Climate change manifested its adverse impacts last year, with an extreme drought leading to a drastically low water level in Lake Velence, Hungary. Nature-based solutions have the potential to alleviate these impacts locally. While a few initiatives have been implemented in Hungary, widespread adoption of these solutions is expected to be a goal for the more distant future.This research focuses on one catchment at Lake Velence to evaluate decision-maker's readiness and urban water management infrastructure for broadly implementing nature-based solutions. Methods include delineating the stormwater system and creating a numerical model to evaluate rainfall-runoff processes and the possible impacts of nature-based retentions. Surveys among local mayors were conducted to assess their perception of existing water infrastructures and implementations of nature-based solutions. Its widespread use may become significant, but its effect on the lake's water level remains negligible.

Climate change has a significant negative impact on water resources in the catchment area of Lake Velence, Hungary, which is a source of increasing conflicts amoung stakeholders and various water users. The area of the lake is an ecologically diverse, partly a Ramsar site, and consecutively, a dynamically developing, economically expanding area with rapid population growth, of which wetlands are a prominent, central element. As a result of significantly increasing new residents and newly built modern properties, the area has a high solar panel capacity, and thus the renewable energy production rate per property is outstanding at a national level. The negative impacts of climate change on water resources can be compensated by replenishing water resources from outside of the catchment area. The hilly nature of the area and the high solar panel supply serve as advantages if combined with pumped hydro-storage reservoirs.The aim of the research is to develop a possible inter-basin water replenishment system based on the territorial characteristics, while fulfilling the economic-social-environmental needs. The water replenishment system considers the ecological aspects, the hilly characteristics of the area and the solar panel capacities of nearby settlements, as pumped water reservoirs are developed that balance the daytime peaks of renewable energy production. At the same time, the reservoirs are suitable for replenishing the water resources of Lake Velence from external watersheds, in a sustainable way with low carbon footprint. Using the excess water volumes above the ecological water demand of the watercourses available in the external, neighboring watershed, and the existing solar panel capacities of the nearby settlements, we optimize a sustainable renewable energy storage and water replenishment system that meets social, economic and environmental needs of the area.

Urban environments are increasingly vulnerable to climate change, with extreme weather events expected to become more frequent and severe. This paper addresses sustainable urban development and the importance of stormwater retention, integrating adaptation and mitigation strategies. It evaluates the publicly funded Hungarian “Green City” program’s water management, focusing on blue-green infrastructures. The 198 implemented projects in the program were assessed for green credentials, vegetation concepts, and rainwater retention using public databases of real municipal data and Google Earth spatial analyses rather than hypothetical scenarios. A lifetime climate change impact assessment with sensitivity analysis was conducted using two case studies from the “Green City” program, highlighting the benefits of prioritizing rainwater over tap water for irrigation. The study proposes a three-pillar—environmental as operational carbon footprint, economic as extended net present value (NPV), and social as accessibility and recreational benefit—evaluation method for urban blue-green developments. It found that many projects rely on tap water irrigation, thus resulting in higher lifetime carbon emissions. The financial assessment of carbon footprint within the extended NPV method emphasizes the need for improved green area irrigation strategies. By modernizing irrigation practices and implementing effective rainwater retention measures, blue-green infrastructures can significantly reduce carbon dioxide emissions while improving long-term economic performance and social benefits through improved usability. The research offers valuable insights into the role of blue-green infrastructures in urban development to combat climate change. The combined three-pillar framework integrating LCA to assess green projects is a transferable decision-support tool that can be adapted to locally available data, advocating the use of rainwater over tap water to achieve environmental, social, and economic benefits. Unlike earlier studies that used hypothetical scenarios, this research relies on the implemented projects of the “Green City” development program with their observed designs and available real data, thus providing a framework for urban blue-green implementations to integrate sustainable practices and effectively address the challenges posed by climate change. Graphical Abstract The alternative text for this image may have been generated using AI.

The Lake Velence watershed faces increasing challenges driven by local and global factors, including the impacts of climate change, energy resource limitations, and greenhouse gas emissions. These issues, particularly acute in water management, are exacerbated by prolonged droughts, growing population pressures, and shifting land use patterns. Such dynamics strain the region’s scarce water resources, negatively affecting the environment, tourism, recreation, agriculture, and economic prospects. Nadap, a hilly settlement within the watershed, experiences frequent flooding and poor water retention, yet it also boasts the highest solar panel capacity per property in Hungary. This research addresses these interconnected challenges by designing a solar-hydrodynamic network comprising four multi-purpose water reservoirs. By leveraging the settlement’s solar capacity and geographical features, the reservoirs provide numerous benefits to local stakeholders and extend their impact far beyond their borders. These include stormwater management with flash flood mitigation, seasonal green energy storage, water security for agriculture and irrigation, wildlife conservation, recreational opportunities, carbon-smart winery developments, and the creation of sustainable blue-green settlements. Reservoir locations and dimensions were determined by analyzing geographical characteristics, stormwater volume, energy demand, solar panel performance, and rainfall data. The hydrodynamic system, modeled in Matlab, was optimized to ensure efficient water usage for irrigation, animal hydration, and other needs while minimizing evaporation losses and carbon emissions. This research presents a design framework for low-carbon and cost-effective solutions that address water management and energy storage, promoting environmental, social, and economic sustainability. The multi-purpose use of retained rainwater solves various existing problems/challenges, strengthens a community’s self-sustainability, and fosters regional growth. This integrated approach can serve as a model for other municipalities and for developing cost-effective inter-settlement and cross-catchment solutions, with a short payback period, facing similar challenges.

Climate change exerts substantial adverse effects on water resources within the catchment area of Lake Velence in Hungary, intensifying conflicts among stakeholders and diverse water users. This region, characterized by rapid urbanization and economic expansion, also exhibits ecological heterogeneity, including significant wetland areas, some designated as Ramsar sites. At the same time, population growth and modern real estate development have led to a high density of solar panel installations, resulting in above-average per-property renewable energy production capacity across the country. This study proposes an inter-basin water transfer system to mitigate the hydrological impacts of climate change, leveraging the area's topography and solar energy production potential by integrating pumped hydro storage reservoirs and surplus solar energy to transfer water from the adjacent Váli-víz watershed is considered. The ecological flow requirements of the donor area are also considered to protect its ecosystem. The objective is to design a sustainable, low-carbon water replenishment system that addresses the region's economic, social, and ecological requirements. By synchronizing excess solar energy production with pumped hydro storage systems, the approach ensures dual functionality: renewable energy storage and strategic water supply enhancement for Lake Velence, thus increasing the system and the area's resilience under climate stress.