3. Impacts of climate change on water availability

Key messages

 

  • Climate change is expected to aggravate the existing pressures on the freshwater resources in Europe, the most so in southern Europe which already faces severe water stress, but also in parts of western and central Europe.

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  • Northern and north-eastern Europe and mountainous areas all across Europe will be affected by reduced snow cover and early snow melting.

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  • More frequent and intense droughts are already striking extended areas across Europe. Climate change will increase weather extremes, such as droughts and floods, and will trigger more frequent seasonal floods and low flows within the same year.

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3.1.        Freshwater availability in Europe

The renewable freshwater resources in the European environment per European citizen([1]) amount to 4 560 m3 per year (averaged for the period 1990-2017). However, this freshwater availability is highly variable and unevenly distributed in both space and time (Figure 3.1). For example, in 2017, the renewable freshwater resources per inhabitant ranged between 120 m3 per year in Malta to 70 000 m3 per year in Norway. At smaller spatial scales, e.g. when comparing a highly urbanized area with its surrounding rural region, even more variation occurs.

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The spatial and temporal variation of freshwater resources is affected by numerous factors, such as global and regional climate circulation, hydrometeorology and local weather patterns, topography, land cover and use, and hydrogeology. Thus, low water availability can be a local issue, which is not compensated by high water availability in another part of the same country or region. Similarly, low water availability can be a temporary issue, which is not compensated by high water availability in another month or season of the year (e.g. a dry summer with a wet winter). National and regional aggregates of freshwater availability should therefore be dealt with caution, as they may obscure the local or seasonal realities, which are encountered by European citizens.

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Freshwater availability alone is not an indication of high or low water stress, as the concept of water stress compares the water consumption by all socio-economic activities with the renewable freshwater resources over a specified area and period. Thus, the spatial distribution of population and socio-economic activities, and the time of their water demand must be factored in as well to identify a lack of capacity to meet the local and temporal needs for water.

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Figure 3.1            Development of water availability per capita (m3/capita – 2000-2017)

 

Source: (EEA, 2020j, 2019l; Eurostat, 2020f)

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Between 1990 and 2017, the available water per inhabitant decreased in southern, western and northern Europe. An increase was observed in eastern Europe. These changes were largely driven by trends in population rather than climate change. For example: in western Europe, the annual renewable freshwater resources increased by 4 % while the regional population increased by 11 %. In eastern Europe there was an increase in renewable freshwater resources, but there was also a reduction (-6 %) in the regional population (EEA, 2018b).

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Freshwater availability is expected to decrease further in some parts of the continent, such as the Iberian Peninsula, due to decreasing precipitation and increasing temperature and evapotranspiration (EEA, 2019g, 2017e, 2016h). The situation will be aggravated by random drought events, which are becoming more frequent and intense in the context of climate change(EEA, 2019g). In other parts of the continent, such as northern Europe, freshwater availability is expected to increase. This is due to projected increases in precipitation, including heavy precipitation that creates problems with excess water (e.g. floods). However, even these areas are projected to face higher temperatures and evapotranspiration, less snow, and more frequent and intense droughts than at present (Section 3.2).

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3.2.        Key meteorological impacts of climate change

3.2.1.        Temperature

Past trends in temperature

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The mean average annual global near-surface temperature is increasing since the mid-19th century. Compared to pre-industrial levels (1850-1900), the global temperature has increased almost 1 °C. This increase has accelerated since the 1970s; it is estimated that the temperature increases 0.1 °C every 5 to 6 years. To prevent serious environmental, economic and societal impacts of climate change, all signatories to the United Nations Framework Convention on Climate Change (UN, 1992) committed in the 2015 Paris Agreement to limiting global temperature increase to well below 2 °C above pre-industrial levels by 2050 and to pursuing efforts to limit the increase to 1.5 °C (UN, 2015a).  The observed warming up so far already amounts to half of the maximum 2 °C increase that would be compatible with the Paris Agreement(EEA, 2020c).

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In Europe, the decade 2009-2018 was the warmest ever recorded, with the mean annual land surface air temperature being 1.6 to 1.7 °C higher than the pre-industrial levels. Since 2000, Europe has been struck by a sequence of extreme heatwaves (2003, 2006, 2007, 2010, 2014, 2015, 2017 and 2018) (EEA, 2020c), and it has recorded 11 of the 12 warmest years on record (Figure 3.2). The warmest year ever recorded in Europe was 2019, followed by 2014, 2015 and 2018 (ECMWF, 2019a). Almost the whole European territory is getting warmer; exceptions only cover a few small areas. The largest annual temperature increases are observed in central and eastern Europe. Warming is observed across all seasons, with changes being more pronounced in autumn (ECMWF, 2019a). The number of significantly warm days has doubled between 1960 and 2018 (EEA, 2020c). Water temperatures have also increased in European rivers and lakes. In major European rivers such as the Danube, Rhine and Meuse, water temperatures have increased by 1 to 3 °C over the last century.

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Figure 3.2            Historic trends in annual and summer land surface air temperature anomalies across Europe between 1979 and 2019 (compared to the annual average for the 1981-2010 baseline period)

 

   

Source: (ECMWF, 2019a)

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Future projections for temperature

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Climate change projections comparing the historic period 1971–2000 with the future period 2071-2100 (under high-emission RCP scenario 8.5), suggest that the climate could become warmer by 2.5 °C to 5.5 °C, which is above the agreed UNFCCC threshold of 2 °C for the whole planet (Map 3.1). Extreme heatwaves are expected to occur much more frequently in the second half of the 21st century (e.g. once every two years) (Russo et al., 2015). In summers, the strongest warming is projected to occur in the Iberian peninsula and other parts of southern Europe. In winter, warming will affect the most north-eastern Europe and Scandinavia (EEA, 2020c).

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Map 3.1               Future projections for annual, summer and winter land surface air temperature across Europe up to 2071-2100 (versus 1971–2000 average)

Source: (EEA, 2020c)

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Projections show that the water in the oceans, rivers and lakes will also continue to warm in the future (EEA, 2020c, 2016i).

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3.2.2.        Precipitation

For the period 1960–2015 (EEA, 2017e), in parts of northern Europe, annual precipitation has increased by up to 7 mm and summer precipitation by up to 1.8 mm. By contrast, in southern Europe, annual precipitation has decreased by up to 9 mm and summer precipitation by up to 2 mm. In mid-latitudes of Europe, the precipitation shows no significant changes on an annual scale, but significant decreases can be observed in the summer season in parts of central and eastern Europe. This applies especially to the Danube river basin district shared by Slovakia, Hungary, Poland and Romania (Map 3.2).

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The precipitation patterns are changing significantly within the year. Between 1960 and 2018, heavy precipitation in winter and summer has generally become more frequent and intense across Europe, especially in northern and north-eastern areas. A decrease is observed in heavy precipitation in the Iberian peninsula and southern France in winter and summer, and in the eastern coast of the Adriatic in summers  (EEA, 2016e).

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Map 3.2               Historic trends in annual and summer precipitation across Europe between 1960-2015

Source: Source: (EEA, 2017e)

Note: Boxes outlined in black indicate areas with at least three stations, so they are more likely to be representative; Areas with significant long-term trends are indicated by black dots.

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Future projections for precipitation

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Climate change projections (under high-emission RCP scenario 8.5), comparing the historic period 1971–2000 with the future period 2071-2100, suggest that (EEA, 2017e; Feyen et al., 2020) mean annual precipitation will decrease by 10-30 % in many parts of southern Europe and by more than 30 % in the south-eastern and south-western Mediterranean. Furthermore, a stronger decrease is expected in the summer season, as summer precipitation is expected to decrease by 20-40 % in an extended area that covers southern and western Europe, the Balkans and the Black Sea. In contrast, an annual increase by 10-30 % is expected in many parts of central, eastern and northern Europe. Especially in the Baltic and Scandinavian countries, significant increases of up to 30 % are also expected in the summer season (Map 3.3).

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Map 3.3               Future projections for annual and summer precipitation across Europe up to 2071-2100 (versus 1971–2000 average)

Source: (EEA, 2017e)

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Heavy precipitation is expected to become more frequent and intense in the future almost everywhere in Europe in winter, with significant increases of up to 35 % in Scandinavia, north-eastern and eastern Europe, due to more frequent extreme extratropical cyclones. Heavy precipitation in summer will remain similar or slightly increase in most parts of Europe. Exception are many coastal areas of southern European countries, as well as the Pyrenees and part of the Alps, where significant decreases are expected. The projected decrease in cyclone frequency in the Mediterranean contributes partly to the phenomena described above (EEA, 2016e).

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Glaciers and snow

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Snow accumulates over the colder period of the year and melts slowly in spring. Melted snow and glaciers flow as surface or groundwater discharges into streams and rivers with a lag time of many months after the initial time of snowfall. The snow cover thus affects significantly the timing of hydrological processes in a river basin. In general, snow cover is more common in areas of central and northern Europe and in mountain areas across the continent.

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In western, northern and eastern Europe climate change has resulted in a shortening of the snow season of up to 25 days. In south-eastern Europe however, the snow season has expanded by up to 15 days, because the snow season starts earlier nowadays. Furthermore, the extent of the snow cover has decreased significantly in the northern hemisphere in the past 90 years, with the greatest part of this decline occurring since the 1980s. Overall, it is estimated that the extent of the snow cover in Europe (EEA 38+UK) has decreased by 13 % for the average March and April and by 76 % for the average June between 1980 and 2015. The equivalent mass of snow in melted water has also decreased in Europe (EEA 38+UK) over the same period by around 30 %, which is above the average observed reduction in the northern hemisphere, around 7 % (EEA, 2016h).

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In recent decades, early snow melt is also observed in the Alps, which are considered the “water tower” of Europe (Box 3.1). Large European rivers, such as the Danube, the Rhine and the Po spring from the Alps. Thus, their flow regimes are affected by the changing patterns of snow fall and melting of glaciers and accumulated snow.

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Future projections in snow cover

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Future climate projections (under high-emission RCP scenario 8.5) indicate that the duration of the snow season in the northern hemisphere could further decline up to 40 days, the March/April snow cover could be reduced up to 25 %, and the respective snow mass could decrease up to 30 % (EEA, 2016h).

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Box 3.1 Glaciers and snow cover are shrinking in the Alps since the 19th century

Sources: (Petita et al., 2017; Elmi et al., 2018; FOEN, 2020a, 2020b, 2020d, 2020c)

 

The Alpine region, which covers approximately 190 700 km2, extends over eight European countries (Austria, France, Germany, Italy, Liechtenstein, Monaco, Slovenia and Switzerland) and it is inhabited by more than 14 million people. The average temperature in the area has risen by almost 2 oC since the 19th century, which is twice as fast as the average rate of temperature rise in the northern hemisphere. Furthermore, future climate change projections show that the average temperature will increase further by 1-2o C in most parts of the region by 2050, which may result in significant impacts.

The extent of the glacier surface in the Alps now is less than 50 %  of what it was in the mid-19th century, and it is projected to decrease further to 30 % or even 10 %, if the temperature increases by another 1 oC and 3 oC respectively (Figure 3.3, left). Furthermore, the Swiss scientists and authorities have observed that the cumulative mass of eight Alpine glaciers shows a decreasing trend which has been accelerated in recent decades (Figure 3.3, right). This is related to the increase of the temperature, which causes larger and earlier melting within the year. And it is also related to the change of the precipitation patterns, which results in an increase of the share of the precipitation falling as rain rather than snow. In the last 50 years, the snowpack in Switzerland has shown decreasing trends across all elevation zones from below 1000 m to over 2500 m.

Figure 3.3              Remaining glacier surface in the Alps (left); annual cumulative glacier mass balance in Switzerland (right)

Source: :(Petita et al., 2017)                                                                   Source: (FOEN, 2020b)

 

The flow patterns of the rivers are impacted in various ways. For example, higher rainfall in winters causes higher winter discharges, increasing the risk of floods. Furthermore, the lower extent and mass of glaciers and snow decreases the storage of equivalent water, which could melt and recharge rivers, especially during the spring months. Higher temperatures are also causing higher evapotranspiration. Thus, summer discharges tend to become lower on average. As drought events are also occurring more frequently, especially in southern and south-eastern Alps, it is expected that climate change will cause further decrease in the observed low river discharges annually. River flow observations in the Swiss part of the Rhône (Porte-du-Scex) since the start of the 20th century show an amplification of seasonal patterns with increased discharges in winter and decreased discharges in summer.

 

The Alpine landscape constitutes a very diverse ecosystem, where 30 000 animal species and 13 000 plant species can be found. As the climate becomes warmer, those species that flourish in colder conditions need to migrate. Therefore, shrinking glaciers and snow cover limit the extent of the suitable habitats for traditional alpine species. It is projected that 30-50 % of the alpine plant species will lose over 80 % of their suitable habitats, resulting in chain effects upon the animal species also.

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3.2.3.        Evapotranspiration

Evapotranspiration is closely related to the type of the land cover and the applied climate conditions (e.g. temperature, wind, humidity, solar radiation) over a specified area. The analysis of the underlying E-OBS data used for the European water accounts (EEA, 2019l; Zal et al., 2017; EEA, 2018b) shows that evapotranspiration is increasing across all regions of Europe for the period 1990-2017. Proportionately, the most significant increases were observed in northern, eastern and western Europe (between 9 and 27 %), whereas the increase was lower (4 %) in already water-stressed southern Europe. These trends show that transpiration from vegetation and evaporation from soil and water surfaces in Europe has increased significantly in the past decades. The increase of evapotranspiration is mainly attributed to the increase of the transpiration from vegetation, which can be further linked with the expansion of agricultural land since the 1980s and the observed increase in the land temperature across Europe (Zhang et al., 2016).

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Future projections for evapotranspiration

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Driven by the projected increase in temperature,  evapotranspiration in Europe will increase further in the future. However, the potential increase could be partly offset by reduced transpiration from vegetation due to higher atmospheric concentrations of CO2 (EEA, 2016b). Most of the projected increase of evapotranspiration will occur during spring and summer, especially in southern Europe and southwestern France. In addition, it could also occur in areas of central Europe (e.g. Switzerland, Germany, the Netherlands) during summers. Increased evapotranspiration could also be observed in northern Scandinavia (Feyen et al., 2020).

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Map 3.5                Evapotranspiration projections: Seasonal change (seasons S1, S2, S3, S4; clockwise) for a 3oC temperature scenario

 

Source: underlying data obtained from (Feyen et al., 2020)

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3.2.4.        Droughts

In southern Europe and in most parts of central Europe droughts have become more frequent, with up to 1.3 additional droughts per decade, for the period 1950-2015 (Map 3.6). Furthermore, droughts have intensified roughly over the same areas, as the minimum discharges during the driest month of the year have decreased by between 5 and 20 %. In contrast, droughts have become less frequent and less intense in areas of Scandinavia and north-eastern Europe (EEA, 2019g).

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Map 3.6                Historic trends in the frequency of meteorological droughts in Europe (1950-2015)

 

Source: (EEA, 2019g)

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Future projections for droughts

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Climate change projections (under high-emission RCP scenario 8.5), comparing the historic period 1981–2010 with the future period 2041-2070, suggest that the frequency of meteorological droughts will increase in most parts of Europe, with the exception of several areas in central-eastern and north-eastern Europe (Map 3.7). Southern Europe is projected to be the hotspot of more frequent and intense droughts in the future. On a seasonal basis, intense droughts will be more likely than today in summer, and then in spring and autumn, whereas intense droughts will become less likely in winter (EEA, 2019g).

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Map 3.7               Future projections for the frequency of meteorological droughts across Europe up to 2041-2070 (versus 1981–2010 average)

Source:(EEA, 2019g)

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3.3.        Impacts of climate change on the hydrological cycle

3.3.1.        Soil moisture

The average annual soil moisture content shows a downward trend between 1979 and 2019, with this trend being more pronounced after 1990 and the last decade being the worst of the last 40 years (Map 3.8).

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Map 3.8                Soil moisture trend (2000-2019) and projected changes in soil moisture in the period 2021-2050 compared to 1981-2010

 

   

 Source: (EEA, 2017f)

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In 2019, the average soil moisture in most parts of Europe was below the average of 1981-2010, with significantly low soil moisture being observed in central Europe during summer and in southeastern Europe during autumn (Figure 3.4) (ECMWF, 2019b).

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Figure 3.4            Annual soil moisture anomalies in Europe between 1979 and 2019

 

Source: (ECMWF, 2019b)

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Future projections for soil moisture content

Future projections of the soil moisture content, comparing the period 2021-2050 with the period 1981-2010, indicate a decrease of the soil moisture content in certain areas of southern Europe (e.g. the Iberian peninsula), especially during summer, and increase in central-eastern and north-eastern Europe (EEA, 2017f, 2019b).

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3.3.2.        Groundwater

In principle, deep groundwater is less affected by seasonal variations in precipitation and temperature and more protected from pollution, compared to the surface waters. The chemical composition of the soil and its granularity may slow down the percolation of water and the leaching of pollutants. Because of this lag time, as well as because of compaction after draw-down, the recharge of depleted aquifers or the treatment of contaminated groundwater can be slow. Therefore, maintaining groundwater in good status is critically important.

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Groundwater is often seen as cheap buffer resource, which can be used to supply high quality water for economic purposes. Water authorities then may turn to groundwater when the local surface waters are not suitable for use or at times of water stress due to drought events. This puts additional pressures to groundwater. The reporting under the WFD shows that 8 % of the groundwater bodies across Europe are in poor condition (EEA, 2018c).

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Future projections for groundwater levels

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In those areas where climate change is projected to cause lower precipitation and increased temperatures and evapotranspiration (see previous sections), it is expected that groundwater recharge will generally decrease. Decreases in groundwater recharge, are expected in southern and western Europe, whereas increases are expected in parts of eastern and north-eastern Europe (Map 3.9)(Feyen et al., 2020).

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Map 3.9               Percental change in projected annual groundwater recharge for a 3 oC temperature scenario.

Source: underlying data obtained from (Feyen et al., 2020).

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Furthermore, climate change is expected to cause a rise in the average sea level. This will affect coastal aquifers, and especially those which are being exploited intensively, when saltwater from the sea intrudes into the coastal aquifers and causes salinisation. This can make the groundwater unsuitable for use. In the above climate context, coastal aquifers are expected to become more vulnerable to saline intrusions.

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Box 3-2 Climate change will lower groundwater levels in the Loire and southwestern France

Sources: (Maréchal and Rouillard, 2020; Delgoulet, 2015)

The Explore 2070 project has developed and assessed strategies to adapt to climate change impacts on hydrological systems and coastal environments in mainland and overseas France up to 2070, based on different climatic, demographic and socio-economic scenarios. Rises in temperature (and consequently evapotranspiration) combined with decreasing rainfall, will lead to a decrease of effective precipitation in the future. The application of seven climate models using the median Green House Gas (GHG) emission scenario (A1B, fourth GIEC report) enabled an estimate of the change in natural recharge rates. With predicted recharge variations of +10 to −30% in the optimistic scenarios, and −20 to −55% in the pessimistic scenarios, a decline of similar proportions in groundwater levels would be expected, and therefore groundwater resources are likely to decline significantly overall by 2070. Two areas which are likely to be more severely affected are the Loire basin with a 25–30% recharge decline across half of the basin area, and the south-west of France with a 30–50% decline in recharge. All of the scenarios also show a decline in average river flow by 2065, which varies from a 10 to 40% reduction in the northern half of the country, and a 30–50% reduction in the southern half, with local extremes of up to 70%. Despite this relative decline in river flow, some models show that very high surface water levels are nevertheless possible during the winter in some catchments (e.g. the Somme and Rhine Rivers), confirming the likelihood of lengthy periods of flooding.

 

Furthermore, water balance studies have shown that many catchments and aquifers present high structural water deficits, impacting environmental flows, leading to the imposition of abstraction caps on water users, in particular agricultural irrigation. In addition, over the last twelve years, more than 50% of the French departments concerned by restriction orders of use - watering, filling swimming pools, cleaning vehicles, etc. - in 2003, 2005, 2006 and 2011. The recurrence of these episodes of water stress has made it necessary to reinforce the security of the supply of drinking water services.

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3.3.3.        River discharges

In southern, western and parts of eastern Europe, the summer discharges in the years 1951-2015 show a decreasing trend. The trend is most pronounced in areas of Spain, Portugal, Italy, Greece, Turkey and France (Map 3.10) (EEA, 2016g).

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Map 3.10 Historic trends in runoff during the driest month of the year in Europe (1951-2015).

 

Source: (EEA, 2020h)

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After a decade of very warm and dry years, 2019 was also a particularly dry year. As a result, the river discharges across Europe fell below average for almost two thirds of the year (i.e. during spring, and throughout July-October). The most extreme low river discharges were observed in central Europe. However, in November and December a rapid turnaround to high river discharges appeared in western Europe, causing a high number of flood events (ECMWF, 2019b).

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Future projections for river discharges

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Climate change is shifting the seasonal patterns of river discharges across Europe and enhancing the occurrence of seasonal extremes (Figure 3.5). Future summer discharges are projected to further decrease in southern Europe and parts of western and northern Europe whereas increase in parts of eastern and north-eastern Europe during all seasons (Map 3.11) (Feyen et al., 2020). In addition, spring and summer peak discharges will generally occur earlier in the season, as a result of proportionately more rainfall instead of snowfall during winter and earlier melting of the snow cover and glaciers (EEA, 2016g).

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Map 3.11             River discharge projections: Seasonal change (seasons S1, S2, S3, S4; clockwise) for a 3 oC temperature scenario

Source: underlying data obtained from (Feyen et al., 2020)

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Figure 3.5            Projected change in seasonal streamflow for twelve rivers

Source: (EEA, 2016g)

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3.4.        Impacts of climate change on habitats and species

 

The latest State of Nature report in Europe (EEA, 2020g, 2020f) shows that 5.4 % of the habitats and 4.6 % of species are currently affected by climate change as a pressure. Furthermore, from all cases related to climate change, almost half are associated with droughts and decreases in precipitation. The highest pressures from decreases in precipitation are observed in habitats, such as bogs, mires and fens. Coastal habitats, and especially those in the Atlantic and the Boreal region, are mostly challenged by sea level rise and wave exposure. In addition, the most affected species are the amphibians, which are very sensitive to shifts of both temperature and precipitation. Other species that are also affected include molluscs, specific mammals, as well as birds associated with reedbeds and reedy ponds.

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As climate change is increasing temperature and changing the precipitation patterns, it is expected that the risks for biodiversity will increase. The loss of current habitats, the creation of favourable conditions for alien species to the European ecosystems and the amplification of the issues with invasive species are predicted to cause additional pressures for biodiversity in the future.

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It is estimated that the average area in Europe affected by severe droughts is around 121 000 km2 for all years between 2000 and 2016 (Figure 3.6). However, this area was actually highly variable, depending on the annual climatic conditions; e.g. ranging between 50 000 and 350 000 km2 each year over the same period. The most affected land use types included forests, scrubs and/or herbaceous vegetation associations, heterogeneous agricultural areas, arable land and permanent crops. Moreover, the most affected geographical areas were the Iberian peninsula and south-western France, measured both in terms of extent of areas under water deficit and in terms of vegetation growth decline. A large part of central Europe and the Balkans (e.g. Bulgaria, Hungary, Romania and Slovenia) were also affected by water deficits that caused decline in the vegetation growth (EEA, 2020i).

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Figure 3.6            Area of vegetation productivity decrease due to water deficit, 2000-2016

Source: (EEA, 2020i)

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[1] Calculated as the ratio of the total volume of renewable freshwater resources and the total population in EEA 38+UK

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