La Charca is a reservoir that has collected the waters from the source of the Fuente de la Reja since medieval times. At first it was a simple dam with a stone retaining wall and gates that regulated the water's outflow through an intricate network of kilometres of ditches. These irrigated the orchards and olive groves to the south of the town, distributed in terraces. The upper ditches served as a southern limit to the population, thus delimiting the urban growth of Pegalajar.