Zahir-‐ul Haque Khan Sarafat Hossain Khan Dr. M. Shah Alam Khan Farhana Akter Kamal Nasim Al Azad Khan
Future ProjecAon of surface water resources of the Ganges coastal zone of
Bangladesh
Present Condition: Spatial variation of Salinity and Freshwater Availability
External Drivers of Change
Final List of Key External Drivers and Their Ranking
Scenario Genera6on
Scenario Genera6on Workshop
Combina6on of Drivers
Scenarios
• Scenarios developed in a par6cipatory approach
• Done collec6vely by experts, policy makers, service providers, prac66oners, and stakeholders
• Examined different combina6ons of external drivers as likely scenarios
• 14 scenarios selected ini6ally • Further consolidated into 5
scenarios
Scenario: Effect of Transboundary flow and Climate Change
Ganges Basin
Upstream Boundaries (Q, Sal = 0pt) Minimum and maximum flow in Gorai in dredged condi6on
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 condi6on (PrecipitaAon, Temperature and Sea
Level Rise)
Scenario : 2030
Scenario: Transboundary Flow, Land-‐Use Change and Climate Change
Ganges Basin
Land-‐use change
Climate change: A1B and A2 condi6ons (PrecipitaAon, 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 condi6on
Downstream Boundaries (WL, Sal) + Sea Level Rise
Scenario: Effect of Mul6ple Drivers on Water Resources
Ganges Basin
Transboundary flow (worst case scenario: minimum flow since GWT)
Popula6on growth: water extrac6on from the river system
Climate change: A1B condi6on (PrecipitaAon, 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 condi6on
Scenario: Effect of Mul6ple Drivers on Water Resources
Ganges Basin
Downstream Boundaries (WL, Sal) + Sea Level Rise
Transboundary flow (best case scenario: maximum flow since GWT)
Popula6on growth: water extrac6on from the river system
Climate change: A1B condi6on (PrecipitaAon, Temperature and Sea
Level Rise)
Scenario : 2030
Land-‐use change
Upstream Boundaries (Q, Sal = 0pt) Maximum flow in Gorai in dredged condi6on
Scenario: Infrastructure Development
Ganges Basin
Land-‐use change
Transboundary flow (best case scenario: maximum flow since GWT
Popula6on growth: water extrac6on from the river system
Climate change: A1B condi6on (PrecipitaAon, Temperature & Sea Level Rise)
Scenario : 2030
Change in water management prac6ces
Change in water governance and ins6tu6ons (including policy change)
Water infrastructure development
Downstream Boundaries (WL, Sal) + Sea Level Rise
Upstream Boundaries (Q, Sal = 0pt) Minimum flow in Gorai in dredged condi6on
Methodology
Salinity Modelling
Water Flow boundary
Q Q
Q
WL WL WL WL
WL
1 Dimensional Model South-‐West Regional Model Known Water flow and water level at boundaries
2 Dimensional Model (Bay of Bengal Model) Water flow boundary from SWRM Water level from Global Tide Model
Q Q Q
WL
River Network Model and Bay of Bengal Model
Salinity boundary
Measured Q Sal 0 ppt
1 Dimensional Model South-‐West Regional Model salinity is zero at upstream Downstream salinity is taken from calibrated BoB model
2 Dimensional Model (Bay of Bengal Model) Measured salinity at upstream boundaries Sea Salinity = 30 to 35 ppt
Sal
Salinity = 32 ppt
Sal Sal
Sal
Measured Q Sal 0 ppt
Measured Q Sal 0 ppt
WL, Salinity in 12 downstream boundaries
Salinity Model
Salinity Model
Driver: Transboundary Flow Transboundary Flow
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
182 m3/s
May2012, Base condi6on with maximum Transboundary flow under Ganges Treaty
Effect of Transboundary Flow :South-‐west Zone of Bangladesh
May2012, Base condi6on with minimum Transboundary flow under Ganges Treaty
Effect of Transboundary Flow :South-‐west Zone of Bangladesh
May, 2030 climate change (A1B) with minimum Transboundary flow under Ganges Treaty
Effect of Climate Change and Transboundary Flow: South-‐west Zone
May, 2030 Climate change (A1B) + Transboundary flow with Ganges Barrage
Effect of Infrastructure Development: 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 area (0-‐2ppt): q Transboundary flow: 1100 sq. km q Climate Change: 800 sq. km
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
Effect of infrastructure development: Ganges Barrage
Ganges Barrage
182 m3/s
Increase of Freshwater and mild brackish-‐water area (0-‐2ppt): q Khulna division: addiAonal 2600 sq. km area become less than 2ppt q Barisal division: addiAonal 60 sq. km area become less than 2ppt
Effect of infrastructure development: Ganges Barrage
Effect of Sea Level on 2ppt Salinity contour (A1B,2050) A1B scenario, March 2050
2ppt salinity line
Base 2050
Addi6onal Area to be affected by salinity: More than 1 ppt: 7000 km2
More than 2ppt: 8400 km2
CONCLUSIONS
• The present fresh water pocket in the south central zone (Barisal) is likely to be more saline (2-‐4ppt) with 52cm sea level rise, in 2050
• Regional CooperaAon is crucial for trans-‐boundary flow sharing for salinity
Control in the changing climate • AdaptaAon measures like Ganges Barrage and Brahmaputra Barrage are
important for water security under climate change • New salt tolerant cropping technology needs to be introduced
• There is abundant fresh water for irrigaAon in much of Barisal Division throughout the dry season. The water will remain suitable for irrigaAon all over the year in the changing climate in 2030 with 22cm SLR.
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Thanks for kind attention