Reservoirs & water production

What am I looking at?

“Storage” is the extractable volume of water in the four reservoirs that supply Athens and the wider Attica region, as published daily by EYDAP, the Athens water company.

“Production” is the water that EYDAP's four water treatment plants send into the distribution network each day: Aspropyrgos, Galatsi, Kiourka (the Polydendri plant) and Menidi (the Acharnes plant). It is larger than consumption, because it includes the water that is lost or not billed in the network, roughly a quarter.

The reservoirs

Mornos (Phocis): the largest reservoir and, together with Evinos, the main supplier of the system.

Evinos (Aetolia-Acarnania): the dam was completed in 2001 and its water is diverted into the Mornos reservoir. That is why it reads zero in the first years of the data.

Yliki (Boeotia): a natural lake. Its water is lifted by pumping stations, and EYDAP uses it as an auxiliary source for emergencies.

Marathonas (Attica): the smallest reservoir, also an auxiliary source for emergencies.

How the comparisons are computed

“Last year” is the same date one year earlier. “Average for this date” is the mean of the same calendar date in every earlier year of the data (since 2000).

“Record high” is the largest value in the data. Isolated one-day extremes are treated as errors in the source and ignored.

“Coverage in the worst case” is a water balance. Storage changes each day by inflows, minus evaporation and leakage, minus the water EYDAP produces. So for every day since October 2002 the natural balance follows from the data: change in storage plus production.

Each historical year is replayed from today's storage, with the production of the last 12 months as demand, for up to 5 years. The tile shows the sequence of years that empties the reservoirs first. Empty means zero, because EYDAP publishes extractable reserves.

Lower bound: with no inflow at all and summer-rate losses, storage would last about 302 days.

It assumes constant demand and that past weather is representative. EYDAP also has boreholes: whatever they supplied in the past counts here as inflow of that year. It is a scenario, not a forecast.

In the “5Y” and “All” ranges the chart shows weekly and monthly averages. The CSV always contains daily values.

Source and updates

Data comes from eydap.mysolon.gr and is checked for new values every three hours. The source usually publishes with a delay of about one day.

Independent page, not affiliated with EYDAP.