One-dimensional sediment transport modelling with Engelund–Hansen and Ackers–White transport equations for the Lower Danube River

Sediment transport can have a negative impact on riparian environments, as it can lead to the deterioration of ecological diversity and increase flood risks. Sediment transport modelling is thus a key tool in river basin management and the development of river training structures. In this study, we examined the appropriateness of 1D modelling for total sediment transport loads using the Engelund–Hansen and Ackers–White transport equations for the Lower Danube River. The study evaluated the effect of sediment grading on the accuracy of 1D model results, the appropriateness of 1D sediment transport modelling within technical or engineering projects, and the appropriateness of the Engelund–Hansen and Ackers–White equations for estimating sediment yield in the area of the Lower Danube River. The model results have been compared to field measurements, with the accuracy of the modelling results being evaluated with statistical tests. The obtained results show: (i) the sediment grading does not have a significant impact on the 1D modelling results, (ii) 1D sediment transport modelling gives sufficiently accurate results for practical engineering use (e.g. the estimation of dredging activities), and (iii) the Engelund–Hansen equation is generally better for sediment transport modelling in the Lower Danube River.

Bibliometric analysis of water footprint research in countries of former Yugoslavia

Sustainable development of water resources requires new tools and research in these fields of study. A systematic overview of water footprint research in countries of former Yugoslavia is presented through bibliometric analysis and publication review. The Scopus database was used as the data source. Among the countries of former Yugoslavia, only researchers from Slovenia, Serbia, Croatia, and Bosnia and Hercegovina published papers focused on water footprint research before March 2021. Research on water footprint in these countries was found to be insufficient in scope and intensity. The contribution of authors from the countries of former Yugoslavia is small compared to research in other countries all over the world but is not insignificant. Almost 2/3 of articles have already been cited by other authors. Two main centers of water footprint research are at the University of Maribor in Slovenia and at the University of Novi Sad in Serbia, respectively. The research is focused on the so-called volumetric water footprint, while the LCA water footprint stands outside the interest of the scientific community in countries of former Yugoslavia.

Application of the Hargreaves method for calculating the potential evapotranspiration in the hydrological modelling

To improve the results of the Slovenian Environment Agency’s hydrological forecasting system, especially in the river basins with lower specific runoff (Pomurje) and during high water events following a long dry period, we decided to find a good method for calculating daily values of the potential evapotranspiration (PET). We were deciding between several temperature-based methods for the daily reference evapotranspiration (ET0) values calculation. For selected meteorological stations we calculated ET0 using three different methods and then compared them to the ET0 values calculated using the much more complex Penman-Monteith method. Among the tested temperature methods the results given by the Hargreaves method fitted best to the results of the Penman-Monteith method. The reason for this may lie in the fact that the Hargreaves method, besides the mean daily air temperature as other temperature-based methods, considers the daily temperature range as well. Afterwards, considering the ground cover factor, we calculated the PET values from the ET0 values and then applied them in the hydrological modelling. The model setups for the Sava, Soča, and Mura Rivers were reanalysed twice, considering firstly the climatologic monthly PET values that were already used in the hydrological forecasting system of the Slovenian Environment Agency for many years, and, secondly the daily PET values calculated according to the Hargreaves method and using hourly air temperature 2 m above the ground, originating from the short-term weather forecasting model ALADIN or the INCA/AT meteorological system. At all selected calculation points, the model setups using daily PET values showed better performance over the model setups using climatological monthly values.

After 2000 Stože Landslide: Part II - Development of landslide disaster risk reduction policy in Slovenia

More than 20 years after the 2000 Stože Landslide that devastated the village of Log pod Mangartom in NW Slovenia, this paper gives a review of the short-term response to and disaster relief provided for this catastrophic event, and further summarises this event’s effects on Slovenia’s efforts to improve its system of preventing natural disasters caused by various forms of landslides. Recent advances in reducing landslide disasters in Slovenia after 2000 are presented, including hazard and risk maps for landslides, rockfalls, and debris flows based on modern methodologies. Also, a short overview is given of Slovenian international cooperation on natural disasters. The developments in the landslide disaster risk reduction policy have unfortunately been less obvious in terms of the state taking preventive measures by adopting relevant legislation for adequate spatial planning.

Heat transfer by seepage in sand: Influence of saturated hydraulic conductivity and porosity

Heat transfer within the soil is a complex process in the presence of seepage flow. In such conditions, the soil’s thermal behavior is influenced by the thermal and hydraulic properties of the medium as well as the initial conditions and boundary conditions to which the medium is subjected. This paper presents the experimental and numerical studies of heat transfer within the sand subjected to the seepage flow. It focuses on the influence of saturated hydraulic conductivity and the porosity of medium on the heat transfer process. The temperature distribution within the sand was monitored by the optical fiber Distributed Temperature Sensor (DTS). The experiment was performed on three types of silica-dominated sands with different saturated hydraulic conductivities and different Soil Water Characteristic Curve (SWCC). In addition to the experimental study, a coupled hydrothermal numerical model was designed in FEFLOW software and validated by comparing its results with the experimental measurements. To determine the influence of porosity and saturated hydraulic conductivity on heat transfer, we analyzed the numerical models for different values of porosity and saturated hydraulic conductivity. The numerical and experimental studies showed that the thermal velocity is higher in sand with higher saturated hydraulic conductivity and temperature declination occurs more quickly due to the heat convection process. Saturated sand with larger porosity has an overall higher heat capacity, wherefore the temperature declination started later in the measuring points but dropped down lower close to the temperature of the upstream water.

Nitrate Nitrogen (NO3-N) Export Regimes Based on High-frequency Measurements in the Kuzlovec Stream Catchment

In the paper, the determination of nitrate nitrogen (NO3-N) export regimes from the Kuzlovec catchment during rainfall events is presented employing various determination methods: the ratio of coefficient of variation of NO3-N concentration and discharge (CVC/CVQ), the slope of the regression line to the points of concentration and discharge logarithms (b), both mentioned indices together, and the relative change of the NO3-N concentration during the event (Crs). According to previous analyses, the amount of exported NO3-N during rainfall events comprises approx. 30% of the total export amount, while from a temporal point of view, rainfall events represent only 10% of the time. Export regimes were identified as chemostatic (concentration does not change with discharge) and chemodynamic (concentration changes with discharge). The latter were further divided into dilution and flushing regimes. 43 rainfall events from the period April 2018–April 2020 were included in the analysis. For these events, high-frequency data of 20-minute intervals were available for concentration and discharge. All applied indices showed that the catchment responds differently from a concentration-discharge perspective and that chemodynamic behaviour is predominant, with flushing most frequently prevalent. A possible seasonal connection with regime diversity was tested using the non-parametric, statistical Wilcoxon test. A statistically significant difference was not found for any of the indices. Nevertheless, a detailed analysis of CVC/CVQ revealed that the ratio is likely related to seasonal variability in rainfall characteristics and consequently to the hydrological conditions in the catchment. Hence, it would be of great importance to include data about rainfall and hydrological properties in future studies.

The impact of crude glycerol from biodiesel production and its trace element content on biomethane production in a batch experiment: modelling as a step towards impartial routine comparison of results

In this study, crude glycerol from the biodiesel industry was tested as a co-substrate in biogas production. To investigate the influence of crude glycerol and the underlying trace element (TE) content on the efficiency of biomethane production, a batch experiment using Automatic Methane Potential Test System (AMPTS II) was carried out. The single addition of crude glycerol significantly contributed only to the total content of K (14.4%), Si (17.3%), and P (11.6%), whereas the contributions of other metals were within the range of other substrates. The addition of crude glycerol increased biomethane production, however, its utilization beyond 1% of total volume resulted in prolonged lag phase and final cessation of biomethane production. The negative effects of inorganic salts present in crude glycerol were reflected in progressively diminishing parts of glycerol and methanol being utilized in its anaerobic digestion, posing serious problems for daily routine use. A nonlinear least square regression analysis was performed to fit the Gompertz, Logistic, Transfer, and Richards models to biomethane production. The most suitable model was the Richards model, exhibiting the best fit to the experimental curves for complex substrates. Glycerol fractions remaining after biodiesel production have to be pre-tested for their negative effects on the content of TEs and inorganic salts, lag phase in biogas production, before they are used as co-substrates in biogas production phase.

The effect of ultrasound for algae growth control on zooplankton

The use of ultrasound (US) to control algal growth in natural water bodies raises concern about the undesirable effects of US on non-target organisms. In this study a lab-scale experiment was performed to evaluate the effects of low-power US to counteract algal growth on adult and juvenile Daphnia magna. The 48-hour experiment was conducted in a 200 L glass aquarium with three fish nets, each filled with five D. magna. Each net was inspected for immobilized D. magna on different times during ultrasonication; additionally, basic physical-chemical parameters were measured. The results showed that tested low-power US device had no acute effect on the mobility of adult or juvenile D. magna, since after 48 h of ultrasonication 87% and 82% of adult and juvenile organisms remained mobile, with the same or higher percentage of mobile D. magna in the control groups. Additionally, no statistically significant effects were noticed on the measured physico-chemical parameters. However, when applied for algae control in field conditions, US is in operation constantly or at least for a long period of time (several weeks or months); therefore, the effect of long-term exposure to ultrasonication on zooplankton should be tested to ensure that US devices are safe for zooplankton.

Analysis of runoff deficit using the treshold method for the case of three gauging stations in Slovenia

This analysis deals with the comparison of volume and duration of runoff deficits using different drought thresholds for the gauging stations Polana on the Ledava, Litija on the Sava, and Kubed on the Rižana Rivers with different climatic conditions for the hydrologically driest years in the period 1960–2016 in Slovenia. Using the threshold method, all events in which discharge fell below a pre-selected threshold value were identified as drought events. Three different values were chosen for the threshold value, namely the mean low periodic discharge sQnp and the percentiles of flow duration curve Q90 and Q80. For each gauging station, the event with the largest deficit volume and duration, as well as the total annual deficit volume and the total duration of drought events for the individual year, were selected using different threshold values. The study’s results demonstrate that the choice of drought threshold can have a great impact on the results of runoff deficit analyses. The absolute values of the duration and volume of the runoff deficits increase with higher threshold values. Also the ratios between the results of the individual years change slightly when the threshold value changes. Regardless of the choice of the threshold, 2003 proved to be the driest year according to all four selected drought characteristics and for all three analysed gauging stations, followed by 1993, 1971, and 2012, respectively. However, drought is a specific phenomenon of a regional character and is reflected differently in the different regions of Slovenia.

After 2000 Stože Landslide: Part I – Development in landslide research in Slovenia

The 2000 Stože Landslide with the consecutive wet debris flow with a volume close to 1 million m3 that hit the village of Log pod Mangartom in November 2000 had many consequences. It triggered vast efforts not only for the mitigation of the devastated area but also sparked many studies in several scientific disciplines. Various studies were performed in order to better understand this type of natural hazard and its consequences for the natural and built environment, and for society as a whole. After two decades since the disastrous event in 2000, this paper provides an aggregate survey different studies on this event performed by researchers and engineers, summarising this event’s impact on in-depth landslide research in Slovenia. The advancement in this field in Slovenia since 2000 is obvious.