Long-term effects of climate change on Europe's water resources

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(1)BTO 2006.032 (s) May, 2006. Long-Term Effects of Climate Change on Europe's Water Resources.

(2) BTO 2006.032 (s) May, 2006. Long-Term Effects of Climate Change on Europe's Water Resources. © 2006 Kiwa N.V. All rights reserved. No part of this book may be reproduced, stored in a database or retrieval system, or published, in any form or in any way, electronically, mechanically, by print, photoprint, microfilm or any other means without prior written permission from the publisher.. Kiwa N.V. Water Research Groningenhaven 7 Postbus 1072 3430 BB Nieuwegein The Netherlands Telephone +31 30 60 69 511 Telefax +31 30 60 61 165 Internet www.kiwa.nl.

(3) Colofon Title Long-Term Effects of Climate Change on Europe’s Water Resources Projectnumber 111.583.300 Project manager Ir. T. Ramaker Quality Assurance Dr. G. Zwolsman Author(s) A. Domnişoru.

(4) Preface This is the report for the internship which I attended at Kiwa Water Research Institute, the Netherlands. The internship is part of the curriculum for the MSc study at the Utrecht University, Faculty of Geographical Sciences, department Physical Geography. This research is part of the Integrated Project Techneau, a project initiated by Kiwa and financed by the European Commission. The aim of the project is the development of adaptive system options for water supply. The internship was carried out in the period September 2005-May 2006 and was supervised by Dr. Gertjan Zwolsman from Kiwa WR and Dr. Thom Bogaard from Utrecht University. The report is the result of a literature research about the long-term effects of climate change on fresh water resources in Europe. Additionally, a case study was performed in Arges catchment, Romania. I would like to thank Gertjan for reviewing this report, for sharing his knowledge and for his contacts without which this project would not have been possible. Many thanks go to Thom for his advises and moral support which helped me not only during this project but also for the whole period that I studied in Utrecht. Ook wil ik bedanken aan mijn “kennishok” collega’s, Barend de Jong and Ad van Bokhoven. A long list of other persons helped me in this project, especially Petru Boeriu (UNESCOIHE), Vasile Ciomos (ARA), Albert de Haas (RIZA), Razvan Micu (Arges River Basin Committee), David van Raalten (Arcadis-Euroconsult), Arthur Roborgh (VROM), Marinela Simota (INMH), Petru Stefan (Apele Romane), all the people from Apele Romane (Arges– Vedea Directorate) and the collective of the department of Physical Geography in Utrecht.. Antoanella Domnişoru Nieuwegein, the Netherlands May, 2006. Climate Change © Kiwa N.V.. -1-. May, 2006.

(5) Contents. Preface. 1. Contents. 2. List of figures. 4. List of tables. 6. Abstract. 8. 1. Introduction. 10. 2. Climate change in Europe. 12. 2.1. Greenhouse effect and GHG. 12. 2.2. Climate models. 13. 2.3. Trends in temperature. 15. 2.4. Trends in precipitation and evaporation. 17. 2.5. Trends in glaciers and snowpack. 20. 3. Climate change effects on terrestrial ecosystems. 3.1. Effects on soil moisture. 22. 3.2. Effects on agriculture. 23. 4. Climate change effects on water resources. 4.1 4.1.1 4.1.2 4.1.3. Effects on surface water quantity Hydrological drought Floods Snowpack dynamics. 28 28 31 32. 4.2 4.2.1 4.2.2 4.2.3 4.2.4. Effects on water quality Temperature Suspended particulate matter Nutrients Eutrophication. 34 34 35 36 37. 5. Case study: Arges, Romania. 40. 5.1 5.1.1 5.1.2. Catchment description Physical characteristics Socio-economical characteristics. 40 40 43. 5.2 5.2.1 5.2.2. Water resources Hydrological characteristics Qualitative characteristics. 44 44 46. Climate Change © Kiwa N.V.. -2-. 22. 28. May, 2006.

(6) 5.2.3. Pollution sources. 47. 5.3 5.3.1 5.3.2 5.3.3. Climate change Effects on water resources Effects on agriculture Effects on soil moisture. 50 53 55 58. 5.4 5.4.1 5.4.2. Water quality analysis Data description Data analysis. 59 59 60. 6. Discussion and conclusions. 72. 6.1. Climate change trends in Europe. 72. 6.2. Effects on terrestrial ecosystems. 72. 6.3. Effects on water resources. 73. References. 76. Appendix A Romanian and EU standards for surface water quality. 84. Appendix B Data statistics. 86. Appendix C Variation of yearly mean values of water quality parameters in Arges 1 (1999-2004) Appendix D Contacts in Romania. 5. Appendix E CD-Rom. 7. Climate Change © Kiwa N.V.. -3-. May, 2006.

(7) List of figures Figure 1 Impacts of climate change on water quality and quantity. Note: feedback relations to the climate are not included..............................................................................................................11 Figure 2 Global mean energy flows between the surface and atmosphere. Source: Harvey, 2000 .....12 Figure 3 Global emissions and changes in average temperature associated with each SRES emission scenario. Source: Arnell, 2004 ....................................................................................................15 Figure 4 Reconstructed and measured relative temperature over the last 1 000 years (northern hemisphere) and projected temperature rise in the next 100 years. Source: EEA, 2004 ............16 Figure 5 Projected changes in summer mean temperature (oC) for HadCM3 and PCM, with A2 scenario for 2080. Source: Accelerates, 2004 ..............................................................................16 Figure 6 Annual temperature deviations in Europe in 2003. Note: temperature deviations, relative to average temperature from 1961-1990 (°C). Source: EEA, 2004 ............................................17 Figure 7 Annual precipitation changes (%) in Europe for the period 1900-2000. Note: black circles denote wetting and white circles denote drying; magnitude of trend is related to circle size; shaded trends are significant at 90%. Source: IPCC, 2001 ........................................................18 Figure 8 Trends in winter (DJF) (top) and summer (JJA) (bottom) precipitation changes (%) in Europe for the period 1900-2000. Note: black circles denote wetting and white circles denote drying; magnitude of trend is related to circle size; shaded trends are significant at 90%. Source: IPCC, 2001 ....................................................................................................................18 Figure 9 Projected changes in summer precipitation (mm/month) for 2080 for HadCM3 and PCM, with A2 scenario. Source: Accelerates, 2004 ..............................................................................19 Figure 10 Change in frequency of very wet days in Europe between 1976 and 1999. Source: EEA, 2004 ............................................................................................................................................19 Figure 11 Aletsch (Switzerland) historical length change: 1856 and 2001. Source: Haeberli and Hoelzle, 2003 ..............................................................................................................................20 Figure 12 Major agricultural regions of Europe. Source: Olesen and Bindi, 2002. Note: 1. Nordic; 2. British Isles; 3. Western; 4. Mediterranean; 5. Alpine; 6. North eastern; 7. South eastern; 8. Eastern ........................................................................................................................................24 Figure 13 Wheat yields with increasing CO2 concentration. Source: Olesen and Bindi, 2002 .........25 Figure 14 Suitability for grain maize, sunflower and soya in 2050s. Note: green / yellow / purple: baseline 1961-1990; red / brown / blue: suitability extension. Source: Parry, 2005 ..................26 Figure 15 Percentage of total irrigated land. Source: UNEP/DEWA, 2004......................................27 Figure 16 Percentage change in average annual water availability (natural discharge without substraction of consumptive water use) for European river basins as compared to today’s levels, realized with two different GCMs (ECHAM4 and HadCM3) for 2020s and 2070s. Source: Lehner et al., 2001.......................................................................................................................29 Figure 17 Month with minimum average discharge. Comparison of results for today’s climate (1961-1990) and for 2070s (HadCM3). Source: Lehner et al., 2001 ..........................................30 Figure 18 Change in occurrence of 100-year droughts. Comparisons of results calculated for today’s climate and water use (1961-1990) and for the 2020s and 2070s (ECHAM4 and HadCM3 climate models and Baseline-A water use scenario). Source: Lehner et al., 2001.......................30 Figure 19 Number of flood events in Europe. Source: EEA, 2004 .....................................................31 Figure 20 Month with maximum average discharge. Comparison of results calculated for today’s climate (1961-1990) and for the 2070s (HadCM3 climate model). Source: Lehner et al., 2001.32 Figure 21 Hypothetical natural and modified average hydrograph for basins with snowfall and snowmelt. Source: Gleick et al., 2001 .........................................................................................33 Figure 22 Change in occurrence of 100-year floods. Comparisons of results calculated with WaterGAP 2.1 for today’s climate (1961-90) and for the 2020s and 2070s (ECHAM4 and HadCM3 climate models). Source: Lehner et al., 2001...............................................................33. Climate Change © Kiwa N.V.. -4-. May, 2006.

(8) Figure 23 Mean monthly NH4+ concentration for the year 2050 with Base run, UKHI and HadCM2 scenarios. Source: Mimikou et al., 2000 .....................................................................................36 Figure 24 Modelled change in water discharge, nitrogen concentration, load (A) and Gross load (full bars) of nitrogen from arable land (B) between present climate (control) and the different scenarios of the climate during 2071–2100 using the HBV-N model. Source: Arheimer et al., 2005 ............................................................................................................................................37 Figure 25 General seasonal variation of phytoplankton, cyanobacteria, and total algae in one of the Lake Ringsjön basins (Lake Västra Ringsjön). Present day simulations with BIOLA should be compared with observations and to the modelled impact of each climate change scenario for the period 2071–2100. Source: Arheimer et al., 2005.......................................................................38 Figure 26 Geographical position of Arges catchment .........................................................................40 Figure 27 Relief (left) and water categories (right) in Arges catchment. Source: Batuca and ZlatePodani, 2005 ...............................................................................................................................41 Figure 28 Periodicity of the meteorological and hydrological regime in Romania for the period 18812001. Source: Anonymous, 2003................................................................................................42 Figure 29 Land use categories in Arges catchment. Source: Serban et al., 2004 ...............................43 Figure 30 Monthly discharged volumes (%) for Arges catchment. Source: Munteanu et al., 2001..44 Figure 31 Flood hydrograph for Arges for the July 1975 (left) and October-November (2005) events ....................................................................................................................................................45 Figure 32 Chemical quality of surface water in Arges catchment. Source: Serban et al., 2004 .........47 Figure 33 Distribution of point pollution sources in the Arges River Basin. Source: Batuca and Zlate-Podani, 2005 .....................................................................................................................48 Figure 34 Location of significant point pollution sources in the Arges basin. Source: Batuca and Zlate-Podani, 2005 .....................................................................................................................48 Figure 35 Nitrogen (left) and phosphorus (right) input from fertilizers. Source: Batuca and ZlatePodani, 2005 ...............................................................................................................................49 Figure 36 Annual mean temperature at Bucharest-Filaret station for the period 1901-2000. Source: MEWM, 2005.............................................................................................................................50 Figure 37 Observed and modelled (CCCM) monthly mean temperature (A) and monthly mean precipitation (B) for the current and 2×CO2 climate scenarios averaged over the Romanian territory. Source: Cuculeanu and Balteanu, 2004 ......................................................................52 Figure 38 Simulated mean multiannual monthly discharge (Ql) and mean multiannual discharge (Qma) for 1× CO2 and 2× CO2 scenarios for Arges catchment. Source: Stanescu et al., 1999 ...53 Figure 39 Pilot and reference basins locations. Source: Cuculeanu and Balteanu, 2004...................54 Figure 40 Changes in grain yield (t/ha of dry matter) of (a) rainfed winter wheat and (b) rainfed and irrigated maize with 2 × CO2 scenarios (average of 5 sites) in the Southern region of Romania. Source: Cuculeanu et al., 1999 ...................................................................................................56 Figure 41 Comparison of difference in amount and duration of soil moisture deficit at the normal, dry and wet year in Calarasi station. Source: MEWM, 2005 ....................................................59 Figure 42 Discharge (m3/s) and precipitation (mm) in Arges basin for the period 1999-2005. Note: the scale for discharge at Mioveni is ten times smaller...............................................................60 Figure 43 Mean monthly discharge distribution for the period 1999-2004 in Arges catchment. Note: the scale for discharge at Mioveni is ten times smaller...............................................................61 Figure 44 Annual mean precipitation distribution for the period 1999-2005 in Arges basin............62 Figure 45 Mean monthly precipitation distribution for the period 1999-2004 in Arges catchment..63 Figure 46 Monthly mean water temperature (°C) in Arges for the period 1999-2005 ......................64 Figure 47 Monthly mean air and water temperature (°C) and their relation (right) at Mioveni for the period 1999-2005 ..................................................................................................................64 Figure 48 Daily maximum water temperatures (°C) in Arges catchment for the period 1999-2004.65 Figure 49 Oxygen concentration of Arges for the period 1999-2004 .................................................66 Figure 50 Mean dissolved oxygen content (mg/l) for April-September (above) and October-March (below) in Arges basin for the period1999-2004.........................................................................67. Climate Change © Kiwa N.V.. -5-. May, 2006.

(9) Figure 51 Relation between oxygen content and water temperature at Mioveni for the period 19992004 ............................................................................................................................................67 Figure 52 Ammonium of Arges for the period 1999-2004 .................................................................68 Figure 53 Seasonal NH4 concentration (mg/l) for April-September (above) and October-March (bellow) in Arges catchment for the period 1999-2004...............................................................69 Figure 54 Chloride concentration in Arges for the period 1999-2004................................................69 Figure 55 Seasonal chloride concentration (mg/l) for April-September (above) and October-March (bellow) in Arges catchment for the period 1999-2004...............................................................70. List of tables Table 1 SRES scenarios. Source: IPCC, 2000.....................................................................................14 Table 2 Major agriculture regions in Europe. Note: Regions 1 to 5 are mainly characterised by market-oriented agriculture, which has been heavily influenced by the EU Common Agricultural Policy (CAP) Source: Olesen and Bindi (2002) ....................................................24 Table 3 Hydrological characteristics of Arges at three locations ........................................................44 Table 4 Water resources in the Arges River Basin. Source: Batuca and Zlate-Podani, 2005 ............45 Table 5 Chemical quality of surface water of Arges and Vedea catchment. Source: Serban et al., 2004 ....................................................................................................................................................46 Table 6 Monthly differences in temperature (°C) between 1xCO2 and 2xCO2 scenarios in Romania. Source: Cuculeanu et al., 1999 ...................................................................................................51 Table 7 Monthly rainfall multiplication coefficients precipitation (-) between 1xCO2 and 2xCO2 scenarios in Romania. Source: Cuculeanu et al., 1999 ...............................................................51 Table 8 CERES-wheat site-level results by climate change scenarios with CO2 effect on rainfed winter wheat. Source: Cuculeanu et al., 1999 ............................................................................56 Table 9 CERES-maize site-level results by climate change scenario with CO2 effect on irrigated maize (I) and rainfed maize (R). Source: Cuculeanu et al., 1999 ...............................................57 Table 10 Irrigated maize yield changes due to altered fertilizer levels (kg/ha) in the Southern region of Romania. Source: Cuculeanu et al., 1999 ...............................................................................58 Table 11 Discharge (m3/s) characteristics for Arges in the period 1999-2005 ...................................61 Table 12 Number of days with minimum discharge for Malu Spart and Budesti for the period 19992005 ............................................................................................................................................61 Table 13 Annual mean precipitation (mm) recorded at three locations in Arges basin the period 1999-2005 ...................................................................................................................................62 Table 14 Annual mean air temperature (°C) at Pitesti for the period 1999-2005 ..............................63 Table 15 Mean summer water temperature and monthly maximum temperature (°C) in Arges for 1999-2005 ...................................................................................................................................65. Climate Change © Kiwa N.V.. -6-. May, 2006.

(10) Climate Change © Kiwa N.V.. -7-. May, 2006.

(11) Abstract Climate variations from last century show a global warming trend. Evidence from the past reveals that the anthropogenic greenhouse effect caused changes in climate parameters (temperature, precipitation and evaporation) at the European scale as well. On long-term this might have essential impact on temporal and spatial distribution of water resources. The long-term effects are related to gradual hydrological changes. For example, changes in the frequency of extreme events (floods and droughts) may affect water quantity and quality while changes in land use (as an adaptive measure to climate change) will possibly alter water’s qualitative characteristics. On long-term climate change might be the most serious issue that the world must face. Assessing now the long-term effects is essential in decision making regarding the adaptation measures to future climate changes. The aim of this report is to identify the long-term effects of climate change on Europe’s water resources. This report has two objectives. The first one is to identify the most important climate related factors and trends that lead to changes on the long-term in Europe. The second objective is to study the trends in availability and quality of water resources based on a case study in the Arges catchment, Romania. The identification of the driving factors and trends is based on available literature. For the case study, necessary information and data was obtained from literature and from different authorities and organizations from Romania. The results show that on long-term water resources in Europe are affected by climate change. The impact is temporally and regionally differentiated. Generally, northern Europe becomes warmer and wetter and water availability increases. More affected will be southern Europe where decrease in discharges and increase in temperature lead to a reduction of water availability. Water quality is also affected by climate change through changes in temperature, suspended sediment, nutrients and eutrophication. For Arges catchment, studies at regional scale reveal that on long-term, water resources may be affected by climate change. The mean annual discharge may decrease, causing water shortages, especially in the dry periods. Data analysis for the period 1999-2004 shows that climate has a much lower impact on water quality than other factors (e.g. technological, political, and economical).. Climate Change © Kiwa N.V.. -8-. May, 2006.

(12) Climate Change © Kiwa N.V.. -9-. May, 2006.

(13) 1 Introduction British authorities introduced water restrictions trying to cope with “one of the worst droughts on record” (Adam, 2006). Danube reaches record level in 111 years causing severe floods in the Balkans (Freeman and LeBor, 2006). Two headlines from April 2006 are only examples of issues that appeared in the media in recent times. This shows that in the last years, climate change has become a hot topic not only in the scientific world but also in every day life. The climate has changed continuously in the course of Earth’s history. These changes have a natural origin and their durations vary from only a few years to hundreds of millions of years. Examples are: changes in the composition of Earth’s atmosphere (CO2), in topography, volcanic activity, internal variability of the atmosphere-ocean system (Harvey, 2000). Humanity introduced a second kind of changes by altering the atmospheric concentration of greenhouse gases (GHGs). One of the most important effects of GHGs emission is the global warming. If in the beginning years of research related to climate change the main question was whether global warming occurs, later the focus shifted to investigate what is the dimension of the changes. Because climate has a direct effect on the hydrological cycle, changes in climate will also bring changes in the hydrological cycle and hence the freshwater resources. Figure 1 illustrates the paths by which water resources are affected by climate change. Water resources are affected through spatial and temporal changes of the driving factors. Spatial effects refer to different response that regions can have on changes. From temporal point of view, there are: short- and long-term effects. The short-term effects are related to the immediate effect of floods or drought. The long-term effects are related to gradual hydrological changes. For example, changes in the frequency of extreme events (floods and droughts) may affect water quantity while changes in land use (as an adaptive measure to climate change) will possibly alter water’s qualitative characteristics. On long-term climate change might be the most serious issue that the world must face (Watkiss et al., 2005). Assessing now the long-term effects is essential in decision making regarding the adaptation measures to future climate changes (Sophocleus, 2004). The aim of this report is to identify the long-term effects of climate change on Europe’s surface water resources. This report has two objectives: • to identify the most important climate related factors leading to changes on water availability and quality on the long-term in Europe. • to study the effects of drought on water availability and quality in the Arges catchment, Romania. The pressure on water resources is also influenced by other factors than the climate ones. These are the so-called SEPTED factors (Socio-cultural, economical, political, technological, ecological, and demographical) and they will be also considered in the report.. Climate Change © Kiwa N.V.. - 10 -. May, 2006.

(14) The identification of the driving factors is based on available literature. For the case study, necessary information and data was obtained from literature and from different authorities and organizations from Romania. A list with institutions and persons contacted for this research is given in Appendix D. This report consists of six chapters, including this introduction. Chapter 2 gives an introduction of climate change in Europe in which topics like greenhouse effect and climate models are shortly described. Projected trends of climate parameters (temperature, precipitation and evapotranspiration) and glaciers are also discussed. Chapter 3 describes the effects of climate change on soil moisture and agriculture. Climate change effects on water quality and quantity are given in chapter 4. Chapter 5 contains the case study. The Arges catchment, the water resources and the effects of climate change in the area are described followed by a water quality analysis. Finally, in the last chapter conclusions are drawn and recommendations are given.. ENHANCED GHG EFFECT. 1. Increase in air temperature 2. Atmospheric and oceanic dynamics. Change in rainfall and evaporation Change in sea level. Change in land use (agriculture). Glaciers and snowpack. Change in aquatic ecosystem. Change in terrestrial ecosystem. dynamics Change in water quality. Change in water quantity Figure 1 Impacts of climate change on water quality and quantity. Note: feedback relations to the climate are not included. Climate Change © Kiwa N.V.. - 11 -. May, 2006.

(15) 2 Climate change in Europe 2.1. Greenhouse effect and GHG Climate change due to greenhouse effect is the subject of many studies from the last decennia. According to Kundzewicz and Somlyody (1997) the next certain thing, next to existence of greenhouse effect is the ever-increasing man-induced emission of carbon dioxide and other greenhouse gases (GHG). Some authors (de Freitas, 2002; Kuznetsov, 2005) dispute the trend of increasing CO2 but it is generally accepted by many others as a general global (IPCC, 2001) and continental trend (EEA, 2004). The source of energy that drives the climate system is the Sun. Figure 2 is an illustration of the average Earth’s energy budget. The greenhouse gases are those gases from the Earth’s atmosphere responsible for the absorption of the infrared radiation leaving the surface of the Earth. The “greenhouse effect” refers to the trapping of the outgoing infrared radiation by the greenhouse gases and re-emitting part of that energy back to the earth’s surface. As a result, the Earth’s surface is warming with great effects on the energy balance. In order to restore the balance, the evapotranspiration and precipitation are increased (Miller and Yates, 2005).. Figure 2 Global mean energy flows between the surface and atmosphere. Source: Harvey, 2000. The main greenhouse gases (natural and anthropogenic) are water vapour, carbon dioxide (CO2), methane (CH4) (from agriculture), nitrous oxide (N2O) and industrial halogenated gases: chlorofluorocarbon (CFCs) and hydrochlorofluorocarbon (HCFCs). EEA (2004) reports that the total rise in all greenhouse gases since the pre-industrial era amounts to 170 ppm CO2- equivalent with contributions of 61% from CO2, 19% from methane, 13% from CFC’s and HCFC’s, and 6% from nitrous oxide. Carbon dioxide (CO2) is the most. Climate Change © Kiwa N.V.. - 12 -. May, 2006.

(16) important greenhouse gas and due to human activities, its atmospheric concentration is increasing (Harvey, 2000). Compared with preindustrial levels, the concentration CO2 has increased by 34%, with an accelerated rise since 1950. If no measures are implemented, by 2100 a further increase to 650 -1 215 ppm CO2- equivalent is projected. The warming of the climate due to the increase of greenhouse gases affects the hydrological cycle and thus water resources. Figure 1 gives a schematic view of the impact of the greenhouse effect on the hydrological cycle without the feedback relation to climate. It can be noticed that the greenhouse effect has a direct and indirect impact on the availability and quality of water resources. Water resources are affected through changes in spatial and temporal patterns of precipitation, temperature and evaporation. As a result, it is likely that alteration in the volume and the timing of river flows and groundwater recharge will occur and this will eventually affect the number and distribution of people affected by water scarcity (Arnell, 2004). Another characteristic of the hydrological cycle is the relation between its parameters that are strongly dependent on each other, which makes assessing climate change effects on water resources a very difficult task.. 2.2. Climate models Climate change will affect availability, temporal and spatial distribution of water resources, as well as the frequency of extreme events. In many studies the difficulty to assess the longterm impact of climate change was shown (Arnell, 1998). GCMs, Global Circulation Models (Kundzewicz and Somlyody, 1997; Varis et al., 2004) or General Circulation Models (Frederick and Major, 1977; Sumner et al., 2003) or Global Climate Models (Ragab and Prudhomme, 2002; Rosenzweigh et al., 2004) are used to generate projections of future climate change. Because the GCMs are not the object of this study, only a brief description will be given. For a detailed illustration of the GCMs and their development, the work of Varis et al. (2004) is recommended. The climate change projections are made for a large spatial and temporal scale. However, for a regional scale study of climate change the GCMs output results are not realistic due to the low resolution. In order to fill the gap between different spatial and temporal scales the regional climate models (RCM) were created (Houghton, 2004; Imbert and Benestad, 2005). The regionalization was done by downscaling methods in which the resulting regional information is based on the data generated by the GCMs (Varis et al., 2004). The physical basis of RCMs is the same as GCMs only the spatial resolution is much finer. At present, a GCM may have a spatial grid with cells of about 200 km-200 km, while the RCMs have achieved resolutions of approximately 20 km-20 km (Loáiciga, 2003). The RCMs rely on the coarser output from GCMs, which they use as initial and boundary conditions to drive their spatially refined simulations of climate change. While these RCMs are beginning to bring more confidence to regional projection of climate change (Houghton, 2004) the output from different models is not always consistent with each other (Varis et al., 2004; Imbert and Benestad, 2005). This is due to the uncertainty aspect of the GCMs, which is one of the fundamental problems in climate change prediction models. The uncertainties regard topics like atmospheric feedbacks, water vapour, ocean processes, termohaline circulation, vegetation photosynthesis and water use and snow. These issues are improving but more work is still to be done.. Climate Change © Kiwa N.V.. - 13 -. May, 2006.

(17) A recent tendency in the development of the GCMs is towards an integrated approach of water resources assessment. The reason behind this is that prediction of the effect of climate change on water resources depends not only on the assumed emission scenarios and the used climate model but also on the assumed rate of population change (Arnell, 2004) and e.g. land use, economic developments which result in changes in water demand. Therefore, next to climate change, the SEPTED dynamics are also considered (Houghton, 2004; Varis et al., 2004). The IPCCs Special Report on Emissions Scenarios (SRES) (2000) contains a series of “storylines” grouped in four scenario families (Table 1) that illustrate how the population, economics, political structure and lifestyles may evolve over few decades (Arnell, 2004). Table 1 SRES scenarios. Source: IPCC, 2000 Scenario Description A1 World Market. A2 Regional Enterprise. B1 Global Sustainability. B2 Local Stewardship. The A1 storyline and scenario family describes a future world of very rapid economic growth, low population growth, and rapid introduction of new and more efficient technologies. Major underlying themes are convergence among regions, capacity building, and increased cultural and social interactions, with a substantial reduction in regional differences in per capita income. The A1 storyline family develops into four groups that describe alternative directions of technological change in the energy system. The A2 storyline and scenario family describes a very heterogeneous world. The underlying theme is self-reliance and preservation of local identities. Fertility patterns across regions converge very slowly, which results in high population growth. Economic development is primarily regionally oriented and per capita economic growth and technological changes are more fragmented and slower than in other storylines. The B1 storyline and scenario family describes a convergent world with the same low population growth as in the A1 storyline, but with rapid changes in economic structures toward a service and information economy, with reductions in material intensity, and the introduction of clean and resourceefficient technologies. The emphasis is on global solutions to economic, social, and environmental sustainability, including improved equity, but without additional climate initiatives. The B2 storyline and scenario family describes a world in which the emphasis is on local solutions to economic, social, and environmental sustainability. It is a world with moderate population growth, intermediate levels of economic development, and less rapid and more diverse technological change than in the B1 and A1 storylines. While the scenario is also oriented toward environmental protection and social equity, it focuses on local and regional levels”.. Figure 3 shows the CO2 and temperature changes by 2100 modelled with the four SRES scenarios. Remarkable are the results for the scenarios for which a decline CO2 is modelled, the rising trend in temperature continues and will reach a stabilized level by 2100. The reason behind this is that climate has a slow reaction to changes. This also means that the mitigation measures considered in present time are not sufficient to prevent temperature increase.. Climate Change © Kiwa N.V.. - 14 -. May, 2006.

(18) Figure 3 Global emissions and changes in average temperature associated with each SRES emission scenario. Source: Arnell, 2004. 2.3. Trends in temperature In recent years, many studies concerning the effects of temperature dynamics on availability of water resources were published. Generally accepted (IPCC, 2001), the global warming trend is also considered to be valid at the continental, European scale (EEA, 2004). In the last 100 years, the global average temperature has increased by 0.7 ± 0.2°C (EEA, 2004). At the European scale, the temperature has increased since 1900 by 0.95 °C, which is much above the average global increase. An exception from the warming trend is Fennoscandia (Finland, Sweden and Norway), where between 1910-1995 warming in mean temperature during summer was recorded, but cooling in winter (IPCC, 2001). The IPCC Report (2001) established that the annual temperature over Europe increases at a rate of between 0.1 and 0.4°C per decade. Without any policy measures this rate could increase the temperature in the year 2100 by 2.0-6.3°C (EEA, 2004). Figure 4 illustrates the reconstructed and measured relative temperature over the last 1 000 years and projected temperature rise in the next 100 years in the northern hemisphere. The warming trend is unevenly distributed over the region and seasons. Figure 5 shows summer temperature simulations in Europe for the year 2080. In the future, the warming of the climate is greatest over southern Europe (Spain, Italy) and Balkan and least along the coastline, in the north and the -west (IPCC, 2001). The temperature increases more during the winter, especially in the continental interior of eastern Europe and western Russia while for the summer the warming rate displays a south –to-north gradient (Figure 5) (Harvey, 2000; IPCC, 2001; EEA, 2004) and during the night (IPCC, 2001).. Climate Change © Kiwa N.V.. - 15 -. May, 2006.

(19) Figure 4 Reconstructed and measured relative temperature over the last 1 000 years (northern hemisphere) and projected temperature rise in the next 100 years. Source: EEA, 2004. Figure 5 Projected changes in summer mean temperature (oC) for HadCM3 and PCM, with A2 scenario for 2080. Source: Accelerates, 2004. A consequence of this warming trend is that hot summers (i.e. the highest temperature occurring 1-in-10 years during 1961-1990) will became more frequent. According to IPCC (2001) by 2080 at many parts of Europe nearly every summer might be hotter than the 10% hottest summer as defined under the present climate. Evidence of this trend in Europe is the situation recorded in the last years. The 1990s were the warmest decade in the observational records, with 1998 the warmest year, followed by 2002 and 2003. Figure 6 illustrates the annual temperature deviations in 2003 when many parts of Europe were hit by a heat wave. The summer of 2003 may be seen as “shape of things to come” (Beniston, 2004).. Climate Change © Kiwa N.V.. - 16 -. May, 2006.

(20) Figure 6 Annual temperature deviations in Europe in 2003. Note: temperature deviations, relative to average temperature from 1961-1990 (°C). Source: EEA, 2004. In contrast with the hot summers, in the European areas where winters classified in the present as being cold (lowest temperature occurring 1-in-10 years during 1961-1990), might become rare by 2020 and almost entirely disappear by 2080 (IPCC, 2001).. 2.4. Trends in precipitation and evaporation Temperature, evaporation and precipitation are important climatic parameters. In the same time as the global and regional temperature are rising, evaporation of water from land and water surfaces will increase as well. On average, more evaporation will result in more precipitation. However, regional precipitation patterns will continue to be very complex and variable (Gleick et al., 2001) given that the changes in the evaporation depend on many factors (humidity, wind patterns, net radiation, available soil moisture, etc.) (Gleick et al., 2000). At global scale, precipitation increased on average with 2% between 1900 and 2000 (EEA, 2004). For Europe the increase is much larger and shows significant regional (Figure 7) and seasonal differences (Figure 8). The results illustrated are obtained from trend analysis of data measured for a period of 100 years, between 1900 and 2000. Figure 7 shows a contrasting trend in annual precipitation between northern (wetter) and southern (drier) Europe. It is estimated that the annual precipitation has increased by 10% over northern Europe, whereas parts of southern Europe experienced a 20% decrease.. Climate Change © Kiwa N.V.. - 17 -. May, 2006.

(21) Figure 7 Annual precipitation changes (%) in Europe for the period 1900-2000. Note: black circles denote wetting and white circles denote drying; magnitude of trend is related to circle size; shaded trends are significant at 90%. Source: IPCC, 2001. Seasonally, the changes in precipitation show a clearer trend than the annual changes. In the winter, some regions of southern (Italy, Greece) and central Europe became drier, while many parts of northwestern Europe became wetter. A winter increase also occurred on the Atlantic and Mediterranean coasts of Spain and France and northern regions around Black Sea. Summer precipitation shows a decrease especially in central and eastern Europe, and central Scandinavian countries (IPCC, 2001). For regions around the Mediterranean coast (southern Spain and Italy) generally an increase in precipitation is recorded. The same situation happens in northern Turkey as well.. Figure 8 Trends in winter (DJF) (top) and summer (JJA) (bottom) precipitation changes (%) in Europe for the period 1900-2000. Note: black circles denote wetting and white circles denote drying; magnitude of trend is related to circle size; shaded trends are significant at 90%. Source: IPCC, 2001. Climate Change © Kiwa N.V.. - 18 -. May, 2006.

(22) Although several projections of future precipitation trends have been modelled (Accelerates, 2004, Parry, 2000) and the scientific confidence in the ability of climate models to estimate future precipitation has increased, a significant degree of uncertainty still exists. Future precipitation trends show more annual precipitation for northern Europe and a decreasing trend in the southern area. In winter, most of Europe is likely to become wetter (with exception of Balkans and Turkey). In summer there is a contrast between the northern region that becomes wetter, whereas southern Europe becomes drier (Figure 9). Remarkable is that for some areas in Spain a decrease in precipitation is predicted while the measured data show a wetter trend. This difference can be caused by the uncertainties and the scale of used models.. Figure 9 Projected changes in summer precipitation (mm/month) for 2080 for HadCM3 and PCM, with A2 scenario. Source: Accelerates, 2004. A special attention is accorded to the extreme rainfall events (rainstorms), which occurred in the last years more frequently. The trend in precipitation extremes is, in many regions (including parts of Russia), more pronounced than the trend in average precipitation (EEA, 2004). Figure 10 gives the changes in the frequency of very wet days (defined as days with precipitation above 20 mm). Since 1976 the number of wet days rises in central and northern Europe and decreases in the southern part.. Figure 10 Change in frequency of very wet days in Europe between 1976 and 1999. Source: EEA, 2004. Climate Change © Kiwa N.V.. - 19 -. May, 2006.

(23) 2.5. Trends in glaciers and snowpack Since the mountains are an important source of fresh water, changes in the mountain hydrology will have a great impact not only on the mountains themselves but also in the lowland regions that depend on the mountain water resources. It is generally accepted that one of the largest changes in the hydrological regime are predicted for the glaciers and snow dominated basins (Arnell, 1998; Nijssen et al., 2001; Beniston, 2003). The characteristics of the glaciers (e.g. volume and surface of ice in a glacier, the thickness and length) are determined by the balance between the inputs (accumulation of snow and ice) and outputs (melting). Because this balance is mainly controlled by the climate, the mountain glaciers are used as valuable indicators for climate change (IPCC, 2001; Beniston, 2003). The changes in temperature and precipitation pattern will affect indirectly water resources by changing the water storage in ice packs. Hence the importance of water storage which is generally thought of as water runoff being delayed by the glacier system (Jansson et al., 2003). The precipitation in the form of snow is stored in the winter and released by melting in summer. Changes in the mountain glaciers and snowpack are already reported in the literature (IPCC, 2001, Beniston, 2003). EEA (2004) reports that eight out of nine European glaciers are in retreat and that annual snow cover in the northern hemisphere had decreased by 10% in the last 35 years. Figure 11 illustrates the length and thickness changes of Aletsch glacier in the Swiss Alps.. Figure 11 Aletsch (Switzerland) historical length change: 1856 and 2001. Source: Haeberli and Hoelzle, 2003. Climatic change causes a shift in the seasonal snowpack. The changes in temperature dominate the effect of snow precipitation in the mass balance (Schneeberger et al., 2003). Because the snowpack in the temperate regions is close to melting point it has a rapid response to even minor changes in temperature (Beniston, 2003).. Climate Change © Kiwa N.V.. - 20 -. May, 2006.

(24) The future projections are not very positive. Schneeberger et al. (2003) studied 17 glaciers of the northern hemisphere and equatorial regions from which five situated in Europe. The results from GCM’s simulations show that all modelled glaciers suffer a substantial retreat within the coming 50 years in the enhanced greenhouse scenario. The projected warming and the reduction of snowfall lead to a strong reduction in mass balance and thus a significant volume loss. The mass loss is larger for small glaciers in lower regions, compared to the larger, heavily glaciated areas in the Arctic. The lower regions in Europe correspond with the Alpine mountains. According to Maisch and Haeberli (2003) it is likely that by 2035, one half –and, by 2050, as much as three quarters- of the present day glaciers in Switzerland will have disappeared. This will have a great impact on major Europe’s rivers that have their sources from the Alps (e.g. Danube, Rhine, Rhone, and Po).. Climate Change © Kiwa N.V.. - 21 -. May, 2006.

(25) 3 Climate change effects on terrestrial ecosystems 3.1. Effects on soil moisture Climate change leads to changes in the physical, biological and chemical soil properties and the outcome of changes towards a warmer and drier climate would be a deterioration of soil properties (Harvey, 2000; IPCC, 2001, Ragab and Prudhomme, 2002; EEA, 2004). The long-term interaction between climate change and soil degradation could have a major impact on availability and quality of water resources through the effect on the rate of actual evaporation, groundwater recharge and runoff generation (IPCC, 2001). Changing the proportion of soil organic matter (Olesen and Bindi, 2002), mineral constituents and soil structure will decrease the water holding capacity of the soil (Tao et al., 2005) and the infiltration capacity (IPCC, 2001; O’Neal et al., 2005) therefore changing one of the most important characteristics of the soil, the soil moisture content (Harvey, 2000). The soil moisture content has an influence on the rate of actual evaporation, groundwater recharge and runoff generation (IPCC, 2001) (Figure 1). The climate and the soil have a closely interrelated relationship. According to Mosier (1998), soil processes contribute by about 30% of NOx, 70% of N2O, 20% of NH3 and 30% of annual global CH4 emissions to the atmosphere. In the other way, soil captures around 10% of the CO2 produced annually from fossil fuel combustion. Increase in soil biological activity due to temperature increase may result in increase in the atmospheric CO2 forcing further climate change. In a recent study about the interactions between climate change and soil degradation with effects on the water resources in China, Tao et al. (2005) affirms that this bidirectional relationship is believed to be the main cause for occurrence of more frequent droughts and floods. Changes in the soil properties are regionally differentiated (Harvey, 2000; Tao et al., 2005) following the changes in temperature and precipitation (IPCC, 2001), parameters that are highly model-dependent (Wang, 2005). At European scale deterioration of soil properties is expected to appear especially in the southern area (IPCC, 2001; Manabe et al., 2004). Simulating the annual mean soil moisture with a coupled ocean–atmosphere–land model in which CO2 is continuously increasing, results show that many semiarid regions of the world will experience a decrease in annual mean soil moisture already at the middle of 21st century. For the European Mediterranean coast, simulated soil moisture is reduced by a substantial fraction during the summer. The reduction in soil moisture content in the semiarid regions is explained by Manabe et al. (2004) by the fact that in long run, soil moisture in semiarid region seeks a level at which evaporation is equal to precipitation. Over the regions of relatively small precipitation (semiarid areas), the annual precipitation is reduced or fails to increase in contrast with the annual rate of potential evaporation that increases everywhere over continents as result of the CO2-induced increase in the downward flux of the infrared radiation. This is why soil moisture is reduced in semiarid regions of the world, thereby restoring the balance between precipitation and evaporation.. Climate Change © Kiwa N.V.. - 22 -. May, 2006.

(26) The same study shows that for middle and high latitudes, over very extensive regions of the Eurasian and North American continents, the sign of soil moisture change often reverses completely between summer and winter. In winter, soil moisture content increases due to increase in precipitation over the continents while the surface temperature is very low and thus the rate of evaporation hardly increases accompanying the global trend. In summer, the temperature will enhance evaporation and reduce the precipitation and therefore the soil moisture is reduced over extensive regions from the middle to high latitudes in the Northern Hemisphere. Special attention is accorded to the relation between the timing of snowmelt and reduction of the summer soil moisture content. Because of global warming, the snowmelt season ends earlier, lowering the albedo1 and soil surface will absorb more solar radiation. Therefore, evaporation from the soil surface is increased, and the spring-to summer reduction of soil moisture begins earlier contributing to the reduction of soil moisture in summer. Another consequence of soil structure alteration is changing in flow paths, which affects the transport of chemical load to the river (Arnell, 1998) by modifying the amount of time water remains within the soil profile (Callow and Petts, 1994). The predicted increase in temperature will lead eventually to an increase in the soils temperature and soils water temperature. Higher soil temperature leads to increase of the microbial reaction rates (Mosier, 1998) which results in increase in organic matter yields (Olesen and Bindi, 2002; O’Neal et al., 2005). Prediction of the magnitude of this increase is highly speculative due to the complexity between the soil-atmosphere exchange of CO2, CH4 and N2O, however it is likely that the highest effects occur during winter time leading to buildup of inorganic nitrogen in the soil and increasing the risk of nitrate leaching (Olesen and Bindi, 2002).. 3.2. Effects on agriculture Land use in Europe is categorised into urban areas, forestry and agriculture (Niehoff et al., 2002). The focus will be set on agriculture. The land use can be changed by natural, economic or political conditions. Considering long-term processes, almost everywhere land use changes can be observed, e.g. increase in urbanization, forest diseases, changes in agricultural use, etc. Such changes have significant influence on hydrological conditions (Schultz, 2000). In a study of the literature dealing with the relationship between land-use change and climate change, Dale (1997) mentions that humanity will change land-use to adjust to climate change and these adaptations will have some ecological effects. In the past, these effects proved to have much greater effects on ecological variables than has climate change. In the present, the trends in European agriculture are dominated by the CAP2 (Common Agricultural Policy) (IPCC, 2001; Olesen and Bindi, 2002).. 1albedo. is a measure of reflectivity of a surface or body. It is the ratio of electromagnetic radiation reflected to the amount incident upon it (earth has an average of 39% and fresh snow up to 90%). 2CAP is a system of European Union agricultural subsidies. These subsidies work by guaranteeing a minimum price to producers and by direct payment of a subsidy for crops planted. This provides some economic certainty for EU farmers and production of a certain quantity of agricultural goods.. Climate Change © Kiwa N.V.. - 23 -. May, 2006.

(27) In the future is anticipated that, next to climate change, the trends in land use will be controlled, by the reforms of CAP, enlargement of European Union, globalisation and technological change (Accelerates, 2004). Considering environmental and socio-economic factors, Olesen and Bindi (2002) divide the agriculture in Europe in eight major regions (Figure 12). A description of the major agricultural regions is given in Table 2.. Figure 12 Major agricultural regions of Europe. Source: Olesen and Bindi, 2002. Note: 1. Nordic; 2. British Isles; 3. Western; 4. Mediterranean; 5. Alpine; 6. North eastern; 7. South eastern; 8. Eastern Table 2 Major agriculture regions in Europe. Note: Regions 1 to 5 are mainly characterised by marketoriented agriculture, which has been heavily influenced by the EU Common Agricultural Policy (CAP) Source: Olesen and Bindi (2002) Region. Description of agriculture. 1. Nordic. Agriculture limited by climatic and soil conditions and only a small percentage of the land is cultivated Agriculture is dominated by the wet conditions along large parts the Atlantic coasts, and grasslands dominate this area.. 2. British Isles 3. Western. More intensive arable and livestock farming, small-scale, mixed or large-scale intensive farming systems.. 4. Mediterranean. Drier and warmer Mediterranean climate leads to a diverse pattern of agriculture. Predominant is a market-oriented type of agriculture with mainly crop cultivation, including fruit trees, olive and grapes. Alternatively, considerable areas of the traditional small-scale type of agriculture still occur. Agriculture is characterized by both market-oriented and transitional forms from extensive mixed farms to market-oriented farming. Traditional, market-oriented and socialized agriculture types are present. The socialized type has declined since the late 1980s and a new type of agriculture that resembles western Europe occurs. Root crops and cereals are important in this region but due to low production intensity, yields are low. This region is the European part of the former USSR, which used to be dominated by large-scale socialized agriculture, but now is slowly adapting to a more quality-oriented agriculture.. 5. Alpine 6. North eastern 7. South eastern. 8. Eastern. Climate Change © Kiwa N.V.. - 24 -. May, 2006.

(28) The impact of climate change on agriculture is the subject of many studies. The focus is set on the general agricultural productivity (Olesen and Bindi, 2002) or on specific crops, e.g. crop land and grassland (Rounsevell et al., 2005), winter wheat (Eitzinger et al., 2003; Eckersten et al., 2001). Additionally, some of the studies take in consideration the influence of the socio-economic factors (Fischer et al., 2005; Vörösmarty, 2002; Bouma et al., 1998). The scale of the studies vary from global (Adams et al., 1998) to continental (Maracchi et al., 2005) and regional scale (Richter and Semenov, 2005; Rosenzweigh et al., 2004). The response of landscape to climate change may be a long time and regionally variable process (Dale, 1997; Bouma et al., 1998), depending on the type of crop, magnitude and direction of temperature and precipitation change and the nature of the CO2 fertilization effect (Adams et al., 1998). The projected climate change may have direct (e.g. response to CO2) and indirect impact (effects of changes in temperature and precipitation) on agroecosystems (Olesen and Bindi, 2002), with positive and negative consequences (Fischer et al., 2005). Increase in CO2 enhances plant production by raising the net photosynthetic activity. Figure 13 illustrates the observed response of grain yield in wheat to variation in CO2 concentration. Data from 12 whole-season studies with different CO2 concentrations, under different experimental conditions show a mean yield increase of 28% for a doubling of current CO2 concentrations (Olesen and Bindi, 2002). Eckersten et al. (2001) predicted for central and southern Sweden for the year 2050 an increase in winter wheat production by 10-20% compared with the values at the time of the research.. Figure 13 Wheat yields with increasing CO2 concentration. Source: Olesen and Bindi, 2002. The potential beneficial effect of increased CO2 may be counteracted by the risk of water shortage in southern and eastern Europe (IPCC, 2001), and by limitation brought by several factors (e.g. nutrients, temperature, precipitation) (Easterling and Apps, 2005). Increase in temperature can enhance plant productivity and decrease the risk of damage by freezing. However, under dry and warm conditions, it can lead to water stress, and consequentially to decline in yield (EEA, 2004) and quality of many crops (cereals and feed grains) (Adams et al., 1998). According to Easterling and Apps (2005), 2-3 °C of warming in the midlatitudes may be tolerated by crops, especially if accompanied by increasing precipitation.. Climate Change © Kiwa N.V.. - 25 -. May, 2006.

(29) Depending on the regional condition and trend, precipitation can have negative or positive effects (EEA, 2004). Changes in precipitation are more crucial to agriculture and forestry, especially at low latitudes where activities are rainfed (Salinger, 2005), changing the crops which are suitable for an area and increasing the need for irrigation (Dale, 1997). Semi-arid and other water short areas may benefit from an increase in precipitation, but this increase could aggravate problems in regions with excess water (Adams et al., 1998). On long term, climatic changes will shift crop suitability in agricultural regions (Schröter et al., 2005). A trend towards northern (IPCC, 2001; Accelerates, 2004; EEA, 2004), central Europe (Olesen and Bindi, 2002) and higher latitudes (Fischer et al., 2005) is foreseen in many studies. According to Fischer et al. (2005), for the developed nations, the expansion of the potential land suitable for crop cultivation will increase in northern Europe with 16% over current 45 million hectares. EEA, (2004) estimates for Finland a northern expansion of the agricultural area by 100-150 km per 1°C temperature rise. Figure 14 illustrates the expansion of suitability for grain maize, sunflower and soya, projected for 2050s. These crops are likely to move to the north or to higher altitude areas in the south. The northern shift of agriculture may lead to abandonment in southern regions. This can cause an improvement of water quality in the region because no more nutrients are added. Even though the production areas may shift in a northerly direction, the effects of climate change on agricultural production for Europe appear rather favourable (Bouma. et al., 1998). Climate change may also change the crop types, frequencies and intensities of various crop rates (Adams et al., 1998), nutrient cycling by changing litter decomposition rate and plant nutrient uptake (Dale, 1997). In an impact study of climate change on agricultural crops, Cuculeanu et al. (1999) show that, in southern Romania, winter wheat will benefit while irrigated maize will have negative response to climatic changes. In the future, in order to maximize the yield production, this might lead to crop substitution.. Figure 14 Suitability for grain maize, sunflower and soya in 2050s. Note: green / yellow / purple: baseline 1961-1990; red / brown / blue: suitability extension. Source: Parry, 2005. Extreme weather (droughts, floods) may induce a higher risk of bad harvest. Drought periods may increase water demand (EEA, 2004) affecting the availability and timing of irrigation water supplies. Decrease in water availability is exacerbated by an increase in water demand if the region becomes drier and warmer (Döll, 2002). In the present, high percentage irrigated land has southern Europe and the Mediterranean area (Figure 15) where the agriculture consumes about 80% of water (EUWI, 2005) (e.g. 80% for Greece, 60%. Climate Change © Kiwa N.V.. - 26 -. May, 2006.

(30) in Spain and around 50% in Italy and Portugal) while the average figure in northern Europe is under 10% (EEA, 1999). In the regions where climate warming may cause an increase in rainfall and temperatures, an increased infestation of disease pathogens and parasites may occur (Fischer et al., 2005; Schijven and de Roda Husman, 2005). This will lead to increased use of pesticides and fertilisers (Olesen and Bindi, 2002; Accelerates, 2004; Rosenzweig et al., 2001; Rosenzweig et al., 2005) which will affect the water quality in a negative way. It is more likely that in the future, the water resources in southern Europe and Mediterranean area will be the most affected. If the water resources are under pressure, contamination and depletion of surface and groundwater will take place causing soil degradation, salinization, and desertification.. Figure 15 Percentage of total irrigated land. Source: UNEP/DEWA, 2004. Climate Change © Kiwa N.V.. - 27 -. May, 2006.

(31) 4 Climate change effects on water resources 4.1. Effects on surface water quantity In the last decennia, many studies regarding the impact of climate change on water resources availability were accomplished. These studies show a high sensitivity of hydrological systems to climate change. Many of the studies have concentrated on streamflow and hydrological regimes (Arnell, 1999; Arnell, 2004) or on the glaciers (Beniston, 2003) as an indirect indicator for water availability. The annual river discharge is used in many studies as climate change indicator because it represents the response of a hydrological basin to changes in temperature and precipitations (EEA, 2004). In the past few decades river discharge has changed, due to changes in precipitation. The changes differ per region, with an increase in north, northeastern Europe and a decrease in the river discharge in south. The difference is due to the combined effect of spatial and temporal changes identified for temperature and precipitation at European scale, which are generally reflected in the distribution of the flow discharges (see chapter 2).. 4.1.1. Hydrological drought The European area around the Mediterranean is recognised as one of the world’s regions where climate change has the greatest adverse impact on water resources (Ragab and Prudhomme, 2002; Arnell, 2004; Hitz and Smith, 2004; Rosenzweig et al., 2004; VicenteSerrano et al., 2004). This is the result of the combined effect of increasing temperatures and precipitation decrease. This combined effect will give higher evapotranspiration rates and result in periods with low river discharges (hydrological droughts). Occurred drought periods were reported in many studies in the area (Alexandrov et al., 2005; Dakova, 2005). The average annual runoff will decrease by 2070 with 50 % in southern and southeastern Europe, and increase by up to 50 % or more in most parts of northern and northeastern Europe (EEA, 2004). The highest decrease in discharge will occur during the summer, especially in June (Mimikou et al., 2000). According to Dakova (2005), in the Balkan peninsula, due to the drought, second order tributaries will be dry towards 2050- 2100 with great impact in the area. These results are similar with the findings of Lehner et al. (2001) (Figure 16, Figure 17). The influence of climate on low flows is not only induced via changes in the spatial distribution of precipitation amounts, but also via temporal changes in the precipitation pattern, or, where snow storage plays a role, via spatial and temporal changes in temperature and evapotranspiration. Figure 16 illustrates the change in annual average river discharge for European river basins in the 2020s and 2070s compared with 2000 modelled with two different climate models: ECHAM4 and HadCM3. In both cases climate models show regional differences in their projections. For example, for 2020s while ECHAM4 simulates a decrease in discharge for Spain, HadCM3 projects an increase for the same region. By 2070 the situation in the same region is also different between the models (see south-eastern mediterranean coast).. Climate Change © Kiwa N.V.. - 28 -. May, 2006.

(32) Climate models show large differences in their projections of precipitation and thus the uncertainty of projected river discharge is also high which may explain the differences in discharge projections.. Figure 16 Percentage change in average annual water availability (natural discharge without substraction of consumptive water use) for European river basins as compared to today’s levels, realized with two different GCMs (ECHAM4 and HadCM3) for 2020s and 2070s. Source: Lehner et al., 2001. Figure 17 presents the changes in low flow characteristics due to climate or global change calculated for today’s climate (1961-1990) and for the 2070s (applying climate scenario results of the General Circulation Model (GCM) HadCM3 (Lehner et al., 2001). The regional pattern shows two characteristic types of low flow regimes: • Typical summer droughts, ranging from June to November (orange/red to green/purple colours) occur in all maritime areas (Iberian Peninsula, western France, Great Britain, Mediterranean countries), reaching as far as central Europe (Germany, Czech Republic, western Poland). The discharge is minimum at the end of summer, induced either by long dry spells without any precipitation (maritime countries) or by prolonged periods with high evapotranspiration (continental countries). • Typical winter droughts, ranging from January to April (dark blue to yellow colours) occur in the northern and some east-central European countries, as well as the Alpine region. Here, precipitation is accumulated throughout the winter months as snow cover and the soils are frozen, hence baseflow falls to minimum values at the end of this period.. Climate Change © Kiwa N.V.. - 29 -. May, 2006.

(33) Figure 17 Month with minimum average discharge. Comparison of results for today’s climate (19611990) and for 2070s (HadCM3). Source: Lehner et al., 2001. Lehner et al. (2001) also modelled the drought frequencies for the 2020s and 2070s with ECHAM4 and HadCM3 (Figure 18). Both climate models agree in their estimates of more pronounced changes for the 2070s, where a 100-year drought of today’s magnitude would return more frequently than every 10 years in parts of Spain and Portugal, western France, the Wisla basin in Poland, and western Turkey. Both models give different regional results. ECHAM4 gives contradictory results between 2020s and 2070s in regions like southern Italy, Balkan, southern Russia wile HadCM3 projects different situation for Scandinavia, Bulgaria. Overall, for the 2070s Scandinavia, the Baltic’s, northern Belarus and Russia, most of Germany and the Alpine region generally tend towards a reducing risk of drought while in Great Britain, Italy, Greece, the Balkan region and large areas in East-Central Europe the risk is higher.. Figure 18 Change in occurrence of 100-year droughts. Comparisons of results calculated for today’s climate and water use (1961-1990) and for the 2020s and 2070s (ECHAM4 and HadCM3 climate models and Baseline-A water use scenario). Source: Lehner et al., 2001. Climate Change © Kiwa N.V.. - 30 -. May, 2006.

(34) The increase or decrease of drought frequency depends on the projected temperature, precipitation and evapotranspiration in the area. In some northern areas, although an increase in precipitation is predicted, no change or increase in river discharge was predicted (Strzepek & Yates, 1997; Arnell, 1999; Smith and Lazo, 2001). The contradictory tendencies in water availability for northern Europe are also pointed out by Lehner et al. (2001). Warmer temperatures tend to increase evapotranspiration and hence to reduce water availability. However, the increase in evaporation might be offset by increase in precipitation to compensate for this, so there is a net large increase in annual water availability. It is reported that regionally, some water shortages can occur. This is the case for the drier parts of Sweden, which by 2030 may know a water shortage situation (Bergström et al., 2001; Andréasson et al., 2004). Climate data of the 2070s give a higher increase in availability over much of north-eastern Europe than the northernmost areas (Figure 16) (Lehner et al., 2001). Many other studies show the sensitivity of hydrological systems to precipitation (Dvorak et al. 1997; Frederick and Major, 1997; Ragab and Prudhomme, 2002). Dvorak et al. (1997) show that for four river basins in Czech Republic, changes in climatological parameters could affect different sites with varying magnitude.. 4.1.2. Floods Increase in rainfall and intensity events lead to the occurrence of flooding. Intensive rainfall events from 2002 and 2005 caused extreme flooding in central and eastern Europe (EEA, 2003, Kundzewicz et al., 2005). Figure 19 shows that the number of flood events in Europe has risen substantially in the last century. However, there are studies that do not show an upward trend in the occurrence of extreme floods in central Europe (Mudelsee et al., 2003).. Figure 19 Number of flood events in Europe. Source: EEA, 2004. It is likely that in the future extreme precipitation will be more frequent, especially in winter (IPCC, 2001) and more intense but the uncertainty in the projections is high (EEA, 2004). In general, for Europe, the timing of the flood risk tends to shift from snowmelt in spring to summer, autumn or even wintertime (Bergström et al., 2001).. Climate Change © Kiwa N.V.. - 31 -. May, 2006.

(35) Figure 20 shows that for most of Europe the maximum monthly discharges occur from January to June and from south-west to the north-east. This reflects, besides the general climatic pattern with winter rains in the maritime areas (Iberian Peninsula, western France, Great Britain, and Mediterranean countries), the rising influence of snowmelt in the continental and northern areas with snow accumulation in winter and melting periods from March until June. In the 2070s, the maximum average discharge occurs about one month earlier than today in northern and parts of central Europe (Rhone, Rhine, Danube, and Po). This can be explained by a general rise in temperature in the climate model for these areas, which induces an earlier snowmelt.. Figure 20 Month with maximum average discharge. Comparison of results calculated for today’s climate (1961-1990) and for the 2070s (HadCM3 climate model). Source: Lehner et al., 2001. 4.1.3. Snowpack dynamics Snow melt influences the rates and the timing of river discharges originating from mountains. With temperature increasing, the precipitation in form of rain is predominant and the snowfall is decreasing. The accumulation of the snow is delayed and the onset of the snow melt is advanced as winter temperatures are warm (Nijssen et al., 2001). This has an effect on the duration and the amount of the snowpack and consequently on the water availability for hydrological basins (Beniston, 2003; Barnett et al., 2005). Because of this cumulative process, the snowpack integrates the effects of climate change over a period of months, and the largest hydrological changes are manifested in the early mid spring period. Consequently, the streamflow regime in snowmelt-dominated basins is most sensitive to increase in temperature during the winter months (Nijssen et al., 2001). The reduction of snowfall causes higher streamflows during the winter months. In Finland, climate change is responsible for the decrease in the snow cover and increase in winter runoff (Bouraoui et al., 2004). However, a reduction of the spring peak flow exists as a result of shallower snowpack. A shift from a combined rainfall-snowmelt regime to a more rainfall dominated regime is also expected for the river Rhine (Middelkoop et al., 2001). Figure 21 shows the hypothetical effects of temperature increase in basins with substantial snowfall and snowmelt increase (Gleick et al., 2001): average winter runoff and average peak runoff increase and peak runoff occurs earlier in the year. The third effect is the occurrence of low discharge in summer and autumn.. Climate Change © Kiwa N.V.. - 32 -. May, 2006.

(36) Figure 21 Hypothetical natural and modified average hydrograph for basins with snowfall and snowmelt. Source: Gleick et al., 2001. The climate change scenarios generally imply a change in flood frequencies for almost all regions of Europe (Lehner et al., 2001). Figure 22 illustrates the flood occurrence frequencies for the 2020s and 2070s. The predictions with HadCM3 give contradictory results between the two time periods for eastern Spain, Alps, Greece whereas the results with ECHAM4 seem to be more monotonic in time (with only few exceptions like central Italy). Central and southern Europe show a decreasing trend in future flood frequencies. The region most vulnerable to a rise in river flood frequencies is north-eastern Europe (i.e. Sweden, Finland and Russia), were today’s 100-year floods is projected to return every 10 years. Furthermore some smaller regions like the Wisla basin in Poland, the Irish Island or Portugal show indications for a rise in flood risk. For some regions like Italy or Greece, the two climate scenarios lead to contradictory results, allowing for no conclusions but rather reflecting the uncertainties of the model calculations.. Figure 22 Change in occurrence of 100-year floods. Comparisons of results calculated with WaterGAP 2.1 for today’s climate (1961-90) and for the 2020s and 2070s (ECHAM4 and HadCM3 climate models). Source: Lehner et al., 2001. Climate Change © Kiwa N.V.. - 33 -. May, 2006.