A geological staircase
The Ruidera Lakes are a series of fifteen interconnected lagoons that descend through the arid plains of La Mancha. They are not man-made reservoirs but a naturally occurring staircase of lakes separated by dams that build themselves. The entire system stretches for about 25 kilometers, dropping 120 meters in elevation from the first lake, Laguna Blanca, to the last, El Cenegal. The largest lakes in the chain are Laguna Colgada and Laguna del Rey.
The water creates this landscape. It flows from the Campo de Montiel aquifer, a vast underground reservoir saturating the Mesozoic dolostone and limestone bedrock. As the groundwater percolates through this carbonate rock, it becomes rich in dissolved calcium bicarbonate. When this water emerges at the surface and flows over the edge of a lagoon, the turbulence and drop in pressure cause it to release, or degas, carbon dioxide. This chemical change makes the water less acidic, forcing the dissolved calcium bicarbonate to precipitate as solid calcium carbonate, the mineral calcite. This process of precipitation creates the porous limestone rock known as travertine or tufa, which builds up the natural dams, layer by layer.
A landscape in slow motion
These travertine dams are in a constant state of slow-motion construction. The precipitation of calcium carbonate happens on the surfaces of mosses and algae, which are nucleation sites for the mineral growth. This organic framework becomes entombed in rock, creating a living dam that grows at a measured rate of about two millimeters per year. This process is not static; it causes the entire waterfall system to migrate upstream over geological time. As new layers of travertine are deposited on the crest and face of a dam, the waterfall slowly builds itself backward.
This geological process has been active since at least the Pleistocene epoch. The area's human history is also deep, with archaeological evidence of settlement dating to the Paleolithic period. The Romans built a road that ran alongside the lagoons. Much later, the landscape found a permanent place in literature. Miguel de Cervantes used the area as a setting for scenes in his 17th-century novel Don Quixote. The author situated an important episode in the Cave of Montesinos, a karstic cave that is in the same hydrological system as the lakes. In the novel, the wizard Merlin is said to have transformed the lady Ruidera and her daughters into the chain of lakes.