By using stable oxygen and hydrogen isotopes in hydrological studies one can obtain answers to questions that are difficult to answer with standard hydrological measurements. For example, with stable isotopes we can determine where the water goes when it rains and identify the flow paths of rainfall to the streams. This paper shows theoretical background of stable isotopes applications in hydrological studies and connection with some of the hydrological processes such as (sub)surface runoff generation. We give a short overview of previous studies (focusing on the last 15 years) that used stable isotopes with an emphasis on studies in Slovenia. In the last part of the paper some preliminary results of an ongoing research project are presented. This project focuses on the hydrological response of the nonhomogeneous Ljubljanica catchment with the aim to enhance the knowledge about hydrological processes using stable isotopes.
COBISS.SI-ID: 8081249
Extreme events such as flash floods and debris flows are frequent phenomena that occur in steep torrential catchments; these kinds of events can cause notable geomorphic changes. Repeated terrestrial laser scanning (TLS) surveys were performed in a steep forested catchment of the Kuzlovec torrent in central Slovenia, where a ~ 200-m long section of the torrent was scanned. The main aim of this study was to perform the geomorphic response detection in the torrent due to hydro-meteorological events of different magnitudes. After applying several pre-processing steps, digital terrain models (DTMs) with a cell resolution of 5 cm were produced. The geomorphic change detection was performed using the DTM of Difference approach (DoD). Several above-average flow events occurred in the period from 2013 to 2015 (some of them can be regarded as floods). The 2014 August extreme flash flood that was initiated by the rainfall event with a return period exceeding 100 years, led to erosion rates of an order of magnitude higher than average annual erosion rates. Moreover, the analysis of the geomorphic changes shows that the August 2014 flash flood caused intense sediment transport processes that resulted in the changes at the location of the main stream channel thalweg and reduced channel roughness.
COBISS.SI-ID: 7507041
In the case of ungauged catchments, different procedures can be used to derive the design hydrograph and design peak discharge, which are crucial input data for the design of different hydrotechnical engineering structures, or the production of flood hazard maps. One of the possible approaches involves using a hydrological model where one can calculate the design hydrograph through the design of a rainfall event. This study investigates the impact of the design rainfall on the combined one-dimensional/two-dimensional (1D/2D) hydraulic modelling results. The Glinščica Stream catchment located in Slovenia (central Europe) is used as a case study. Ten different design rainfall events were compared for 10 and 100-year return periods, where we used Huff curves for the design rainfall event definition. The results indicate that the selection of the design rainfall event should be regarded as an important step, since the hydraulic modelling results for different scenarios differ significantly. In the presented experimental case study, the maximum flooded area extent was twice as large as the minimum one, and the maximum water velocity over flooded areas was more than 10 times larger than the minimum one. This can lead to the production of very different flood hazard maps, and consequently planning very different flood protection schemes.
COBISS.SI-ID: 8314209
The geophysical and hydrological processes governing river flow formation exhibit persistence at several timescales, which may manifest itself with the presence of positive seasonal correlation of streamflow at several different time lags. We investigate here how persistence propagates along subsequent seasons and affects low and high flows. We define the high-flow season (HFS) and the low-flow season (LFS) as the 3-month and the 1-month periods which usually exhibit the higher and lower river flows, respectively. A dataset of 224 rivers from six European countries spanning more than 50 years of daily flow data is exploited. We compute the lagged seasonal correlation between selected river flow signatures, in HFS and LFS, and the average river flow in the antecedent months. Signatures are peak and average river flow for HFS and LFS, respectively. We investigate the links between seasonal streamflow correlation and various physiographic catchment characteristics and hydro-climatic properties. We find persistence to be more intense for LFS signatures than HFS. To exploit the seasonal correlation in the frequency estimation of high and low flows, we fit a bi-variate meta-Gaussian probability distribution to the selected flow signatures and average flow in the antecedent months in order to condition the distribution of high and low flows in the HFS and LFS, respectively, upon river flow observations in the previous months. The benefit of the suggested methodology is demonstrated...
COBISS.SI-ID: 8649313
Suspended sediment load (SSL) observations are usually less frequent than precipitation and river discharge measurements; therefore a reliable procedure is needed for the estimation of SSL. One year of precipitation, SSL, and discharge measurements at 20-min intervals were performed at the Kuzlovec torrent in Slovenia. The Frank copula was selected to construct an event-based model using the following variables: precipitation sum (P), peak discharge (Q), and SSL. The idea was to estimate the SSL based on the measured P and Q. The proposed model was additionally tested using the daily data from the Gornja Radgona station on the Mura River, for which 29 years of data were available and where Khoudraji-Liebscher copulas were used. The estimated SSL values using the copula were compared with different regression models. The proposed copula model yielded meaningful SSL estimates. Some performance criteria and tests indicated that the copula model gives a better fit to the measured data than other tested methods.
COBISS.SI-ID: 8124769