Fresh water resources in numbers - Croatia

The amount of water per inhabitant places the Republic of Croatia among the best endowed countries in Europe. The average volume of the country’s own and transit waters is 25,160 m3/cap/year of which the own waters account for 5,880 m3/cap/year. The total length of all natural and artificial watercourses in the area of Croatia is 21,000 km. The rivers belong to the Black Sea (62% of the territory) and the Adriatic catchment area (38%) (5).

The specific discharge of the Adriatic catchment area waters is twice as large as that of the Black Sea catchment area, due to considerably larger amounts of precipitation (by over 40%) and the karst nature of the base causing higher discharge coefficients (5).

The river Danube, the largest and richest in water, flows through the eastern borderland of Croatia over a length of 137.5 km. Other major rivers are the Sava (562 km) and the Drava (505 km). The rivers of the Adriatic catchment area are short, have rapids and canyons (5).

There are not many lakes in Croatia. The artificial storage lakes with a total volume of 1,050 million m3 have been created as a part of hydropower plants. They are Dubrava Lake (17.1 km2) on the river Drava and Peručko Lake (13 km2) on the river Cetina (5).

Croatia belongs to a group of countries for which water issues are not a limiting factor of development (5).

The presence of karst causes that the parts of the border between Slovenia and Croatia, and that between Bosnia-Herzegovina and Croatia have numerous underground connections and streamflows which are hard to determine. This makes the management of the border and transboundary water resources shared with the neighbouring countries very difficult (6).

Approximately 40% of the Croatian territory is covered with limestone-dolomite rocks, in which deep karstic underground forms prevail. These forms are causing specific complex hydrological and hydrogeological runoff conditions. Due to the karstic terrain in the western coastal region of Croatia, the average annual runoff coefficient is about 0.60. In the eastern flatland nonkarstic region it is about 0.20 (6).

In spite of extensive research activity, the knowledge on the amount and the condition of underground water is inconclusive. Alluvial, karstic, artesian and other aquifers are not sufficiently explored. … It can be concluded that Croatia is a country rich in water, especially considering the low population density and modest demand for industrial and agricultural water, which is well below average of developed countries. Relatively high quality of both surface and ground water can certainly be considered a positive element, with most problems occurring during warm summer periods when the natural discharge is small, the groundwater level low and water demand increased due to the tourism and irrigation demands. … In potable water supply 86% is groundwater and 14% surface water (6).

Central sewer systems are constructed only in large urban and industrial centres. Less then 35% of wastewater in Croatia is discharged into the sewer systems and less than 10% is treated in wastewater treatment plants (6).

Vulnerabilities - Croatia

There is no doubt that the hydrological regime follows the changes in climate characteristics and that the future climate changes will considerably reflect on the water resources and their availability. The water resource systems in Croatia have been designed and operated on the assumption that future climate variations might be expected to be similar to those observed within the past 30 to 50 years (6).

The climate changes initiated by global warming have the potential to cause major changes in hydrological processes and hence water availability. The present state of knowledge however does not enable that the actual impacts on climate change be estimated with certainty. The hydrological impact in a small but climate-wise and geologically extremely diverse country, such as Croatia, depends upon estimated changes in rainfall and evapotranspiration. Such changes are difficult to estimate with precision from the available climate simulation models (6).

According to the existing climate change estimates for Croatia, the runoff in a typical basin in western Croatia (Dinaric karst region) by the middle of the 21st century could be expected to decrease by 10 to 20% compared to the present. In the eastern flatland part of Croatia the expected change will be less than 10 percent (6).

It is very likely that both the seasonal and regional distribution of water resources will change, with an increasing concentration of available water in winter and central western basins. Supplies during the warmer and, possibly, drier summers would need to be maintained by larger storing or inter-basin transfer. The transfer of water from one Croatian basin to another is realistic because three rivers with abundant quantity of water are running through the Croatian territory: the Danube, Drava and Sava rivers (6).

In croatia, a large amount of water is wasted due to leakages in pipes, which leads to a revenue loss of up to EUR 286 million (0.9% of GDP) (22).

A possible decrease of runoff and its probable redistribution during the year will cause shortages in water supply in summer season. It should be stressed that such shortages are already being experienced, since Croatia is a tourist country with large agricultural production. Demand for water will increase in Croatia during the summer and vegetation season (from April to September). Domestic demand will increase during the dry summer tourist season. The increased evapotranspiration can be expected to lead to large increase in demand for water for irrigation (6).

Special attention should be given by water resources managers to groundwater recharge and depletion in the Croatian flatlands, namely the area between the Sava, Drava and Danube rivers (eastern part of Croatia). In this region the surface runoff is significantly lower in comparison with evapotranspiration and infiltration. It means that the vertical hydrological component dominates over the horizontal one. During the last 50 years the water regime of this area has dramatically changed. The groundwater level decrease has been noticed, which influences the water supply reliability. The process of surface and groundwater availability decrease in this region is enduring and hard to be stopped. Possible climate change will affect it negatively. Because of all this, and also due to increase in groundwater pumping in the area and building of a dense drainage system for agricultural purposes, the situation might in the future be critical.

The planned large regional water supply system, construction of hydroelectric power plants in the downstream sections of the Drava and Danube rivers, and especially a multi-purpose canal Danube – Sava (navigation and irrigation), in combination with the climate change will probably cause very dangerous consequences. The decrease in the groundwater level at the right Sava bank, in City of Zagreb area, has been noticed during the last fifteen years. The phenomenon can be explained by a multitude of erosion control works, construction of various dams, regulation works on the Sava river and its tributaries, including embankment construction, and possibly due to the climate change. The changes are particularly significant in the Sava profile in the very city, where the minimum annual water levels dropped by about 200 cm in the last thirty years. This causes great problems in water supply during the low water level period, mostly during the summers (6).

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).

Vulnerabilities - Mediterranean

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 (1,7). Future projection of this trend will reduce drastically water supplies in these areas, affecting considerably the population and economy of the Mediterranean countries (8).

In south-eastern Europe annual rainfall and river discharge have already begun to decrease in the past few decades (9).

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 (10).

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 (10). Summer low flow may decrease by up to 80% in some rivers in southern Europe (11,12).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 (13).

Temperature rise and changing precipitation patterns may also lead to a reduction of groundwater recharge (14) 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 (15). Inland waters in southern Europe are likely to have lower volume and increased salinisation (16).

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 (17). 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 (18).

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 - 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).

Fresh water resources in numbers - Wordwide

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 (20):

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 (20):

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 (21):

• 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 (23), 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 (24,25). 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 - Mediterranean

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 (19).

Measures - Croatia

Technically, it is possible to protect threatened regions by adaptation of water management systems in such a way that the major functions of these areas be maintained. However, the economic and environmental impacts will often make such a protection strategy unfeasible or unacceptable. Consequently, different strategies will need to be developed and the best one chosen for implementation (6).

There is a need to increase awareness and understanding of the importance of droughts and floods in Croatia which may be caused by possible climate change. The knowledge of assessment, mitigation and response strategies and means of improving drought and flood preparedness in Croatia should be increased. Research capacities at national and sub-regional levels should be reinforced. An inventory of technology and traditional international and local knowledge and know-how for mitigating the effect of drought and flood should be prepared (6).

The possible solutions include on-site adjustment or solutions far in time and space. The response to expected impacts can be technical, natural (to replace lost or damaged resources) or non-structural (modification of the human use of area or resources). No major project should be approved without taking into account the results of the relevant climate impact studies. The future water supply-demand relations are a central problem in the climate change impact assessment. Particularly, the climate change could considerably affect the agricultural engineering and economic development at the regional and state level. The development of water resources systems and their adaptive management strategies have to be considered. The new policy should be oriented towards more resilient and robust water resources and agricultural engineering systems in order to achieve sustainable development (6).

Croatia should undertake measures to improve the efficiency of the public water supply. The current loss is immense and may lead to problems if water resources become scarcer (22).

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 Croatia.

1. Arnell (2004)
2. Eisenreich (2005)
3. EEA (2003); EEA (WQ03b), both in: Eisenreich (2005)
4. European Environment Agency (EEA) (2005)
5. Republic of Croatia, Ministry of Environmental Protection, Physical Planning and Construction (2006)
6. Republic of Croatia, Ministry of Environmental Protection and Physical Planning (2001)
7. Rosato and Giupponi (2003), in: European Environment Agency (EEA) (2005)
8. Trigo et al. (2004), in: Eisenreich (2005)
9. Hulme (1999); UNEP/MAP/MED/POL (2003), both in: European Environment Agency (EEA) (2005)
10. Alcamo et al. (2007)
11. Santos et al. (2002), in: Alcamo et al. (2007)
12. WHO (2007)
13. Arnell (2003), in: Arnell (2004)
14. Eitzinger et al. (2003), in: European Environment Agency (EEA) (2005)
15. Mimikou et al. (2000), in: European Environment Agency (EEA) (2005)
16. Williams (2001); Zalidis et al. (2002), both in: Alcamo et al. (2007)
17. Döll (2002), in: European Environment Agency (EEA) (2005)
18. Lehner et al. (2006), in: Alcamo et al. (2007)
19. Alvarez Cobelas et al. (2005), in: Alcamo et al. (2007)
20. Kuusisto (2004)
21. Commission of the European Communities (2007)
22. UNDP (2008)
23. Faunt (2009), in: Taylor et al. (2012)
24. Scanlon et al. (2012), in: Taylor et al. (2012)
25. Sukhija (2008), in: Taylor et al. (2012)