Base condition with maximum Transboundary flow under Ganges Treaty Effect of Transboundary Flow :South-west Zone of Bangladesh
  24. 24. May2012, Base condition with minimum Transboundary flow under Ganges Treaty Effect of Transboundary Flow :South-west Zone of Bangladesh
  25. 25. May, 2030 climate change (A1B) with minimum Transboundary flow under Ganges Treaty Effect of Climate Change and Transboundary Flow: South-west Zone
  26. 26. May, 2030 Climate change (A1B) + Transboundary flow with Ganges Barrage Effect of Infrastructure Development: Ganges Barrage
  27. 27. Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
  28. 28. Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
  29. 29. Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
  30. 30. Effect of Drivers: Trans-boundary flow, Climate Change and Ganges Barrage
  31. 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. 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. 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. 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. 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. 36. • Dredging and Re-excavation of rivers and khals • Additional drainage structure Drainage Improvement Measures
  37. 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. 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. 39. Considerations for Sub-polderization:  Land level  Canal system Polder-30: Subpoldering and Community based Water Management
  40. 40. Considerations for Sub-polderization:  Land level  Canal system  Tidal characteristics of the peripheral rivers Polder-30: Subpoldering and Community based Water Management
  41. 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. 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. 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. 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. 45. Polder-3: Water Management (Drainage and Flushing)
  46. 46. Polder-3: Water Management (Drainage and Flushing)
  47. 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. 48. Assessment of risk of polders for cyclonic storm surge 19 Severe Cyclone Track ( 1960-2009)
  49. 49. Embankment damage during Cyclone SIDR Assessment of risk of polders for cyclonic storm surge
  50. 50. Assessment of risk of polders for cyclonic storm surge
  51. 51. Assessment of risk of polders for cyclonic storm surge
  52. 52. Polder No: 43/2f Assessment of risk of polders for cyclonic storm surge
  53. 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. 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. 55 Thanks for kind attention

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