Water, rivers, lakes

1. Location

As far as water is concerned, the Czech Republic lies on the watershed of three seas - the North Sea, the Baltic Sea and the Black Sea. Its territory is source area of waters for the European rivers - Dunaj (Danube), Labe (Elbe) and Odra (Oder). The previous is reason why is the Czech Republic called "roof of the Europe".

What does it mean? Almost all the water in the Czechia comes from precipitation. No significant river flows into this territory from another state. On the contrary, rivers spring here and drain water outside the state border. This also results in a large water dependence of the Czech Republic on the amount of precipitation.

Fig. 1. Main European drainage basins (Source: https://www.eea.europa.eu).

Fig. 2. Three main drainage basins in the Czech Republic. The Elbe basin is the largest (63.3 % of the state territory), the second largest is Morava river basin (27.5 %, Morava is part of the Danube drainage basin) and the smallest Odra river basin (9.2 %) (Source: Ministry of the Agriculture of the Czech Republic, www.eagri.cz)

Task:

Repeat the concepts watershed, river basin, and drainage divide.

What consequences could have the recent climate change on the water supply and self-sufficiency of the Czech Republic?

2. Water resources

The precipitation is the only source of water in the territory of the Czech Republic. It is accumulated in the water reservoirs (lakes, dams) or in the groundwater. You can see in the table below that the volume of the usable groundwater recently decreases. Most of the precipitation is lost by the evapotranspiration and outflow.

Fig. 1. Renewable water resources in the years 2013-2019 (Source: Ministry of the Agriculture).

Task:

Repeat the water cycle and the hydrological balance of a river basin.

3. Groundwater resources

Spatial and temporal distribution of groundwater depends primarily on the geological conditions (rock type, tectonic structures), climate and land use. In the temperate climate, the groundwater recharge depends on precipitation in the non-vegetative period (December till March). Only 10-25 % of precipitation infiltrates to the ground.

Three types of groundwater can be distinguished - fissured-bedrock aquifer, porous aquifer and karst aquifer. Fissured-bedrock aquifers are typically located in the magmatic rocks (e.g. granite) or metamorphic rocks which have a large number of fractures. This type of groundwater is only local  importance. Porous aquifers are located in the porous material with higher permeability such as in unconsolidated sediments (e.g. fluvial sediments) and porous sedimentary rocks (e.g. sandstones). This type of aquifers are regional importance and serve as a drinking water resources for the municipalities. Karst aquifers are located in limestones. The groundwater flows through the system of fissures which originate in dissolution of rock. It is a local importance.

Fig. 1. Groundwater in different sediments and rocks.

3.1. Spatial distribution of groundwaters

Groundwater is everywhere but not all the rocks are able accumulate huge volume of the water.

The most important reservoirs of groundwater in the Czech Republic are located in Quaternary, Tertiary and Cretaceous sediments and sedimentary rocks:

1. Česká křídová tabule (Bohemian Cretaceous Basin) - Cretaceous sediments

2. Třeboňská pánev (Třeboň Basin) - Tertiary and Cretaceous sediments

3. Dyjsko-svratecký úval (Dyje-Svratka valley) - Tertiary and Cretaceous sediments

4. Quaternary sediments - fluvial sediments along the main rivers

5. Crystalline complex of Eastern Sudetes - metamorphic rocks

Fig. 1. Areas of usable groundwater resources (numbers correspond to the text above). Orange - drought risk, grey - balanced groundwater reserves, green - slight groundwater reserves, blue - important groundwater reserves (Source: Czech geological survey).

3.2. Mineral waters

The Czech Republic is rich in mineral water. All of it is a meteoric origin (originates from precipitation). Mineral water resources are often concentrated in the Tertiary and Quaternary volcanic areas.

Many types of mineral waters could be find in the territory of the CR. They are saturated by carbon dioxide, sodium carbonate, sodium chloride, sulfates, magnesium, iodine etc. Some of them are thermal water and a rarity is water with high radioactivity (springs in the town of  Jáchymov in the Western Bohemia have the radioactivity 5-20 thousands of Bq per litre which is unique in the world). Mineral waters are mostly use in spas and food industry.

Fig. 1. Map of the mineral water springs. Types of the mineral water: orange - magnesium water, violet - iodine water, black - radioactive water, yellow - hydrogen sulfide water, red - thermal water, blue - carbon dioxide water. Size of the circle indicates the spring yield.

Fig. 2. Bottled mineral waters which can be found in the shops.

The most famous spa cities in the Czech Republic (Karlovy Vary, Mariánské Lázně and Františkovy Lázně) are located in the Western Bohemia. There are many health resorts with thermal bath and mineral springs.

Task:

1. What is mineral water? What types of mineral water exist?

2. What diseases are treated in Karlovy Vary, Mariánské Lázně, Františkovy Lázně and Jáchymov?

4. Rivers

5. Lakes

The Czechia is poor on lakes but glacial, fluvial, karst, organogenous lakes and lakes dammed-up by landslides could be found here. Nevertheless, the antrophogenic lakes are most abundant lake type . These lakes are all the water bodies which

6. Dams and ponds

There are in total 24 340 water reservoirs and fishponds within the territory of the Czech Republic, holding a total volume of 4,159 million m³. Out of this number, there are 115 large reservoirs (in the year 2000), with a total volume of 3,521 million m³. The construction of the dams in the Czech Republic has been particularly intensive in the second half of 20th century, when the largest dammed lakes were built. In the year 1945, there were only 41 dam reservoirs in Czechoslovakia, in the year 1975 their number increased to 100 only in the

Czech Republic. Nowadays, the number of large water reservoirs is approximately 115.

The dam reservoirs have wide spectrum of uses and for the most part they are multifunctional. The most important uses are:

• water supply for the local population (for example w. r. Švihov on Želivka River, main source of drink water for Prague)
• water supply for the industry and energetics (w. r. Hněvkovice, providing cooling water for Temelín nuclear power plant)
• water power production (w. r. Orlík, with biggest peak water power plant)
• flood protection (w. r. Šance, w. r. Morávka in Beskydy Mts.)
• discharge regulation and retention of the water in the landscape (Vltava cascade - serie of water reservoirs on the Vltava River)
• irrigation (w. r. Rozkoš in NE Bohemia)
• other uses (including fish-breeding, ship transportation and sports and leisure activities).

Fig. 1. Fishpond areas. Dot size indicates summed hectarage of fishponds per grid square of 3 × 5 geographical minutes. (Source: Chytrý, 2012).