It lies in a 53,600 ha natural basin known as El Campo de Bello, encircled by the Iberian System mountain ranges of Sierra de Santa Cruz and Sierra de Pardos in the north, Sierra Menera in the south and Sierra del Caldereros in the east. It is an intermittent rain-fed lake, largely dependent on abundant autumnal and spring rains if it is to maintain a sizeable amount of water into the hot summer months. During the summer of 1969 drought the lake dried completely, leaving a crust of salt and remaining dry for a long spell.