14. Slavičí Valley
Shelter in Slavičí Valley, 26 August 2022
The Slavičí Valley Nature Reserve was established in 1988. It protects a valley with natural communities of thermophilous oak woodland and hornbeam–oak woodland, as well as spring areas, meadows, and a local fossil site.
General view of Slavičí Valley Photo: Jakub Mareš
The meadow in the lower part of the valley is botanically remarkable. Here, species of tall‑grass meadows mix with those of dry pastures, creating exceptional diversity: on an area of only half a hectare, around 50 plant species can be found.
A small but highly valuable site lies along the southern boundary of the reserve — a rocky ridge with diabase outcrops, hosting communities of rocky steppe and forest‑steppe. These include narrow‑leaved and feather‑grass dry grasslands with species such as blue moor‑grass (Sesleria caerulea), feather grass (Stipa capillata, S. pennata), hoary rock‑rose (Helianthemum canum), yellow bluestem (Bothriochloa ischaemum), mountain alyssum (Alyssum montanum) and branched white asphodel (Anthericum ramosum). A fragment of downy oak woodland also grows here.
Another stand of downy oak woodland (Quercion pubescenti‑petraeae) is found on the slope of the right bank of the stream, with abundant cornelian cherry (Cornus mas). The forest communities in the reserve are well preserved and closely resemble natural woodland.
Regular mowing and removal of self‑seeded shrubs prevent the meadow from becoming overgrown and losing biodiversity. A long‑term conservation goal is the complete removal of invasive non‑native plants, such as black locust and snowberry.
In the valley floor lies a spring area that feeds the Skalní Stream. Until recently, the stream was classified as an intermittent watercourse. Today, however, it is entirely dry, with only isolated stagnant pools remaining. This is a consequence of disrupted natural hydrological conditions caused by the construction of the motorway and by increased evapotranspiration due to rising temperatures — the overall evaporation of water from the land surface into the atmosphere.
Photo: Jakub Mareš
Why Is There No Water in the Skalní Stream?
Water enters the subsurface through infiltration of rainfall into the soil. In the Czech Republic, typically 10–30% of precipitation infiltrates; the rest evaporates — either directly from the surface (evaporation) or through plants (transpiration). Together, these processes are known as evapotranspiration.
Approximate natural catchment area of the Skalní Stream at its spring
Approximate catchment area after subtracting negative influences (worst‑case scenario)
The natural catchment area covers roughly 1 km², as shown on the map. About 10% of this lies within the built‑up area of Lahovská, where part of the rainwater (from roads and some roofs) is diverted into the sewer system outside the catchment.
Another reduction in infiltration occurred with the construction of the Lochkov Tunnel. Its drainage system effectively creates a secondary “catchment” inside the Skalní Stream basin, diverting additional water away. The exact extent of this influence cannot be determined precisely — it depends on factors such as tunnel depth, drainage design and local geology. In the worst‑case scenario, where the entire northern section is cut off, the catchment area would shrink to one third of its original size. With average annual precipitation of 583 mm and a baseflow of 1 l/s/km², this would reduce the stream’s discharge from 1 l/s to 0.3 l/s.
A further major factor is evapotranspiration. In the river floodplain, where groundwater is easily accessible to plant roots, evapotranspiration is not limited by water availability. It can therefore reach potential evapotranspiration, which is controlled mainly by temperature. As temperatures rise, evapotranspiration in the floodplain increases as well.
In recent years, during summer months, evapotranspiration has reached 40–60 l/s/km². Even a narrow floodplain can therefore completely drain the stream.
Both of these factors — loss of catchment area and increasing evapotranspiration — explain why the Skalní Stream and the springs in Slavičí Valley are dry for most of the year.
Photo: Jakub Mareš
Source: Bruthans J., Kadlecová R., Slavík M., Králová M., Fryč T., Čurda J. (2020): The cause of the sharp decrease in flows of several small streams in Central Bohemia in the summer of 2019 and the extremely low specific runoff: the influence of evapotranspiration from the riparian zone and areas with shallow groundwater. Geoscience Research Reports, 53: 47–54.
The presence of water in the valley is also indicated by the meadow saffron lily (Gagea pratensis), a modest spring plant that thrives in moist meadows and grows here in abundance.
Photo: Jakub Mareš
A striking feature of Slavičí Valley is the number of dead standing trees, especially oaks. These are intentionally left in place even after they die, serving as habitat trees. Thanks to their naturally formed cavities, they provide shelter and nesting sites for a wide range of animals and insects.
hoto: Jakub Mareš
In the central part of the valley lies a well‑known spring, which is now dry for most of the year. Nevertheless, groundwater remains close to the surface in its surroundings. This is evident from the presence of water‑dependent plants, such as the yellow iris.
Photo: Jakub Mareš
Geology
Slavičí Valley is also significant from a geological perspective. The partially exposed geological profile begins with the Kosov Formation (Ordovician) northwest of Lahovská. Above it lie the Litohlavy Formation shales (Llandovery, Silurian), overlain by a massive body of Silurian basalt, which forms the entire left slope of Slavičí Valley. Here, basalts of varying chemical composition appear at the surface — representing a differentiated basalt body whose older parts form dykes, while the younger parts are lava flows, including classic examples of pillow lavas.
Above the basalt lies a narrow band of Motol Formation shales (Wenlock, Silurian). The right slope of the valley is formed by younger Kopanina Formation shales (Ludlow, Silurian). In the northern part of the reserve, in a narrow ravine leading toward Lochkov, the overlying Požáry Formation limestones and shales (Pridoli, Silurian) emerge at the surface.
The youngest part of the geological profile consists of the lower beds of the Lochkov Formation (Lochkovian, Lower Devonian), including a well‑developed Antipleura Bed, rich in bivalves and cephalopods. A typical exposure of this layer can be found at the site known as “U umučeného dubu” at the end of the ravine toward Lochkov.
Panel No. 7 and the tourist shelter are located on land owned by Lesy České republiky.
