www.espadelta.net ESPA Deltas Project Assessing Ecosystem Services - - PowerPoint PPT Presentation

Modelling Climate Change and Socio-economic Pathways in the Ganges, Brahmaputra and Meghna Rivers

Paul Whitehead and Emily Barbour (Oxford), (BUET, IIT Kanpur) www.espadelta.net

Lecture 4. Climate change and the integrated coastal system. Wednesday 25 July 2007

ESPA Deltas Project Assessing Ecosystem Services And Poverty Alleviation In Populous Deltas: A case study of the Ganga-Brahmaputra- Meghna Delta in India and Bangladesh

Extensive Modelling Strategy Models developed for Rivers, Groundwaters, Estuaries, Bay of Bengal, and sectors of the economy eg agriculture , fisheries, Plus a team studying the socio-economics of poverty, migration, livelihoods, and poverty alleviation

Modelling Ganges, Brahmaputra and Meghna River Systems

• How will future climate change and socio-economic change in the

Ganga, Brahmaputra and Meghna Rivers impact flows and nutrient fluxes into the Delta?

• How can management and policy interventions reduce these impacts?

Integrated Catchment Model (INCA)

• Can account for diffuse and point sources of

pollution, land use change and climate change

• Semi distributed and ssuccessfully applied to over 50

catchments (including catchments in Nepal)

PLOT HILLSLOPE & SUBCATCHMENT CATCHMENT

(Hydrology, Nitrogen, Phosphorus, Sediments, Carbon, Metals and Ecology)

The INCA-N NITROGEN Model Process Pathways

Source: P.G. Whitehead et al./The Science of the Total Environment 210/211 (1998) 547-558

INCA reach divisions for Ganga basin

7

Total 70 reaches Ganga – 21 reaches Yamuna – 10 reaches Other tributaries – 39 reaches

Tributary confluence Sampling/monitoring point Effluent input/abstraction

Modelled Sub-Catchments in Ganga

Detailed Land Use Mapping

(Based on NRSC, Hyderabad) 26 classes aggregated into 6 classes for INCA

Met Office Hadley Centre HadRM3P RCM 25km grid- evaluated for spatially and temporal Patterns in Temperature and Precipitation

10

A1B-SRES, RCP 2.6 and 8.5

Total of 17 Climate Realizations with perturbed parameters

Q0 – Moderately warmer/wetter Q8 – warmer/drier Q16 – warmer/wetter

Climate Q0 Realisation

Moderately warmer/wetter

5 10 15 20 25 30

1960 1980 2000 2020 2040 2060 2080 2100 2120

Temp

Temperature: Yearly average (0C)

Ganges Brahmaputra Meghna

Climate Scenario

Moderately warmer/wetter

2 4 6 8 10 12 14 16 1971 1981 1991 2001 2011 2021 2031 2041 2051 2061 2071 2081 2091

mm/day Year

Rainfall: Yearly average (mm/day)

Ganga Brahmaputra Meghna

Integrated Catchment Model (INCA)

PLOT HILLSLOPE & SUBCATCHMENT CATCHMENT

INCA Reach Structure for the Ganges

Time Series Inputs for INCA Model

1981-2000 (Daily time series data)

Model Calibration - flow gauges on the Ganga River system

GA04 Kachla GA05 Ankinghat GA06 Kanpur GA07 Garh Hardinge Bridge Bangladesh

Brahmaputra Simulation 1981-2000

Calibration of N concentrations and Flux

At Kanpur (Reach GA06)

19 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Nitrate mg/L Month Simulated Nitrate Observed Nitrate

10000 20000 30000 40000 50000 60000 70000 80000 20000 40000 60000 80000 Observed N Load-Tonnes/Year Simulated N Load-Tonnes/Year

Climate Change Effects for Estimated Flows, Nitrate and Ammonia at Farakka

Blue – 1990s Red – 2050s Green – 2090s

Flow Nitrate Ammonium

• No major shift in timing of monsoon season
• Large Change in peak flows
• Nitrate and Ammonia follow the dilution trend due to increased flows

Effects of Different Climate Realisations in the Ganges at Farakka

Impact of climate on low flows - number of days below Q80 (5700 m3/sec) showing increased drought periods in the 2090s

Shared Socio-economic Pathways (SSPs) IPCC approach

SSP1

Sustainability

SSP2

Middle of the Road

SSP3

Regional Rivalry

SSP4

Inequality

SSP5

Fossil-fuelled Development

More Sustainable Business as Usual Less Sustainable Moderately warmer/ wetter 1 2 3 Warmer/ drier 4 5 6 Warmer/ wetter 7 8 9

SRES A1B

(RCP4.5/6 -8.5)

Climate Change

• incl. sea level rise

Development

Socio-economic Scenario Analysis

UNDP Population Centre Trends (India)

• 40.0
• 20.0

0.0 20.0 40.0 60.0 80.0 100.0 120.0 2011 2021 2031 2041 2051 2061 2071 2081 2091

% change year More Sustainable - low fertility BaU - medium fertility Less Sustainable - high fertility

• Population changes
• Sewage treatment works capacity and

design for water quality control

• Water demands for irrigation and public

supply

• Atmospheric nitrogen deposition
• Land use change
• Water transfer plans

Water Infrastructure

Major Transfer Plans (River Interlinking project)

Effects of Socio-economics on Ganga Flow and Water Quality

Blue – BaU; Red – MS; Green – LS; Dotted – baseline 1990s Flow Nitrate Ammonium

• No major difference in flows (no major change in irrigation flows & water transfers simulated)
• Large reduction in N and NO3 under MS scenario – reflects improved effluent treatment,

implications for river ecology and reduced nitrogen load into Bangladesh (similar results for P)

Full GBM Results- baseline

Assessing the impact of climate and socio-economic changes on flow and water quality in the Ganges-Brahmaputra-Meghna Basin

0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Nitrate mgN/l Month

1981-2000 2041-2060 2080-2099 20000 40000 60000 80000 100000 120000 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Flow m3/sec Month

GBM 1990s GBM 2050s GBM 2090s

Change in Nitrate-N Monthly Concentrations for the SRES A1B scenario for the 2050s and 2090s. Change in monthly flow for the SRES A1B scenario for the 2050s and 2090s.

Water Infrastructure

Major Transfer Plans (River Interlinking project)

Water transfer Scenarios

• Impact of water transfers on flows is very significant
• 22% reduction in peak flows for 2090s; 48% reduction in low flows for 2090s
• => Large scale impact on delta ecosystem

Stakeholder Scenarios for Bangladesh

Integrated Model Socio/Environmental Models Data

Simulations S1, S2, …, Sn

Adaptation Responses

(e.g. coastal defence, irrigation projects, etc.)

Climate change

Qualitative Quantitative Semi- Qualitative Quantitative

Scenarios

Narrative Baseline Literature

iterative learning loop

What Next---Stakeholder driven process to evaluate scenario analysis– do they make sense – if so how should they affect policy at a National, Regional and Local Level

Conclusions

1. INCA model simulates the spatial and temporal complexity of flows and N-flux (P and Sediments) in a large river system.

2. Significant climatic shift with increased temperatures and change precipitation could have significant impact on flows, increasing peak flows and more frequent droughts. 3. Socio Economic Changes could have a large effect on flows during droughts where increased irrigation will reduce low flows, plus impact of Water Transfers could be very significant in the GBM delta. 4. Clean up of the Ganga River will reduce Nitrogen (and Phosphorus) fluxes into Bangladesh. 5. Process based model of the GBM rivers can now be used to evaluate alternative policies in more detail (e.g. dam effects, different agricultural strategies, point source pollution, different Ganga Clean up strategies etc.).