Climate Change and the European Water Dimension - Agri ...

Mountain lakes can be found in most of Mediterranean countries like Italy, France,
Spain, Albania, and Greece where they should be allocated to alpine rather than to
Mediterranean types.
The most important Italian lake district is located in northern Italy and includes the
deep sub alpine lakes and some small-medium Insubrian lakes, which together make
up more than 80% of the total volume of lakes in Italy (Premazzi et al., 2003). One of
the most important hydrodynamic features in the great lakes (i.e. Como, Garda,
Maggiore) is their specific holo-oligomixis. The rainfall regime in this area is typical of
the Alpine Region with the precipitation maximum between May and November.
Approximately 70-75% of the annual precipitation volume is concentrated to this
period. The climate is of continental type.
The Central Italian lakes belong to the Middle Thyrrenian Climatic District, and
occupy the highest part of the volcanic area characterised by a maritime climate with
generally mild winters and hot summers (Ambrosetti and Barbanti, 2002). The lakes
in this region are of different origin: volcanic crater lakes (like Lake Bolsena), alluvial
lakes (like Lake Trasimeno) or coastal (like Lake Lesina and Lake Varano in Puglia).
The Latium lakes (Bolsena, Bracciano, Nemi, Vico) have some hydrodynamic
features characteristic of lakes in an oceanic climate. As a consequence of this, the
thermocline in these lakes develops much deeper than in the northern district, though
not as deep as in lakes with a really oceanic climate (Pompilio et al., 1996).
Greek lakes can be divided into three categories: warm monomictic deep lakes,
warm monomictic shallow lakes, and dimictic shallow lakes (Zacharias, 2002).
Spanish lakes range by their salinity level from freshwater to hypersaline lakes and
by their permanency from ephemeral, filled with water for less than one month, to
deep stratified permanent lakes. Temporary lakes with increased salt content are
characteristic of endorheic basins (without outflow) in semi-arid and arid climate
zones while permanent lakes are located at higher altitudes and in carstic areas.
Besides natural lakes, there are about 4000 large dams in the Mediterranean region
(Table IV.B.2). The top five countries in terms of the number of dams are Spain, with
1,196 large dams, or just under one third of the Mediterranean total, Turkey (625),
France (569), and Italy (524) (Haas, 2002).
56