A Conceptual Model of Groundwater Dynamics in the Catchment Area of the Zagorska Mrežnica Spring, the Karst Massif of Kapela Mountain

Abstract

The investigation area is located in the world-famous Dinaric karst. This study presents a conceptual model of groundwater dynamics and its interaction with surface waters, extending from the natural water retention of the Drežničko Polje to the spring zone on the far side of the Kapela Mountain range, including a description of the regional groundwater flow in the Zagorska Mrežnica spring zone. The aim of this research was to determine the possibility of an artificial enlargement of the natural retention of this karst field. Large amounts of water could be exploited in this way for the existing hydroelectric power plants of Gojak and Lešće on the Donja Dobra River. The prolonged retention of the water wave in the Drežničko Polje would extend its efficiency in regards to the production of electrical energy, and simultaneously achieve the mitigation of floods that frequently occur in the broader area of Ogulin. Photogeological analysis of the area was performed, together with geological and hydrogeological mapping, groundwater tracing, measurements of water flows in streams and springs, exploratory drilling and measurements of water levels in 26 piezometric boreholes in the Drežničko Polje. Available meteorological data from nearby weather stations (Jasenak, Drežnica and Modruš) were exploited, as well as hydrological data collected specifically for the modelling of runoff. Based on the results of the data processing, this study has determined: (1) the dynamics of the groundwater flow from the Drežničko Polje to the spring area of the Zagorska Mrežnica, (2) the dynamics of recharge and discharge of the natural retention of the Drežničko Polje; and (3) an improved interpretation of the Zagorska Mrežnica karst spring dynamics. The obtained results of groundwater flow dynamics indicate typical karst flow conditions in the Dinaric Karst, but also contain some specific features.

Impact of Land Use on Karst Water Resources—A Case Study of the Kupa (Kolpa) Transboundary River Catchment

“…Poorly permeable rocks (dolomites, dolomitized limestones from the Upper Triassic to Lower Cretaceous) have the permeability ranging from 10 −6 to 10 −8 m/s. Flysch complex from the Lower Triassic to Eocene has permeability <10 −8 m/s as mentioned by Buljan et al [6] based on [44]. The groundwater level in Jurassic and Cretaceous limestone corresponds to the nearest surface flows.…”

“…Due to the hydrogeological complexity of its karstic part, the exact catchment boundaries are difficult to determine. The SW catchment boundary, which represents the contact between the Adriatic Sea and the Danube River basins [3,6,21], and the N boundary in Slovenia are clearly defined with tracing experiments [22,23]. The NE boundary, which corresponds to the contact between the Dinarides and the Pannonian basin, was previously defined by several authors, namely Bura [24], Roglić [25], Herak [26], and Bogunović and Bensa [27].…”

“…The spring of Zagorska Mrežnica occurs with several other smaller springs and was dammed to form the artificial hydro-technical lake Sabljaci, while its water is transported through the tunnel towards Bukovnik Lake and the HPP Gojak. Moreover, during the rainy season, a significant volume of water flows over the dam, forming the flow of Zagorska Mrežnica River that sinks several kilometers downstream and flows underground into the adjacent catchments of the Tounjčica and Dobra rivers [6]. The Mrežnica River has Peripannonian pluvial-nival regime with the first discharge maximum in March or April and the second in December, while a minimum is observed in August and February [36].…”

Analysis of the hydraulic connection of the Plitvica stream and the groundwater of the Varaždin alluvial aquifer

“…In case of replacing the order of the time series, the same correlogram will be obtained, only of the opposite sign. Cross-correlation analysis was usually performed in karstic catchment (Fronzi et al, 2020;Buljan et al, 2019;Pavlić and Parlov, 2019).…”

Uloga nagiba padina, gustoće vrtača i analize vodne bilance u izdvajanju kompleksnog slivnog područja rijeke Slunjčice (Hrvatska)

“…Cross-correlation and cross-spectral analysis of hydrographs in the northern part of the Dinaric karst of Croatia showed that the hydrogeological characteristics of karstic aquifer systems can present more controlling factor related to the runoff regime when compared to climate change influence (Pavlić and Parlov, 2019). Hydrogeology research of the catchment area of the Zagorska Mrežnica spring was focused to the definition of influence related to designing an injection curtain (Buljan et al, 2019), while in the southern part of Dinaric karst different kind of statistical analysis have been used to evaluate the functioning of Rumin springs (Denić-Jukić et al, 2020). In the northern part of Dinaric karst it has been shown that in the Nanoščica River and Ljubljanica River catchment lower summer discharge can be expected which indicates increase of karst river vulnerability and groundwater availability in near future (Sapač et al, 2019).…”