servizio informativo

problems

Lagoon morphology

The measurement and study campaigns initiated by the Consorzio Venezia Nuova in the second half of the 1980s showed lagoon morphology to be in a worrying state of degradation as a result of the annual loss of a million cubic metres of sediment per year. Since the beginning of the 1900s, half the existing salt marshes have disappeared and a general deepening of the shallows and silting up of the channels has been triggered, in turn triggering and encouraging the diffuse expansion of the tides, to the detriment of natural directional propagation along the network of channels. A generalised deepening of the lagoon bed (partly caused by the subsidence and eustatism which have increased the mean depth of the lagoon basin by 23 cm in the space of a century) has increased wind-generated wave motion, one of the main mechanisms of erosion. So, diversion of rivers away from the lagoon, a drop in land level and a rise in sea level on one hand, and on the other, dredging of large shipping channels, in particular the Canale Malamocco-Marghera (completed in 1970) have created conditions which encourage transformation of the lagoon into a bay. Through the acquisition of maps, bathymetric and photogrammetric surveys and studies of lagoon hydrodynamics, the work of the Information Service has enabled the actual situation of the lagoon morphology to be understood and analysis tools able to record transformations of the area to be set up.

Lagoon pollution

The studies initiated in implementation of the conventions drawn up between the Venice Water Authority and the Consorzio Venezia Nuova since the 1980s have enabled an initial evaluation to be made of the enormous quantity of pollutant substances of agricultural, industrial, civil, urban and animal rearing origin entering the lagoon from the drainage basin. At the end of the 1980s, a series of algal blooms highlighted the oligotrophic condition of the lagoon, in other words, the presence in the lagoon water of large quantities of nitrogen and phosphorous compounds (nutrients) responsible for the excessive algal growth and the dystrophic manifestations occurring during the summers of 1988 and 1989. On the basis of detailed data on the distribution of the resident population, location of drains and sewers, land use, discharge of agricultural effluent, climatic conditions, functioning of the hydraulic network and the hierarchy of hydrographic basins and sub-basins, the work of the Information Service has enabled a temporally and spatially reliable assessment to be made of the total load of nutrients generated in the drainage basin and transferred to the lagoon.

Communications

Since the beginning of the 1990s, the Information Service has paid particular attention to the matter of communications in order to make the wealth of documents and knowledge acquired easily consultable, facilitate the reciprocal exchange of data with the authorities and administrations operating in the lagoon area and prepare plans and programmes aimed at providing the public with information. The importance of producing a greater number of descriptive, illustrative and explanatory texts integrated into ad hoc information systems was recognised, with the principal aim of enhancing regional analysis and facilitating consultation and use of the data. The added value of these support systems lies in the extension and development of the regional analyses.