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

Water Resources of Coastal Zone

Ganges Basin Development Challenge

Ganges Basin Development Challenge

Objective: Improve resource productivity and increase the resilience of agriculture and aquaculture systems of brackish coastal areas of the Ganges

What the Ganges BDC Hopes to Achieve?

Goal:Reducing poverty, increasing resilience, through improved water governance and management & intensified and diversified agricultural and aquacultural systems in brackish water of the coastal Ganges.

Objective:Improve resource productivity and increase the resilience of agriculture and aquaculture systems of brackish coastal areas of the Ganges.

Mayanmar

Geographical Setting of Bangladesh

Ganges Basin:

Ganges Basin Area = 1,087,300 sq. km

Study Area:

Ganges Dependent Area in Bangladesh

Coastal Divisions: Barisal: Patuakhali, Barguna, Jhalakati & Pirojpur districtsKhulna: Khulna & Satkhira districts

Project Target Area:Coastal Zone of the Ganges basin in Bangladesh except the Sundarbans

Problems and Challenges in the Coastal Region of Bangladesh

Water logging

Increase in precipitation in monsoon

Decrease in precipitation in dry season

Salinity intrusion

Cyclone

Sea level rise

Increased frequency of tropical cyclone

Added siltation on the drainage route

Salinity intrusion

Flood

Salinity Intrusion

Coastal Polders in Bangladesh

In the early sixties and seventies, 125 polders (of which 49 are sea-facing) were constructed to protect low lying coastal areas from tidal flood & salinity intrusion.

DRIVERS PRESSURE/CONSEQUENCES

Demographic/SocietalPopulation growthDietary patterns of the populationLand use change including increase area under rice cultivationUrbanization

Pressure on SpaceWater demand & useLoss of biodiversity and wetlands

Economic/TradeEconomic develpopment in coastal zone (change in per capiata income)Market value of agricultural products Water pricing and increaseIndustrialization

Shift in land useWater DemandRoads, railway & portsWater pollution

Political/Institutional/LegalWater policy (national and regional)Change in water governance and institutionsWater sharing mechanisms between the riparian parts of the basinChanges in water management practicesChange in trans-boundary flow

Improved Irrigation and drainage systemFlood protection systemWater availability in the dry season

Environmental/Climate ChangeSea level rise due to Climate ChangeChanges in precipitation and temperature due to Climate Change Subsidence

Fresh water shortage, Salinity intrusionFlood Hazard,Coastal/fluvial erosionChange in Sediment balanceCyclone & Storm surge with higher frequency and intensity

Technological/Important InnovationsChanges in aquaculture and agriculture intensificationWater Use change; Water infrastructure development

Enhanced knowledge and use of HYVEnabling environment for agricultural development

Drivers of Change: Participatory Approach

QuestionnaireName Age Gender Male FemaleOccupation

Please indicate how do you think the external drivers will affect water resources of your area/coastal region of Ganges basin ?

Sl External Drivers

Score (1-5)

Remarks1. No

2. To a very

limited

extent

3. To a moderate

extent

4. To a significant

extent

5. To a very significant

extent

1 Do you think the pressure of population growth on water resources will continue in the future?

2 Is market value an important factor in crop divesification?

3 Will sea level rise reduce freshwater availability and land availability for agriculture?

4 Will decrease of rainfall in the dry season and increase in the monsoon renderadverse impact on water resources?

5 Does political change or institutional issues cause any change in water management?

Popu

latio

n G

rowt

h

Chan

ges

in W

ater

Mgt

Sea

leve

l rise

Land

use

cha

nge

Wat

er S

harin

g

Tran

sbou

ndar

y flo

w

Aqua

cultu

re in

tens

ifica

tion

Econ

omic

Deve

lpop

men

t

Urba

niza

tion

Wat

er in

frast

ruct

ure

deve

lop.

..

Chan

ges

in p

recip

itatio

n

Wat

er P

olicy

Indu

stria

lizat

ion

Wat

er G

over

nanc

e &

Inst

itut..

.

Wat

er U

se c

hang

e

Mar

ket V

alue

of A

gro

Prod

ucts

Chan

ges

in te

mpe

ratu

re

Diet

ary

patte

rns

Wat

er P

ricin

g &

Insu

ranc

e

6.5%6.1%5.9%

5.7%5.7%5.5%5.4%5.4%5.4%5.4%

5.2%4.8%

4.6%4.6%4.4%4.3%4.2%

3.2%2.8%

Perc

enta

gePreliminary Results of Questionnaire Survey

Methodology:

(100 or 200 km grid)

(20 to 50 km grid)

High resolution regional climate change surface

Generation of climate change scenario

Ganges, Brammaputra and Meghna Basin Model

Meghna Basin82,000 sq.km

Brahmaputra Basin552,000 sq.km

Ganges Basin1,087,000 sq.km

B A Y O F B E N G A L

N E P A L

BHUTAN

I N D I A

C H I N A

MYA

NMAR

BANGLADESH

I N D I A

Bangladesh rivers receive runoff from a catchment of 1.72 million sq. km, around 12 times its land area

Water flow and salinity model for south-west region of Bangladesh

Methodology:Gorai

Padma

Meg

hna

Upstream Boundaries (Q, Sal = 0ppt)

Downstream Boundaries (WL, Sal)

Evaporation & Other loss

Rainfall

We need:

-Cross-section of the rivers

- Structure information

- Rainfall and evaporation data

- Time-series WL, water flow and salinity data (from primary/secondary sources and calibrated Bay of Bengal model)

- Measured WL, water flow and salinity data for calibration and validation

Land-use management practices and water inflow:

Methodology:

SWAT Model: A process-based continuous hydrological model that predicts the impact of land management practices on water, sediment and agricultural chemical yields.

Water balance equation:SWt = SWo +

SWt = final soil water content (mm)

SWo = initial soil water content (mm);

t = time (days)

Rday = amount of precipitation on day i (mm)

Qsurf = amount of surface runoff on day i (mm)

Ea = amount of evapotranspiration on day i (mm);

Wseep = amount of percolation on day i (mm)

Qgw = amount of return flow on day i (mm)

Where,

Hydrologic Trend Analysis in the Study Area:

1930 1940 1950 1960 1970 1980 1990 2000 20100

10000

20000

30000

40000

50000

60000

70000

80000

90000Hardinge Bridge on the Ganges

Max Q Linear (Max Q) Min Q Linear (Min Q)Average Q Linear (Average Q)

Disc

harg

e (m

3/s)

• Increasing trend of annual maximum flow

• Decreasing trend of annual minimum flow

Trend Analysis of Upstream River Discharge

Hydrologic Trend Analysis in the Study Area:

Trend Analysis of Downstream Water Level

1980 1985 1990 1995 2000 2005 2010-2

-1

0

1

2

3

4 Hiron Pointon the Pussur River

Max of WL Linear (Max of WL) Min of WLLinear (Min of WL) Average of WL Linear (Average of WL)

Wat

er L

evel

(mPW

D)

• Rising trend of water level near the sea

1999 2001 2003 2005 2007 20090

1

2

3

4Hiron Pointon the Pussur River

Max of WL Linear (Max of WL)

Wat

er L

evel

(mPW

D)

The increase of maximum water level is 6 cm/yr at Hiron Point in the last 10 years.

Jan/

2005

Jan/

2005

Mar

/200

5Ap

r/20

05M

ay/2

005

May

/200

5Ju

n/20

05Ju

l/20

05Au

g/20

05Se

p/20

05O

ct/2

005

Nov

/200

5De

c/20

05Ja

n/20

06Fe

b/20

06M

ar/2

006

Apr/

2006

May

/200

6Ju

n/20

06Ju

l/20

06Au

g/20

06Se

p/20

06O

ct/2

006

Nov

/200

6De

c/20

06Ja

n/20

07Fe

b/20

07M

ar/2

007

Apr/

2007

May

/200

7Ju

n/20

07Ju

l/20

07Au

g/20

07Se

p/20

07O

ct/2

007

Nov

/200

7De

c/20

07Ja

n/20

08Fe

b/20

08M

ar/2

008

Apr/

2008

May

/200

8Ju

n/20

08Ju

l/20

08Au

g/20

08Se

p/20

08O

ct/2

008

Nov

/200

8De

c/20

08Ja

n/20

09Fe

b/20

09M

ar/2

009

Apr/

2009

May

/200

9Ju

n/20

09Ju

l/20

09Au

g/20

09Se

p/20

09O

ct/2

009

0

2

4

6

8

10

12

Noapara Ghat Fultola Ghat Charerhat Ghat Rupsha Ghat Mollarhat

Salin

ity (P

PT)

Salinity Trend in the Region

Monthly Salinity Monitoring (Data Source: Department of Environment, DOE)

Impact of SLR: Intrusion of 5ppt Salinity line Dry Season

`

0 SLR60 cm SLR120 cm SLR

Sea Level Rise (SLR)

Affected area (ha)due to SLR

Affected Population due to SLR

60cm 512,590 4,613,306120cm 1,061,016 9,549,144

Impact of Sea Level Rise: Intrusion of 5ppt Salinity line (compared to present scenario)

Population growth• One of the densely

populated country

• Projected population

o 2025: 180million

o 2050: 220 million

• Urban: 25 million (2001), 80 million (2025) & 140 million (2050)

• Reduction of agricultural land 1% annually

70

80

90

100

110

120

130

140

Po

pu

lati

on

(m

illio

n)

7.0

7.5

8.0

8.5

9.0

Cro

pp

ed

are

a (

millio

n h

a)

Cropped areaPopulation growth

020406080

100120140

1998

2005

2015

2025

2035

2045

Rural Urban

35.1

41.844.2

49.0

53.6

57.9

2001 2015 2020 2030 2040 2050

Projected Coastal population (in million)

46.6

2025