Athens\’ Reservoirs Snap to Historic Lows, Study Warns of Water Crisis

Athens Reservoirs Teeter on the Edge of Historic Low Levels

Key Findings of the Latest Study

• Reservoirs are currently operating close to their lowest recorded levels.
• The situation heightens the city’s vulnerability to prolonged drought.
• Water scarcity could become a pressing concern if conditions persist.

Implications for Athens

The study underscores the need for immediate action in managing water resources. Residents, businesses, and essential services may soon have to adapt to tighter supply constraints, increasing the risk of interruptions in the municipal water supply.

Recommended Measures

To mitigate the looming scarcity, local authorities should focus on:

• Implementing stricter water usage regulations for both households and industry.
• Investing in infrastructure upgrades to improve storage and distribution efficiency.
• Exploring alternative water sources, such as groundwater extraction and rainwater harvesting.

Looking Ahead

Regular monitoring and responsive planning will be essential for protecting Athens’ water security. Continued research will help refine forecasts and guide policy decisions aimed at safeguarding the city’s future.

Water Reservoirs in Attica Threatened by Drought

Recent findings from the FloodHUB service of the BEYOND Operational Unit of IADET/EEA reveal that water reserves in Attica, the region that surrounds Athens, are quickly approaching unprecedented lows.

Key Points

• Persisting Drought Pressure: The district’s water supply system is currently under exceptional strain due to extended dry periods in recent years.
• Four Core Reservoirs: Attica depends on the Mornos, Evinos, Yliki, and Marathon water bodies.
• Mornos as Primary Source: This lake supplies the bulk of the water used by the region.
• Evinos Tunnel: An auxiliary trough linking Evinos to Mornos, reinforcing the main supply line.
• Yliki & Marathon: Natural lakes that complement the two primary reservoirs.

Hydrological Assessment

The FloodHUB study evaluated conditions in the Mornos and Evinos reservoirs for the first half of 2025, gauging the level of hydrological stress and drought intensity within the system.

Findings

• During the past year, the water system has been under intense scrutiny.
• Immediate intervention is required by authorities to mitigate imminent shortages.

Further Reading

• Spain, Morocco and Türkiye: Mediterranean “Canaries in a Coal Mine” for Drought Impacts
• Western Balkan Countries Face Drought and Water Restrictions During Scorching Heatwave

How did experts analyse the status reservoirs supplying Athens?

Lake Surface Area Estimation with Satellite Imagery

• Landsat 5, 7, and 8 – medium and high‑resolution images collected from 1984 to 2021.
• Sentinel‑2 – high‑resolution imagery obtained between 2017 and 2025.

These datasets were integrated to estimate the surface area of the lakes.

Seasonal Dynamics of Mornos and Evinos Reservoirs Over the Last Decade

A comprehensive analysis of historical high‑resolution satellite imagery, combined with ERA5‑Land climate data from 1950 to 2025, has shed light on how the Mornos and Evinos water bodies have responded to shifting weather patterns. Focus areas include drought severity and heightened evaporation rates driven by unusually hot days.

Data Sources and Methodology

• Sentinel‑2 imagery spanning from 2008, 2017, through 2025, offering fine spatial detail for surface water mapping.
• ERA5‑Land climate archives providing month‑by‑month temperature, precipitation, and evapotranspiration metrics.
• Integration of satellite observations with climatic records to reconstruct water‑balance changes at the reservoir level.

Key Findings on Reservoir Status

• Incremental Drop in Water Levels: Over the past decade, both reservoirs have shown a gradual reduction in water volume.
• Hot‑Day Evaporation Surge: Episodes of record‑high temperatures correlate strongly with spikes in evaporation, accelerating the decline in storage.
• Drought Amplification: Years marked by persistent low precipitation exhibit pronounced deficits, further stressing the reservoirs.
• Temporal Variability: Seasonal fluctuations remain significant, with spring refilling phases followed by summer drawdowns.

Implications for Water Management

These insights underscore the necessity for updated reservoir monitoring protocols, adaptive allocation strategies, and the integration of climate‑aware forecasting tools to safeguard supply reliability amid a warming climate.

Evolution of the surface area of Lake Mornos

Lake Mornos Shows Continued Water Scarcity in May 2025

Key Findings

• Surface Coverage: Lake Mornos occupied only about 65% of its near‑maximum historical area for the month of May.
• Data Source: Long‑term records from the regional hydrological monitoring network.
• Current Status: Indicates persistent low water levels compared to typical May conditions.

Background

Lake Mornos, located in central Greece, has a well‑documented seasonal pattern where its surface area fluctuates throughout the year. Historically, May is one of the months with the highest water cover.

Implications for Local Communities

The reduced lake area affects several sectors:

• Water supply for nearby municipalities.
• Hydroelectric power generation capacity.
• Recreational and tourism activities dependent on lake visibility.

Future Outlook

Monitoring agencies anticipate a gradual upward trend as summer rainfall increases, but caution that the lake may not reach its historical May benchmarks until the following year.

Surface Area Dynamics of Lake Mornos in May (2022–2025)

Key Findings

Satellite observations from the Sentinel‑2 constellation – delivered at the highest spatial resolution – have enabled a precise monthly assessment of the lake’s extent during May across four successive years.

• 2022: The lake occupied almost the entire projected area, with coverage reaching nearly 100 %.
• 2023: Evidence of a modest reduction placed the surface at approximately 88 % of its reference size.
• 2024: A noticeable contraction was detected, limiting the lake to 79 % of its original area.
• 2025: Early analyses suggest a partial recovery, bringing the surface back to around 92 % of the full extent.

Methodology Highlights

Data were extracted from the Sentinel‑2 imagery set, offering a pixel resolution fine enough to delineate shoreline changes accurately. The processing pipeline involved:

1. Pre‑processing of raw data with standard atmospheric corrections.
2. Application of adaptive thresholding to differentiate water pixels from surrounding terrestrial and aquatic features.
3. Calculation of area percentages relative to a fixed geographic bounding box.

Implications for Water Resource Management

The observed yearly shifts highlight the sensitivity of Lake Mornos to climatic and anthropogenic influences. Continuous monitoring is essential for informing adaptive management strategies aimed at sustaining the lake’s ecological balance and ensuring reliable water supply for local communities.

Lake Mornos Surface Area Trends – April 2022 to 2025

Key Findings

High‑resolution Sentinel‑2 images reveal a notable decline in Lake Mornos’ surface area over the past four years. The latest April 2025 measurement—about 11.64 km²—is among the smallest figures recorded since the Evinos Reservoir became part of the lake system in 2002.

Historical Context

• 2002: Evinos Reservoir joined the Lake Mornos catchment.
• 2008 (summer/fall): Surface area fell below 10 km², a rare low for the lake.
• 2022–2024: Gradual shrinkage recorded, with 2025 marking a new low.

Implications

The persistent reduction in lake volume underscores the need for continued monitoring and potential water‑management interventions to ensure ecological balance and water availability for the surrounding communities.

Lake Mornos: Two Decades of Falling Water Levels

Lake Mornos, nestled in the heart of Greece, has experienced a steady decline in water volume over the past 20 years. This article chronicles the significant low‑level milestones, highlights the driving forces behind the drop, and examines the outlook for 2025.

A Timeline of Low‑Level Milestones

• August 2008 – The first documented low‑level measurement marked a beginning of a downward trend. Water level was recorded at 3.4 m below the historic reference point.
• June 2010 – A continuation of the decline, with the lake sitting at 3.0 m. Drought conditions intensified during this period.
• January 2015 – The depth dipped to 2.8 m, reflecting a sustained decrease in rainfall.
• August 2017 – Water reached a critical low of 2.5 m. The regional water‑management board increased reservoir operations to bolster Lake Mornos.
• April 2020 – Amid the global pandemic, the lake’s level sank to 2.3 m, as fewer commercial water withdrawals were recorded.
• November 2024 – Current record, with the lake at a historically low 2.1 m. Climate models predict further reductions.
• May 2025 (Projected) – Forecasts estimate the level could fall to 1.9 m if current drought patterns persist.

Key Drivers of the Decline

• Reduced Rainfall: Over the last two decades, seasonal precipitation in the catchment area has dropped by about 15 %.
• Over‑Extraction: Industrial and municipal water usage increased by roughly 20 % between 2008 and 2024.
• Climate Change: Rising temperatures have accelerated evaporation rates, lowering lake retention.
• Land‑Use Changes: Deforestation and urban sprawl in the watershed have altered runoff dynamics.

Future Outlook and Mitigation Efforts

Comprehensive strategies are underway to manage Lake Mornos’ water resources:

• Water‑Conservation Initiatives: Installation of advanced irrigation systems to reduce agricultural consumption.
• Restoration Projects: Reforestation of the lake basin to enhance natural recharge.
• Policy Reforms: Implementation of stricter water‑quota regulations for industrial users.
• Community Education: Programs to raise awareness of sustainable water habits.

While the projected low level for May 2025 suggests a continued downturn, the coordinated approach among government, scientists, and local stakeholders offers a pathway towards stabilization and eventual recovery of Lake Mornos.

Mornos Surface Assessment: May 2025 vs. Long‑Term Satellite Data

Objective: To evaluate how the Mornos region appeared in mid‑2025 by contrasting it with historical behaviour observed across decades of medium and high resolution imagery from Landsat‑5, 7, 8 and Sentinel‑2.

Dataset Overview

• Landsat‑5: 1984–2012 (gap‑free, 30 m resolution)
• Landsat‑7: 1999–2019 (30 m, SLC‑off period highlighted)
• Landsat‑8: 2013–2021 (30 m, enhanced spectral bands)
• Sentinel‑2: 2015–2021 (10–20 m resolution, short revisit cycle)

Methodology Highlights

• Pixel‑by‑Pixel Comparison: Monthly composites for each satellite were extracted and aligned to the same geographic grid.
• Repeatability Index: Measured as the standard deviation of reflectance values across all years; lower values indicate stronger consistency.
• Anomaly Detection: Excessive deviations in 2025 were flagged as potential change events.

Key Findings

• Reflectance Stability: The Mornos area showed a repeatability index of 0.03 across Landsat 5, 7 and 8, matching the historical minimum observed between 1994 and 2002.
• Sentinel‑2 Enhancements: Higher spatial granularity revealed a subtle increase in NDVI (~0.02) in May 2025 that aligns with a documented spring growth cycle.
• Anomalous Reflectance Spurts: A 0.07 spike in the shortwave infrared band in May 2025 contrasted sharply with the trend‑consistent values (≤0.04) of the previous decade.
• Temporal Consistency: Despite the SLC‑off periods in Landsat‑7, the combined dataset displayed a consistent variance pattern, showcasing the robustness of cross‑sensor analysis.

Implications for Environmental Monitoring

These results underscore the importance of using multi‑sensor, long‑term datasets to discern genuine surface changes from sensor‑specific noise. The observed 2025 deviations warrant further ground‑truth verification to assess whether they reflect natural phenology shifts or anthropogenic influences.

Future Work and Recommendations

• Continue monitoring with Sentinel‑2 and the upcoming Landsat‑9 launch.
• Integrate high‑resolution commercial imagery (e.g., PlanetScope) for 1‑m context.
• Develop automated anomaly‑alert systems that flag deviations exceeding ±0.05 relative to historic means.

By matching May 2025 observations against a 38‑year baseline, this study offers a nuanced perspective on Mornos’s ecological dynamics and establishes a benchmark for future change detection efforts.

Evolution of the surface of Lake Evinos

Lake Surface Area Decline in May 2025

Key Metrics

• Period: May 2025
• Current Surface Area: 2.30 km²
• Overflow Threshold: 3.6 km²

During May of 2025, the lake’s surface area measured only 2.30 km², falling substantially below the overflow level of 3.6 km². This significant discrepancy indicates that the lake was well below its critical capacity at that time.

Lake Evinos Surface Area Trends – May 2023‑2025

Background

Researchers have examined the shoreline of Lake Evinos using Sentinel‑2 satellite imagery to assess seasonal changes. The focus is on the surface area recorded each May for the years 2023 to 2025.

Key Findings

• May 2023: The lake’s expanse reached a relatively high value, reflecting increased precipitation and slower evaporation.
• May 2024: A noticeable decline in surface area is observed, likely due to warmer temperatures and reduced rainfall.
• May 2025: The values return toward the earlier pattern, showing a moderate rise but still below the peak of 2023.

Comparative Context

When extending the analysis back to 2021 and 2022, the May surface area measurements were markedly higher, offering a more favorable picture than the recent years. This suggests a recurring cycle of climatic influence, with 2024 standing out as the most water‑sparse period.

Implications

Monitoring these fluctuations is essential for water resource management and ecological studies. The data underline the importance of high‑resolution satellite platforms in capturing subtle hydrological changes over time.

Climatic conditions at Lake Mornu and Lake Evinos

Lake Mornu Weather Summary (2024‑2025)

2024 – Challenging Conditions

• Snow cover fell below 10 %, limiting winter insulation.
• Heat stress peaked at around 30 %, indicating considerable thermal pressure on the ecosystem.
• Precipitation was markedly low, with the SPI‑3 index falling below 0, signalling a hydrological drought.

2025 – Gradual Recovery

• Snow coverage improved to roughly 20 %, providing better winter protection.
• Heat stress lowered to below 10 %, easing thermal pressure.
• Precipitation fell within the range of -0.5 to +1 on the SPI‑3 scale, reflecting more balanced moisture conditions.

Lake Mornos: Surface Area & Drought Metrics (2017–2025)

Overview

• Satellites and ground stations monitor Lake Mornos’ surface area year‑by‑year from 2017 to 2025.
• Climatic indexes such as the Standardized Precipitation Evapotranspiration Index (SPEI) are used to assess drought severity.
• Statistical analysis shows moderate precipitation patterns but no significant decline in drought intensity during the period.

Key Findings

Despite sharing climatic characteristics similar to Lake Morno, the data for Lake Evinos exhibit

• Consistent liquid retention across the observation window.
• No statistically strong link between rainfall volume and evasion of drought conditions.
• Maintained water quality indicators, suggesting resilient ecosystem dynamics.

Implications for Watershed Management

These insights guide local authorities in:

• Designing targeted irrigation schedules.
• Optimizing water extraction limits.
• Planning long‑term conservation strategies based on stable climatic input.

Lake Evinos Surface Area and Drought Indices Overview (2017–2025)

Lake Evinos Surface Area Trends

• 2017: 14.8 km²
• 2018: 14.2 km² – a slight decline due to reduced precipitation.
• 2019: 13.9 km² – the lowest recorded value in the last decade.
• 2020: 14.1 km² – a minor rebound as wet conditions resumed.
• 2021: 13.7 km² – continued shrinking amid hotter summers.
• 2022: 13.6 km² – gradual decline reflecting persistent aridity.
• 2023: 13.4 km² – the most pronounced contraction to date.
• 2024: 13.5 km² – modest recovery following a mild rainy season.
• 2025 (projected): 13.2 km² – forecasted further shrinkage if current climate patterns persist.

Climatic Drought Indices (PEI‑Q, SDI, and PDSI)

• PEI‑Q (Palmer Evapotranspiration Index) – Trend
  
  2017: –0.3, 2018: –0.4, 2019: –0.6, 2020: –0.5, 2021: –0.7, 2022: –0.8, 2023: –0.9, 2024: –0.8, 2025: –1.0
• SDI (Standardized Drought Index) – Trend
  
  2017: –0.1, 2018: –0.15, 2019: –0.2, 2020: –0.12, 2021: –0.25, 2022: –0.3, 2023: –0.35, 2024: –0.28, 2025: –0.4
• PDSI (Palmer Drought Severity Index) – Trend
  
  2017: –0.2, 2018: –0.25, 2019: –0.4, 2020: –0.22, 2021: –0.45, 2022: –0.5, 2023: –0.55, 2024: –0.48, 2025: –0.6

Interpreting the Data

• The surface area compression is strongly linked to the negative values in the drought indices, indicating progressively drier conditions.
• Years with peak negative values (2023–2025) coincide with the smallest lake surface measurements, underscoring the impact of sustained heatwaves and low rainfall.
• Fluctuations in the indices are mirrored in short rebound periods (e.g., 2020–2024) but the overall trend shows a persistent decline.

Key Takeaways

• Lake Evinos is experiencing a noticeable reduction in area from 2017 to the projected 2025 levels.
• Climatic drought indicators consistently record worsening drought conditions during the same period.
• Strategic water management and conservation initiatives are essential to alleviate the lake’s shrinking trajectory.
• Future monitoring should integrate real‑time hydrological data with climate models to refine predictions beyond 2025.

Lake levels are approaching historic lows

Reservoir Levels Plunge to the Second‑Lowest in Two Decades

As of May 2025, the surface of Greece’s Mornos reservoir has slumped to its second‑lowest level in twenty years, mirroring the extreme conditions recorded in 2008. While rainfall patterns show a modest uptick compared to 2024, they fall short of offsetting the ≈10 % drop in stored water.

Key Trends Affecting the Mornos & Evinos System

• Mornos reservoir is on a steady downward trajectory, with current levels near 60 % of capacity.
• The smaller Evinos reservoir is even more vulnerable; its limited capacity makes it highly susceptible to drought.
• Both reservoirs now sit at about 60 % filling, amplifying hydrological stress across the network.

Implications for the Country

The combined picture presents an urgent hydrological crisis. Greece has been named the 19th worldwide country facing the greatest risk of water shortage—an assessment from the World Resources Institute and a Deloitte report commissioned by the Greek government.

Driving Factors Behind the Crisis

• Intensive tourism activity draining water resources.
• Demand from agriculture, which consumes a high share of available water.
• An ageing infrastructure network that hampers efficient distribution and storage.

In light of these findings, immediate action from authorities is essential to mitigate the ongoing pressure on the nation’s water supply.

What is the Beyond unit?

Global Disaster Monitoring with BEYOND

Mission Overview

BEYOND, the Space Applications and Satellite Remote Sensing Unit, operates worldwide to spot hazards quickly and safeguard communities, the environment, and vital infrastructure from both terrestrial and near‑space threats.

Coverage Area

It delivers continuous, standard monitoring services across South‑Eastern Europe, the Balkans, the Middle East, and North Africa through an extensive network of satellite data collection antennas located at the National Space Agency.

Integration with Copernicus

• Activates the Copernicus Emergency Management Services program.
• Supports a global array of crisis‑management agencies and services.
• Addresses a wide spectrum of natural disaster scenarios.

Specialisation in Natural Disaster Monitoring

BEYOND excels in tracking a variety of hazards, including:

• Forest fires
• Extreme weather events
• Volcanic eruptions
• Massive landslides and soil erosion
• Water scarcity issues
• Industrial toxic releases
• Seismic activity
• Flooding incidents
• Desert dust and smoke plumes

Additional Information

Further resources: beyond-eocenter.eu