Andrej Vidmar

The experimental watersheds in Slovenia

Experimental watersheds are critical to the advancement of hydrological science. By setting up three experimental watersheds, Slovenia also obtained its grounds for further development of the science and discipline. In the Dragonja experimental watershed the studies are focused on the afforestation of the watershed in a mediterranean climate, on the Reka river the water balance in a partly karstic area is examined, and on the case of the Glinscica stream the implications of the urban environment are studied. We have obtained valuable experience and tested new measuring equipment on all three experimental watersheds. Measurements and analysis on the experimental watersheds improved the current understanding of hydrological processes. They resulted in several PhD Theses, Master Theses and scientific articles. At the same time the experimental watersheds provide support to the teaching and studying process.

Climate Change Impact on Flood Hazard in the Sava River Basin

In the past few years, the topic of climate change impact on the water regime of the Sava River basin has been presented in several studies. Average seasonal precipitation and temperature data were calculated and presented, but results are not useful for climate change impacts on floods. The maximum daily precipitation data for each season and temperature data from the meteorological report are taken for the hydrological analysis. Maximum daily precipitations were provided with twenty-year and hundred-year return periods. The hydrological analysis was derived using a hydrological model calibrated for the flood event in 1974 before large flood protection scheme was developed along the Sava River. Flood peak discharges were calculated for autumn season by twenty- and hundred-year return period daily precipitation for the periods 2011–2040, 2041–2070 and 2071–2100. Changes in peak discharge probability functions were developed for the water station along the river for each period. The peak discharges will increase by the end of the twenty-first century for the 100-year return period from 9 % at the mouth up to 55 % at the head part of the river basin.

The role of seasonal and hydrological conditions in regulating dissolved inorganic nitrogen budgets in a forested catchment in SW Slovenia

During two consecutive years the monitoring of rainfall nitrate (NO3-) and ammonium (NH4+) concentrations, combined with high-frequency measurements of streamwater NO3- concentrations, provided insight into the mechanisms controlling the dissolved inorganic nitrogen (DIN) budgets of the forested Padež stream catchment in SW Slovenia. During both years, the catchments annual wet atmospheric DIN deposition (12.6 and 13.8kg-N/ha) exceeded the annual DIN export (10.7kg-N/ha and 8.8kg-N/ha). The analysis of the monthly DIN budgets discloses seasonal patterns. In winter and early spring, the catchment behaves as a net source of DIN, whereas during late spring, summer, and early fall the catchment generally behaves as a net sink of the atmospheric DIN. Due to large evapotranspiration in the growth period, most of the DIN remains in the catchment and is flushed during the dormant season. Despite high evapotranspiration and consequently low runoff coefficients characteristic for the Mediterranean climate, large rainfall events in the growth period can cause intensive washout of DIN from the catchment. At a monthly basis, the DIN flushing might exceed the catchments DIN retention capacity and the catchment might behave as a net source of DIN. Therefore, the hydrological conditions have the ability to shift the catchments role in regulating the DIN budgets. The high responsiveness of the streamwater NO3- concentration in the growth period indicates a large pool of DIN in the forest soils which can become mobile by runoff formation. Wet atmospheric DIN deposition at the Padež catchment is considerable; highest DIN inputs can be expected when air masses approach the catchment from the southwest to southeast where there are extensive urban areas along the Italian, Slovenian and Croatian coast. However, the Padež catchment does not appear to be approaching N saturation, presumably due to strong internal N cycle in the forest soils.

Development of model for the estimation of direct flood damage including the movable property

In recent decades, an increase in flood damage has been observed; therefore, the assessment of potential damage is becoming more important. Estimation of potential flood damage can be achieved with various existing models. However, their transferability is questionable and the actual availability of input data is often limited. To overcome these shortcomings, a new model has been developed to effectively estimate flood damage in Croatia. The proposed model uses only publicly available data such as the CORINE data set and information from censuses. The model was developed in an open source Geographic Information System programme. Validation of the model’s performance was performed using data from the extreme May 2014 flood that occurred in the Balkan Peninsula. Furthermore, the model has already been used in practice and has proven to be user-friendly due to the minimum input required from open source data, allowing for insights to be gained from data updates.

Slovenian experience in applicability of remote sensing data in hydrology

Nowadays remote sensing data are great value for many ways of use as for snow hydrology. Snow cover mapping on basis of satellite images is widely spread because it is easier than in-situ measuring and interpolating. To verify the use of satellite imagery (MODIS product) we used all available data of snow cover and satellite images and compared detected snow cover on images and in-situ measured snow cover. The information about clouds and snow cover measured on the Ljubljana climatological station were acquired and analysed. The use of satellite images showed out to be useless because of climate characteristics of Slovenia and low elevation of much area.