UK – China Workshop, July 2008 Dr Richard Harding Centre for Ecology & Hydrology Wallingford UK Coordinator of the FP 6 WATCH – Water and Global Change Integrated Project Global Change and Water

Global Drivers of Change Increasing population Increasing water consumption Land cover/use change Increasing greenhouse gases

Global Drivers of Change: interactions Land cover Population, Increasing consumption Climate rainfall GHGs food fuel GHGs Water Resources

Consumption, km 3 /year Agriculture Industry Municipal needs Reservoir Total Assessment Forecast Water Consumption - after Shiklomanov 2000

Regional Water Scarcity One Indicator is the ratio of Water Consumption to Water Availability –World: 1995: 8,4 %2025: 12,2 % But: –South America:2025: 1 – 2 % –Asia: 1995: 40 – 80 %2025: 60 – 85% –North Africa: 1995: 95 %2025: 130 % –In some countries already more than 100% of the yearly water supply is consumed. This is unsustainable!

Impacts of Climate Change

FIGURE SPM-6. Relative changes in precipitation (in percent) for the period 2090–2099, relative to1980–1999. Values are multi-model averages based on the SRES A1B scenario for December to February (left) and June to August (right). White areas are where less than 66% of the models agree in the sign of the change and stippled areas are where more than 90% of the models agree in the sign of the change. Regional Rainfall Changes

Areas of physical and economic water scarcity (IWMI, 2006)

Precipitation/Runoff transform curves Discharge Precipitation ‚hard rock‘ catchment Groundwater catchment Time

Runoff production at each grid-cell. Kinematic wave routing from grid to grid. Grid-to-Grid Hydrological modelling systems

UK application of prototype model: using the UK Hadley Centre 25km RCM output Percentage change in flood peaks at a 20-year return period (from 1970s to 2080s) River S max Subsurface flow-routing Surface flow- routing S Drainage, D = K d S 3 Topographic gradient,g Precipitation,P Evaporation, E Return flow River flow Saturation-excess surface runoff Grid to Grid

Climate Impacts Uncertainty in flood estimation River Beult in South East England (Kent) Kay, A.L., Davies, H.N., Bell, V.A. & Jones, R.A. Comparison of uncertainty sources for climate change impacts: flood frequency in the UK. Submitted: Climatic Change. Recurrence interval (years) Natural variability:-34to +17 Emissions:-14to - 9 Global Climate Model structure:-13to +41 GCM initial conditions:-25to - 5 Downscaling:-22to - 8 RCM structure:-5to +8 Hydro’ model structure:-45to - 22 Hydro’ model parameters:+1to + 7

SAGARMATHA: Snow and Glacier Aspects of Water Resources Management in the Himalaya %change in decadal mean flow for Ganges from regional climate model output (RCM2) Precipitation change Temperature change

 analyse and describe the current global water cycle  evaluate how the global water cycle and its extremes respond to future drivers of global change  evaluate feedbacks in the coupled system as they affect the global water cycle  evaluate the uncertainties in the predictions  develop a modelling and data framework to assess the future vulnerability of water as a resource The WATCH Integrated Project

New data products: 1. forcing data

New data products: 2. global fields -soil 30” degree resolution Combines data from ESB, USDA, SOTER, FAO, CHINA for the best soil dataset available.

New data products: 3. global fields – population past and future 0.5 degree resolution 10 year time steps IPCC SRES A2r, B1, B2 scenarios International Institute for Applied System Analysis (IIASA) GGI Scenario Database, Available at:

GHM Global Hydrological Models:  High resolution  Good representation of processes and anthropogenic interventions (dams, landuse, abstractions etc)  Good links to water requirements  Quick to run/modify LSHM Land Surface Hydrology Models  Realistic representation of energy and evaporation  Limited calibration  Include many feedbacks (CO 2, snow etc)  Poor on anthropogenic river modification  Complex to run and modify (need diurnal forcing etc) RBHM River Basin Hydrological Models  Realistic – particularly flow processes, quality etc  Good on floods etc  Often rely on calibration to particular basins Characteristics of models

WaterGAP 2 Model - Overview - Global Water Use Global Water Use PopulationPopulation IncomeIncome TechnologyTechnology ClimateClimate Global Hydrololgy Global Hydrololgy River Basin Water Stress River Basin Water Stress Land CoverLand Cover ClimateClimate WaterWithdrawals Water Availability Runoff Groundwater recharge WastewaterLoadings River discharge calibration

Global hydrology models Land surface hydrology models River basin models Land Surface Hydrology Mode/ Global Hydrology Model Intercomparison G2G

WATCH – some deliverables Improving hydrological components of global hydrology models: groundwater, routing (incl. dams etc), irrigation, inundation, ice.... New validation – runoff, evaporation.. Improved driving fields – global 0.5 o fields for 20 th and 21 st century Regional reanalyses Improved land cover/land use fields Model intercomparison with GHMs and LSHMs Uncertainty analyses of current and future runoff

24-28 November 2008 (tentative) Beijing, China WATCH / MAIRS / UKRC China Science Workshop: Climate Change & Global Water Cycle The workshop will explore: our current state of knowledge of components of the water cycle, globally and regionally. recent advances in large scale climate and hydrological modeling in China and Europe. research interests in China and Europe. possibilities for joint research

Thank you