Karst aquifers provide drinking water for 10% of the world's population, support agriculture, groundwater-dependent activities, and ecosystems. These aquifers are characterised by complex groundwater-flow systems, hence, they are extremely vulnerable and protecting them requires an in-depth understanding of the systems. Poor data accessibility has limited advances in karst research and realistic representation of karst processes in large-scale hydrological studies. In this study, we present World Karst Spring hydrograph (WoKaS) database, a community-wide effort to improve data accessibility. WoKaS is the first global karst springs discharge database with over 400 spring observations collected from articles, hydrological databases and researchers. The dataset's coverage compares to the global distribution of carbonate rocks with some bias towards the latitudes of more developed countries. WoKaS database will ensure easy access to a large-sample of good quality datasets suitable for a wide range of applications: comparative studies, trend analysis and model evaluation. This database will largely contribute to research advancement in karst hydrology, supports karst groundwater management, and promotes international and interdisciplinary collaborations. Background & Summary Karst aquifers are essential sources of drinking water to about 10% of the world's population 1. In many regions across the globe, karst groundwater is also an indispensable resource for ecosystems, agriculture and, economic activities, as well as for tourism and recreation 2,3. For example, in Europe, 21.6% of the land surface is underlain by carbonate rock 4 which contributes up to 50% of supplied drinking water in some countries 5-7. However, groundwater flow in karst aquifers is characterised by a complex interplay of fast-flowing conduit and slow-flowing matrix systems 8,9. Hence, the storage capacity of karst aquifers is variable and systems are extremely vulnerable to climatic pressures, human impacts and contamination 10. In order to ensure adequate protection of karst water sources, in-depth hydrogeological knowledge is necessary. Large-scale modelling and comparative water resource research have shown the great value of large datasets in hydrology 11. Numerous studies have applied these large datasets for several purposes such as model evaluation, global parameter estimations, impact studies, statistical and comparative analyses. For instance, large-scale hydrological models such as WaterGAP 12 used discharge data from the Global Runoff Data Centre (https://www. bafg.de/GRDC) for parameter estimation. Likewise, streamflow data from the Model Parameter Estimation Experiment (MOPEX) 13 and the Global Runoff Data Centre (GDRC) were combined to derive global base flow indexes and recession constants 14. Streamflow observations of near-natural catchments obtained from UNESCO's European Water Archive (EWA) were used to investigate the streamflow trends across Europe and differentiated the impacts from climatic variability and anthropogenic dri...

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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.

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