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Pliego Reservoir


The Segura River Basin is, amongst all those in the national territory and throughout history, the one that has suffered the greatest number of catastrophes as a result of the floods produced by rivers overflowing their banks.

Photo of Pliego Reservoir

There are historical references since almost five hundred years ago that speak of the disasters suffered in the area due to these meteorological phenomena, including losses of human lives.

During the 18th and 19th centuries some works were carried out in the Segura river basin in order to guarantee its maximum exploitation: this is the case of Puentes Reservoir, on the River Guadalentín, and Valdeinfierno Reservoir, on its tributary, the Luchena.

At the beginning of the 20th century, work started on the systematized construction of reservoirs at river headwaters, in accordance with a preliminary plan drawn up in 1887 by Mr. Ramón García and Mr. Luis Gaztelu to mitigate the devastating consequences of the Santa Teresa flood, occurred in 1875. From this period are Fuensanta and Cenajo reservoirs, on the Segura river, Talave and Camarillas reservoirs on the Mundo river; Alfonso XIII Reservoir on the River Quípar, Santomera Reservoir on Rambla Salada, La Cierva Reservoir on River Mula and Argos Reservoir on the River Argos.

Photo of Pliego Reservoir

The extension of the irrigation areas, especially in the Vega Baja and Vega Media of the Segura river caused the narrowing of the Segura river, reducing the capacity of the bed in some stretches to just 100 m³/s.

The construction of a reservoir to control the flooding of the River Pliego had already been taken into consideration in 1937 by the Engineer Mr. Juan Alcaraz Pavia, the project in question being called Pablo Iglesias Reservoir. In 1940, Mr. Enrique Albacete Ayuso drafted the Project for the Transfer from the River Pliego to Corcovado Reservoir, which would later be called La Cierva Reservoir.

In May 1977 the “General Flood Control Plan of the Segura river Basin” was drawn up.

Entre las obras prioritarias incluidas en dicho Plan se encontraba la Presa de Pliego.

Photo of Pliego Reservoir

Amongst the main works included in this Plan was the Pliego Reservoir. The Pliego Reservoir project was drawn up in June 1987, including the construction of a dam in the wadi Rambla de Doña Ana, as additional closing, naming it Doña Ana Dam.

Among the possible natural downstream boundaries considered in the “General Plan” for the location of the dam, the one considered to be most suitable in the preliminary project study was the one of the Molino de Carrancha, with a catchment basin of 206 km².

In order to cover practically all the basin, the decision was made to build a second dam in addition to that of Pliego in Rambla de Doña Ana, tributary on the left bank of the River Pliego, downstream from the location chosen for the Pliego dam.

In the preliminary project study the following types of dam were analyzed:

1) Spillway dam made of concrete with a straight ground plan.
2) Spillway dam made of concrete with a curved ground plan.
3) Heterogeneous earth dam with a core and rock facing.

Since the budgets were very similar, the concrete dam with a curved ground plan was chosen, believing it offered a series of functional advantages in comparison to the earth dam and resistance advantages in comparison to the concrete one with a straight ground plan.

Photo of Pliego Reservoir

In July 1988, the Dam Surveillance Service published a report recommending the need to proceed to waterproof the land on the right abutment, thus avoiding the risk of the regressive internal erosion of the existing materials, Plio-Quaternary silts forming the upper part of this ravine bank. It also pointed out the need to carry out a further geological reconnaissance campaign to determine the morphology of the contact between the Plio-Quaternary and the Oligocene epochs on this abutment.

The contract for the Pliego Reservoir works project, including Doña Ana Dam, was awarded through public competition and by Council of Ministers agreement on 14th October 1988, being given 36 months as a term for completion.

The document verifying readiness for construction was drawn up on 21st November 1988.

In November 1988 the “Additional Geological Report and Proposal for Dealing with the Waterproofing of the Right Abutment of Pliego Dam” was issued, proposing a series of measures for waterproofing this abutment, in accordance with the recommendations laid down in the Dam Surveillance Report.

In May 1989 Pliego Reservoir Amendment I was published, which contained the actions required for waterproofing and consolidating the right abutment.

While the works were being carried out, the decision was taken to perform a series of changes with regard to what had been established in the project: laying the foundations of the viaduct abutments, removal of the cappings below the dam crest road, substitution of the concrete wall by gabions downstream on the right embankment and a new design of Doña Ana Dam. In December 1990, an application was submitted for permission to draft Amendment II, which was authorized on the 9th July 1991 and published in September of the same year.

In December 1992 authorization was requested to draft the “Pliego Reservoir Additional Works Project I. Easement Replacement and Improvement of the Facilities”, which was drawn up in February 1993. These works referred to Pliego Reservoir, with the exception of a connection for the electricity supply at Doña Ana Reservoir, and can be summarized as follows:

  • Definitive replacement of irrigation easements and rights of way to the affected properties.
  • Additional works for diversions, including ditches and drainage, safety barriers and signposting.
  • Diversion of the telephone line and connection of power lines. The diversion was included of the Pliego-Casas Nuevas telephone line and two connections for supplying the dams, one for Pliego and another for Doña Ana, plus another underground one for connection with the CT Pliego.
  • Provisional Conditioning of roads affected.
  • Demolitions and adaptation of the riverbed, consisting of conditioning the bed by demolishing the cofferdam and counter-cofferdam.
  • Improvement of the imperviousness and safety of the dam, through the construction of a cut-off wall from the gallery
  • Control devices. Installation of piezometers in the area of the right abutment and the casing of the inverse pendulum.

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