G4: Assessment of the Impact of Anticipated External Drivers of Change on Water Resources of

the Coastal Zone

Ganges Basin Development Challenge

Ou

tco

me

Lo

gic

Mo

de

lOUTCOMES

Change in KAS Change in Practice/ behavior

ImpactPlanning

Commission, ministries of water resources,

environment & forests, agriculture

and fisheries in Bangladesh –

Scaling up

Understanding of the 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.

Project outputs

Existing condition:

• Data on WL, Flow, Salinity

•Digital Elevation Model

• Freshwater & salinity zoning map

• Drainage Conditions and Inundation maps of polders

Acquiring data, information & knowledge

Understanding external drivers, scenarios and their effects

Use of data & information

Extrapolation Domain, new database,

Planning of cropping system

Future condition:

• Climate change projections

• Population projection

• Landuse change projection

• Freshwater & salinity zoning map

• Drainage Conditions and Inundation maps of polders

• Improved Drainage plan of the three polders

Improved and resilient water infrastructure and operation

Improved Polder

management for

maximizing crop & fish production

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

Use in Improving planning, design and

implementation

LGI, BWDB, WARPO, LGED, DOF 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, Planning Commission

Farmers and fishers of polder 3, 30 and 43/2F

Awareness buildingKnowledge enhancement

Encouraged to participate in discussions to contribute in planning

• External drivers

• Scenarios

Outcome Logic Model

Polder-3High Salinity

Polder-30Medium Salinity

Polder-43/2FLow Salinity

Coastal Zone of the Ganges Basin in Bangladesh

Study Area

5-A

ug

14-S

ep

24-O

ct

3-D

ec

12-J

an

21-F

eb

1-A

pr

11-M

ay

0.0

4.0

8.0

12.0

16.0

20.0

24.0Polder 43-2f (Station-2 (In Side),Para River)

Date

Salin

ity

(ppt

)

POLDER-43/2f

Mar

-201

1

May

-201

1

Jul-2

011

Sep-

2011

Nov

-201

1

Jan-

2012

Mar

-201

2

May

-201

2

Jul-2

012

Sep-

2012

Nov

-201

2

Jan-

2013

Mar

-201

3

May

-201

3

Jul-2

013

Sep-

2013

Nov

-201

3

Jan-

2014

Mar

-201

40.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0Polder 43-2f (Paira River)

Date

Salin

ity

(ppt

)

Rabi Kharif-1 Kharif-2

2 PPT

Data:Temporal variation of Salinity

POLDER-30

Salinity at Kazibacha River

Temporal variation of Salinity

Rabi Kharif-1 Kharif-2

2 PPT

8 Fe

b 20

12

19 Ju

n 20

12

POLDER-3

Data:Temporal variation of Salinity

Apr-

2011

Jun-

2011

Aug-

2011

Oct

-201

1

Dec

-201

1

Feb-

2012

Apr-

2012

Jun-

2012

Aug-

2012

Oct

-201

2

Dec

-201

2

Feb-

2013

Apr-

2013

Jun-

2013

Aug-

2013

0.0

4.0

8.0

12.0

16.0

20.0

24.0Polder 3 (Ichamoti River)

Date

Salin

ity

(ppt

)

Rabi Kharif-1 Kharif-2

2 PPT

17 D

ec 2

011

14 S

ep 2

012

Spatial and Seasonal Variation of Salinity in the Coastal Ganges in Bangladesh

May, 2012 Base Year: 2012

KHULNA

BARISAL

Fresh and Brackish water zone

Output: External Drivers of Change

Final List of Key External Drivers and Their Ranking

External Drivers and Future Scenarios

Scenario Generation Workshop

Combination

Scenarios

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

Trans-boundary flow Best case scenario: maximum flow since GWTworst case scenario: minimum flow since GWT

Climate change: A1B condition (Precipitation, Temperature and Sea

level rise)

Scenario : 2050

Scenario: Transboundary Flow, Land-Use Change and Climate Change

Ganges Basin

Land-use change

Climate change: A1B and A2 condition (Precipitation, Temperature and Sea

level rise)

Scenario : 2030 and 2050

Trans-boundary 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

Scenarios: Effect of Multiple Drivers on Water Resources

Ganges Basin

Trans-boundary 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

Scenario: Population Growth

Ganges Basin

Downstream Boundaries (WL, Sal) + Sea Level Rise

Trans-boundary 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

Scenario: Infrastructure Development

Ganges Basin

Land-use change

Trans-boundary 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

Transboundary FlowTransboundary Flow

Effect of Transboundary Flow on Salinity

Salinity variation with upstream freshwater flow during dry season (Salinity Data Source: IWM)

Salinity in the south-west zone is very much

dependent on upstream freshwater flow

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: BWDB)

Fara

kka

Bara

ge

GW

T

May, Base condition with maximum Transboundary flow under Ganges Treaty

Effect of Transboundary Flow :South-west Zone of Bangladesh

May, Base condition 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) 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):Transboundary flow: 1100 sq. kmClimate Change: 800 sq. km

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

Drainage Condition

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

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

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 type2030

(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

%%

%

%

%

%

%

%

• Dredging and Re-excavation of rivers and khals

• Additional drainage structure

Drainage Improvement Measures

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

Drainage Improvement Measures

25 Year Flood Event : A1B Scenario; 2030With improvement measures

Drainage Improvement Measures

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

Polder-30: Subpoldering and Community based Water Management

0 1000 2000 3000 4000 50000

0.5

1

1.5

2

Distance (m)

Land

Lev

el (m

PWD

)

0 1000 2000 3000 4000 5000-0.5

0

0.5

1

1.5

2

Distance (m)

Land

Lev

el (m

PWD

)

0 1000 2000 3000 4000 5000-0.5

00.5

11.5

2

Distance (m)

Land

Lev

el (m

PWD

)

Considerations for Sub-polderization: Land level

Considerations for Sub-polderization: Land level Canal system

Polder-30: Subpoldering and Community based Water Management

Considerations for Sub-polderization: Land level Canal system Tidal characteristics

of the peripheral rivers

Polder-30: Subpoldering and Community based Water Management

Considerations for Sub-polderization: Land level Canal system Tidal characteristics

of the peripheral rivers

Road network

Polder-30: Subpoldering and Community based Water Management

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

Considerations for Sub-polderization: Land level Canal system Tidal characteristics

of the peripheral rivers

Road network

Polder-30: Subpoldering and Community based Water Management

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-polderCommunity based water management Unit/ Block

Community Based Water management Unit/Block Water management Group (WMG)

Sub-polder Water management Association (WMA)

Polder Water management Federation (WMF)

Water Management Organization (WMO)

Sub-polderization : Community Participation in Water Management and Governance

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)

Level (mPWD) Area below %

0.60 151.00 611.20 801.60 951.80 982.00 99

Digital Elevation Model

Average water level 1.0 m

Lower-Shalta river0 10 20 30 40 50 60

0 20 40 60 80 100

0

0.5

1

1.5

2

2.5

3

3.5

4

Area (sqkm)La

nd le

vel (

mPW

D)

Area (Percent)

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

0 0.5 1 1.5 2 2.5 3 3.5 40

5

10

15

20

25

30

35

40

45

0

20

40

60

80

100

Area Elevation curve (Polder 43/2F)

Elevation (mPWD)

Area

(Sq

Km)

Area

(Per

cent

)

Level (mPWD) Area below (%) 1.0 91.2 231.4 521.8 922.0 98

Kharif-1 Kharif-2 RabiAvg WL 1.00m PWD Avg WL 1.20m PWD Avg WL 0.80m PWD

Tidal window above 1.40 mPWD

Polder-43/2F: Opportunity for Gravity Drainage

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 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

Opportunity for crop diversification

Polder-3: Water Management (Drainage and Flushing)

Trans-Boundary and Food issuesBy IWMI

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.

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

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

2013Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

0 0 0

0 0 0

Policy Brief

0 0 0 0 0

0

0 0

0 0

0 0

Water Availability Transboundary flow

Final Closure Report

Description of Activities2014

Drainage Management

Outscaling

Land-use projectionAssessment of the effect of Land-use and Population growthWater management of Sub-polder in Polder-30

Infrastructure Development

Storm surge modelling for selected 3 polders

Closure Plan

THANK YOU