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A grid-based model for developing regional water scenarios – applications in Europe and elsewhere

A grid-based model for developing regional water scenarios – applications in Europe and elsewhere. Frank Farquharson. 1. What is going on in Europe on topics related to “European water Scenarios” ?. European river flow regimes ( Report to European Environment Agency ), Arnell et al., 1993

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A grid-based model for developing regional water scenarios – applications in Europe and elsewhere

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  1. A grid-based model for developing regional water scenarios – applications in Europe and elsewhere Frank Farquharson

  2. 1. What is going on in Europe on topics related to “European water Scenarios” ? • European river flow regimes(Report to European Environment Agency), Arnell et al., 1993 • The impact of Climate and other Hydrological events on European Water Supply (CHEWS), Farquharson et al, 1997 (ENV4-CT95-0138) • Estimation of Renewable water resources in the European Union(ERASM), Rees & Cole, 1997 (EUROSTATfor the European Environment Agency) • Advances in Regional Hydrology through East European Cooperation, Gustard & Cole, 1997 (ERB CIPA CT92-4018) • Groundwater and River Resources Action Programme on a European scale (GRAPES), Acreman et al, 2000 (ENV4-CT96-0186) • Assessment of the Regional Impact of Droughts in Europe (ARIDE), Demuth & Stahl (Eds), 2001 (ENV4–CT97-0553) • Establishment of a Regional Data Centre of the European Water Archive for the European territory of the former Soviet Union, 1999 (INTAS 94-4451) • European FRIEND Programme (CEH maintains a database of daily mean flows from 5000 stations from 30 countries in Europe) (UNESCO IHP) • Hydrological and hydrodynamic studies and predictions of Caspian Sea level rise; Impact of Climate and Man’s activities, Farquharson et al, 2000 (INCO-COPERNICUS IC15-CT97-0101) • Grid-based model of the Caspian Sea Basin, Meigh & Tate, 2001 (TACIS, ENVREG 9504)

  3. Average Annual Runoff gridded at 10km x 10km

  4. Irrigation Demand vs Average Annual Runoff

  5. Urban Demand vs Average Annual Runoff

  6. 2. Projection of possible scenarios on a 25-50 years scale • Much of CEH’s experience has been restricted to impacts of climate change scenarios • However, we have also considered socio-economic factors: • Changing demand • Water Poverty Index • Climate Vulnerability Index

  7. The UKCIP02 Report – the ‘definitive’ source of information on probable UK climate change scenarios for impact studies

  8. Mean Annual rainfall over the UK – very variable !

  9. Resolution of climate models Global model Regional model 300km grid 50km grid

  10. Present day winter precipitation over BritainObserved, and simulated with RCM and GCM

  11. ANNUAL

  12. WINTER

  13. SUMMER

  14. Winters are getting wetter and Summers are getting drier

  15. UK Summer daily rainfall (showing ability to simulate extremes) Probability %

  16. Predicted increase in summer temperatures (2080s compared to the present day) Global climate model Regional climate model Climate on islands changes very differently to the surrounding Mediterranean Sea, and can only be predicted using an RCM A2 Scenario

  17. How do hydrologists consider “Water Scarcity” & “Future Scenarios” ? • 1980s and early 1990s – Too much reliance on modelling Surface Runoff • Surface runoff alone does NOT represent water resources or availability • Models often ignored Groundwater • Took no account of DEMAND • Grid-based models used – BUT, in many cases, grids were not linked • Runoff accumulated in grid cells – not allowed to ‘runoff’ • Grid size too coarse (constrained by data availability and computer power)

  18. How have approaches changed ? • Mid to late 1990s • Recognition that grid must be linked to represent river system • Improved representation of groundwater • Finer grid size possible due to improvements in computers and in data availability • Recognition that DEMANDS must be built into water availability assessments

  19. 3. To address the FP6 call, there is a need for modelling at a range of scales: • A ‘Top-down’ approach of European scale modelling using Water-GAP or GWAVA • Regional or basin-scale modelling • ‘Bottom-up’ approaches • Water Poverty Index • Climate Vulnerability Index

  20. GWAVA Model • Global Water AVailability Assessment • Not yet applied Globally • Developed and applied to 20 countries in Eastern and Southern Africa (1994-98) • Applied to Volga Basin (Russia) and Caspian Sea basin (1999-2000) (INCO-COPERNICUS & TACIS funding) • Also applied to 20 countries in West Africa (2001-02) (FP5) • Studying impacts of climate change on Bangladesh (2003-05)

  21. GWAVA Model 2 0 N 1 0 N 1 0 W 0 N 0 W 2 0 E 1 0 E

  22. GWAVA – General approach • 0.5 by 0.5 degree grid for both water availability and demands (approx 50x50 kms) • Rainfall-runoff model for surface water • Groundwater availability assessed separately • Long series of climate inputs (30 years) used to estimate actual availability – now using RCM data • Linking grid cells to simulate river network • Model components to account for effects of: • lakes, reservoirs and wetlands • abstractions and return flows • inter-basin transfers

  23. APPROACH – contd. • Groundwater availability based on aquifer properties (areal extent, transmissivity, specific yield etc.) and recharge estimates • Water demands based on current and projected population and livestock numbers, information on irrigation and industrial use (i.e. socio-economic factors) • Indices of water availability versus demand derived at the grid cell scale

  24. Rainfall-runoff model - PDM INPUT Rainfall Potential Evaporation OUTPUT Runoff SURFACE STORAGE Surface runoff Moisture storage Groundwater recharge SUBSURFACE STORAGE River Flow Baseflow Probability Distributed Moisture Storage

  25. Does GWAVA work ?

  26. Application in Caspian Sea Basin River inflows to the Caspian under climate change scenarios Rainfall change for 2050s based on HadCM3

  27. Uncertainty !! Range of temperature change predictions from several climate modelling groups

  28. Uncertainty !! Runoff changes for 2050s estimated from 3 GCMs CGCM1 Echam4 HadCM2

  29. Water use features Long term gauging station Point of interest The flow estimation Problem in Practice – MEDIUM SCALE MODELLING

  30. Medium-scale modelling -LowFlows 2000

  31. “Bottom-up”, Semi-qualitative approach • Use techniques developed at Wallingford by Caroline Sullivan and Jeremy Meigh • Water Poverty Index • Climate Vulnerability Index

  32. CONCLUSIONS • Problems need to be tackled at a variety of scales – both in space and time • Data availability is more of a constraint than models/tools • The challenge is to bring together a range of uncertain future scenarios, derived from a variety of sources; some of which are quantified, others just quality descriptors • Natural scientists must continue to learn how to collaborate with social and economic specialists

  33. Thank You !

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