Lago della Trinità, lake in Sicily

Lago della Trinità is an artificial reservoir on the municipal territory of Castelvetrano, oriented almost north to south and fed from the north by the Delia river, which is called Arena at the basin. At its southern end a roughly 250-metre-long earthen dam, built in the second half of the 1950s, holds back the water. The reservoir also has a coastal strip of about 600 metres in the territory of Mazara del Vallo.

The lake formed when engineers built an earthen dam across the Arena River between 1954 and 1959. This construction transformed the natural river course into a large water storage system, fundamentally reshaping the landscape to support irrigation for the surrounding farmland.

The name Trinità means Trinity in Italian, as the German-language source notes. The reservoir supplies drinking water to Castelvetrano, Campobello di Mazara and Mazara del Vallo, and Mazara del Vallo holds a roughly 600-metre strip of shoreline on the lake.

The reservoir lies on the Arena River in the territory of Castelvetrano, with a roughly 600-metre strip of its shore in Mazara del Vallo. The lake runs almost north to south, fed from the north and held at its southern end by an earthen dam about 250 metres long. Silt washed down from the Delia has already filled in parts of the northern section, so the water body is smaller than the basin outline suggests.

The reservoir has silted up so much that large parts of its northern section are now dry land, cutting its storage capacity. This is the result of deforestation upstream on the Delia river and the soil erosion that followed, since no hydraulic or forest works were carried out in the catchment.