Hydroelectric power station


San Juan

The first stage in the use of the San Juan River in the province of the same name, involves the Ullum hydroelectric plant with 45 MW of installed capacity, designed to supply the city of San Juan and neighboring districts as part of the Cuyo electricity grid.

The main structure, the movable diverter dam built at Punta Negra, 34 km from the capital of the province, has the function of impounding and diverting the waters of the San Juan river.

This was the initial phase of the works required to develop the comprehensive projects on the San Juan River

128.000 m3


1.800.000 m3


45 MW

installed capacity


Civil works for the Hydroelectric power plant of Ullúm (today known Ullum I and II), Province of San Juan.


Agua y Energía Eléctrica Sociedad del Estado


Ullum Hydroelectric Plant (45 MW) is located on the middle reaches of the Rio San Juan, about 34 km from the capital of the Province and was the initial phase of the works aimed at making the most of the San Juan River.

The work performed involved the construction of a movable diverter dam, the headrace (desander), the water catchment (an irregular weir), a tunnel 170 m long and 720 mm in diameter, a rectangular adductor channel excavated in the rock and lined with concrete, a desanding camera, a collector channel, an adductor forebay channel of 9.5 km in length as well as artwork and an opencast tailrace of 2.8 km.

The diverter dam has a length of about 176 m and has six circular sector metallic gates with a 20 m span and 7 m in height, each supported by concrete 3 m thick piles set into the rock.

The desanding chamber is a structure which covers an area of more than 10,000 m2. It comprises 24 cells of 80 m in length and a variable rectangular section of 5.00 m x 2.75 m to 5.00 m x 4.75 m.