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Reservoirs

Moratalla Reservoir

Territorial framework.

Physical characteristics of a basin.

The Moratalla river is an affluent of the right margin of the Segura river, and it is the object of a toponymic dichotomy in the National Geographic Institute Official Maps, where it appears, interchangeably, under both the names of Benamor and Moratalla

According the people of the area, and confirmed by the 1982 edition of the Regional Map of the Autonomous Community of Murcia which contains the actual toponymy of the hydrographic network, the Motaralla is called Alhárabe river from its source to the confluence with its main tributary on the right margin, which is the Benamor river. This confluence takes place approximately 5 km downstream, near the site known as El Cobo.

The Moratalla river is born 1,450 meters above sea level at the foothills of the Arcaboche Mountains with the name Alhárabe. After flowing for 50 km, it empties into the Segura river at a place known as La Esperanza, close to the Sanctuary of the Virgin of the same name, patron saint of Calasparra. By the time the two rivers join, the Segura has traveled a distance of 170.5 km from its source, and it rises 273 m a.s.l., while the average slope of the Moratalla river along its course is 2.4%.

The Moratalla river basin by its mouth is 345 km², while at the Moratalla dam enclosure, it becomes 328.56 km², of which 76.8 km² belong to the sub-basin of the La Risca dam, upstream from the Moratalla dam.

Watercourse upstream from the dam
Watercourse upstream from the dam

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Environmental information.

It must be noted that the environmental factor had a decisive influence over the decision taken by the Survey of alternative locations for the dam prior to drafting the project, because of the environmental advantages of its basin over other options.

Annex Nº12 of the Building Project is the Environmental Impact Assessment, which includes the necessary measures to minimize or eliminate the environmental impact of the construction of the dam and its presence over the watercourse.

The results of the study did not reveal any high risk, parameter value or impact indicator requiring corrective o minimizing measures.

The measures adopted in the project's Environmental Impact Assessment to eliminate or reduce the detected alterations are briefly listed below:

  • Reconstruction of roads and access, as well as the construction of paths
  • Protective and corrective actions for the slopes.
  • Reforestation of the affected areas.
  • Conservation and improvement of wildlife in the affected areas.
  • Compensatory measures to the affected population.
  • Landscape integration of degraded areas.
  • Establishment of a Surveillance and Control Plan to monitor the effectiveness of the measures adopted and the possibility of introducing new ones in case of additional alterations that have not been previously detected.

Through a resolution dated April 24, 1995, the General Directorate of Environmental Policy (DGPA in Spanish) submitted the Environmental Impact Statement (DIA in Spanish), listing a series of conditions to be met so that the Moratalla dam project may be considered environmentally viable.

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Intake tower (upstream from the dam) for replacement of irrigation easement and drainage chamber
Intake tower (upstream from the dam) for replacement of irrigation easement and drainage chamber

Geology and seismology.

Geology

The Moratalla reservoir is located in the northeastern section of the Baetic System, which at the same time is the northwestern segment of the Peri-Mediterranean Alpine Orogen (aligned mountains with a runoff layers structure created during the Cretaceous and the Tertiary, centrifugally arranged in relation to the sea; Martín Algarra, 1987).

Within the Baetic System, the area under study is framed within the external area, just on the limit between the internal Pre-Baetic and the internal Sub-Baetic.

General geological map of the Baetic System
General geological map of the Baetic System

Within this area, the Moratalla river runs eastwards through marly materials, turning NE to avoid the calcareous outcrops of the Serrezuela de San Miguel, on whose eastern foothills rests the municipality Calasparra.

The basin is mainly shaped by waterproof Miocene marl, limestone and sand. The presence of limestone and marl from the Cenomanensis-Turonensis does not cause any waterproofing problems, given the predominance of marl and the impossibility of continuing towards the Argos river or downstream.

The basin is mostly made up of Tertiary materials based on limestone, marly limestone, calcareous marl and marl, with white and grayish-white coloring due to the continuous insets and lateral changes of facies.

Seismology

In November 1999, the proposal for classification of the Moratalla dam according to potential risk was submitted, and it received category A classification.

Pendulum
Pendulum

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