Cornalvo
About
The Cornalvo Dam still backs a reservoir east of Merida behind packed earth and rubble faced with dressed stone, standing 194 meters long and up to 24 meters high. It formed a second water source for Emerita Augusta alongside Proserpina, feeding the city through its own aqueduct and a sluice tower that still works. Most scholarship dates it to the first or second century CE, though a few Spanish studies argue for a later Hadrianic date near 130 CE. Water still flows to Merida from it today.
What happened here
Built to hold water for a town, a farm or a mine, and shaped by what the local rock allows: a straight wall of masonry backed with earth, or a curved one where the gorge is narrow. The core is concrete and rubble, faced in cut stone, and the upstream face is often waterproofed with mortar. Water is drawn from a tower with sluices at different heights, so the supply keeps running as the level drops and the silt stays at the bottom. Overflow channels carry the winter flood past the wall rather than over it — the detail that decides whether a dam survives. Silt is the long enemy; a reservoir has a working life and everybody involved knows it.
Sources
Roman Maps shows the empire frozen at 11 August 117 CE, the day Trajan died — its moment of greatest territorial extent. Explore the full map →