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
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
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) (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
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 Total 70 reaches Tributary confluence Ganga – 21 reaches Sampling/monitoring point Yamuna – 10 reaches Effluent input/abstraction Other tributaries – 39 reaches 7
Modelled Sub-Catchments in Ganga
Detailed Land Use Mapping 26 classes aggregated into 6 classes for INCA (Based on NRSC, Hyderabad)
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 Q 0 – Moderately warmer/wetter Q 8 – warmer/drier Realizations with Q 16 – warmer/wetter perturbed parameters
Climate Q0 Realisation Moderately warmer/wetter Temperature: Yearly average ( 0 C) 30 25 Ganges 20 Brahmaputra Temp Meghna 15 10 5 0 1960 1980 2000 2020 2040 2060 2080 2100 2120
Climate Scenario Moderately warmer/wetter 16 Rainfall: Yearly average (mm/day) 14 12 10 Ganga mm/day 8 Brahmaputra 6 Meghna 4 2 0 1971 1981 1991 2001 2011 2021 2031 2041 2051 2061 2071 2081 2091 Year
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 GA07 Garh GA04 Kachla GA05 Ankinghat GA06 Kanpur Hardinge Bridge Bangladesh
Brahmaputra Simulation 1981-2000
Calibration of N concentrations and Flux At Kanpur (Reach GA06) 0.8 80000 Observed N Load-Tonnes/Year 0.7 70000 0.6 60000 0.5 50000 Nitrate mg/L 40000 0.4 30000 0.3 Simulated Nitrate 20000 0.2 Observed 10000 0.1 Nitrate 0 0 0 20000 40000 60000 80000 Simulated N Load-Tonnes/Year Month 19
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 m 3 /sec) showing increased drought periods in the 2090s
Shared Socio-economic Pathways (SSPs) IPCC approach SSP1 SSP2 SSP3 SSP4 SSP5 Sustainability Middle of the Road Regional Rivalry Inequality Fossil-fuelled Development Development SRES A1B (RCP4.5/6 -8.5) More Business as Less Sustainable Usual Sustainable Climate Change incl. sea level rise Moderately warmer/ 1 2 3 wetter Warmer/ 4 5 6 drier Warmer/ 7 8 9 wetter
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 UNDP Population Centre Trends (India) 120.0 More Sustainable - 100.0 low fertility 80.0 BaU - medium 60.0 fertility 40.0 Less Sustainable - 20.0 high fertility 0.0 2051 2011 2021 2031 2041 2061 2071 2081 2091 -20.0 year -40.0
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 NO 3 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 0.800 1981-2000 120000 GBM 1990s 0.700 2041-2060 GBM 2050s 100000 2080-2099 Nitrate mgN/l 0.600 GBM 2090s Flow m 3 /sec 80000 0.500 60000 0.400 40000 0.300 20000 0.200 0.100 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Month Change in Nitrate-N Monthly Concentrations for the Change in monthly flow for the SRES A1B scenario SRES A1B scenario for the 2050s and 2090s. 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
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 Scenarios Literature Narrative Baseline Stakeholder Integrated Scenarios for Model Bangladesh Quantitative Qualitative Socio/Environmental Adaptation Models Responses (e.g. coastal defence, irrigation Data projects, etc.) Climate iterative change learning loop Quantitative Qualitative Simulations Semi- S 1 , S 2 , …, S n
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.).
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