Most Slovak rivers have increasing spring flow followed by a period or two of low flow in the summer, autumn, and, in some cases, winter. The flow rate fluctuations in two different streams in Slovakia are being investigated in this study. The study focused on an under-mountain and a lowland-highland river to investigate the low and peak flow periods and to identify the trends in monthly and annual mean flows for both rivers. Analysing daily mean discharge data from two different types of streams requires the use of a robust normalization approach to verify the comparability between the chosen streams. On both streams, a broad statistical low-flow analysis was performed over different study periods, as well as a hydrological drought analysis utilizing the water-bearing coefficient approach over the period 2010-2020. The evaluation for the foothill river in Slovakia demonstrates that snow melting has a significant impact on annual runoff in the spring months, and both rivers have a low flow period in August, September, and October. Despite the considerable variations in the catchment area, geographical, and hydrological characteristics, drought analysis for the years 2010 to 2020 found a lack of normality and a dry hydrological situation in both streams.

Drought is one of many critical problems that could arise as a result of climate change as it has an impact on many aspects of the world, including water resources and water scarcity. In this study, an assessment of hydrological drought in the Gidra River is carried out to characterize dry, normal, and wet hydrological situations by using the Slovak Hydrometeorological Institute (SHMI) methodology. The water bearing coefficient is used as the index of the hydrological drought. As machine and deep learning are increasingly being used in many areas of hydroinformatics, this study is utilized artificial neural networks (ANNs) and support vector machine (SVM) models to predict the hydrological drought in the Gidra River based on daily average discharges in January, February, March, and April of the corresponding year. The study utilized in total 58 years of daily average discharge values containing 35 normal and wet years and 23 dry years. The results of the study show high accuracy of 100% in predicting hydrological drought in the Gidra River. The early classification of the hydrological situation in the Gidra River shows the potential of integrating water management with the deep and machine learning models in terms of irrigation planning and mitigation of drought effects.

No abstract

The Slovak lowlands have been threatened by floods recently. The Levice district is one of the regions endangered by floods from extreme hydrological situations. The investigated river, which passes through this district is the River Podluzianka with the Cajkovsky brook and the Rybnicky brook as right-bank tributaries. The present conditions of the flood protection in the Levice district area are not sufficient. For this reason, it was necessary to analyze the river flow regime and propose appropriate flood protection measures in the mentioned region. This evaluation based on hydrological, geological and meteorological information and was performed by numerical modeling using computer code HEC-RAS. The main results of this research are presented in the paper.

Flash floods are becoming a phenomenon that troubles people more and more often in many Slovak under-mountain regions and society needs to deal with these extreme natural events. This article is showing an example of mathematical modeling of flood protection measures in Small Carpathians region. To secure flood protection, detention reservoirs have been proposed, because of their automatic function that is important due to rapid progress of flash floods. As a base for this project a previous work that attempted to reconstruct the flood has been used. HEC-RAS 4.1.0 software package was used for numerical modeling, which includes flood mitigation calculation. Six variants of proposed detention reservoirs were created and checked by a design flood wave that was created according to rainfall with recurrence period of 100 years. All of the proposed detention reservoirs have exact proportions needed to secure flood protection including height of the dam, length of the dam in crest, type and dimension of outlet and dimensions of emergency spillways. The modeling included flood wave passing during several situations-normal function of detention reservoirs, blocked outlet and dam break. This study should be considered as a base for future flood protection project. An extensive terrain survey has been performed in frame of this project.