Prehradni nadrz HRACHOLUSKY EarthCache

[CZ] Hracholusky je prehradni nadrz v okresech Tachov a Plzen sever. Ma rozlohu 470 ha a maximalni hloubka je 31 m. Pres prehradu vede Pnovansky most. Jeji soucasti je sypana hraz o delce 270 m a sirce v korune 5 m a vysce priblizne 26,5 m. Kvalitu vody je mozne zjistit na Krajske hygienicke stanice: Vodni nadrz Hracholusky - Hraz, Vodni nadrz Hracholusky - Radost.

Vodni dilo Hracholusky bylo vybudovano v letech 1959 - 1964 na rece Mzi, ktera prameni v Ceskem lese a vteka do Berounky. Prehrada je zasobnikem vody pro prumyslove, energeticke a zemedelske vyuziti v Plzenskem kraji. Slouzi take k castecne ochrane pred povodnemi.

Hraz je vybudovana jako zemni sypana se sikmym jilohlinitym tesnenim v navodni casti. Navodni lic je chranen dlazbou z betonovych prefabrikatu a vzdusni strana je zatravnena. V leve casti hraze je vybudovan sdruzeny vezovy objekt, ktery obsahuje malou vodni elektrarnu s Kaplanovou turbinou, ovladani dvou uzaveru vypustneho zarizeni a sachtovy preliv. Ale vice o vodni elektrarne si povime v dalsi casti listingu. Hlavnim ucelem tohoto vodniho dila je akumulovat vody pro prumyslove, energeticke a zemedelske vyuziti v zapadoceskem regionu. Dale slouzi k castecne ochrane uzemi pred ucinky velkych vod. Blizkost mesta Plzne i hranice se SRN zvysuji vyuzivani vodniho dila take k rekreaci. Na nadrzi je vyhlasen rekreacni rad, zvlaste pro soustredenou rekreaci v oblastech Butov, Hracholusky a Radost.

Priroda kolem a geologie

Hracholusky jsou obklopeny Krivoklatskymi lesy a radou chranenych prirodnich oblasti. Vedle zakonem chranenych rostlin koniklec, netresk, taricka skalni, rozchodniky a lomikameny muzete v okolnich lesich nalezt i vzacne dreviny jako jerab muk, jalovec obecny, skalnik celokrajny, cerny tis nebo tresen krovitou. V letnich mesicich je na jezere provozovana lodni doprava s motorovou lodi pro 150 osob. Pri projizdce lodi muzete obdivovat nadherne skalni masivy, ktere lemuji brehy prehrady.

Zvlaste na jiznim brehu lze pozorovat vyraznou foliaci, misty jemne vrasneni, cetne kremenne sekrece. Metamorfni foliace je blizka vrstevnatosti a ma smer severovychodni az jihozapadni s uklonem kolem 70-80° k jihovychodu. Oblast radime jako barrandienske proterozoikum a cistecko-jesenicky masiv. Vyskytuji se zde horniny typu bridlice, fylit a droba.

Cela prehrada je ve fylitickych bridlicich a drobach. Tyto horniny jsou neoproterozoickeho stari a patri do kralupsko-zbraslavske skupiny Barrandienu, jako celek to patri pod bohemikum. Plochy teren nad prehradou je vetsinou prekryty tretihornimi sterky a pisky, je to videt treba v zarezu silnice pod kapli v Hracholuskach a na spouste dalsich mist.

Manipulacni rad a povodne

Podle soucasneho manipulacniho radu prehrady Hracholusky je mozne vypoustet vodu tak, ze snizeni hladiny muze dosahnout rychlosti maximalne 50 centimetru za den, za tyden to pak muze byt v souctu maximalne 2,5 metru. Planovane zmeny by mely v nadrzi vytvorit vetsi rezervu pro vodu a zabranit dalsi hrozbe povodni. K manipulaci s vodni hladinou by pritom melo dochazet zejmena behem zimnich mesicu. Navrh noveho manipulacniho radu take pocita s tim, ze bude mozne snizovat hladinu i podle toho, kolik snehu lezi v povodi. Od hydrometeorologu totiz dostavaji vodohospodari jednou tydne odhad mnozstvi vody, ktere je akumulovano ve snehove pokryvce v povodi nadrze. Podle toho by se mela preventivne postupne snizovat hladina tak, aby na jare i pri pozvolnem tani bylo garantovano opetovne doplneni nadrze na pozadovanou rekreacni uroven. Pri velkych jarnich povodnich v lednu 2003 Hracholusky Plzni citelne pomohly. Zadrzely vodu na Mzi tak dlouho, dokud pres mesto neodtekly dalsi tri kulminujici reky. Napor vody nebyl pro mesto na soutoku ctyr rek nakonec tak silny. Zvolil se takovy postup, kdy se postupne zvedali klapku na bezpecnostnim prelivu tak, aby co nejdele drzeli neskodny odtok z prehrady.

Vodni elektrarna

Nedilnou soucasti prehrady je i vodni elektrarna. Je zvlastni tim, ze nestoji v proudu pod prehradou jako jine elektrarny, ale nad hrazi v klidne vode. Elektrinu vyrabi trimegawattova Kaplanova turbina. Vytahem se da dojet az dvacet pet metru pod hladinu. Tato elektrarna funguje pouze vahou vody, ktera je nad ni. Kaplanova turbina je pretlakova axialni turbina s velmi dobrou moznosti regulace. Toho se vyuziva predevsim v mistech, kde neni mozne zajistit staly prutok, nebo spad. Turbinu vynalezl profesor brnenske techniky Viktor Kaplan. Od sveho predchudce, Francisovy turbiny, se lisi predevsim mensim poctem lopatek, tvarem obezneho kola a predevsim moznosti regulace naklonu lopatek u obezneho i rozvadeciho kola.

Mze

Prehrada Hracholusky je vybudovana na rece Mze. Je to vyznamna reka v zapadnich Cechach, zdrojovy tok Berounky. Delka toku je 106,5 km. Plocha povodi meri 1828,6 km2. Prameni v nadmorske vysce 726 m na uzemi Nemecka v Griesbasskem lese (Griesbacher Wald) asi 1 km jizne od osady Asch. Na kratkem useku tvori statni hranici a po 3 kilometrech toku, v nadmorske vysce 639,7 m, vstupuje zcela na uzemi Ceske republiky. Dale pokracuje jihovychodnim az vychodnim smerem a proteka mesty Tachov a Stribro (nemecke jmeno Stribra je shodne se jmenem reky). Na Mzi se nachazeji vodni nadrze Lucina (vodarenska) a Hracholusky (viceucelova). K nejvyznamnejsim pritokum patri z leve strany Hamersky potok a Kosovy potok (Kosi potok), z prave strany je to Uhlavka. V Plzni se Mze v nadmorske vysce 301 m spojuje s Radbuzou a od tohoto mista nese nazev Berounka. Vetsi pritoky: leve – Hamersky potok, Kosovy potok (Kosi potok), Cernosinsky potok, Utersky potok, Zebracky potok prave – Sklarsky potok, Luzni potok, Sedlistsky potok, Uhlavka, Vejprnicky potok

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The dam was built as a ground strewn with inclined sealing of clay and clay in the upstream section. Upstream face is protected from precast concrete pavement and air side of the grass. On the left side of the dam is built tower clustered object, which contains a small hydro power plants with Kaplan turbines, two valves control the discharge device and shaft spillway. But more about hydro power plant will discuss in the next section listing. The main purpose of this dam is to accumulate water for industrial, energy and agricultural uses in the West Bohemian region. It also provides partial protection against the effects of floods. The proximity of the city of Pilsen and the borders with Germany increased use of water works also for recreation. The tank is designated recreational procedure, especially in areas of concentrated recreation Butov, Hracholusky and Radost.

About nature and geology

Hracholusky is surrounded by Krivoklat forests and a number of protected natural areas. In addition to proprietary products Pulsatilla, houseleek, taricka rock, Sedum and saxifrage can be found in the surrounding forests and rare species such as cranes torment, juniper, cotoneaster entire, black or cherry krovitou thousand. In summer the lake is operated shipping cruiser for 150 people. When you drive a boat you can admire the magnificent rocks, which line the shores of the dam.

Especially on the south bank can observe a strong foliation, fine folding seats, numerous quartz secretion. Metamorphic foliation is close to the layering and has a northeast to southwest direction with the inclination around 70-80 ° to the southeast. The area we rank as Barrandian Proterozoic and cistecky-jesenicky massif. Morphologicaly interesting locality of Neoproterozic phylites with net of quartz veines.

Handling procedure and floods

Under the current order handling HRACHOLUSKY dam to drain the water by lowering the speed can reach up to 50 inches per day, per week, then it may be, for up to 2.5 meters. Planned changes should be in the tank to create a larger reserve of water and prevent further flood threat. To manipulate the water level would take place while especially during the winter months. Proposal for a new order handling also anticipates that it will be possible to reduce the surface and depending on how much snow is in the basin. From hydrometeorologu water resources is receiving a weekly estimate of the amount of water that is accumulated in the snow cover in the catchment tank. Accordingly, should gradually reduce the level of precaution so that even in a slow spring thaw was guaranteed re- filling of the required recreational level. The big spring floods of January 2003 HRACHOLUSKY Pilsen significantly helped. Water detained on Mze until flowing too through the city culminating three rivers. The onslaught of water was for the city at the confluence of four rivers in the end so strong. He chose such an approach, which has gradually raised the flap on the safety overflow, so that as long held harmless outlet from the dam.

Hydroelectric power station

An integral part of the dam and hydroelectric power. It is special because it stands in the stream below the dam, like other plants, but the dam in the calm water. Electricity produces 3 MW Kaplan turbine. The lift can reach up to twenty five meters below the surface. This power works only water weight that is above it. Kaplan turbine is pressurized axial turbine with a very good possibility of regulation. This is used mainly in places where it is not possible to control the flow or momentum. Turbine technology invented by professor Viktor Kaplan Brno. From his predecessor, Francis turbines differ by small numbers of blades, shape of the impeller and the opportunity to control the angle of blade runner manifold and wheels.

River Mze

Hracholusky dam is built on the river Mze. It is an important river in western Bohemia, the source flux Berounka. Length of river is 106.5 km. Basin area measuring 1,828.6 square kilometers. It rises at an altitude of 726 m in Germany in Griesbach Forest (Forest Griesbacher) about 1 km south of the village of Asch. The short section forms the border at 3 kilometers and flows, at an altitude of 639.7 meters, comes entirely in the Czech Republic. He continued south to east and flows through the towns Tachov and Silver (silver German name is identical with the name of the river). The Mze are Lucina water (water) and HRACHOLUSKY (multipurpose). The largest inflows are from the left side of the Kosi creek and Hamersky Creek, from the right side is Uhlavka. In Pilsen, the river at an altitude of 301 m and joins the Radbuzou from this place called Berounka. Larger tributaries: Left - Hamersky creek, Kosi creek, Cernosin creek, Utery creek, Zebrak Creek; Right - Sklar Creek, Luzni creek, Sedlistsky creek, Uhlavka, Vejprnicky creek.