Türkiye's water
Is groundwater declining?
Short answer
25 of 25 basins: groundwater and surface water together have been falling over the last 10 years; no basin is rising or unclear (NASA GRACE satellite, latest data month March 2026).
Falling most: Euphrates-Tigris (−2.5 cm per year), Asi (Orontes) (−2.4), Lake Van (−2.3).
No basin is rising.
Türkiye as a whole: −2.0 cm per year on average (same method, May 2016 – March 2026).
Basin averages; no value is given for a province or a plot of land. The satellite measures groundwater, surface water, soil moisture and snow together, not groundwater alone.
Summary
Satellite water storage has fallen in 25 of 25 basins over the last 10 years. Largest fall: Euphrates-Tigris (−2.5 cm per year). NASA GRACE satellite, basin average, groundwater and surface water combined; latest data month March 2026. Map and table below use the same method as the province pages.
25-basin map: 10-year trend, cm per year
| Basin | Trend (cm/year) | Class | Period | Months | Basin page |
|---|---|---|---|---|---|
| Euphrates-Tigris Basin | −2.5 | Critical decline | May 2016 – March 2026 | 102 | Euphrates-Tigris Basin (Turkish) |
| Asi (Orontes) Basin | −2.4 | Critical decline | May 2016 – March 2026 | 102 | Asi (Orontes) Basin (Turkish) |
| Lake Van Basin | −2.3 | Critical decline | May 2016 – March 2026 | 102 | Lake Van Basin (Turkish) |
| Ceyhan Basin | −2.2 | Critical decline | May 2016 – March 2026 | 102 | Ceyhan Basin (Turkish) |
| Seyhan Basin | −2.0 | Critical decline | May 2016 – March 2026 | 102 | Seyhan Basin (Turkish) |
| Konya Closed Basin | −1.9 | Critical decline | May 2016 – March 2026 | 102 | Konya Closed Basin (Turkish) |
| Aras Basin | −1.9 | Critical decline | May 2016 – March 2026 | 102 | Aras Basin (Turkish) |
| Eastern Mediterranean Basin | −1.8 | Critical decline | May 2016 – March 2026 | 102 | Eastern Mediterranean Basin (Turkish) |
| Akarçay Basin | −1.8 | Critical decline | May 2016 – March 2026 | 102 | Akarçay Basin (Turkish) |
| Burdur Basin | −1.8 | Critical decline | May 2016 – March 2026 | 102 | Burdur Basin (Turkish) |
| Antalya Basin | −1.7 | Critical decline | May 2016 – March 2026 | 102 | Antalya Basin (Turkish) |
| Sakarya Basin | −1.6 | Critical decline | May 2016 – March 2026 | 102 | Sakarya Basin (Turkish) |
| Büyük Menderes Basin | −1.6 | Critical decline | May 2016 – March 2026 | 102 | Büyük Menderes Basin (Turkish) |
| Gediz Basin | −1.5 | Decline | May 2016 – March 2026 | 102 | Gediz Basin (Turkish) |
| Çoruh Basin | −1.5 | Decline | May 2016 – March 2026 | 102 | Çoruh Basin (Turkish) |
| Susurluk Basin | −1.3 | Decline | May 2016 – March 2026 | 102 | Susurluk Basin (Turkish) |
| Kızılırmak Basin | −1.3 | Decline | May 2016 – March 2026 | 102 | Kızılırmak Basin (Turkish) |
| Küçük Menderes Basin | −1.2 | Decline | May 2016 – March 2026 | 102 | Küçük Menderes Basin (Turkish) |
| Western Mediterranean Basin | −1.2 | Decline | May 2016 – March 2026 | 102 | Western Mediterranean Basin (Turkish) |
| North Aegean Basin | −1.0 | Decline | May 2016 – March 2026 | 102 | North Aegean Basin (Turkish) |
| Yeşilırmak Basin | −1.0 | Decline | May 2016 – March 2026 | 102 | Yeşilırmak Basin (Turkish) |
| Marmara Basin | −1.0 | Decline | May 2016 – March 2026 | 102 | Marmara Basin (Turkish) |
| Eastern Black Sea Basin | −1.0 | Decline | May 2016 – March 2026 | 102 | Eastern Black Sea Basin (Turkish) |
| Meriç-Ergene Basin | −1.0 | Decline | May 2016 – March 2026 | 102 | Meriç-Ergene Basin (Turkish) |
| Western Black Sea Basin | −0.9 | Decline | May 2016 – March 2026 | 102 | Western Black Sea Basin (Turkish) |
| Türkiye (all land cells) | −2.0 | Critical decline | May 2016 – March 2026 | 102 | — |
Class counts: 13 critical decline, 12 decline, 0 stable, 0 rise. Thresholds: −1.5 cm per year and below is critical decline; between ±0.5 cm is stable.
Detailed data
method · what is measured · data delay · source and citation
Method
- Trend: a least-squares line through the actual months of the last 10 years of each basin's monthly satellite series; unit cm of equivalent water thickness per year. Missing months are not filled in; a basin with fewer than 60 actual months gets no trend and the table gives the reason as "no data".
- Same as the province pages: the line "satellite water storage in your province's basin, 10 years, on average ±x cm per year" on the Turkish province pages is this very value; there is a single point of calculation.
- Classes: −1.5 cm per year and below critical decline; −1.5 … −0.5 decline; −0.5 … +0.5 stable; +0.5 and above rise. On the map the rise colour darkens one step at +1.5 cm; the class name does not change.
- Resolution: the source grid is half a degree, the true resolution about 3° (~300 km); the basin average is approximate and cannot be used at province or district scale. That is why the map colours the provinces a basin covers in one colour; the site holds no basin boundary line.
What is measured
Caution: the GRACE satellite measures total water storage: groundwater + surface water (lakes, dams, rivers) + soil moisture + snow. The trend here is the change in this total, not groundwater alone; that is why the short answer says "groundwater and surface water together". The value is a change relative to the 2004–2009 mean, not an absolute amount of water.
Data date
Satellite water storage: latest data month March 2026; the source (NASA GSFC) has published no new data since. The 2017–2018 gap between GRACE and GRACE-FO and the missing months are left as they are. The page is recalculated when new data arrives; no forecast or extrapolation is made.
Source and citation
- Data: NASA GSFC GRACE/GRACE-FO mascon RL06 v2.0 (yarım-derece grid; açık erişim, earth.gsfc.nasa.gov); processed 16 July 2026; source page earth.gsfc.nasa.gov.
- Citation (requested by the source): Loomis, B. D., Luthcke, S. B., Sabaka, T. J. (2019). Regularization and error characterization of GRACE mascons. Journal of Geodesy, 93, 1381–1398.
- Licence: the source names no licence and asks for citation; reuse terms on the sources page (Turkish).
- Raw series: 25-basin monthly series (CSV); the Turkish basin pages also show the 5-year trend of the same series.