Estonian rivers

Estonia can be divided into three main watersheds (Lake Peipsi, the Gulf of Finland, and the Gulf of Riga) and 27 main river basins. There are 7,000 rivers, brooks, and canals in Estonia. As many as 90% of the rivers are up to 10 km long and only 1% are over 50 km in length. The longest river is the Pärnu River in West Estonia. There are over 1400 natural and man-made lakes, covering 6.1% of the territory (1).

Observed changes in river runoff and water supply

During the period 1961–2004 the winter seasonal air temperature increased by 3.2°C on average and precipitation increased over 45 mm. Increased air temperature has caused a decrease in the maximum discharge of spring floods and their earlier beginning. Before the 1960s the average beginning time of flood was the end of March or the beginning of April, whereas after the 1960s the floods have begun in February and for the last decade even in January. If the tendencies continue, Estonia can expect earlier and lower spring floods, smoothing the boundaries between the seasonality of river flow (2).

Projected changes in river runoff and water supply

In general, an increase of annual runoff by 20-30% or by 40-50% is modeled for the year 2100, depending on the assumed climate change scenario. Not only is the total increase of annual runoff important, but also its annual distribution (1).

A projected decrease in the contribution to the annual runoff in the spring season by 4%–10% and an increase in the contribution to the annual runoff in the winter season by 24%–34% will have different impacts on water resources management in the future (2).

Possible changes in the annual course of runoff should be more substantial in the western part of Estonia, in regions with a maritime climate. In southern and eastern Estonia, the modeled annual curve of runoff is similar to the baseline. A decrease of modeled runoff in spring and its increase in autumn are typical of the western part of Estonia, especially of the West-Estonian Archipelago. Instead of four hydrological periods in a year, only two periods occur in this region: maximum runoff in autumn and winter, and minimum runoff from May to August (1).

A shift in the spring runoff maximum to an earlier time will result in a longer duration of the summer low-water period and in a decrease of total runoff during the vegetation period (April-September) in many river basins of Estonia. Climate warming is likely to lead to milder winters in Estonia, with a decrease in the duration of snow and ice cover. Mild winters lead to a more rapid snow melt and an earlier beginning of the spring season. Frequent melting periods in winter prevent accumulation of snow. The mean maximum runoff will move from April to March, and spring runoff will consequently decrease (1).

There may, on the other hand, be an increase in river runoff in autumn caused by a significant increase in autumn precipitation. In some watersheds in West Estonia, autumn runoff maximum (in November) will exceed the spring maximum (1).

The period of minimum runoff in summer will be lengthened, as the dry period will begin earlier. During this period, rivers receive the majority of water from groundwater. This could cause a severe water deficit in some small river basins in West-Estonia. However, it is important to note that all modeled changes in river runoff can be considered to be within the observed natural variation during the baseline period (1).

Estonia - Benefits from climate change

The impacts of climate change to Estonia are relatively small compared with those in other countries of Europe. The rise in temperature and precipitation are expected to have positive rather than negative effect on the Estonian economy (3). The groundwater resources can guarantee a sufficient supply of good quality domestic water in all regions of the country (3).

If the climate warms, precipitation will mostly reach the ground surface as rain, capable of instant percolation into the unfrozen soil. As a result, groundwater recharge will significantly increase during warm autumn and winter. Groundwater recharge may be expected to increase by 20-40% as a result of climate change. The accession of the groundwater recharge may reach even 75% in comparison with the present time, under extreme climate change scenarios. Owing to climate change, the ratio of the groundwater recharge to the total surface runoff will increase from 30 to 40% (1).

The predicted increase of groundwater recharge and the rise of the groundwater table will simultaneously be conducive to and complicate water management in Estonia. The rising of the groundwater table will benefit water supply. In Estonia, a large portion of the rural population gets their domestic water from shallow wells. They are commonly only a half-meter deeper than the mean low groundwater table under natural conditions. In hot summers and in cold winters, many of these wells become unfit for water supply, or even run dry. Such a situation is quite common in the limestone plateau of northern Estonia and especially in the region of oil shale mines. To guarantee an adequate yield, the  deepening of shallow wells has been recommended up until now. A rise in the groundwater table will significantly improve both the productivity and reliability of shallow wells. As a result of the general increment of groundwater recharge, the safe yield of bored wells mentioned will augment by some 20% or even more. However, many towns and villages in northern Estonia along the coast of the Gulf of Finland get their drinking water from deep aquifers that belong to the zone of passive water exchange. Pumping conditions of deep groundwater aquifers will not be altered on account of climate change (1).

On the one hand, the decrease in spring runoff is good for designing and constructing road bridges and culverts whose cost will decrease. A more evenly distributed river flow throughout the year will lead to a profitable situation for the hydropower industry. It is also good for water level regulation against floods and droughts. The increased flow in winter will improve the water quality of rivers and is better for fish farming management (2).

Estonia - Vulnerabilities

On the negative side, the increase of groundwater circulation may favor the transport of pollutants in the water-bearing formation. The movement of pollutants may gather speed and the pollution plumes enfold greater areas than today. As a result, a portion of wells kept pure so far may become polluted (1).

The rising of the groundwater table and thinning of the aeration zone will ultimately make it more difficult to cultivate arable lands suffering from over moisture. Therefore, it will be necessary to reconstruct almost drainage systems for wet agricultural lands (1).

If intensive mining of oil shale or phosphorite is undertaken in Estonia still at the time of the expected climate change, then it must be taken into account that the water inflow will increase into goafs or quarries by some 30% in comparison with the present time. It will complicate the dewatering of mines and make mining of mineral resources more expensive (1).

The basements of existing buildings may suffer from intruding subsurface flows due to the rising groundwater table. The foundations of new buildings and the isolation of their basements from groundwater will probably be more complicated and expensive (1).

The earlier and shortened spring and the longer low flow period after spring may deteriorate water quality and have a negative impact on aquatic habitats (2).

Along low-lying coasts at the Baltic Sea, the intrusion of salt water may affect the quality of ground water. With a rising sea level, saltwater intrusion may lead to broader-scale limitations of water-extraction possibilities (3).

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 (4):

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.

Adaptation strategies

EU policy orientations for future action

According to the EU, policy orientations for the way forward are (5):

• 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 (6), 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 (7,8). 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 - Estonia

Demand-side adaptation options play an increasingly important role in the Baltic region countries. Seeking savings (`negaliters`) rather than supplying extension (`megaliters`) is increasingly emphasized. From the sustainable development perspective, the adaptation in the water sector should reduce the vulnerabilities of people and societies to shifts in hydro-meteorological trends, increased climate variability, and extreme events, and should protect and restore ecosystems that provide critical land and water resources and services (3).

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 Estonia.

1. O’Brien (ed.) (2000)
2. Ministry of the Environment of Estonia (2009)
3. Kundzewicz (2009)
4. Kuusisto (2004)
5. Commission of the European Communities (2007)
6. Faunt (2009), in: Taylor et al. (2012)
7. Scanlon et al. (2012), in: Taylor et al. (2012)
8. Sukhija (2008), in: Taylor et al. (2012)