Measurements of the Outflow Along the Eastern Border of Planinsko Polje, Slovenia

Abstract

Gabro�šek: Merit�e odtoka na �zhodnem robu Planinskega polja, Slo�enijaPlaninsko polje je najbolj severozahodno kraško polje v nizu dinarskih polj. Je tipično pretočno-strukturno polje s kraškimi izviri na južni strani, ki napajajo vodotok Unico. Unica preko polja vijuga proti severu, kjer je glavno ponorno območje. Na poti se tok povsem približa vzhodnemu robu polja, kjer reka izgublja vodo v več ponornih območjih skozi izrazite požiralnike, nize drobnih odprtin in dobro pretrto kamnino. Za oceno odtoka so bili izmerjeni pretoki Unice gorvodno in dolvodno od teh ponornih območij. Z akustičnim Dopplerjevim merilnikom pretoka je bilo izmerjenih sedem profilov, na podlagi njih pa so bile preračunane vrednosti za posamezno ponorno območje. štiri ure trajajoče meritve so potekale v času upadanja vode po delno poplavljenem Planinskem polju. V tem času je imelo šest ponornih območij odtok v vrednosti med 1 m 3 /s in 5.6 m 3 /s. V danih hidroloških razmerah je bil skupen odtok 18 m 3 /s. Rezultati prispevajo k boljšemu razumevanju delovanja kraških polj in so pomemben vhodni podatek morebitnih hidroloških modelov. Ključne besede: polje, odtok, ponori, pretok, akustični Dopplerjev merilnik pretoka, Planinsko polje, Unica. AbstractUDC 551.435.83:556.16(497.471) Matej Blatnik, Peter Frantar, Denis Kosec & Franci Gabro�šek: Measurements of the outflow along the eastern border of Pla� ninsko Polje, Slo�eniaPlaninsko Polje is the westernmost active polje of Dinaric karst. It is a typical overflow-structural polje, with springs on the southern side feeding the superficial flow of Unica River. The river meanders over the polje towards the terminal outflow area on its northern side, where it sinks back into the aquifer through several ponors. Along the reach in proximity to the eastern border of the polje, the Unica River loses water through several outflow zones into distinct ponors and into a set of small openings and fracture zones. To estimate the outflow rate along these zones, the Unica discharge was measured upstream and downstream to the outflow zone. Seven velocity profiles were recorded with an Acoustic Doppler Current Profiler and the corresponding discharges were calculated. The measurements were taken within four hours during the flow recession following a partial flooding of the Planinsko Polje. Therefore, six outflow zones were evaluated with an outflow rate ranging between 1 m 3 /s and 5.6 m 3 /s. The total loss of water along the eastern border summed up to 18 m 3 /s under the given hydrological conditions. These results give new insight into the functioning of karst poljes and provide an important input for eventual future hydrological modelling of the area.

Karst Brackish Springs of Albania

“…Sinkholes with an initial depth of a few meters can evolve to reach 15 m in depth, at the same time widening; often transformed into lakes, they are the most distinctive landform of the Dumre plateau, which hosts about 80 karst lakes (most of them being permanent), for a total area of 7.70 km 2 . This is also typical of similar karst settings and poljes in other countries [48][49][50][51][52].…”

Slovene Classical karst: Kras Plateau and the Recharge Area of Ljubljanica River / Klasični kras: planota Kras in kraško zaledje izvirov Ljubljanice

“…The springs located on the southern side recharge the Unica River that sinks in two major outflow zones located along the eastern and northern borders of polje (Figure 15). The polje surface is slightly undulating and about 10 km 2 large, with a bottom elevation between 444.5 m and 450 m a.s.l (Blatnik et al 2017). Apart from the wetlands close to the Unica, the polje is used for field crops and grass.…”

Understanding the temporal variation of flow direction in a complex karst system (Planinska Jama, Slovenia)

“…The Idrija Fault Zone forces the groundwater to surface, which led to the formation of a series of Dinaric Poljes, with springs and ponor zones at the rims and over-crossing superficial streams Blatnik et al 2017;Blatnik et al 2019).…”