Water reserves supplying Athens have recovered significantly compared with last year, easing concerns over the water shortages that had raised alarm in recent months. However, a continued decline in reservoir levels throughout October suggests that the recovery remains fragile, with the coming winter likely to prove decisive.

According to the latest figures from Athens Water Supply and Sewerage Company (EYDAP), the four reservoirs supplying the Greek capital, Mornos, Evinos, Yliki and Marathon, held a combined 565.5 million cubic metres of water on 21 October 2026, an increase of 47.2% compared with the 384.2 million cubic metres recorded on the same date in 2025. The latest total is also reflected in data drawn from EYDAP’s daily reservoir records.

The difference amounts to 181.3 million cubic metres, highlighting the substantial improvement over the past year. It gives Athens a considerably stronger starting position ahead of winter, following an extended period of pressure on its water supply system.

Nevertheless, comparisons with previous years show that the recovery has yet to make up for the losses accumulated over the longer term.

From the pressures of 2025 to the recovery in water reserves

The situation in 2025 was particularly worrying, with water reserves falling to low levels and the Mornos reservoir becoming a major focus of concern.

An extended period of reduced inflows had placed increasing pressure on the water supply system, while the capital’s demand continued to draw down available reserves.

Higher rainfall in December 2025 and January 2026, combined with snowfall in western Greece, helped replenish water supplies, particularly in Mornos and Evinos.

By 30 January 2026, total reserves had exceeded 500 million cubic metres, after remaining below that threshold for several months.

The recovery continued over the following months, with reserves reaching 597.2 million cubic metres on 17 September 2026, representing an increase of 41.5% compared with the same period a year earlier.

How much water is stored in Athens’ four reservoirs?

The distribution of reserves on 21 October 2026 reveals significant differences between the four reservoirs, with Mornos accounting for by far the largest share.

Water reserves on 21 October 2026, million cubic metres

Mornos: 365.6m m³

Yliki: 130.6m m³

Evinos: 46.3m m³

Marathon: 23.0m m³

Mornos remains the largest water storage reservoir in the system, with reserves more than double those recorded on the corresponding date in 2025.

Yliki holds the second-largest volume, while substantially smaller quantities are stored in Evinos and Marathon.

Reservoir levels continue to fall in October

Despite the significant year-on-year improvement, water reserves have followed a downward trend throughout October.

On 1 October 2026, combined reserves stood at approximately 582.9 million cubic metres. By 21 October, they had fallen to 565.5 million cubic metres.

That represents a decline of approximately 17.5 million cubic metres in just 20 days.

The figures indicate that the replenishment of reserves has not continued at the same pace. However, this decrease alone is insufficient to establish a definitive trend for the water supply system.

Any assessment must also take account of inflows from the reservoirs’ catchment areas, the volumes of water supplied to the distribution network and other factors affecting overall storage levels.

Moreover, rainfall in Athens does not necessarily result in a corresponding increase in water reserves.

What matters is where the rain falls, how long it lasts, its intensity and whether the resulting runoff reaches the catchment areas feeding the reservoirs.

Water reserves remain below 2023 and 2024 levels

Although the comparison with 2025 is encouraging, a longer-term perspective reveals that current reserves remain below the levels recorded in both 2023 and 2024.

On 21 October 2024, the four reservoirs held approximately 608.7 million cubic metres of water. On the same date in 2023, the figure stood at a substantially higher 911.8 million cubic metres.

Athens’ water reserves on 21 October

Combined volume across the four reservoirs, in million cubic metres

Based on the figures for 21 October 2026, current reserves are approximately 43.2 million cubic metres below their 2024 level and 346.3 million cubic metres below that of 2023.

The figures underscore the scale of the challenge, despite the strong recovery over the past 12 months.

The crucial test over the coming months

Athens is entering winter with substantially more water in storage than it had in autumn 2025, having gained 181.3 million cubic metres across its four reservoirs over the past year.

The improvement is considerable, but the threat of water shortages cannot yet be regarded as a thing of the past.

The coming months will be particularly important, as winter rainfall and snowfall will directly influence how much water accumulates in the reservoirs.

Although reserves have recovered significantly compared with last year, they remain below their 2023 and 2024 levels. The decline recorded throughout October adds another element of uncertainty.

Ultimately, whether Athens can further replenish its water reserves, and consolidate the gains made over the past year, will depend largely on weather conditions in the months ahead.