Hungarian Journal of Hydrology

Foreword

Veronika Major — Sun, 14 Sep 2025 16:34:05 +0000

Foreword to Volume 105/3

Estimated 1-km resolution monthly land evaporation in Hungary between 2000 and 2022

József Szilágyi, László Báder, János Józsa — Sun, 14 Sep 2025 16:25:38 +0000

There is a growing need for reliable estimates of evaporation for the analysis of the causes and consequences of global warming. Estimation of land evaporation rates, based on five basic meteorological variables (net radiation, air temperature, dew point, wind speed and air pressure) has become possible with the development of the complementary relationship of evaporation. With the help of ERA5-Land data, we prepared 0.1° resolution evaporation maps for Hungary on a monthly basis for the period of 2000-2022, and then using MODIS surface temperature values measured by remote sensing, we increased the spatial resolution to 1-km. The mean annual value of land evaporation became 538 mm/year for the study period, with a linear increase of 0.42 mm per year. Interpreting spatial and temporal changes in evaporation, however, requires further studies. In order to facilitate this process and aid stake holders and experts in shaping the future of water resources management in the country we share the results. The data are freely accessible to anyone at figshare.com.

Operational methodology for determining environmental flow

Máté Chappon , Emil Janák, Ferenc, Mikós Szalay, Katalin Bene — Sun, 14 Sep 2025 16:28:17 +0000

As part of Subproject 6C of the National Laboratory for Water Science and Water Security Project (RRF-2.3.1-21-2022-00008), we are currently reviewing the methodology for determining ecological water demands related to surface waters. This study presents our findings to date.

The lawful application of ecological water demand in the field of operational water management has become a fundamental task. At the same time, in the context of mitigating and adapting to the impacts of climate change, it represents a continuously revisable responsibility for water resource managers. It is crucial to adopt a consensus-based methodology so that ecological water demand is not viewed merely as a limiting factor within water resources management, but rather as an essential water use that contributes to achieving or maintaining good water status, the survival of natural ecosystems, and, through this, the availability of sufficient and high-quality water resources for sustainable and equitable water uses.

Following a review of the international literature, we provide recommendations on the use of key terms. We propose to adopt the concept of environmental flow requirements, which enables the reconciliation of the ecological water demands – describing the needs of aquatic ecosystems – with the water demands of society within the framework of integrated water resources management.

As a first step in defining environmental flow requirements, we recommend a simple, standardizable hydrological methodology. The key innovative element of this methodology is that the minimum ecological flow value is determined on a monthly basis, depending on the size of the river basin. Similarly, the value of the natural water resource with 80% exceedance probability must also be calculated monthly. The difference between these two values represents the utilizable water resources, i.e., the maximum water quantity available for use by society – effectively defining an upper limit. This would ensure that the actual runoff available to ecosystems – shaped by water uses follows the natural flow dynamics of a given year, while also enabling more efficient utilization of water resources.

In line with the concept of environmental flow requirements, the ecological water demand values determined using this hydrological method provide a first approximation of the real water conditions necessary for the survival of natural ecosystems. In order to conserve nature, the specific ecological water demand values calculated in this way can be reviewed considering the hydromorphological parameters of the watercourse and the needs of biological elements. If necessary – for example, in data-deficient catchments, or in the presence of protected natural values and/or increased societal water demand – the ecological water demand may be modified based on a holistic assessment methodology, reflecting compromises agreed upon by societal stakeholders

The importance of microscopic biological analysis in the control of drinking water quality – the presentation of the laboratory aspects of the water pollution in a Hungarian settlement

Anett Lippai — Sun, 14 Sep 2025 16:29:36 +0000

The application of indicator organisms is crucial in the monitoring of drinking water quality. According to national regulations, the monitoring protocol also includes the microscopic biological examination of water samples, which focuses on the detection of the living organisms. Most of the organisms found in the distribution systems are non-pathogenic and do not pose a risk to human health; however, they can play a role in the transmission of pathogens and contribute to protection against disinfectants and also cause taste and smell changes at the consumer endpoints. Their examination is also important because they can indicate the changes within the water system: they may signal raw water contamination, post-contamination growth within the system, stagnation, biofilm formation, and, not least, technological issues.

One of the main advantages of microscopic biological examinations is that they are not time-consuming, which is particularly crucial in cases of severe contamination, as it allows the testing laboratory to provide results as soon as possible after the sampling. During our work, we participated in the laboratory analysis of a Hungarian settlement’s water contamination event: we performed microscopic biological examinations on 35 samples from various sampling points. Protozoa (Protozoa sp.), nematodes (Nematoda sp.), rotifers (Rotatoria sp.), and arthropod mosquito larvae (Chironomidae sp.) were identified from the samples. However, the occurrence of these organisms was stochastic throughout the examined period. Microscopic organisms were mainly detected at the consumer endpoints of the drinking water system; they only appeared once in the reservoir pools and were not present in the water going directly into the system. This suggests that the problem was not related to the technology of the water production wells but rather to changes within the distribution system itself (e.g., household water purifiers, stagnation, biofilm formation). The arthropods, however, may have entered the system due to damage to the reservoir pools, which is supported by their appearance not only at consumer endpoints of the drinking water system but also in the pools themselves. Thanks to the appropriate water treatment processes, the number of microscopic organisms decreased, and, by the end of the examined period, they were no longer detectable in the samples. Following the emergency period, sampling continued monthly in accordance with the self-monitoring plan, and the water samples have had appropriate drinking water quality.

Presence of per- and polyfluoroalkyl substances in domestic wastewater and their public health significance

Gábor Györki, Judit Knisz — Sun, 14 Sep 2025 16:31:07 +0000

Per- and polyfluoroalkyl substances (PFAS) are synthetic, fluorinated compounds that exhibit exceptional resistance to chemical reactions and biodegradation due to the extraordinary stability of their carbon-fluorine bonds. As a result of these properties, PFAS compounds persist in the environment as persistent micropollutants and can be detected worldwide in natural waters, drinking water, food, and biological samples. Due to their favorable technological characteristics, low reactivity, and thermal resistance, they are widely used in various industrial and everyday consumer products. However, conventional wastewater treatment systems are not capable of effectively removing PFAScompounds, allowing them to continuously enter environmental cycles, surface waters, and even drinking water sources via wastewater and from other human activities. The persistent environmental presence and bioaccumulative potential of PFAScompounds threaten ecosystem functioning and also pose significant health risks, as they have been linked to cancer, developmental and reproductive disorders, and numerous other health problems. Although in recent years an increasing number of studies have focused on the occurrence of PFAS in municipal wastewater, household-originated wastewater and decentralized, individual wastewater treatment units remain underrepresented in such investigations. There is limited data on the PFAS removal efficiency of these systems, as well as on the quantitative and qualitative characteristics of emissions from them. As these alternative solutions are becoming increasingly widespread worldwide, they require prioritized research and regulatory attention, especially regarding micropollutants. A more precise understanding of the environmental impact of such systems is essential for the effective reduction of PFAS contamination and for mitigating public health and ecological risks.

A bucket of bait, the future of a lake – Fishing in Lake Balaton

Sára Rozina Kovács — Sun, 14 Sep 2025 16:32:29 +0000

This study examines the potential environmental impact of recreational fishing on Lake Balaton, the largest freshwater lake in Central Europe, which is predominantly used for leisure activities, including angling. In recent years, fishing activities have steadily increased, with an estimated 20 000 to 35 000 individuals engaging in fishing during the summer months. The Hungarian National Angling Association (MOHOSZ) currently reports its membership exceeding 1 million. Despite statistical evidence indicating a rise in fishing activity, limited data are available concerning its effects on the lake’s water quality, thereby prompting this project. The initial hypothesis posited that fish feeders may substantially contribute to the nutrient load that threatens the ecological integrity of lake ecosystems. This is primarily due to the widespread, often unregulated use of groundbait, both locally and globally. Fish feeders introduce nutrients such as phosphate, nitrate, nitrite, and ammonium into the aquatic environment–compounds that are recognized drivers of algal blooms and ecological deterioration in freshwater systems. However, the specific influence of these feeders remains uncertain due to a lack of targeted studies. The objective of this research is to quantify the release of plant nutrients from fish feeders, which are commonly based on corn or fishmeal, along with various additives. Laboratory experiments were conducted using suspensions made from Lake Balaton water and selected fish feeders, mixed in predefined ratios that reflect typical angling practices. Concentrations, including phosphate, nitrite, nitrate, and ammonium ions, were determined by using a spectrophotometer. The data obtained were subsequently compared with findings from analogous studies.

The results demonstrate that fish feeders contribute approximately 0.11 to 0.35 metric tons of phosphorus per week, corresponding to a cumulative input of 1.37 to 4.25 metric tons over a three-month period. For inorganic nitrogen compounds, weekly contributions ranged from 0.10 to 1.69 metric tons, resulting in a total input of 1.21 to 20.32 metric tons during the same duration. These findings suggest that recreational fishing may play a more significant role in the eutrophication of Lake Balaton than previously thought.

The legacy of István Zsuffa, who was more than just a hydrologist

Gábor Albert — Sun, 14 Sep 2025 16:35:34 +0000

The work and colourful personality of István Zsuffa (1933-2004) remain alive in the memories of his contemporaries and former students. His name is preserved by the College of Professional Studies at the Faculty of Water Sciences in Baja. In the experimental hydrology station Magyaregregy, Hungary, a memorial plaque inaugurated in 2014 commemorates the hydrometric measurement exercises Zsuffa led at the Lászlóffy Woldemár Hydrometric Measuring Station. The bust erected in the auditorium of the Ludovika University of Public Service’s Faculty of Water Sciences in Baja also pays tribute to the memory of this former hydrologist. This article aims to introduce Zsuffa’s versatile and humanistic professional activities. The phrase “more than a hydrologist” in the title reflects this sentiment.

HUNGARIAN HYDROLOGY SOCIETY XLII. NATIONAL ANNUAL MEETING SZÉKESFEHÉRVÁR, July 2-4, 2025.

Veronika MAJOR — Sun, 14 Sep 2025 00:00:00 +0000

We report on the XLII National Annual Meeting of the HUNGARIAN HYDROLOGY SOCIETY, which was held in Székesfehérvár, at the Sóstó Stadium, and at the Alba Regia Faculty of Engineering of the University of Óbuda.

Greetings from Judit Padisák on her 70th birthday

Csilla Stenger-Kovács, Krisztina Buczkó , Gábor Borics — Sun, 14 Sep 2025 00:00:00 +0000

Birthday and scientific oeuvre: We congratulate Professor Judit Padisák on her 70th birthday. .

István Almási and János Szanyi(2021): Hydrogeology of the Pannonian Basin

László Lénárt — Sun, 14 Sep 2025 16:41:49 +0000

István Almási and János Szanyi (2021): Hydrogeology of the Pannonian Basin

Publisher: The Groundwater Project, Guelph, Ontario, Canada, 2024.

Printed version: 73 pages https://doi.org/10.21083/978-1-77470-044-0

Dr. Lajos Szlávik ed.: 70 years of the water management service (1953-2023)

László Fejér — Sun, 14 Sep 2025 16:42:52 +0000

Dr. Lajos Szlávik ed.: 70 years of the water management service (1953-2023)

Water Management Bulletin special issue, Budapest

Printed version: 612 pages

Sándor Kabay

László Fejér — Sun, 14 Sep 2025 00:00:00 +0000

OBITUARY - Sándor KABAY – Commemoration by László FEJÉR