Projected future situation in Slovakia

For most of Slovakia a drop in river runoff is expected. The projected drop depends on the climate change scenario and the part of Slovakia under consideration, and varies between 5% and 40% in 2030 and 5% and more than 40% in 2075, compared with the reference period 1951-1980. The biggest drop is anticipated in the lowlands, where average decreases in long-term average runoff by 29% and 45% are expected in 2030 and 2075, respectively. Slighter decrease in runoff is expected in the mountains (8% in 2030 and 14% in 2075). The largest decreases are expected in the south of central Slovakia (35% in 2030 and 50% in 2075) (11). Over the whole territory of Slovakia intra-annual changes in the runoff distribution are expected: an increase in winter and spring runoff, a decrease in late spring and summer runoff. The projected changes in 2075 are in the order of tens of percents. These numbers should be intrepreted very carefully, due to uncertainties in methodologies and scenarios. The trends of changes are highly probable, though (11).

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 (9):

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.

Present situation in Europe

Water demand

In the EU as a whole, energy production accounts for 44% of total water abstraction, primarily serving as cooling water. 24% of abstracted water is used in agriculture, 21% for public water supply and 11% for industrial purposes (3).

These EU-wide figures for sectoral water use mask strong regional differences, however. In southern Europe, for example, agriculture accounts for more than half of total national abstraction, rising to more than 80 % in some regions, while in western Europe more than half of water abstracted goes to energy production as cooling water. In northern EU Member States, agriculture's contribution to total water use varies from almost zero in a few countries, to over 30% in others (7). Almost 100% of cooling water used in energy production is restored to a water body. In contrast, the consumption of water through crop growth and evaporation typically means that only about 30% of water abstracted for agriculture is returned (3).

Currently, just two countries, Germany and France, account for more than 40% of European water abstraction by manufacturing industry (3).

Water supply

In general, water is relatively abundant with a total freshwater resource across Europe of around 2270 km3/year. Moreover, only 13% of this resource is abstracted, suggesting that there is sufficient water available to meet demand. In many locations, however, overexploitation by a range of economic sectors poses a threat to Europe's water resources and demand often exceeds availability. As a consequence, problems of water scarcity are widely reported, with reduced river flows, lowered lake and groundwater levels and the drying up of wetlands becoming increasingly commonplace. This general reduction of the water resource also has a detrimental impact upon aquatic habitats and freshwater ecosystems. Furthermore, saline intrusion of over-pumped coastal aquifers is occurring increasingly throughout Europe, diminishing their quality and preventing subsequent use of the groundwater (3).

Virtually all abstraction for energy production and more than 75% of that abstracted for industry and agriculture comes from surface sources. For agriculture, however, groundwater's role as a source is probably underestimated due to illegal abstraction from wells. Groundwater is the predominant source (about 55%) for public water supply due to its generally higher quality than surface water. In addition, in some locations it provides a more reliable supply than surface water in the summer months (3).

Fresh water reservoirs

Currently about 7000 large dams are to be found across Europe, with a total capacity representing about 20% of the total freshwater resource (3). The number of large reservoirs is highest in Spain (ca 1200), Turkey (ca 610), Norway (ca 360) Italy (ca 570), France (ca 550), the United Kingdom (ca 500) and Sweden (ca 190). Europe's reservoirs have a total capacity of about 1400 km3or 20% of the overall available freshwater resource (6).

Three countries with relatively limited water resources, Romania, Spain and Turkey, are able to store more than 40% of their renewable resource. Another five countries, Bulgaria, Cyprus, Czech Republic, Sweden and Ukraine, have smaller but significant storage capacities (20–40%). The number and volume of reservoirs across Europe grew rapidly over the twentieth century. This rate has slowed considerably in recent years, primarily because most of the suitable river sites for damming have been used but also due to growing concerns over the environmental impacts of reservoirs (3).

Projected future situation in Europe

Water demand

Appliance ownership data is not currently readily available for the new Member States but it is believed that rates are currently relatively low and likely to rise in the future. Higher income can also result in increased use and possession of luxury household water appliances such as power showers, jacuzzis and swimming pools. Changes in lifestyle, such as longer and more frequent baths and showers, more frequent use of washing machines and the desire for a green lawn during summer, can have a marked effect on household water use. The growth in supply within southern Europe has been driven, in part, by increasing demand from tourism. In Turkey, abstraction for public water supply has increased rapidly since the early 1990s, reflecting population growth and a rise in tourism (3).

Water stress over central and southern Europe is projected to increase. In the EU, the percentage of land area under high water stress is likely to increase from 19% today to 35% by the 2070s, by when the number of additional people affected is expected to be between 16 and 44 million. Furthermore, in southern Europe and some parts of central and eastern Europe, summer water flows may be reduced by up to 80% (4).

Supply

Runoff is estimated to increase north of 47°N by approximately 5-15% by the 2020s and 9-22% by the 2070s. North of 60°N, these ranges would be considerably higher, particularly in Finland and northern Russia (1). Average annual runoff in Europe varies widely, from less than 25 mm in southeast Spain to more than 3000 mm on the west coast of Norway. Climate change is thus going to make the distribution of water resources in Europe much more uneven than it is today. And even today's distribution is highly uneven, particularly considering the distribution of population density. Almost 20% of water resources are north of 60°N, while only 2% of people live there (2).

Not only will climate change affect the spatial distribution of water resources, but also their distribution in time. In northern Europe, the flows in winter (December to February) will increase two- to three-fold, while in spring they will attenuate considerably, in summer increase slightly and in autumn almost double by the period 2071-2100 (2).

Adaptation strategies

EU policy orientations for future action

According to the EU, policy orientations for the way forward are (10):

• 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 (12), 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 (13,14). 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

A number of measures exist that may potentially reduce the use of publicly supplied water. These can be broadly grouped into the categories of water saving devices; greywater re-use; rainwater harvesting and the efficient use of water in gardens and parks; leakage reduction; behavioural change through raising awareness; water pricing; and metering. Since treating, pumping and heating water consumes significant amounts of energy, using less publicly supplied water also reduces energy consumption (3).

In Denmark and Estonia, for example, a steady rise in the price of water since the early 1990s has resulted in a significant decline in household water use. Metering leads to reduced water use; in England and Wales, for example, people living in metered properties use, on average, 13% less water than those in unmetered homes (5).

Planned adaptation measures in Slovakia are (8, 11):

• re-evaluation of the estimation of design floods and reassessment of the safety of dams and water structures;
• re-evaluation of future water needs;
• re-evaluation of the safety of existing water withdrawals from reservoirs for water supply and energy production, and low flow augmentation;
• development of methodologies for drought assessment, and investigation of droughts and their impacts on the ecology of water bodies;
• reduction of specific water consumption per capita using technical means, reducing losses etc.;
• use of subsidies and taxes, charges and fines, to enhance public awareness;
• better legislation: current policy does not take into account the need to prepare adaptation measures;
• optimization of the exploitation and management of existing water systems. It is necessary to take into account the possibility to compensate for the decline in water resources yield, especially in the lowlands of central and east Slovakia. It is necessary to assess the possibility of the construction of retention reservoirs that would allow for the regulation of runoff;
• better water management.

In general, climate change may have different impacts on runoff in the southern and the northern regions of Slovakia. A man-made redistribution of runoff may be needed in the future between the north (higher parts) and the south (lower parts) of the country (11).

References

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

1. Alcamo et al. (2007)
2. Eisenreich (2005)
3. EEA (2009)
4. EEA, JRC and WHO (2008)
5. Environment Agency (2008a), in: EEA (2009)
6. EEA (2007), in: EEA (2009)
7. IEEP (2000), in: EEA (2009)
8. Ministry of Environment of the Slovak Republic (2005)
9. Kuusisto (2004)
10. Commission of the European Communities (2007)
11. Ministry of Environment of the Slovak Republic and the Slovak Hydrometeorological Institute (2009)
12. Faunt (2009), in: Taylor et al. (2012)
13. Scanlon et al. (2012), in: Taylor et al. (2012)
14. Sukhija (2008), in: Taylor et al. (2012)