Environmental Engineering Reference
In-Depth Information
Figure 5.12 presents the calculated history of subsidence at two points
respectively 5 and 8 km from the center of the model for the case when pumping is
kept constant from 1969 onwards. In the same figure the values recorded at a point
6.6 km from the industrial zone (center) are also shown.
The elastic rebound caused by the reduction (after 1970) and the end of pumping
is shown in Figure 5.13.
Figure 5.13
.
Modeling of rebound after pumping has completely stopped
We recall again that the calibration of the model and the first set of calculations
have been performed using the spatial mesh in Figure 5.8a. The calculations have
then been repeated with the more refined mesh in Figure 5.8b, using a parallel
computation algorithm. The results of the first set of analyses have been confirmed,
obtaining more detailed information at the same time.
A very detailed leveling exercise was repeated in 1993, as shown in Figure 5.6.
The results indicate the present tendency of the subsidence after water withdrawal is
reduced and stopped: the mainland and surrounding areas of Venice and the city are
substantially stable (see also Figure 5.13). At the extreme edges of the lagoon and
the littoral land, sinking is still ongoing, with a very limited subsidence rate. This
takes place because the areas are of more recent formation and are close to the river
outflows. Hence natural compaction is more active here and a relationship with
aquifer exploitation is questionable.
