Munsur RAHMAN, Professor, Institute of Water and Flood Management, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh(on behalf of the  ESPA Deltas Full Consortium)

Implications of Biophysical Trajectory for policy Decision in the Ganges‐Brahmaputra‐Meghna Delta

ESPA 2015 Annual Science ConferenceWednesday, 25th – Thursday, 26th November 2015 London, UK

ESPA Delta- ‘Assessing Health, Livelihoods, Ecosystem Services and Poverty Alleviation in Populous Deltas’ (NE-J002755-1)’

Ecosystem Services in GBM Delta10

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Lecture 4. Climate change and the integrated coastal system. Wednesday

25 July 2007

Cyclones/ Marine Processes

River Floods/ Sediment Supply

Sedimentation,Tectonics, Subsidence, salinization, water logging, storm surges, polderization

NATURAL PROCESSES

ClimateVariability

Stresses in the GBM Delta

Lecture 4. Climate change and the integrated coastal system. Wednesday

25 July 2007

Cyclones/ Marine Processes

River Floods/ Sediment SupplyChanging Land Use/Catchment Management

Sedimentation,Tectonics, Subsidence, salinization, water logging, storm surges, polderizationGrowing Populationand Economy

NATURAL PROCESSES

HUMAN‘PROCESSES’

‘GlobalClimate Change’

ClimateVariability

Multiple Stresses in the GBM Delta

During the ESPA Deltas project activities (2012‐ 2015): Key Questions from policy makers and local community?

Sealevel rise?(… cm/100y)

Or diff time scale

More /extremeFloods/ storms?

More/intenserainfall?

Spatialdevelopments

Subsidence?

More summer Drought?

Salt Intrusion?

Decreasedriver

Discharge?

Increased river

Discharge?

Increased Erosion?

5

Potential Impact of those above on ES Resources (agriculture, fisheries,Forestry, fresh drinking water), infrastructure, disaster preparedness atdifferent time scale

To answer the above Questions and related issues:

What are the key drivers? How will these change with time and how do they interact?What are the consequences of these changes for the Ecosystem 

System services of Delta? How will these affect the people, particularly the poor? How can policy processes use this science?

THE CONSORTIUM (around 100 members)

• University of Southampton‐Lead Robert Nicholls PI (Biophysical Modelling)

• University of Oxford (Scenario Development)

• Exeter University (Ecosystem Services and Poverty)

• Dundee University (Legal context)

• Hadley Centre MET office (Climate Change Modelling)

• Plymouth Marine Laboratories (Fisheries Modelling)

• National Oceanography Centre Liverpool (Marine Modelling)

• JadavpurUniversity (MangroveModelling): Indian Lead

• IIT Kanpur (Hydrological Modelling) 

• Institute of Water and Flood Management, Bangladesh University of Engineering and Technology (BUET) – Prof Rahman Lead PI (Physical Modelling)

• Bangladesh Institute of Development Studies (BIDS) Institute of Livelihood Studies (ILS)

• Ashroy Foundation• Institute of International Centre for 

Diarrhoeal Disease Research, Bangladesh (ICDDR,B) 

• Center for Environmental and Geographic Information Services (CEGIS)

• Bangladesh Agricultural University• Bangladesh Agricultural Research Institute 

(BARI)• Technological Assistance for Rural 

Advancement (TARA)• International Union for Conservation of 

Nature (IUCN) • University of Dhaka• Water Resources Planning Organization 

(WARPO) Database/others

UK (7)

Bangladesh (12)India (2)

ESPA Delta Project elements: Coupling of human and natural dynamics

Hossain et al. (2014)

Since the 1950s, increasinggross domestic productand per capita incomemirror rising levels of foodand inland fish production(PS).

In contrast, non‐foodecosystem services (RS)such as water availability,water quality and landstability (RS) havedeteriorated.

Trade‐offs between use of environmental resources and development

Fact: Historical trends and trade‐offs 

ESPA Deltas Scenario Structure

•Climate scenarios•Catchment models

1.GBM flows and water quality2.GBM sediment modelling3.Groundwater

•Bangladesh models1.Delta and Bay of Bengal models2.Fisheries3.Mangroves4.Agriculture

•Integrated model

Mid‐century

• There are 17 ensemble members of the regional climate model (called Q0‐Q16) for 1971‐2099.

• All ensemble members indicate warming over the region by end of 21stcentury (range from about 2.5°C to 5.0°C by 2080‐99).

• All ensemble members indicate increased annual rainfall by end of century (5‐30% increases by 2080‐99).

Sea Level RiseSea level rise of 0.25 to 1 m, with an upper extreme of 1.5 m

End of centuryClimate Scenario

Caesar et al. (2015)

Shared Socio‐Economic Pathways (SSPs)

ESPA Deltas Scenario Title

IPCC SSP equivalent

More Sustainable SSP1

Business as Usual SSP2

Less Sustainable SSPs 3 and 4

ESPA Deltas project: we considered 3 plausible SSPs which have beenadapted from the 5 proposed SSPs.

BaU: Business as Usual, MS: More Sustainable and LS: LessSustainable

Climate and SSP scenarios examined by WP5 modelsQ0 with SLR Q8 with SLR Q16 with SLR SLR 1.5m max#

BaU INCAHydroTrendsMODFLOW*FVCOMDeltft3D‐morphology(50y)Delft3D (snapshot)GCOMSFisheries+Agriculture/Aq*Mangrove*

INCAHydroTrendsDelft3D (snapshot)Agriculture/Aq*

INCAHydroTrendsDelft3D (snapshot)Agriculture/Aq*

FVCOMDelft3D (snapshot)

MS INCAHydroTrendsMODFLOW*Delft3D (snapshot)Agriculture/Aq*Mangrove*

INCAHydroTrendsFVCOMDelft3D (snapshot)Agriculture/Aq*

INCAHydroTrendsDelft3D (snapshot)GCOMSFisheries+Agriculture/Aq*

LS INCAHydroTrendsMODFLOW*Delft3D (snapshot)Agriculture/Aq*Mangrove*

INCAHydroTrendsDelft3D (snapshot)GCOMSFisheries+Agriculture/Aq*

INCAHydroTrendsFVCOMDelft3D (snapshot)Agriculture/Aq*

Quantitative Scenario of Delta Model Scenario

Scenario No.

Scenario Description

Snapshots

Upstream Discharge Boundary(Has provided by Oxford Group)

Downstream Sea Level Boundary(Has provided by Met Office Group)

1 Q0   + BaU + A1B

Maximum discharge year (2040 –2060)

Q0 + BaUHourly time series data

SnapshotMaximum Discharge Year

Q0 + BaU + A1BHourly time series data

SnapshotMaximum Discharge Year

Snap shots of Catchment Models

Changes in river flows

• Increase in flow projected potential for increased flooding.

• Dry season flows projected to improve with climate change – but extreme low flow durations may increase.

• Impact of major infrastructure in neighbouringcountries may mean reduction in dry season flows

Climate change

Socio-economic change in the GBM Basin

Changes in river flows, water quality and sediment

Whitehead et al. (2015)

Sediment Load from Ganges and Brahmaputra Basins

Preliminary results

Under climate change scenarios, river flows will increase, and there will be a corresponding increase in sediment supply by 2090s

Apparent potential to increase resilience of the delta to SLR  through sedimentation‐based adaptation approaches

However, increased damming in the catchments may reduce this increase and even reduce it relative to today 

Darby et al. (2015)

Mid Century: +16%-18%End Century: +25%-28%

Mid Century: +34%-37%End century: +52%-60%

Projected Sediment Budget

Salinisation of the Groundwater (2015)

Complex groundwater system represented by conceptual numerical model at regional scale

• Lateral sea water intrusion is an extremely slow process (thousands of years)• SLR will have little impact on increasing groundwater salinity over smaller time 

scales (e.g. 100 years)• River salinity changes (via SLR and reduced u/s flow) is the major driver of 

change for groundwater salinity in upper aquifer over most of coastal zone• Pumping is another potential driver of change for groundwater salinity

• Shallow GW pumping  concentrated in northern areas

Ground Water Salinity

Snap Shots of Delta Scale Models

Examples of snap shots of Biophysical Trajectory

• Erosion‐ Sedimentation• Flooding• Cyclonic storm surges • SalinizationRelationships with ES• Agriculture • Fisheries and • Sundarban mangrove forest 

Subsidence and sedimentation in coastal zone

• Land subsidence in the region (eastern and the western estuarinesystems) from mid‐century will be largely compensated by netfloodplain sedimentation.

• With increased sediment load, net accretion increases in easternand western estuarine systems

Eastern Area

Central Area

Western Area

Changes in Coastal Flooding

• Coastal floods will start earlier than the present and will last longer.

• Some of the existing polders will be overtopped in mid‐century and end‐century for fluvio‐tidal flooding

Fluvio-tidal flooding 2100

Storm Surge Snap shot:Present Day Inundation

Inundated Area: 1445 km2

Maximum Inundation Depth: 5.03 m

Inundated Area: 1024 km2

Maximum Inundation Depth: 3.22 m

Mid Century Inundation Scenario for Sidr-like Cyclone

Inundated Area: 6190 km2

Maximum Inundation Depth: 5.04 m

Inundated Area: 7045 km2

Maximum Inundation Depth: 5.74 m

Inundated Area: 4677 km2

Maximum Inundation Depth: 5.74 m

End Century Inundation Scenario for Sidr-like Cyclone

Inundated Area: 6372 km2

Maximum Inundation Depth: 6.70 m

Inundated Area: 5491 km2

Maximum Inundation Depth: 6.97 m

Inundated Area: 7401 km2

Maximum Inundation Depth: 6.70 m

River salinity to increase with SLR and changes in upstream flow: Implication to ES

Haque and others (2014, 2015, 2016)

Past TrendSalinity affected area has increased by about 27% during the last 4 decadesYield expected to decrease with soil salinity increaseCropping patterns have changed

Salinisation and climate change impacts on agriculture

Spatial distribution of increasing salinity impacts on dry season agricultural yields (2050)

Future climate change impactsBoro rice ‐ drastic reduction in yield (high heat stress during flowering)Wheat ‐ increase in yield (favourable temp. during flowering and CO2 fertilization)Mustard – No significant impact

Fisheries Production

Sundarbans critical in providing ES to the poor• Sundarbans significant in providing a buffer to protect the region from

storm surge flooding.• Mangrove area projected to decrease moderately (13%) under moderate

SLR, but substantially (43%) under high SLR projections by 2100• Increasing dominance of salt tolerant species suggests salinisation of the

Sundarbans.

Anirban et al. (2015)

Sundarban as a Buffer against Storm Surge FloodingSakib et al. (2015)

Summary: policy Implication of Biophysical Trajectory   

Climate scenarios: Policy/local stakeholders Question onRainfall, temperature

Catchment models1.GBM flows and water quality: Water flow2.GBM sediment modelling: Sediment flow3.Groundwater/River: Salinity

Bangladesh models1.Delta and Bay of Bengal models (Flooding/erosion)2.Fisheries (Impact on Fishesries)3.Mangroves (impact on mangrove forest)4.Agriculture (impact on agriculture)

For more information

http://www.espadeltas.net

Or email to: mmrahman@iwfm.buet.ac.bd