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Fresh water resources

Fresh water resources in numbers - Greece

Dozens of drought stricken Greek islands in the Aegean are being forced to import greater amounts of water every year (5). Faced with a water shortage crisis on its hands, the Greek government is currently trying to tackle the problem by importing millions of cubic metres of water to the islands of Milos, Nisyros, Amorgos, Koufonisia, Shinoussa, Folegandros, Tinos, Sikinos, Thirasis, Donoussa, Patmos, Symi, Halki and Palionissos (5).

According to local governors, the problem is not just that there is not enough rainfall to fill up the dams and rivers for irrigation but that the area also suffers from a 70% reduction in the replenishment of the aquifer, and this has had a catastrophic effect on agriculture (5).

According to local governors the Greek islands are not receiving the imported water the government has promised in the height of the tourist season. They also mention that dozens of islands in the eastern Aegean have been promised desalination plants to solve the problem, but until now the government has failed to deliver (5).


The current annual water balance of Crete breaks down to 68–76% evapotranspiration, 14–17% infiltration and 10–15% runoff. Total water use in 2000 amounted to approximately 5.5% of the precipitation of a normal year and 16% of the total water potential. An average of 65% of the total water use is supplied by groundwater exploitation while the remaining 35% is obtained from winter spring and stream discharges. Of this, 16% is used for domestic, tourist, and industrial uses, 3% for livestock and a vast 81% for irrigated agriculture on less than 30% of the total cultivated land, using mainly ground water in drip irrigation methods. Irrigation and tourism create a marked seasonal pattern in water demand with heavy summer loads (37).

Vulnerabilities Greece - Current situation

The Vocha plain, bounded by the Korinthiakos Gulf in southern Greece, has experienced a 65% increase in population since the 1970s and continued growth is predicted over the coming years (18). During the summer the population increases by 25% due to an influx of tourists and weekend visits by inhabitants of nearby Athens. Agriculture accounts for approximately 80% of the region's water demand. Groundwater abstraction now exceeds recharge and the aquifer system is overexploited.

Water balance estimates for the Vocha plain for 2000–2001, for example, estimate a deficit of 15 million m3/year, reflecting a 38% exceedance of the renewable freshwater resource. As a result, the water level has declined significantly in wells and boreholes, driving a progressive deepening of those still operating. In addition, seasonal seawater now intrudes into the aquifer (19).

Unfortunately, water demand in the Greater Athens region has continued to grow at an excessive rate, currently reaching 6% per year. This expansion has been driven by a growth of the urban region and the movement of people from city apartment blocks to houses with gardens on the fringes of the region (20). Should this growth in demand continue, within a few years the available resource will not be sufficient to meet requirements (21).

Vulnerabilities Greece - Future projection

The likely effects of climate change on the water resources of the eastern Mediterranean and Middle East region have been investigated using a high-resolution regional climate model (PRECIS) by comparing precipitation simulations of 2040–2069 and 2070–2099 with 1961–1990 (29). The projected change in internal water resources is assumed to be the same as the projected change in precipitation. Greece is expected to have an 18% precipitation decrease by midcentury, and 22% by the end of the century. With modest population decline expected, Greece’s per capita water resources are expected to decline somewhat by midcentury but still remain high compared to the majority of surrounding countries. Thus, climate change is likely to necessitate modest changes to Greece’s water resources management.

The cumulative costs of climate change for drinking water supply has been estimated for the decades 2041‐2050 and 2091‐2100, based on three SRES scenarios A1B, A2 and B2. The estimated costs for 2041‐2050 are 0.89% (Α1Β) to 1.32% (Α2) of GDP. The estimated costs for 2091‐2100 are 0.51% (A1B) to 1.84% (A2) of GDP (27).


Data analysis for the period 1970–2100 reveals an overall decreasing precipitation trend for Crete which, combined with a temperature rise, leads to substantial reduction of water availability (28). Today’s extreme events will intensify, i.e., precipitation on average is likely to be less frequent but more intense and droughts are likely to become more frequent and severe. Shorter rainy periods could seriously affect the water resources by significant reduction of water availability with wide ranging consequences for local societies and ecosystems. The quantitative impact of these changes on water availability can be substantial at watershed level, especially in a Mediterranean island like Crete.

The rapid development of Crete since 1980 has exerted strong pressures on many natural resources. Due to urbanization and the growth of agriculture and tourism industry, water demand has substantially increased by over 55% during the period 1985 - 2000 (36). However, any arising water stress issue will be due to poor extraction or retention technology rather than actual availability (37).

The impact of climate change on the water resources status for the island of Crete has been assessed for a range of 24 different scenarios from a combination of projected hydro-climatological regimes, demand and supply potentials. These scenarios were based on three Global Climate Models and an ensemble of Regional Climate Models under IPCC emission scenarios B1, A2 and A1B. Overall, a robust signal of water insufficiency is projected for all the combinations of emission, demand and infrastructure scenarios, with the estimated deficit ranging from 10% to 74% (37).

Abstraction non-renewable groundwater reserves

‘‘Non-renewable groundwater’’ denotes groundwater gained by abstraction in excess of recharge. The amount of non-renewable groundwater abstraction that contributes to gross irrigation water demand has been calculated for a large number of countries, allowing for a global overview. The results of this study show that non-renewable groundwater abstraction globally contributes nearly 20%, or 234 km3 annually, to the gross irrigation water demand (for the reference year 2000) and has more than tripled in size since the year 1960. From 1960 to 2000 an increased dependency was shown of irrigation on non-sustainable groundwater with time. Thus, irrigation is more and more sustained by an unsustainable water source (26).

Country assessments reveal that non-renewable or non-sustainable groundwater supplies large shares of current irrigation water, particularly for semi-arid regions where surface freshwater and rainfall are very scarce: Pakistan, Iran, Saudi Arabia, Libya, UAE and Qatar. Much of current irrigation in these regions is sustained by non-sustainable groundwater (26).

For Europe, the contribution (%) of non-renewable groundwater abstraction to gross irrigation water demand was calculated for Italy (15%), Spain (7%), Turkey (7%) and Greece (2%) (26). Projected increases in irrigation demand in southern Europe will serve to stress limited groundwater resources further (32).

Substantial reduc­tions in potential groundwater recharge are projected for the 21st century in southern Europe (Spain and northern Italy) whereas increases are consist­ently projected in northern Europe (Denmark, southern England, northern France) (30). Along the southern rim of the Mediterranean Sea decreases in potential groundwater recharge of more than 70% by the 2050s have been simulated using output from two climate models (ECHAM4, HadCM3) under two emissions scenarios (A2, B2) (31).

Fresh water resources in numbers - Mediterranean basin

The Mediterranean basin is 3,800 km long and 400 to 740 km wide. It takes 90 years for the water in this sea to be completely renewed. Hence, it is especially susceptibility to pollution. The population is between 150 and 250 million depending on whether just the actual coastal strip is taken into account or the drainage basin of the Mediterranean (4).

Fresh water resources in numbers - Europe

By 2005 for Europe as a whole (including New Member States and Accession Countries) some 38% of the abstracted water was used for agricultural purposes, while domestic uses, industry and energy production account for 18%, 11%, and 33%, respectively (2). However, large differences exist across the continent.

In Malta, Cyprus and Turkey, for example, almost 80% of the abstracted water is used for agriculture, and in the southwestern countries (Portugal, Spain, France, Italy, Greece) still about 46% of the abstracted water is used for this purpose. In the central and northern countries (Austria, Belgium, Denmark, Germany, Ireland, Luxembourg, Netherlands, UK, and Scandinavia), to the contrary, agricultural use of the abstracted water is limited to less than 5%, while more than 50% of the abstracted water goes into energy production (a non-consumptive use) (2).

Southern countries use ca. three times more water per unit of irrigated land than other parts of Europe. The large amount of water dedicated to irrigation in the southern countries is problematic since most of these countries have been classified as water stressed, and face problems associated with groundwater over-abstraction such as aquifer depletion and salt water intrusion (3).

The total renewable freshwater resource of a country is the total volume of river run-off and groundwater recharge generated annually by precipitation within the country, plus the total volume of actual flow of rivers coming from neighbouring countries. This resource is supplemented by water stored in lakes, reservoirs, icecaps and fossil groundwater. Dividing the total renewable freshwater resource by the number of inhabitants leads to water availability per capita. Thirteen countries have less than 5,000 m3/capita/year while Nordic countries generally have the highest water resources per capita. The Mediterranean islands of Malta and Cyprus and the densely populated European countries (Germany, Poland, Spain and England and Wales) have the lowest water availability per capita. The water availability is an annual data which therefore does not reflect at all seasonal variations (24).

Vulnerabilities - Europe

Water availability in the Mediterranean is highly sensitive to changes in climate conditions. In the last century the Mediterranean basin has experienced up to 20% reduction in precipitation (2). Such a trend is expected to worsen with increasing demand for water and reduction in rainfall in the region (1,6). Future projection of this trend will reduce drastically water supplies in these areas, affecting considerably the population and economy of the Mediterranean countries (7).

In southeastern Europe annual rainfall and river discharge have already begun to decrease in the past few decades (8).

Water stress will increase over central and southern Europe. The percentage area under high water stress is likely to increase from 19% today to 35% by the 2070s, and the additional number of people affected by the 2070s is expected to be between 16 million and 44 millions. The most affected regions are southern Europe and some parts of central and eastern Europe, where summer flows may be reduced by up to 80%. The hydropower potential of Europe is expected to decline on average by 6% but by 20 to 50% around the Mediterranean by the 2070s (9).

Annual average runoff in southern Europe (south of 47°N) decreases by 0 to 23% up to the 2020s and by 6 to 36% up to the 2070s, for the SRES A2 and B2 scenarios and climate scenarios from two different climate models (9). Summer low flow may decrease by up to 80% in some rivers in southern Europe (10,11). Other studies (1) indicate a decrease in annual average runoff of 20–30% by the 2050s and of 40–50% by the 2075s in southeastern Europe.

Climate change must be seen in the context of multi-decadal variability, which will lead to different amounts of water being available over different time periods even in the absence of climate change. … the average standard deviation in 30-year average annual runoff is typically under 6% of the mean, but up to 15% in dry regions (12).

Temperature rise and changing precipitation patterns may also lead to a reduction of groundwater recharge (13) and hence groundwater level. This would be most evident in southeastern Europe. Higher water temperature and low level of runoff, particularly in the summer, could lead to deterioration in water quality (14). Inland waters in southern Europe are likely to have lower volume and increased salinisation (15).

Most studies on water supply and demand conclude that annual water availability would generally increase in northern and northwestern Europe and decrease in southern and southeastern Europe (1). In the agricultural sector, irrigation water requirements would increase mainly in southern and southeastern Europe (16). The risk of drought increases mainly in southern Europe. For southern and eastern Europe the increasing risk from climate change would be amplified by an increase in water withdrawals (17).

Water shortages due to extended droughts will also affect tourism flows, especially in southeast Mediterranean where the maximum demand coincides with the minimum availability of water resources (4).

Fresh water resources in numbers - Worldwide

In the absence of climate change, the future population in water-stressed watersheds depends on population scenario and by 2025 ranges from 2.9 to 3.3 billion people (36–40% of the world’s population). By 2055 5.6 billion people would live in water-stressed watersheds under the A2 population future (the A2 storyline has the largest population), and ‘‘only’’ 3.4 billion under A1/B1(1).

Climate change increases water resources stresses in some parts of the world where runoff decreases, including around the Mediterranean, in parts of Europe, central and southern America, and southern Africa. In other water-stressed parts of the world, particularly in southern and eastern Asia, climate change increases runoff, but this may not be very beneficial in practice because the increases tend to come during the wet season and the extra water may not be available during the dry season (1).

Europe: five lake categories

There are almost one and a half million lakes in Europe, if small water bodies with an area down to 0.001 km2 are included. The total area of lakes is over 200,000 km2; in addition the manmade reservoirs cover almost 100,000 km2. The response of European lakes to climate change can be discussed by dividing the lakes into five categories (23):

Deep, temperate lakes

Typical representatives of this class are e.g. Lakes Maggiore, Ohrid, Geneva and Constance with mean depths of 177, 164, 153 and 90 meters, respectively. Due to the great depth and relatively mild winters, there is usually no ice cover. The future climate change in Europe may suppress the turnover in deep lakes. This implies the enhancement of anoxic bottom conditions and an increased risk of eutrophication. The oxygen conditions can also be anticipated to deteriorate due to increased bacterial activity in deep waters and surficial bottom sediment.

Shallow, temperate lakes

Balaton (600 km2, 3 m) in Hungary and Müritz (114 km2, 8 m) in Germany belong to this class. Increasing water temperatures may result in intensified primary production and bacterial composition. The probability of harmful extreme events, e.g. mass production of blue-green algae, will increase. The impacts may extend to fish life; changes in species composition and reduced fish catches will be anticipated. The use of the expression 'thermal pollution' is well justified for these lakes.

Boreal lakes

Ladoga (17 670 km2, 51 m), Onega (9670 km2, 30 m) and Vänern (5670 km2, 27 m) are the largest in this class, being also the three largest lakes in Europe. This group includes about 120 lakes with an area exceeding 100 km2. Most lakes of the boreal zone mix from top to bottom during two mixing periods each year. Shortening of the ice cover period will be the most obvious consequence of climate change in these lakes. This could improve the oxygen conditions in winter and spring.

Arctic lakes

These are mainly small water bodies in northern Scandinavian mountains and in the tundra region. Arctic lakes are generally considered to be particularly sensitive to environmental changes. Melting permafrost may seriously threaten the ecosystems of arctic lakes. In some cases the whole lake may disappear as a consequence of ground thaw and enhanced evaporation.

Mountain lakes

To this class belong all high altitude lakes in central Europe and also those located in southern Scandinavia. Even if mountain lakes were connected by channels, physical and ecological constraints limit species migration between them. In a warming climate, there is no escape route; the only possibility for survival is adaptation.

South-eastern Europe: four types of lakes

In order to discuss the effect of climate change to lakes in south-eastern Europe, the region is divided into three climatic sub regions. The main characteristic in this subdivision is the mean temperature in January, because the severity of winter has an essential influence to the lakes. The sub regions and the anticipated influences of climate change, around the year 2050, are as follows (23):

The Mediterranean sub region

In today's climate the mean temperature varies in January between +10 and -2°C, in July it is generally 20 - 25°C. This sub region covers the narrow coastal area on the Adriatic Sea, most of the Greek territory and the lowlands on the southwest side of the Black Sea.

Only the smallest lakes have short ice cover season every winter in today's climate, in the future climate ice will be almost non-existent. Summertime water temperatures will get very high, leading to algal and water quality problems. Water balance will be negatively affected by climate change; evaporation will increase and inflows tend to decrease. The use of lakes as water sources, e.g. for rising needs of irrigation, will be limited.

In today's climate, the runoff in the Adriatic part of this sub region is generally over 1000 mm, while it ranges between 30 and 200 mm in the vicinity of the Black Sea. The difference of lake precipitation and lake evaporation is 200 - 600 mm in the former area, whereas it is between -200 and -400 mm in the latter. In the climate of 2050, shallow lakes in the latter area will become intermittent and reservoirs will have considerably high water losses.

Northern lowlands

Mean temperature in January is between -5 and -2°C, in July around 20°C. This sub region covers large parts of Hungary, eastern Croatia, central parts of Serbia, southern and eastern Romania, and Moldova. As to the runoff, this is the driest area in south-eastern Europe; in Hungary and on the Black Sea coast annual runoff is locally less than 20 mm. The difference of lake precipitation and lake evaporation is between 0 and -300 mm.

In today's climate most lakes in this sub region mix from top to bottom during two mixing periods each year and have an ice cover for 1-3 months. They may still freeze in 2050, but the possibility of ice-free winters will increase. Adverse water balance changes may affect many lakes; intermittency and increased salinity can be anticipated.

Mountaineous regions

South-eastern Europe is topographically one of the most diverse regions in the world. In addition to two main mountain ranges, Carpathians and Dinaric Alps, there are numerous other ridges and plateaus. At highest elevations, mean temperature in January can be as low as -10°C and extremes below -30°C have been recorded. In July typical mean temperatures are between 10 and 20°C. Precipitation is generally abundant but very variable even at small scale.

Most lakes are located in river valleys, but smaller ones occur also at high plateaus and depressions. Ice cover season may be as long as 5-6 months, snow on lakes further reduces the penetration of radiation into the water mass. Some of the highest lakes mix once a year but mixing twice a yearis much more common.

Climate change may not cause very harmful changes in water balance of these lakes. Increased erosion by intense precipitation may lead to sedimentation and degradation of water quality. At lower elevations, the occurrence of ice cover may become uncertain. For water supply, the mountain lakes and river basins will probably be very important in south-eastern Europe in the future, because run-off may considerably decrease at lower altitudes.

Underground (karstic) lakes

This is a special type of lakes. Due to the karstic geology, there are underground lakes in the Balkan region. They are not immune to the impacts of climate change; in fact their water balance and ecology may be sensitive to changes of the quantity and quality of inflowing waters.  

Adaptation strategies

EU policy orientations for future action

According to the EU, policy orientations for the way forward are (25):

  • Putting the right price tag on water;
  • Allocating water and water-related funding more efficiently: Improving land-use planning, and Financing water efficiency;
  • Improving drought risk management: Developing drought risk management plans, Developing an observatory and an early warning system on droughts, and Further optimising the use of the EU Solidarity Fund and European Mechanism for Civil Protection;
  • Considering additional water supply infrastructures;
  • Fostering water efficient technologies and practices;
  • Fostering the emergence of a water-saving culture in Europe;
  • Improve knowledge and data collection: A water scarcity and drought information system throughout Europe, and Research and technological development opportunities.

Managed aquifer recharge

Comprehensive management approaches to water resources that integrate ground water and surface water may greatly reduce human vulnerability to climate extremes and change, and promote global water and food security. Conjunctive uses of ground water and surface water that use surface water for irrigation and water supply during wet periods, and ground water during drought (33), are likely to prove essential. Managed aquifer recharge wherein excess surface water, desalinated water and treated waste water are stored in depleted aquifers could also sup­plement groundwater storage for use during droughts (34,35). Indeed, the use of aquifers as natural storage reservoirs avoids many of the problems of evaporative losses and ecosystem impacts asso­ciated with large, constructed surface-water reservoirs.

Measures southern Europe

In southern Europe, to compensate for increased climate related risks (lowering of the water table, salinisation, eutrophication, species loss), a lessening of the overall human burden on water resources is needed. This would involve stimulating water saving in agriculture, relocating intensive farming to less environmentally sensitive areas and reducing diffuse pollution, increasing the recycling of water, increasing the efficiency of water allocation among different users, favouring the recharge of aquifers and restoring riparian vegetation, among others (22).

Measures Crete

According to future projections of demand and supply, local water management planning and adaptation strategies for Crete need to be improved and updated in order to attain future water security. Priority should not only be given to the increase of irrigated areas but also to promoting a more sustainable irrigation practice for existing and new agricultural land (37). Besides, strategies of adaptation to consider should include wastewater recycling and reuse that are estimated to lead to water savings of up to 5% of the total irrigation water of Crete (38).


The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Greece.

  1. Arnell (2004)
  2. Eisenreich (2005)
  3. EEA (2003); EEA (WQ03b), both in: Eisenreich (2005)
  4. European Environment Agency (EEA) (2005)
  6. Rosato and Giupponi (2003)
  7. Trigo et al. (2004), in: Eisenreich (2005)
  8. Hulme (1999); UNEP/MAP/MED/POL (2003), both in: European Environment Agency (EEA) (2005)
  9. Alcamo et al. (2007)
  10. Santos et al. (2002), in: Alcamo et al. (2007)
  11. WHO (2007)
  12. Arnell (2003), in: Arnell (2004)
  13. Eitzinger et al. (2003), in: European Environment Agency (EEA) (2005)
  14. Mimikou et al. (2000), in: European Environment Agency (EEA) (2005)
  15. Williams (2001); Zalidis et al. (2002), both in: Alcamo et al. (2007)
  16. Döll (2002) in: European Environment Agency (EEA) (2005)
  17. Lehner et al. (2006), in: Alcamo et al. (2007)
  18. Voudouris (2006), in: European Environment Agency (EEA) (2009)
  19. Voudouris et al. (2000), in: European Environment Agency (EEA) (2009)
  20. Xenos et al. (2002), in: European Environment Agency (EEA) (2009)
  21. Koutsoyiannis et al. (2001), in: European Environment Agency (EEA) (2009)
  22. Alvarez Cobelas et al. (2005), in: Alcamo et al. (2007)
  23. Kuusisto (2004)
  24. European Commission (DG Environment) (2007)
  25. Commission of the European Communities (2007)
  26. Wada et al. (2012)
  27. Bank of Greece (2011), in: Shoukri and Zachariadis (2012)
  28. Tsanis et al. (2011)
  29. Chenoweth et al. (2011)
  30. Hiscock et al. (2011), in: Taylor et al. (2012)
  31. Döll (2009), in: Taylor et al. (2012)
  32. Falloon and Betts (2010), in: Taylor et al. (2012)
  33. Faunt (2009), in: Taylor et al. (2012)
  34. Scanlon et al. (2012), in: Taylor et al. (2012)
  35. Sukhija (2008), in: Taylor et al. (2012)
  36. Donta et al. (2005), in: Koutroulis et al. (2013)
  37. Koutroulis et al. (2013)
  38. Tsagarakis et al. (2004); Agrafioti and Diamadopoulos (2012), both in: Koutroulis et al. (2013)

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