Weir on Hucava River
The name of the river Hucava reveals a lot about its character, as it reflects the sound of falling water. Hucava flows from the caldera of Polana, which is one of the greatest volcanic remnant and also the highest volcanic mountain in Slovakia (1458 m a.s.l.). Polana is part of the Polana Protected Landscape Area (designated in 1981), it is a Site of Community Interest and Special Protected Area under NATURA 2000 Network. Since 1990, it is on the UNESCO list of Biosphere Reserves.
The river springs right under the Polana main peak (Velka Polana) at an altitude of 1330m. Thirty eight kilometres later on it flows into the Zolna River. Several interesting species can be found there apart from the common fish population, such as Noble crayfish (Astacus astacus, IUCN Red list – category Vulnerable) in the upper part of the river, together with Eurasian otter (Lutra lutra), Common kingfisher (Alcedo athis) or Black stork (Ciconia nigra). In the past, two barriers were built on this river near the village Ocova. This one represents an impermeable barrier for aquatic organisms, sediments and other important suspended solids in water.
Removal process in detail: The above-ground part of the weir will be demolished. Only the concrete foundation necessary for weir stabilisation will be left. Below the weir, scour hole will be preserved as a valuable habitat for fish. Sediments from the riverbed above the weir will be moved and placed downstream into the existing bank cavity without further technical stabilisation; natural hydromorphological processes of the river will ensure its modelling into a natural shape. Riparian vegetation strengthens the banks with its root system, therefore we recommend not to remove it.
Weir removal will support a free flow of aquatic organisms and sediments, which directly increases the natural riverine processes, river biodiversity and creates favourable conditions especiall for natural fish population.