Climate change has further exacerbated long-standing water use conflicts in the Lake Velence catchment area in Hungary. The lake is the ecological, social and economic central element of the area, with water scarcity as water levels having fallen to record lows in recent years due to severe summer droughts. As a result of infrastructure developments in the 20th century and the significant waves of immigrants in recent decades, the lake and its surroundings have been heavily modified, transformed into an artificial waterbody, while land and water use has significantly altered. Besides these negative effects on water resources and the lake’s water level, settlements in the catchment area have become the top solar energy producers per housing in Hungary in recent years. The aim of this research is to identify and develop a possible inter-basin water recharge solution that meets societal needs based on the suggested development ideas formulated in questionnaire responses. A sustainable alternative of these solutions is pumping from a nearby catchment, that was evaluated in detail. Based on ecological considerations, a multi-criteria analysis summarizing nearly 100 water quality and quantity parameters was developed to ensure that water supply meets qualitative requirements. To ensure economically sustainable operating costs, the nearby solar capacities were used for pumps operation and energy storage. For energy demand and carbon emissions reduction, the uphill pumping was complemented with a downhill turbine hydropower recovery system. Several scenarios of the pumped water recharge system were considered and hydrodynamically optimized in Matlab. The return on investment of the inter-basin pumped water replenishment systems were evaluated as well as the carbon emissions to assure additional economic benefits and low carbon-footprint. A bottom-up methodology with large scale stakeholder involvement that assesses social needs and applies well-balanced the three pillars of sustainable development, can achieve a Pareto effective displacement even during the development of a water replacement system at the catchment level and beyond, on an inter-basin level. With a comprehensive methodology developed for pumped water recharge from an external catchment using existing renewable energy sources, the deteriorating social atmosphere and ecological conditions caused by climate and land use changes may be improved. In the meantime, even economic benefits can be increased, all with a low energy demand and carbon footprint, in a sustainable way.

Study region: Lake Velence. Study focus: Soda lakes are extreme habitats whose special hydrochemical characteristics can partly be explained by groundwater inflow. The relationship between groundwater and Lake Velence has never been properly investigated. A significant decrease in the lake's level in recent years urged an evaluation of the components of the lake's water budget, including groundwater as well. A 3D transient numerical groundwater flow simulation, using Visual MODFLOW, was performed between 1990 and 2021 to evaluate the lake's relationship with groundwater and quantify the groundwater discharge into the lake. To assess future lake level changes until 2050, six lake level simulations were run based on three different regional climate models and two global warming scenarios (RCP2.6 and RCP8.5). New hydrological insights for the region: Our results showed that groundwater inflow accounts for up to 12 % of the total annual inflow into Lake Velence. It has been numerically shown that precipitation and evaporation are the primary drivers of lake level changes, meaning that the variation of these two parameters will impact the lake's future. As for the future lake level changes, the RCP2.6 scenario resulted in an increase of 11 cm, while the RCP8.5 scenario led to a decrease of 30 cm compared to the observed annual average lake level until 2050. Our results emphasize the importance of integrating soda lakes into topography-driven groundwater flow systems to develop climate change adaptation strategies.

Large-sample hydrology datasets have become increasingly available, contributing to significant scientific advances. However, in Europe, only a few such datasets have been published, capturing only a fraction of the wealth of information from national data providers in terms of available spatial density and temporal extent. We present “EStreams”, an extensive dataset of hydro-climatic variables and landscape descriptors and a catalogue of openly available stream records for 17,130 European catchments. Spanning up to 120 years, the dataset includes streamflow indices, catchment-aggregated hydro-climatic signatures and landscape attributes (topography, soils, geology, vegetation and landcover). The catalogue provides detailed descriptions that allow users to directly access streamflow data sources, overcoming challenges related to data redistribution policies, language barriers and varied data portal structures. EStreams also provides Python scripts for data retrieval, aggregation and processing, making it dynamic in contrast to static datasets. This approach enables users to update their data as new records become available. Our goal is to extend current large-sample datasets and further integrate hydro-climatic and landscape data across Europe.

Szigetköz—a large island of the Danube in Hungary—is attracting a new wave of interest in water-related regional development projects from the public and private sectors alike. The revived interest in the Szigetköz floodplain area, which has historically endured the adverse effects of large-scale water management initiatives, draws attention to the necessity for careful consideration and the active involvement of local stakeholders in the decision-making process. In our research, we conducted various stakeholder engagement activities, including interviews, questionnaires, and workshops. These activities helped define the problems and objectives of each stakeholder group. Through collaborative consultations, we gathered over 100 proposed water related development project ideas. Additionally, to address key issues in project development and selection, we evaluated the integrative potential of each proposed project, considering the number of distinct water management issues it addressed. We also assigned an attitude score to each project, derived from the diverse objectives of various stakeholder groups, and analysed these quantities using a multiple-criteria analysis. This paper details a novel approach to assess and rank the proposed water-related regional development project ideas based on the calculated integrative potential and attitude scores. The goal was to prioritise and further develop these proposed projects to benefit Szigetköz and its surrounding areas. Main results of the study have shown the average project scored between 0.33–0.50 in integrative potential out of a maximum of 1.00 For positive attitude score the average was between 0.28–0.43, out of a maximum of 1.00 while for the negative attitude score the average project scored between -0.14–0.00 out of a minimum of -1.00. The ranking of projects that was based on these scores, highlighted three types of proposed projects that need to be further developed in different ways. The top-ranked positive attitude integrative projects need cost-benefit calculations involving all ecosystem services to justify their economic sustainability. Top-ranked opposing attitude integrative projects need conflict resolution to be socially sustainable. Finally, project ideas that scored low on integrative potential need to be developed to make use of blue-green infrastructure, and circular economical advancements to foster their environmental sustainability.

Szigetköz, a large island in the Hungarian Upper Danube, features unique gravel subsoils ranging from 10 to 600 m thick. The region’s groundwater levels, profoundly influenced by the Danube’s flow, are crucial for drinking water, irrigation, flood retention, and ecosystem functioning. Groundwater levels also impact topsoil moisture, affecting agriculture and forestry. Throughout the 20th century, human interventions, such as river regulation and hydropower plants, disrupted the groundwater balance in Szigetköz. Over the past three decades, water replenishment systems have been implemented to mitigate these effects and restore natural water levels. This study analyses long-term groundwater data from the 1950s until 2022, utilizing over 50 monitoring wells to map fluctuations in groundwater levels. For three periods, decadal, annual, and seasonal groundwater level analyses revealed the impacts of human intervention and the impacts of revitalization. Results of this study show that in the crucial spring and summer seasons, particularly in the vulnerable central regions of Szigetköz, the water table has been elevated by an average of 20-30 cm, recovering more than one-third of the water level reduction caused by the Danube’s diversion. However, in the winter period, groundwater levels dropped further in the last 30 y in the upper areas of Szigetköz. These partly unexpected insights highlight the need for further investigations to identify the main drivers of groundwater level dynamics, including studying the effect of bed clogging and the possible consequences of restoring the water levels of the Old Danube.