Ombla Spring EarthCache
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Welcome to the start of the Ombla Spring. This system is caused by
a reverse fault and also is part of the Trebisnjica River which is
a river in Bosnia and Herzegovina; it was one of the longest
sinking rivers in the world.
English
Ombla spring/river is on the Adriatic coast near the town of Dubrovnik. The spring discharges at sea level and to eliminate the influence of tide, a small dam was constructed 50 meters downstream of the spring outlet. The spring water overflows the dam wall at an elevation of 2.4 meters. The spring outlet/river is here due the top section of rocks moving up and the bottom section of rocks moving down in this area, this is what’s known as a reveres fault. The top section of rocks that were formed during the Jurassic times (Volcanic, limestone and dolomite) moved up over the Flysch sediment (overthrusted). Flysch is basically sedimentary deposits consisting of a thin bed of shale or marl or it can have coarser deposits. This almost forms a water barrier known as Hydro geological barrier.
The top layers of rocks (dolomite and limestone) from the fault are strongly fractured, and these splits can go for a few 100 meters below the surface. The top surface of this landscape is Karstified, which means the landscape under lain by limestone has been eroded, producing ridges, towers, fissures, sinkholes and many other landforms.
From doing research on the internet I found that more than 100 swallow holes, caves and shafts were investigated in the catchment area. The catchment area is about 600 km2, this area or the Flysch zone been a Hydro geological barrier (water barrier) catches all the water in the catchment area, and due to erosion at this point which is at sea level Ombla spring/river is formed. There is some help with recharging or filling up of water in this catchment area from inland catchment with an area of 1630 km2
So basically this whole area is one big swimming pool (600km2) filled with rocks and water and at one point there is a small hole letting the water out, and this is Ombla spring/river.
Lots of water so much in fact that the average recorded amount of water coming out at Ombla was 33.8m3/s, until construction took place on the Trebišnjica Hydro system, this system is a river that flows through the catchment area. In order to have more water flow through the river for other use and not sink into the catchment area the river bed was cemented for about roughly 60 km. After this then the yearly average of water coming out at Ombla dropped to 24.4m3/s. The recorded minimum and the maximum amount of water coming out was 2.3m3/s and 112.5m3/s. Water temperature of Ombla does vary during the year from 12.0 to 14.8 °C.
After there has been rain in the catchment area the Spring can respond in less than four hours, and within 10 hours sometimes discharge can increase from 20m3/s to 88m3/s.
With all this water coming out and always coming out, Dubrovnik water works started using the water to supply Dubrovnik with water from 1897. There are future plans to build a hydroelectric plant in this area, but the plant will be built into the mountain and only the control house/building will be located on the outside.
To Log this Cache: E-mail your answers to us.
1) When looking at the mountain at the back of the spring from the waypoint. What is the angle that the rocks are laying to a horizontal imaginary line, due to the reverse fault action in this area?
2) (Optional, but nice) Once you have reached the waypoint, you could walk through the alley (NNE) way between the two ruined buildings and turn left. Take a photo in Landscape with you and your GPS or just GPS. The left of the photo could have the dam wall and the right three crank handles of the sluice gates..
SOURCES & Links of Interest:
(visit link)
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(visit link)
(visit link)
Croatian/Hrvatska
Dobro došli na pocetak rijeke Omble.
Ovaj sustav je dio Trebišnjice, rijeke u Bosni i Hercegovini; bio je jedna od najdužih ponornica na svijetu.
Ombla je na jadranskoj obali, u blizini grada Dubrovnika.
Da se eliminira utjecaj plime izgradena je mala brana 50 m nizvodno od vrela. Izvorska voda prelijeva zid brane na visini od 2,4 m.
Izvor rijeke je ovdje zbog toga sto se na ovom podrucju gornji dio stijena podize a donji dio spusta , to je poznato kao inverziona greska.
Gornji dio stijena koje su nastale tijekom Jurskog vremena (vulkanski, vapnenac i dolomit) se popela preko flišne podloge. Fliš je u osnovi sedimentna naslaga koja se sastoji od tankog kreveta od škriljca ili lapora, a može imati i dublje depozite. To skoro formira vodenu barijeru poznatu kao hidrogeološka barijera.
Gornji slojevi stijena (dolomit i vapnenac) imaju snažne frakture i ti procjepi mogu ici nekoliko stotina metara ispod površine.
Gornja površina tog krajolika je okršena, što znaci da su postojale erozije tvoreci grebene, kule, pukotine, ponikve i sl. Više od sto rupa, špilja i jama su istraživane u slivnom podrucju.
Slivno podrucje je oko 600 km2, ovo podrucje ili zona fliša kao hidrogeološka barijera hvata sve vode u slivnom podrucju te zbog erozije u ovoj tocki koja je na razini mora Ombla se formira. Tu je pomoc oko punjenja vode u tom slivu iz unutrašnjosti sliva s površinom od 1630 km2.
Tako je u osnovi taj cijeli prostor jedan veliki bazen (600 km2) ispunjen stijenama i vodom i u jednom mjestu je rupa koja pušta vodu van tvoreci Omblu.
Prosjecna zabilježena kolicina vode koja izlazi na Omblu je 33,8 m3/s. Da bi bilo više protoka vode kroz rijeku i za druge svrhe, a da ne potone u slivno podrucje rijeke krevet je cementiran oko 60 km.
Nakon toga godišnji prosjek protoka vode je pao na 24,4 m3/s. Zabilježen minimum i maksimum protoka vode je 2,3 m3/s i 112,5 m3/s.
Temperatura vode varira tijekom godine od 12-14,8 stupnjeva Celzijusovih. Nakon kiše u slivnom podrucju može odgovoriti u manje od cetiri sata, te u roku od 10 sati protok može pojacati od 20m3/s do 88 m3/s. Dubrovnik je zapoceo opskrbu vodom 1897.g.
Da biste prijavili ovaj Cache pošaljite e-mailom Vaše odgovore:
1. Kad se gleda na planine u pozadini pod kojim kutem stijene leže na horizontalnu zamišljenu liniju zbog obrnutog djelovanja na ovom podrucju?
2. Nakon što ste dosegli putne tocke, možete prošetati kroz ulicu (SSI) putem izmedu dvije srušene zgrade i skrenite lijevo. Slikajte se u krajoliku sa Vašim GPS-om ili samo GPS. Fotografija lijevo može imati zid brane, a desno tri rucke od zaštitnih vrata.
SOURCES & Links of
Interest: (visit link)
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Additional Hints
(No hints available.)