Josip Rubinić

Review of Monitoring Parameters of the Kostanjek Landslide (Zagreb, Croatia)

Since 2011, in the framework of the Croatian-Japanese SATREPS FY2008 Project, scientists have been working on the establishment of the Kostanjek landslide monitoring system in the City of Zagreb (Croatia). External triggers at Kostanjek landslide are measured with rain gauge and accelerometers. Displacements at the surface are measured by GNSS sensors and extensometers, while subsurface displacement is measured by vertical extensometers and inclinometer. Hydrological measurements consist of groundwater level measurements, discharge measurements, chemical and isotope analysis. Monitoring sensors recorded landslide reactivation due to external triggers in the winter period of 2012/2013. During the period from September 2012 to March 2013 the total cumulative precipitation was 793.7 mm and horizontal displacements were in the range of 9–20 cm. The installed monitoring sensor network proved to provide reliable data for the establishment of relations between landslide causal factors and landslide displacement rates aimed at establishing threshold values for early warning system.

Stable isotope analysis of the karst hydrological systems in the Bay of Kvarner (Croatia)

Here we present the results of the first systematic analysis of the stable isotope composition of the karst hydrological systems in the Bay of Kvarner. Gaussian mixture modelling, time series analysis and autoregressive integrated moving average (ARIMA) modelling were applied using the stable isotope compositions of the karst groundwater. This study revealed that the recharge is dominated by winter precipitation, the dual-porosity system is dominated by baseflow, the hinterlands of the individual springs have different degrees of karstification and the springs within the Rječina River catchment have higher recharge elevations than the springs in the Bakar Bay catchment.

Annual runoff estimation—an example of karstic aquifers in the transboundary region of Croatia and Slovenia

Abstract An approach to the global estimation of water balance elements and their spatial distribution using GIS is presented. It is primarily related to the catchments where measured data are scarce and the spatial differentiation of the hydrological characteristics is not possible without climatological data. Emphasis is placed on estimating the water balance of transboundary karstic aquifers, where problems concerning the hydrometeorological data, catchment boundaries and determination of water balance elements in general are far more complex. The runoff estimation was done using the Turc and Langbein methods, which are the most frequently applied in this region. The years 1961–1990 were used as the reference period. Based on comparison of the results, the applicability of the methods is discussed. The approach proposed is suitable for estimation of water balance in the study area and may also be applied in a wider region.

Water regime of Vrana Lake in Dalmatia (Croatia): changes, risks and problems

Abstract Vrana Lake in Dalmatia is a karstic kryptodepression connected to the nearby sea through the karstic subsoil and a canal. Due to interactions with the sea, lake water salinity increases greatly during severe dry periods, seriously endangering the ecosystem. Trend analysis (1961–2010) reveals a decrease in precipitation and surface inflow, but an increase in air temperature, and in sea and lake water levels. Lake inflow and water losses are only partially monitored. Average annual inflow from the monitored part of the catchment is 1722 m3 s-1, but total inflow is significantly greater; the average difference between total inflow and cumulative water losses is 3072 m3 s-1. The paper uses modelling to evaluate total inflow into the lake system, taking into consideration projected climate changes/variations till 2100 from the RegCM3 and ALADIN climate models. The analysis indicates marked decrease in discharge values by the end of this century, by as much as 60%. Editor Z.W. Kundzewicz

Groundwater Protection and Climate Change Predictions of a Complex Dinaric Karst Catchment. A Case Study of the Bokanjac-Poličnik Area, Croatia

The paper deals with two main issues: climate change impact on water supply and sanitary protection zones of a very sensitive Dinaric karst catchment “Bokanjac-Policnik” in Zadar area, northern Dalmatia, Croatia. Within this complex hydrogeological system there are five public extraction sites (Bokanjac wells, Jezerce estavelle, Oko well, Golubinka spring, and Boljkovac well). Their catchments (subcatchments of the Bokanjac-Policnik system) are interwoven and share common areas—at this moment there is no possibility of their delineation and they should be treated as one hydrogeological karst system. Since this area is close to the Adriatic Sea coast, some of these water supply sites are subjected to the underground seawater influence. In the paper it is discussed how changes (decreases of recharge) of water balance will cause decrease of extracted quantities and possible deterioration of water quality (increase of salinity). Therefore, sanitary protection zones should be established and further research of this karst system corroborated by the continuous water quality monitoring is needed, with the special regard to climate changes.

Analysis of interrelation between water quality and hydrologic conditions on a small karst catchment area of sinking watercourse Trbuhovica

Sinking watercourse Trbuhovica is located at the topping karst of Gorski Kotar in Croatia, near the Slovenian border. About 900 inhabitants live in Trbuhovica catchment area. Sewage system had not been built. The project KEEP WATERS CLEAN (INTERREG III A project) was approved by EU commission and has a purpose of investigating water resources of that area, their appropriate protection and improving management of those resources. This paper presents projects 1st phase investigation results: hydrologic conditions and water quality at several locations on stream and at the springs of Trbuhovica, Mlake and Obrh. Climatologic (precipitation, air temperature and snow cover), basic hydrologic characteristics (flow and water temperature), water quality parameters (pH, electric conductivity, alkalinity, oxygen regime, nutrients and mineral oils) and microbiology indicators have been monitored. Samples of micro invertebrates and samples of periphyton have been collected in the field. Biological results have been elaborated via Saprobial Index according to Pantle-Buck. Analyses results showed a strong connection between hydrologic condition and selected water quality parameters. The groundwater quality changes are very quick. Maximum pollutions occur during the period of intensive rain. Water at the spring of Mlaka is very clean and is classified in the first to second water category, while Trbuhovica shows higher organic pollution.