# Garda needs 26.8 years to renew its water > Garda's theoretical water renewal time is 26.8 years, against 4.1 for Maggiore and 4.2 for Iseo. That single ratio explains most of the lake's politics. URL: https://myitalia.it/stories/garda-takes-27-years-to-renew-itself Last updated: 2026-09-02 Lake Garda takes a theoretical 26.8 years to renew its water, against 4.1 years for Lake Maggiore and 4.2 for Lake Iseo, so what enters Garda stays there for decades. ## 26.8 years against 4.1 and 4.2 The theoretical renewal time of Garda is 26.8 years. Maggiore does it in 4.1 and Iseo in 4.2. That is more than 6 times slower than either neighbor, and it is the single most consequential number about the lake. A pollutant that goes into Maggiore is largely gone within a presidential term. The same substance in Garda is a problem for a generation. It also cuts the other way, which is less often said. Garda's inertia makes it slow to degrade and slow to recover, so improvements take as long to show up as damage does. ## 49 cubic kilometers is the reason Garda holds around 49 cubic kilometers of water over a surface of 369.98 square kilometers, and the Mincio carries a mean 58.4 cubic meters per second out of it. Divide a very large volume by a modest outflow and you get 26.8 years. There is no mystery in the mechanism: the lake is deep, wide and drained through a single river. The catchment feeding it covers 2,260 square kilometers and rises to 3,556 meters, with the Sarca as the main inflow. Everything that happens in that basin arrives here and then stays. ## 346 meters, or 350: 2 official answers The Comunità del Garda, the body of the lakeside comuni and provinces, publishes a maximum depth of 346 meters. The first OLL report of 2004, produced by the Lombardy Region with ARPA, the Fondazione Lombardia per l'Ambiente and CNR-IRSA, gives 350 meters. We record 346 m, because the source is more recent and closer to the lake, and we record the disagreement rather than hiding it. It has not been resolved. The other dimensions are not in dispute: 51.6 km long, up to 17.2 km wide, 158.4 km of shoreline, mean depth 133.30 meters, surface at 65 meters above sea level. ## In 2023 Maggiore only mixed to 60 meters The winter mixing of Lake Maggiore reached 60 meters in 2023, staying inside the top 100 meters for the tenth consecutive year, and oxygen in the deep water hit the lowest values in the historical series. Winter mixing is how a deep lake breathes: cold surface water sinks and carries oxygen down. When the surface no longer gets cold enough, the bottom is cut off from the atmosphere. Ten consecutive years is not a bad winter. It is a regime, and it is the measured local face of a warming climate on water bodies that people swim in. ## What a 26.8-year lake means for a visit Nothing about the renewal time changes your afternoon: Garda's 158.4 km of shoreline are swum, sailed and cycled exactly as before. What it changes is how you read the arguments you will hear locally, about sewage plants, about lake levels in a dry spring, about agricultural withdrawal for the Mincio. In a lake that turns over every 4 years those are seasonal disputes. In a lake that takes 26.8, they are decisions with a 30-year tail. That is the honest reason to put a limnological number on a travel page. It is not a warning about the water you are about to swim in. It is the timescale on which this particular lake answers for what is done to it. ## Where these numbers come from, and what is missing The morphometry here comes from a single primary source, the Comunità del Garda, which is why the depth is recorded as 346 meters with the 2004 alternative flagged beside it. We could not obtain independent confirmation. The CNR-IRSA limnological database resolves to a working address but the connection times out, so the second reading that would settle the 346 against 350 was not available. The 2023 Maggiore figure is an annual measurement and will be superseded by the next monitoring report. The 26.8 years, by contrast, is a structural property of a lake 346 meters deep with 1 outflow, and it will still be true when everything else on this page has been revised. ## FAQ ### How long does Lake Garda take to renew its water? 26.8 years, on the theoretical renewal time. Lake Maggiore takes 4.1 years and Lake Iseo 4.2, so anything that enters Garda stays in the system more than 6 times longer than in its neighbors. ### How deep is Lake Garda? 346 meters at its deepest, on the figure published by the Comunità del Garda, with a mean depth of 133.30 meters. A 2004 regional report gives 350 meters instead. The discrepancy between the 2 official numbers has never been resolved. ### How big is Lake Garda? 369.98 square kilometers of surface, 51.6 km long and up to 17.2 km wide, with a shoreline of 158.4 km. It holds around 49 cubic kilometers of water and its surface sits 65 meters above sea level. ### Which river flows into and out of Lake Garda? The Sarca is the main inflow and the Mincio the outflow, which carries a mean 58.4 cubic meters per second. The catchment covers 2,260 square kilometers and rises to 3,556 meters. ### Are the Italian lakes warming? The measurements say yes. In 2023 the winter mixing of Lake Maggiore reached only 60 meters down, staying within 100 meters for the tenth consecutive year, and oxygen in the deep water hit the lowest values in the historical series. ## Sources | Fact | Source | Confidence | Valid until | |---|---|---|---| | Il Lago di Garda ha un tempo teorico di ricambio delle acque di 26,8 anni, oltre sei volte quello del Maggiore (4,1) e dell'Iseo (4,2). | [Osservatorio dei Laghi Lombardi - Regione Lombardia, Fondazione Lombardia per l Ambiente, ARPA Lombardia, CNR-IRSA](https://fondazionefla.it/wp-content/uploads/2021/07/Qualita-acque-lacustri-in-Lombardia.pdf) | medium | 2030-12-31 | | Il Lago di Garda ha una superficie di 369,98 chilometri quadrati, una profondita' massima di 346 metri e una profondita' media di 133,30 metri, con lo specchio d'acqua a 65 metri sul livello del mare; contiene circa 49 chilometri cubi d'acqua, e' lungo 51,6 chilometri e largo al massimo 17,2, con 158,4 chilometri di perimetro e un bacino imbrifero di 2.260 chilometri quadrati. | [Comunita' del Garda (ente associativo dei comuni e delle province rivierasche, Salo')](https://www.comunitadelgarda.it/il-lago/geomorfologia/165-55.html); [Osservatorio dei Laghi Lombardi - Regione Lombardia, Fondazione Lombardia per l Ambiente, ARPA Lombardia, CNR-IRSA](https://fondazionefla.it/wp-content/uploads/2021/07/Qualita-acque-lacustri-in-Lombardia.pdf) | medium | 2099-12-31 | | Nel 2023 il rimescolamento invernale del Lago Maggiore si e' fermato a 60 metri di profondita', restando per il decimo anno consecutivo entro i 100 metri, e l'ossigeno nelle acque di fondo ha toccato i minimi assoluti della serie storica. | [CIPAIS - Pannello di Controllo del Lago Maggiore 2023](https://www.cipais.org/web/wp-content/uploads/2025/01/CIPAIS_PdC_Lago_Maggiore_2023.pdf) | medium | 2027-06-30 | ## Image https://media.myitalia.it/media/theme.laghi.v2.1600.jpg Author: kallerna. 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