The Ganges Basin Development Challenge (GBDC)

Increasing the resilience of agricultural & aquaculture systems in the coastal zone of the Ganges

Delta

OutputsTarget area for extrapolation domainsThe coastal zone of Bangladesh & West Bengal

India

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• Among world’s poorest, most food insecure, vulnerable rural families• Dense population >36 million people; >760/km2 (>7.6 per 100 m x 100 m) (2001)• Low land productivity – 1 low yielding traditional aman crop, much of the land is

fallow during much of the dry season - missed out on the Green Revolution• Opportunity to build on the achievements & networks of 2 CPWF Phase 1

projects (PN10 Tuong et al.; PN7 Abdel Ismail et al.)• Good potential to greatly increase land & water productivity (rice, upland crops,

aquaculture, homestead production systems), improve rural livelihoods in the coastal zone

• The coastal zone offers the potential for Bgd to make a quantum leap in meeting future food security requirements

Why the coastal zone of the Ganges Delta?

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Polder 31

Polder 30

River

Inlet to sluice gate

Sluice gate on river side

Sluice gate inside the polder

G4. Understanding of water resources – data & models

(current & future scenarios)

G2. More productive, resilient & diversified cropping systems (rice, upland, aquaculture)

G3. Understanding polder water governance – recommendations for

improvement

G1. Cropping system suitability maps from comprehensive GIS data base

G5. Co-ordination, liaison with CPWF, policy dialogues, communication with stakeholders for up & outscaling

The Ganges Basin Development Challenge – 5 Projects

CPWF Ganges Partner Organisations

BANGLADESHCGIAR

BFRI Bangladesh Fish Research Institute World FishIWM Bangladesh Institute of Water Modelling IWMIBRRI Bangladesh Rice Research Institute IRRIBWDB Bangladesh Water Development BoardLGED Local Government Engineering BoardSRDI Soil Resource Development Institute

BRACSocioConsultShushilan

PSTU Patuakhali Science and Technology UniversityBUET Bangladesh University of Engineering & Technology

INDIACIBA Central Institute of Brackish Water Aquaculture - KakdwipCSSRI Central Soil Salinity Research Institute – Canning Town

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2. Improved cropping systems

IRRI-BRRI-BRAC-WFish-BFRI-

SocioConsult-PSTU

5. Extrapolation domains

IRRI-IWM-BWDB-SRDI-LGED

IWMI-Sushilan-BWDB-

LGED-BAU

Socio-economic data

-Biophysical-Census data

4. GIS data baseWater & environmental

criteria

3. Water governance recommendations

IWM-BWDB-BUET-IWMI

1. Water levels, salinity & drainage conditions

- Current- Future

WFish-IRRI-BRACG2

G3

G5

G4

G1

1,2,3,4,5 = Intermediate outputs

• Too much water in rainy season (tidal surges in non-protected lands;

excessive rainfall)• Lack of fresh water in dry season (or lack of access…)• Salinity, more so in dry season• Cyclonic events (severe flooding, storm surges sea water intrusion;

death & destruction)

These will worsen due to:• climate change (sea level rise, more extreme events)• reduced river flows from India in the dry season• sinking of the lands protected by polders (consolidation & lack of

siltation)

Biophysical constraints to increasing productivity

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May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr0

100

200

300

400Mean monthly rainfall - Khulnamm

Annual rainfall ~2,000 mm (range 1,100-2,900 mm)

Aus

BoroAman

Rabi

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Shrimp

Rabi

Boro

Shrimp

River

Draining water out of polder at low tide

RiverRiver

Rivers are tidal (to ~150 km inland)

Tidal fluctuations up to 2-3 m during the rainy season,depending on location

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High tide Low tide (still going down)

Elevation (above mean sea level, m) %

<0. 0 0<0.60 15<1.00 61<1.20 80<1.60 95<1.80 98

Average water level 1.3 m

Kazibacha river

Low tide water level 0.0 m

High tide water level 2.9 m

Average water level 1.0 m

Lower-Shalta river

High tide water level 2.7 m

Low tide water level -0.50 m

River levels relative to land level

Average water level 1.0 m

Wet season Sept 2001 Dry season March 2002

Salinity creeps up the rivers during the dry season – more so in the south west (1 ppt = ~1.5 dS/m)

0-2 ppt

2-4 ppt

8-10 ppt 22-27 ppt

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Soil salinity is increasing over time in the coastal zone (dry season)

SalinityNone-very slightVery slight-slightSlight-moderateModerate-highHigh-very high

200920001973

Salinity boundary

SRDI13

0

3

6

9

12

15

18

21

24

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

Month

Riv

er w

ater

Sal

inity

(ds/

m)

High tide Low tide

River salinity dynamics in a moderately saline region

Batiaghata, KhulnaPolder 30

1990-2007

(Sharifullah 2008)

This is not the situation everywhere, e.g. – fresh water year round in significant parts of the S Central - river salinity increases earlier & to higher values in the SW

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Polder 31

Polder 30

River

Inlet to sluice gate

Sluice gate on river side

Sluice gate inside the polder

1960-70s 139 polders constructed to protect the lands from:• tidal flooding in the rainy season• salinity intrusion in the dry seasonAnd to enable production of a rainy season (aman) rice crop

Polders of SW & SC Bangladesh~1 Mha~8 million people

Polder-3Satkhira

HIGHLY SALINE

Polder-30Khulna

MODERATELY SALINE

Focal study areas in Bangladesh for cropping systems & HH surveyPolder-43/2F

PatuakhaliVERY SLIGHTLY

SALINE

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* Categories based on Bangladesh Household Income and Expenditure Survey (2010)

More than 50% households are functionally landless

Polder 30 Polder 3-H Polder 3 L Polder 43 ALL Polder 0

100

200

300

400

500

600

700

800

Functionally landless < 0.2 ha Small 0.2-0.6 ha Marginal 0.6 - 1.0 ha

Medium 1.0-3.0 ha Large >3 ha

# of

hou

seho

lds

CPWF G2 World Fish survey, February 2012 (1,259 HH)

Rural households in the polders have very little land

(<0.2 ha)50 m x 40 m !

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Polder 30 (~4,000 ha)

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Polder embankment /dyke protecting land from flooding athigh tide

River-side

Dyke

River on eastern sideof polder 30

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River

Sluice gate letting water into the polder at high tide

RiverRiver

Sluice gate draining water out of the polder at low tide

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Polder 30

Dense natural drainage network (former river/creek canals – “khals”)

Most fields within ~1 km of a khal in polder 30

11 sluice gates connecting larger khals to the rivers

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Khals within polders vary greatly in size, can store fresh water during the dry season, but often heavily silted up (some no longer exist)

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

Traditional Rice (2-3.5 t/ha)

Sesame, Keshari0.5-1.0 t/ha)

Traditional Rice (2-3.5 t/ha)

……........Fallow…………………...

....Fallow……

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Predominant agricultural cropping systems in the low & moderately saline regions of the coastal zone

• Traditional variety• Tall, photoperiod sensitive (late maturing – harvested Dec/Jan)• 35-70 day old seedlings

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Soil salinity

AFTER RICE HARVEST - much fallow land – for 5-7 months

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SesameMungbean

Often damaged by early monsoon rains – destroyed in May 2013

AFTER RICE HARVEST – some areasLow input legume crops – late sown (Feb/Mar) because of late rice harvest

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High salinity areas

Brackish water shrimp production in “ghers”- extensive to semi-

intensive- - high risk

Aquaculture

Aman rice in some ghers in some locations in some years

National (2005)

Surveyed Households

marginal small Functionally landless

0

10

20

30

40

50

60

70

80

90

100%

of p

eopl

e

CPWF G2 survey by WorldFish, February 2012

Poverty of rural households is extreme in the polders

Mean

% people living below National Poverty Line (income <$1.25/person/day)

<0.2 ha

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High potential of the Ganges coastal zone