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Open Data

Water Reserves in Attica from 1985 to the Present Day 

Chrysoula Marinou

We have collected historical data on the water reserves in Attica’s reservoirs and are publishing it as an open dataset.

We collected the water savings data by the OpenWaterAPI platform which provides historical open data on water savings and production by Athens Water Supply and Sewerage Company (EYDAP) for Attica, Greece. 

From this information, we created and are providing a dataset that includes data on the daily water reserves, in cubic meters, in the reservoirs that supply the capital city of Athens, starting from January 1, 1985, and onwards — except for the Evinos reservoir, where data begins on December 26, 2001. The full dataset, which is freely available here, will be updated monthly by the iMEdD team. In this first version, which we are publishing today, data is available up to July 10, 2025. The raw data from EYDAP is updated daily. 

According to EYDAP’s website, the company obtains raw water from surface water reservoirs: Evinos, Marathonas, Mornos, and Yliki — the latter being the only natural one, as the others were created through dam construction. The main water sources are Mornos and Evinos, while Yliki and Marathonas serve as auxiliary suppliers. Additionally, EYDAP uses groundwater pumping, but this volume of water is not included in the dataset we collected from the platform. 

In the dataset, each row corresponds to a single day. The first column (“date”) contains all the dates for which data has been collected. The next four columns in the dataset with water reserves (“Evinos”, “Marathonas”, “Mornos”, “Yliki”) correspond to the reservoirs and display the amount of water in cubic meters for each date. The last column (“Total”) refers to the total volume of water for each respective date, as shown in the “date” column. 

Daily water reserves in the four reservoirs of Attica

dateEyinosMarathonasMornosYlikiTotal
1985-01-010187441485617360004914250001071905148
1985-01-020182883945620600004993400001079688394
1985-01-030179590915644900005038800001086329091
1985-01-040176329165669500005068310001091413916
1985-01-050169560005692600005095550001095771000
1985-01-060172929085717350005115980001100625908
1985-01-070165887285742100005136410001104439728
1985-01-080162085555783350005161380001110681555
1985-01-090157997965851400005184200001119359796
1985-01-100153636285901500005218700001127383628
1985-01-110149009425914860005248600001131246942
1985-01-120143665865929890005267000001134055586
1985-01-130140099975943250005280800001136414997
1985-01-140135810885958280005294600001138869088
1985-01-150131426525963290005308400001140311652
1985-01-160126953225973310005322200001142246322
1985-01-170168888605983330005340600001149281860
1985-01-180167218005993500005405000001156571800
1985-01-190164229646003700005456260001162418964
1985-01-200161593106012200005498200001167199310
1985-01-210158160656020700005528490001170735065
1985-01-220154117606025800005554120001173403760
1985-01-230150120506032600005572760001175548050
1985-01-240146641126041100005589070001177681112
1985-01-250145228306049600005605380001180020830
1985-01-260143353986059800005619360001182251398
1985-01-270140099976070000005631010001184110997
1985-01-280136572686081900005640330001185880268
1985-01-290134292326095500005644990001187478232
1985-01-300131126066107400005649650001188817606
1985-01-310127693876119300005661300001190829387
1985-02-010123419406129500005668290001192120940
1985-02-020119927386132900005668290001192111738
1985-02-030115760516136300005665960001191802051
1985-02-040111652326139700005661300001191265232
1985-02-050107741506144800005658970001191151150
1985-02-060103750396148200005654310001190626039
1985-02-07099549306149900005651980001190142930
1985-02-08095542406153300005647320001189616240
1985-02-09091309526156730005642660001189069952
1985-02-10087377606158460005640330001188616760
1985-02-11084776566160190005638000001188296656
1985-02-12080421186180950005633340001189471118
1985-02-13077157786201710005631010001190987778
1985-02-14075548706225930005633340001193481870
1985-02-15074932506238040005633340001194631250
1985-02-16073708806243230005631010001194794880
1985-02-17072979746250150005631010001195413974
1985-02-18072493706257070005628680001195824370
1985-02-19074075916260530005626350001196095591
1985-02-20074932506263990005624020001196294250
1985-02-21076289016263990005621690001196196901
1985-02-22078030906263990005619360001196138090
1985-02-23077905926262260005619360001195952592
1985-02-24078781656262260005619360001196040165
1985-02-25079410906262260005619360001196103090
1985-02-26080674626260530005619360001196056462
1985-02-27080421186260530005619360001196031118
1985-02-28081564276258800005619360001195972427
1985-03-01082329816244960005619360001194664981
1985-03-02082714326246690005619360001194876432
1985-03-03086465156250150005621690001195830515
1985-03-04081564276253610005626350001196152427
1985-03-05089470366244960005633340001196777036
1985-03-06088161306238040005638000001196420130
1985-03-07086595506253610005642660001198286550
1985-03-08084776566260530005644990001199029656
1985-03-09081947046260530005644990001198746704
1985-03-10079410906260530005644990001198493090
1985-03-11077406006260530005644990001198292600
1985-03-12075918426262260005644990001198316842
1985-03-13074932506262260005642660001197985250
1985-03-14074198286262260005642660001197911828
1985-03-15074932506265720005640330001198098250
1985-03-16074687766274370005644990001199404776
1985-03-17073831176283020005651980001200883117
1985-03-18073708806291670005654310001201968880
1985-03-19076041666314160005654310001204451166
1985-03-20076289016333250005654310001206384901
1985-03-21077281896340250005654310001207184189
1985-03-22078280866343750005654310001207634086
1985-03-23079159206347250005658970001208537920
1985-03-24080041026350750005663630001209442102
1985-03-25080547906354250005665960001210075790
1985-03-26080674626357750005668290001210671462
1985-03-27080421186364750005668290001211346118
1985-03-28080167746371750005665960001211787774
1985-03-29081436686377000005665960001212439668
1985-03-30084259286382250005665960001213246928
1985-03-31086856206385750005665960001213856620
1985-04-01089208086387500005665960001214266808
1985-04-02091836466389250005665960001214704646
1985-04-03094746086389250005665960001214995608
1985-04-04097541146387500005665960001215100114
1985-04-050100627386387500005663630001215175738
1985-04-060103613506387500005661300001215241350
1985-04-070106358506387500005658970001215282850
1985-04-080108853586385750005656640001215124358
1985-04-090111511886387500005654310001215332188

The OpenWater API 

To obtain the water reserve data, we used the API (Application Programming Interface) service provided by the platform. The API, or application programming interface, is the interface through which a platform’s or application’s data is sent to the user in response to the request made by the user. The call to the OpenWater API returns the amount of water (in cubic meters) in all Attica’s reservoirs, from the user-defined date and backward. 

In this case, the platform, which provides detailed instructions for using the API, offers the following link: 

 
https://opendata-api-eydap.growthfund.gr/api/Savings

The following parameters apply: 

:duration accepts values of time periods from the date specified in the date parameter (see below). This means that the data returned to the user can be for the duration of a Day, Week, Month, or Year. 

:date takes any date in the format “DD-MM-YYYY” (day-month-year) and sets it as the end date for which the data will be collected. 

The final format of the link will be as follows: 

 
https://opendata-api-eydap.growthfund.gr/api/Savings/:duration/:date

Example: 

https://opendata-api-eydap.growthfund.gr/api/Savings/Day/30-12-2004

Data collection and cleaning 

To “request” and collect the data via the OpenWater API, we used the Python Requests library. We then used the Pandas library to organize the data in dataset format. In most cases, our API calls used the duration parameter set to Year and the date parameter set to December 31 of each year. Exceptions were made in cases of data entry errors originating from the platform itself. Specifically, for the water reserves of the Marathonas reservoir, the dates 31-12-2011, 30-12-2013, and 31-12-2013, and for Mornos, the last two days from each data update period appeared as blank when the call was made with duration = Year, but showed valid values when the call was made with duration = Day. Therefore, this data was collected and filled in on a daily basis. 

What you can produce from this dataset 

Water production 

The platform also provides data on daily water production, in cubic meters, as it is carried out at the Water Treatment Plants (WTPs) of Attica, from January 1, 1996, up to March 10, 2025 — except for the Aspropyrgos plant, whose data starts from December 2, 1996. You can find the corresponding dataset available here, which includes data collected up to July 10, 2025. 

Water is processed at the WTPs. There, it is disinfected from bacteria and microorganisms, cleared of solid materials it may have carried, and filtered. This process makes the water suitable for consumption. In the Attica basin, the WTPs are located in Galatsi, Acharnes (Menidi), Polydendri (Kiourka), and Mandra-Aspropyrgos. The water production dataset has a similar structure to that of the water reserves. The difference lies in the columns, where instead of the reservoirs, the four WTPs of Attica are listed (“Aspropirgos”, “Galatsi”, “Kiourka”, “Menidi”). 

To collect the water production data, EYDAP offers the following link: 

 
https://opendata-api-eydap.growthfund.gr/api/Production

How to collect the data yourself 

You can collect water reserve data yourself from the OpenWaterAPI platform using Python. Below, we include parts of the code we used to collect data. You can find the full code here. Even if you don’t have Python or the required libraries installed on your computer, you can simply copy and paste the code into a Google Colab notebook and follow the step-by-step process below to see the data being collected in real time. 

 
#imports
import requests
import json
import time
import pandas as pd
import datetime

#set ups
pd.set_option('display.max_rows', None)
pd.set_option('display.max_columns', None)
 
# We create all the links (URLs) corresponding to the years we are researching
# and we store them in a list called "webpages"

webpages = []

for n in range(1985, 2026):    
    webpage = 'https://opendata-api-eydap.growthfund.gr/api/Savings/Year/31-12-' + str(n)
    webpages.append(webpage)
webpages
 
# We make a request to the API endpoint and store the response in the "data_list" as a dict

data_list = []

for api in df1.apis:
    
    api_response = requests.get(api)
    data = api_response.text
    parse_json = json.loads(data)
    data_list.append(parse_json)
    
    time.sleep(5)
 
# We collect all the dicts and convert them into a dataframe (df)
dictionaries = []

for dl in data_list:
    dictionaries.extend(dl)

df = pd.DataFrame(dictionaries)
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