Happy New Hydrological Year: 2025/26 in Review, and What the Dams Can Expect in 2026/27

Today the Water Development Department's inflow counter goes back to zero and Cyprus starts a new hydrological year. The one that just ended opened with the dams at their lowest in seventeen years and spent five months short of rain. Then came a record-breaking spring, nine overflowing reservoirs and the wettest August since 1902. The island ends the year with 2.9 times as much water as a year ago. That turns out to be roughly what an average year looks like. Here is 2025/26 in numbers, and what 2026/27 is likely to bring.

Happy New Hydrological Year!

In Cyprus the water year runs from 1 October to 30 September, so that a whole rainy season fits inside one year. From today every "since 1 October" figure in the daily bulletin starts again from zero, and "last year" in the comparisons now means the year we are about to review.

It was a year worth reviewing.

A year that started in the red

When the season opened, the island had just come through three dry years in a row, with 93%, 75% and 62% of normal rainfall. The first bulletin of 2025/26, on 10 October, put the 18 main dams at 34.4 mln. m³, 11.8% of capacity. That was the lowest October start since 2008, the year Cyprus shipped drinking water in by tanker from Greece.

The autumn made it worse. October brought 43% of its normal rain and November 42%, and November was also the warmest since 1981 at six of the Met Department's eight reference stations. The dams kept falling for three more months, to 26.9 mln. m³ (9.2%) on 29 December, the lowest level since January 2009. Kouris, the island's largest reservoir, bottomed at 7.6% six days earlier, lower than at any time since 2018.

That was the floor. Here is the whole year in one line:

Five months late

The rain did come in December and January: 123 and 122 mm, a little above normal both times. Storm Byron put 113 mm on Polis in a single day on 7 December, the second-wettest December day there since 1916. On 24 January every one of the Met Department's 54 automatic stations recorded at least 10 mm, the only day of the year when that happened. February was extremely warm, 2.8 °C above normal, and brought 90% of its usual rain.

Yet at the end of February the season was still behind, at 95% of normal to date. For five months 2025/26 was a below-normal year. Then came March.

*To 29 September. May–September figures are preliminary.

March, April and May together brought 214 mm, 192% of normal. In Kairika's reconstruction of island rainfall going back to 1940 it is the wettest spring of all, well ahead of 1967. At the Met Department's own gauges it was the wettest spring on record at 13 of the 29 stations with at least twelve years of data. The gauge at Kouris Dam caught 212 mm, more than twice its previous record (100 mm, in 2011).

The dams answered. March inflow was 35.4 mln. m³ and May's 13.2, both the highest for their month in the eleven seasons the Water Development Department's inflow table covers, and March–May together delivered 72.2 mln. m³, the best spring in the table. Storage rose by 63.5 mln. m³ between 1 March and 1 June, the largest spring gain in the 39 years of our records, ahead of 1988 (56.1) and 2019 (50.9). About 87% of the season's inflow arrived after 1 February. In the other ten seasons that share was between 31% and 63%.

So the year peaked absurdly late: 123.4 mln. m³ (42.4%) on 4 June, tied with 2009 for the latest annual peak on record. 2009 was also the year after the last great drought. We watched the line flatten in real time.

The summer then refused to be one: a 100 mm cloudburst over Agros in July, the wettest August since 1902, and a record late-summer inflow, all of which we covered last week. It was also milder than the last two. Athalassa recorded 18 days at 40 °C or more, against 35 in 2024 and 23 in 2025.

The sponge

The most useful lesson of the year is hidden in those first five months. From October to January the island received 282 mm of rain, 96% of normal for the period. The dams received 14.9 mln. m³. In 2016/17 a similar 299 mm produced twice that, and in 2021/22, 405 mm produced 87 mln. m³.

Compare two storms.

• Storm Byron, 5–10 December: about 69 mm across the Met Department's stations and 111 mm on the high Troodos. The dams gained 0.7 mln. m³.
• The storms of 10–14 February: about 45 mm on average, less than Byron. They brought 10.7 mln. m³.
• The storm of 19–22 March: about 51 mm on average and 89 mm in the mountains. It put 12.3 mln. m³ into the dams in three days, and another 12.9 mln. m³ drained in over the following week on just 15 mm more rain.

The March storm had less rain than Byron and brought seventeen times the water.

The monthly figures are just as stark. Every 10 mm of rain in December was worth 0.15 mln. m³ of inflow, in January 1.0, in February 3.3. In April it was worth 4.35, almost thirty times as much as in December.

The reason is the ground itself. After three dry years, and a 2024/25 in which not one of the 21 reservoirs filled, the soil and the aquifers under the Troodos had to be recharged before the rivers could run. Most of the first 280 mm of the season, from October to January, went into the ground. Only from February, with the ground saturated, did the rain reach the dams in earnest.

That matters for next winter, as we will see.

Nine spills and a relay

By spring the mountains had the opposite problem. Kalopanagiotis overflowed first, on 19 January. Klirou-Malounta and Pomos followed on 16 February, then Solea on 9 March, Argaka on 16 March, Xyliatos on 23 March, Agia Marina on 30 March and Tamassos on 2 April. Vyzakia, which held about a thousand cubic metres in November, overflowed on 27 April. That makes nine of 21 reservoirs full, after a year in which not one had filled, only the second such year since 1988.

Every one of them is small. None of the eight dams larger than 13 mln. m³ got past 61%, and Kouris, which holds 40% of the island's capacity, peaked at 42.0%. The regions diverged just as sharply. Nicosia's three mountain dams went from 2% to 100% and still stand at 78%. The Southern Conveyor, with 65% of all capacity, went from 12.5% to 38.6% and now holds 34.1%.

Our awards for the year:

• Comeback of the year: Vyzakia, from 0.06% to overflowing in five months. Runner-up: Germasoyeia, Limassol's dam, from 1.1% in January to 60.3% in May. It ends the year at 49.3%, against 8.1% a year ago.
• Workhorse: Arminou. A dam that holds 4.3 mln. m³ took in 22.5 mln. m³ this year, 5.2 times its own size, and passed 20.4 mln. m³ on to Kouris. That is 43% of all the water that entered Kouris this year.
• First to spill: Kalopanagiotis, on 19 January. It was full on 98 bulletins and still stands at 96%.
• Biggest year-on-year jump: Argaka, from 0.4% on this date last year to 46.6%.
• Slow burner: Lefkara. It never got above 18.5% and ends only 2.5 points ahead of last year. Kalavasos never passed 25%.
• Mystery of the year: Achna. Zero inflow all season, yet its highest level of the year came in the last week of September, by pipe.

Back to average, not to plenty

Add it all up and 2025/26 was a very good year. The dams end it at 104.1 mln. m³ (35.8%), 2.9 times the 36.1 mln. m³ they held on this date last year. The net gain of roughly 68 mln. m³ is the sixth-largest since 1988, behind 2018/19, 2001/02, 2011/12, 1991/92 and 2009/10.

But it was a good year, not a historic one. Officially the island received 617.8 mm, 123% of normal: the 25th-wettest year since 1901/02 and the fourth-wettest this century, well short of 2018/19's 796 mm. The level the dams end on is almost exactly the average for the close of a hydrological year since 1988 (106.8 mln. m³). The comeback has brought Cyprus back to normal, not to plenty.

The three dry years before it left a hole that one wet year cannot fill. From 2022/23 to 2024/25 the island ran a rainfall deficit of about 355 mm, and this year repaid about a third of it. In storage terms, the dams lost 173 mln. m³ between October 2022 and October 2025 and have won back about 68, some 40%. In March we called the crisis cyclical, not catastrophic. The cycle has turned, but it has not yet come full circle.

2026/27: what the next year holds

Now for the question everyone asks. Nobody can forecast a Cyprus winter in October. We showed last month that even a record El Niño tells us nothing. A wet year doesn't make the next one wetter either: since 1961 the correlation between one year's rainfall and the next is 0.04. What history can tell us is what the dams need, and how often they have got it.

The level will keep falling for a while. In years that began at a similar level, the dams lost another 11% or so after 1 October before the winter inflows turned them around. That points to a low of about 90–94 mln. m³ (31–32%) around December or January, so don't be alarmed when the numbers keep dropping in November.

The break-even point is higher than it looks. Over the past eleven seasons, the water that leaves the dams each year has tracked the level they start from very closely. That covers taps, farms, recharge releases, evaporation and leakage. Starting from about 104 mln. m³, the dams need about 77 mln. m³ of inflow just to end next September where they are now. That takes roughly 525 mm of rain, a little above a normal year. Only four of the last eleven seasons delivered that much.

Replay each of those eleven winters from today's level and seven end lower than they start. For rough odds, we drew next year's rainfall from the island's record since 1991 and converted it to inflow and outflow in the same way:

• about a 1-in-3 chance that the dams end next September higher than today. The middle of the range is around 80–85 mln. m³ (29%);
• about a 60% chance that the spring 2027 peak beats this year's 123 mln. m³, and about a 1-in-3 chance of topping 50% at some point;
• about a 1-in-5 chance of ending below 20%, and only about a 2% chance of falling back to where we started this year.

In plain words: at today's level, Cyprus uses more water in a year than an average winter brings in. One dry winter would hurt. But even a repeat of the worst of the last eleven would leave about 45 mln. m³ next autumn, more than this year started with. It would take two.

There is one thing in our favour: the ground is wet. Kouris and Arminou took in 10 to 20 thousand m³ a day all summer, the Troodos is still draining, and the August and September storms fell on soil that never fully dried out. Last winter most of the first 280 mm of rain disappeared into the ground. This winter some of it may not have to.

Thank you

This was Fragmata's first full hydrological year. We processed 128 bulletins from the Water Development Department and published fifteen articles. Two of them, on Achna and Kalavasos, began as questions from readers. We also added Zen Mode for the long summer exhale. Thank you for reading, asking and sharing.

The counter is back at zero. Let it rain.

Author: Vladimir Bugay, Fragmata developer Data: Cyprus Water Development Department, daily bulletins to 30 September 2026. Storage figures cover the 18 main dams (290.804 mln. m³ capacity), excluding recharge reservoirs; historical comparisons use Fragmata's record from 1988, with readings twice a month before 2014. Rainfall: Cyprus Department of Meteorology monthly area averages for the government-controlled areas against the 1961–90 normal (October–April final, May–August preliminary, September provisional to 29 September), monthly weather reports, and the annual island series from 1901/02 via data.gov.cy (CC BY 4.0). Station rainfall and temperature: Department of Meteorology automatic weather stations (CC BY 4.0, raw data) via kairika.info; spring ranks count stations with at least twelve years of data. Rainfall since 1940: ERA5 via Open-Meteo (CC BY 4.0), average of Kairika's seven places. The outlook replays WDD inflow for 2015/16–2025/26 against an outflow fitted on the same seasons; the odds draw annual rainfall from the 1991/92–2025/26 record. They are a range of precedents, not a weather forecast. Outflow here is WDD inflow minus the change in storage. Water that goes over a spillway is mostly in neither figure: the inflow counters largely stop while a dam is full. Dam levels updated daily at fragmata.info.