The indicator measures the increase in the average sea level in Venice, being of fundamental importance for the studies and conservation interventions of the city of Venice, as well as the lagoons and high Adriatic coastal areas at risk of flooding. In Venice, the average sea level has increased since the beginning of the recordings: in the period 1872-2024 the level increases by an average of 2.6 mm / year, with a trend not always constant and uniform over time. In this regard, it is considered appropriate to highlight the rate for the last thirty years (1993-2024), where the average sea level rise is almost doubled (4.8 mm/year).

The weather variables observed in the Venice Lagoon (the average annual atmospheric pressures, the total annual rainfall, the number of rainy days and thermal anomalies) allow to photograph the climate changes taking place. During 2024, in the presence of an average annual pressure of 1,0155.9 mbar (below 0.3 mbar compared to the average of the reference period), 1,127 mm of rain were recorded (+34% compared to the average) over a period of 96 rainy days, while temperatures continue to show themselves in trend and continuous increase.

The indicator shows the number of annual cases of tidal maximums, divided by height classes, detected at the station of Venice - Punta della Salute, representative of the historic city center. Monitoring the trend of the high and medium-high tide classes (above 80 cm compared to the ZMPS reference plane) allows you to control the pressure exerted both on the historic center of Venice (effects on the estate of the banks and buildings), and on the surrounding lagoon (environmental effects on the vegetation of the barenal habitats and on the greater erosion of the natural banks). In the last period, 2019 was an exceptional year as there were 28 cases of “high water”, i.e. exceeds of the threshold 110 cm on the ZMPS, record value of the entire historical series. As of 2020, the entry into operation of mobile barriers against flooding from high tide (model system "Mo.S.E.") has led to a differentiation in the number of cases of high water between the lagoon and the sea. 2024 recorded 12 cases of “high water” at sea and a single pass in Venice (on May 16, first case from 2021), thanks to the drive of the Mo.S.E. which defended the city.

A continuous monitoring over time of the variations of the astronomical tidal amplitude allows to highlight the hydrodynamic and therefore morphological changes inside the Venice Lagoon, which owes its survival to the maintenance of delicate environmental balances. The width of the tide in the lagoon is compared with the characteristic one of the Gulf of Venice, belonging to the same area from a geological point of view, but exempt from the anthropic intervention that distinguishes the transition environment considered. The tidal height trend is now substantially stable throughout the lagoon, after the strong variations observed as a result of profound changes introduced to the lagoon morphology during the first decade of the century.

A continuous monitoring over time of changes in the delay in the propagation of the astronomical tide allows to highlight the hydrodynamic and therefore morphological changes inside the Lagoon of Venice, which owes its survival to the maintenance of delicate environmental balances. The tidal propagation delays within the lagoon are calculated with respect to the Gulf of Venice, belonging to the same area from a geological point of view, but exempt from the anthropic intervention that distinguishes the lagoon environment considered. Tidal propagation delays are greater the greater the distance of the observation point from the port mouth from which it is fed. The tidal wave takes about 35/40 minutes to enter the lagoon through the narrowing of the three port mouths, while it takes about three hours to reach the most inland and remote areas.

The Ecological Classification Index of the Macroinvertebrate Biological Quality Elementary for Coastal Lagoons, M-AMBI (Multivariate-Azti Marine Biotic Index), is based on the analysis of the structure of the mobile macrozoobentonic community and takes into account the tolerance/sensitivity of species, community diversity and specific wealth. The M-AMBI index responds to anthropogenic and natural pressures affecting transition areas and describes the ecological quality status in 5 classes: high, good, sufficient, scarce and bad. 
The monitoring of benthic macroinvertebrates for the application of the M-AMBI index has been active in the Venice Lagoon since 2011 with a three-year frequency. In the 12 years of monitoring, 4 sampling campaigns were carried out; in 2022 four water bodies out of eleven are in a “poor” state, the remaining in a “sufficient” state and the trend of comparison between all the years of monitoring is stable.

The MaQI (Macrophyte Quality Index) (Sfriso et al., 2014) formally adopted by Italy for the classification of the ecological status of transition environments under Directive 2000/60/EC, integrates the two organic quality elements macroalgae and aquatatal fanerogages. 
The MaQI responds to anthropogenic pressures affecting transition areas and describes the ecological quality status in 5 classes: high, good, sufficient, scarce and bad.
The monitoring of macrophytes for the application of the MaQI index has been active in the Venice Lagoon since 2011 with a three-year frequency. In the three-year period 2020-2022 (21 data) of the eleven natural water bodies of the Venice Lagoon, two were in a “high” state, four in a “good” state, three “sufficient” and two in a “poor” state. The trend, although statistically not significant, is overall positive, considering the improvement of the state of some bodies of water.