Impact of climate change on water cycle: global trends and challenges

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1 Impact of climate change on water cycle: global trends and challenges Dr Richard Harding Centre for Ecology & Hydrology Wallingford UK Coordinator of the FP 6 WATCH Integrated Project Water and Global Change

2 Global Drivers of Change Increasing water consumption Increasing population Land cover/use change Increasing greenhouse gases (climate change)

3 Global Drivers of Change: interactions Climate rainfall green house gasses Land cover green house gasses Water Resources food fuel Population, Increasing consumption

4 EU FP6-7 Projects addressing Global Water Challenges Climate Science ENSEMBLES CarboEurope NitroEurope WATCH Adaptation SCENES NeWater AquaStress Floodsite SWITCH Mitigation ADAM

5 Impacts of Climate Change

6 Regional Rainfall Changes 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.

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

8 EU funded Regional Climate Studies ENSEMBLES CLAVIER (Eastern Europe) WATCH CLARIS LPB (South America) AMMA (West Africa) CIRCE (Mediterranean) ADAM Himalayan Region Africa East-West SADC??? CHINA

9 Changing drought severity (IPCC 2007)

10 Trends in heavy precipitation (Klein Tank & Können, J.Climate, 2003)

11 Precipitation/Runoff transform curves Precipitation hard rock catchment Discharge Groundwater catchment Time

12 Characteristics of models GHM LSHM RBHM Global Hydrological Models: High resolution Good representation of anthropogenic interventions (dams, landuse, abstractions etc) Good links to water requirements Quick to run/modify 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) River Basin Hydrological Models Realistic particularly flow processes, quality etc Good on floods etc Often rely on calibration to particular basins

13 Land Cover Climate Example of Global Hydrology 0.5 model: grid cell WaterGAP 2 Global Hydrololgy Vertical water balance Simulation of monthly time series of runoff from daily water balances Water Availability Runoff Groundwater recharge calibration River flow River Basin Water Stress Population Income Technology Climate Global Water Use Use Lateral water balance Water Withdrawals Wastewater Loadings

14 A typical Land Surface Model: JULES hydrology

15 New hydrological modelling systems Precipitation, P Evaporation, E Grid-to-Grid Surface flowrouting Topographic gradient, g S max Saturation-excess surface runoff River S River flow Return flow Drainage, D = K d S 3 Subsurface flow-routing Runoff production at each grid-cell. Kinematic wave routing from grid to grid.

16 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) Precipitation, P Evaporation, E Surface flow - routing Topographic gradient, g Smax Saturation -excess surface runoff River S River flow Return flow Drainage, D=KdS 3 Grid to Grid Subsurface flow -routing

17 Climate Impacts: Uncertainty in flood estimation River Beult in South East England (Kent) Change in recurrence interval (years) Uncertainty in future flood estimation Natural variability: Natural Emissions: variability: -34 to +17 Emissions: Global Climate Model structure: -14 to - 9 Global GCM Climate initial conditions Model structure: -13 to +41 GCM Downscaling: initial conditions: Downscaling: RCM structure: RCM Hydro structure: model structure Hydro Hydro model model structure: parameters: to - 5 to - 8 to +8 to - 22 Hydro model parameters: +1 to + 7 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.

18 The WATCH Integrated Project 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 Feedbacks in the climate hydrological system Past, present and future population, LUCC and water demand Extremes and scales of hydrological events WB5 WB2 WB4 20 th Century Global water cycle WB1 21 st Century Global water cycle WB3 evaluate the uncertainties in the predictions develop a modelling and data framework to assess the future vulnerability of water as a resource Assessing the vulnerability of water resources WB6 Management, training and dissemination WB7 WATCH

19 Envisioning the Future of Water in Europe Juha Kämäri and Joseph Alcamo The SCENES project Water Scenarios for Europe and Neighbouring States is a 4-year research project that started in late The aim is to develop and analyze a set comprehensive scenarios of Europe s freshwater futures up to The project area covers all of Greater Europe reaching to the Caucasus and Ural Mountains, and including the Mediterranean rim countries of north Africa and the near East.

20 Regional studies BLACK SEA REGION change in agriculture, unknown future salinization of the irrigated fields decapitalization of hydraulic structures unknown future for the ownership and operation of water supply and sewage treatment plants consumption of water by heavy industry negative population trends LOWER DANUBE REGION economic transition water pollution issues change in agriculture and land-use flood and drought management BALTIC REGION transition of agriculture privatization of water supply systems mixed trends in water consumption both municipal and industry probably increasing GDP and changes in the life style HELCOM future MEDITERANEAN REGION water stress land use change water use, irrigation population trends, immigration change in agricultural policy

21 Climate change is just one of multiple stresses on future Water Resources Generally dry areas will get drier and wet wetter Extremes floods and drought are more likely We have a good range of tools to investigate current and future water resources But there is considerable uncertainty about regional detail this will not improve in the near future, we need: * More regional studies * Better understanding and use of uncertainty * Integrated models including multiple drivers (CC, population, development, globalisation)

22 Research Priorities : Improved research Infrastructure: Better use of historical data Support future long term observations Modelling toolkits Hydrological observatories Improving regional research capacity training, infrstructure and knowledge transfer National and international collaboration within and without Europe

23 Thank you for your attention