Paul Whitehead and Emily Barbour (Oxford), (BUET, IIT Kanpur)

Transcription

1 Modelling Climate Change and Socio-economic Pathways in the Ganges, Brahmaputra and Meghna Rivers Paul Whitehead and Emily Barbour (Oxford), (BUET, IIT Kanpur)

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

3 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

4 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?

5 Integrated Catchment Model (INCA) (Hydrology, Nitrogen, Phosphorus, Sediments, Carbon, Metals and Ecology) 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

6 The INCA-N NITROGEN Model Process Pathways Source: P.G. Whitehead et al./the Science of the Total Environment 210/211 (1998)

7 INCA reach divisions for Ganga basin Total 70 reaches Ganga 21 reaches Yamuna 10 reaches Other tributaries 39 reaches Tributary confluence Sampling/monitoring point Effluent input/abstraction 7

8 Modelled Sub-Catchments in Ganga

9 Detailed Land Use Mapping 26 classes aggregated into 6 classes for INCA (Based on NRSC, Hyderabad)

10 Met Office Hadley Centre HadRM3P RCM 25km grid- evaluated for spatially and temporal Patterns in Temperature and Precipitation 10

11 A1B-SRES, RCP 2.6 and 8.5 Total of 17 Climate Realizations with perturbed parameters Q 0 Moderately warmer/wetter Q 8 warmer/drier Q 16 warmer/wetter

12 Climate Q0 Realisation Moderately warmer/wetter 30 Temperature: Yearly average ( 0 C) 25 Temp Ganges Brahmaputra Meghna

13 Climate Scenario Moderately warmer/wetter 16 Rainfall: Yearly average (mm/day) mm/day Ganga Brahmaputra Meghna Year

14 Integrated Catchment Model (INCA) PLOT HILLSLOPE & SUBCATCHMENT CATCHMENT

15 INCA Reach Structure for the Ganges

16 Time Series Inputs for INCA Model (Daily time series data)

17 Model Calibration - flow gauges on the Ganga River system GA07 Garh GA04 Kachla GA05 Ankinghat GA06 Kanpur Hardinge Bridge Bangladesh

18 Brahmaputra Simulation

19 Nitrate mg/l Observed N Load-Tonnes/Year Calibration of N concentrations and Flux At Kanpur (Reach GA06) Simulated Nitrate Observed Nitrate Month Simulated N Load-Tonnes/Year 19

20 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

21 Effects of Different Climate Realisations in the Ganges at Farakka

22 Impact of climate on low flows - number of days below Q80 (5700 m 3 /sec) showing increased drought periods in the 2090s

23 Climate Change incl. sea level rise Shared Socio-economic Pathways (SSPs) IPCC approach SSP1 Sustainability SSP2 Middle of the Road SSP3 Regional Rivalry SSP4 Inequality SSP5 Fossil-fuelled Development SRES A1B (RCP4.5/6-8.5) Moderately warmer/ wetter Warmer/ drier Warmer/ wetter More Sustainable Development Business as Usual Less Sustainable

24 Socio-economic Scenario Analysis 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 % change year UNDP Population Centre Trends (India) More Sustainable - low fertility BaU - medium fertility Less Sustainable - high fertility

25 Water Infrastructure Major Transfer Plans (River Interlinking project)

26 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 NO 3 under MS scenario reflects improved effluent treatment, implications for river ecology and reduced nitrogen load into Bangladesh (similar results for P)

27 Full GBM Results- baseline

28 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Flow m 3 /sec Nitrate mgn/l Assessing the impact of climate and socio-economic changes on flow and water quality in the Ganges-Brahmaputra-Meghna Basin GBM 1990s GBM 2050s GBM 2090s Month Change in monthly flow for the SRES A1B scenario for the 2050s and 2090s. Month Change in Nitrate-N Monthly Concentrations for the SRES A1B scenario for the 2050s and 2090s.

29 Water Infrastructure Major Transfer Plans (River Interlinking project)

30 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

31 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 Baseline Semi- Qualitative Quantitative Qualitative Quantitative Scenarios Narrative Literature Stakeholder Scenarios for Bangladesh Integrated Model Adaptation Responses (e.g. coastal defence, irrigation projects, etc.) Socio/Environmental Models Data Climate change iterative learning loop Simulations S 1, S 2,, S n

32 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.).