Angeliki Mentzafou

Structural flood-control engineering can create negative impacts and societal conflict, yet few studies critically examine such projects while explicitly evaluating Nature-based Solutions (NbS) as alternative applications. This article presents a real Mediterranean case in which a large structural flood-control project was halted following ecological and legal scrutiny, creating an opportunity to reconsider flood management through an NbS framework. The study focuses on the Erasinos stream (Attica, Greece), where a government- and EU-funded flood-control project proposed extensive river channelization, flood-retention dams and other “hard” measures within and adjacent to a protected Natura 2000 area. Rather than proposing a detailed engineering redesign, our study compares two contrasting planning paradigms: the original engineering scheme, initiated in 2021, and a conceptual Nature-based Solutions (NbS) framework based on Natural Flood Management (NFM) and ecological restoration initiatives. The proposed NbS framework would substantially reduce structural river-training works while emphasizing distributed flood-water retention, restoration of river connectivity, floodplain reconnection and biodiversity enhancement. Such an approach has the potential to reduce flood risk while simultaneously enhancing biodiversity, cultural and protected-area values. The Erasinos case demonstrates that integrating ecological restoration, NbS and flood-risk management can shift peri-urban river planning away from rigid structural control toward a nature-positive management paradigm for Mediterranean catchments.

Rivers are vulnerable to hydrometeorological and climatic pressures, while effective water resources management during low-flow season can be challenging. This paper studies the impacts of extreme hydrometeorological events and climate change on Greek rivers, and presents a framework for the incorporation of these pressures into the Program of Measures (PoMs) of the River Basin Management Plans (RBMPs) for the implementation of the Water Framework Directive 2000/60 (WFD). The final aim is the adaptation to drought and water scarcity. The proposed methodological approach incorporates a process-based model, climate change projections, drought indices and low-flow boundaries, so as to assess the impact of hydrometeorological and climatic pressures on the quantitative quality status of rivers. Then, the quantitative response of rivers under different predicted climate scenarios was examined. Based on the results, a water management plan was adopted and tested regarding its effectiveness, so as to promote evidence-based water strategies. Additionally, comprehensive measures and an operational scheme and adaptations actions for the mitigation of the hydrometeorological and climate related pressures in rivers of Greece were proposed. This operational framework is based on quantitative thresholds that trigger actions and measures for adaptation and can be used by decision-makers and stakeholders as guidelines for mitigation actions. The framework proposed was applied to the Spercheios river basin, which was selected as a demonstration site.

Floating photovoltaic systems (FPV) are one of the emerging technologies that are able to support the “green” energy transition. In Greece, the environmental impact assessment of such projects is still under early development. The scope of the present study was to provide insights into the potential impacts of a small-scale FPV system on the water quality of the oligotrophic Kremasta Lake, an artificial reservoir. For this reason, a hydrodynamic and water quality model was employed. The results showed that the water quality parameter variations were insignificant and limited only in the immediate area of the FPV construction and gradually disappeared toward the shoreline. Likewise, this variation was restricted to the first few meters of depth of the water column and was eliminated onwards. The water temperature slightly decreased only in the area of close proximity to the installation. Average annual dissolved oxygen, chlorophyll-a, and nutrient concentrations were predicted not to change considerably after the panels’ construction. FPV systems can provide an attractive alternative for energy production in artificial reservoirs, especially in regions of land use conflicts that are associated with land allocation for alternative energy development. Given the limited data on the long-term impact of such projects, robust monitoring programs are essential. These initiatives rely on public support, making collaboration between stakeholders and the local community crucial.

The water resource management of transboundary mountainous river basins under climate change is expected to be challenging. In order to contribute to the better understanding of climate change effects on the water resources of the mountainous and transboundary Prespa Lakes basin, a hydrological model of the Agios Germanos River, one of the main rivers discharging to Great Prespa Lake, was developed, and two water management plans under two different climate scenarios were examined. Based on the results, the impact of climate change on surface water resources was evident in all climate change scenarios examined, even under the most favorable water abstraction practices. Nevertheless, sensible water management can moderate the impact of climate change by up to 10% in an optimistic scenario in both the near- and long-term, and by up to 6% and 1% for the near- and long-term, respectively, in a pessimistic scenario. Integrated water management practices that moderate the impact of climate change on the water ecosystem services should be prioritized. Nature-based approaches could provide solutions regarding climate change adaptation and mitigation. Transboundary cooperation, data exchange mechanisms, common policy frameworks, and monitoring, reporting, and evaluation systems, could reduce human and ecosystems’ vulnerabilities and improve the water security of the area.

Unmanned surface vehicles (USVs) equipped with integrated sensors are a tool valuable to several monitoring strategies, offering enhanced temporal and spatial coverage over specific timeframes, allowing for targeted examination of sites or events of interest. The elaboration of environmental monitoring programs has relied so far on periodic spot sampling at specific locations, followed by laboratory analysis, aiming at the evaluation of water quality at a catchment scale. For this purpose, automatic telemetric stations for specific parameters have been installed by the Institute of Marine Biological Resources and Inland Waters of Hellenic Centre for Marine Research (IMBRIW-HCMR) within several Greek rivers and lakes, providing continuous and temporal monitoring possibilities. In the present work, USVs were deployed by the Athens Water and Sewerage Company (EYDAP) as a cost-effective tool for the environmental monitoring of surface water bodies of interest, with emphasis on the spatial fluctuations of chlorophyll α, electrical conductivity, dissolved oxygen and pH, observed in Koumoundourou Lake and the rivers Acheloos, Asopos and Kifissos. The effectiveness of an innovative heavy metal (HM) system installed in the USV for the in situ measurements of copper and lead was also evaluated herewith. The results obtained demonstrate the advantages of USVs, setting the base for their application in real-time monitoring of chemical parameters including metals. Simultaneously, the requirements for accuracy and sensitivity improvement of HM sensors were noted, in order to permit full exploitation of USVs’ capacities.

Environmental monitoring programs rely on periodic spot sampling at specific locations, followed by laboratory analysis, aiming at the evaluation of water quality at a catchment scale. For this purpose, automatic telemetric stations for specific parameters have been installed by the Institute of Marine Biological Resources and Inland Waters of Hellenic Centre for Marine Research (IMBRIW-HCMR) within several Greek rivers and lakes, providing continuous and temporal monitoring possibilities. Nevertheless, the employment of unmanned surface vehicles (USV) equipped with integrated sensors represents a tool valuable to several monitoring strategies, offering enhanced temporal and spatial coverage over specific timeframes, allowing for targeted examination of sites or events of interest. The USVs have been deployed by Athens Water and Sewerage Company (EYDAP) as a cost-effective tool for the environmental monitoring of surface water bodies of interest, with emphasis on the spatial fluctuations of chlorophyllα, electrical conductivity, dissolved oxygen and pH, observed in Koumoundourou Lake and rivers Acheloos, Asopos and Kifissos. The effectiveness of an innovative heavy metal (HM) system installed in the USV for thein situ determination of copper and lead was also evaluated herewith. The results obtained demonstrate that both the timely detection of potential pollution from both anthropogenic activities and natural processes as well as the monitoring of inland waters are made feasible through the employment of USV.