El Moro Reservoir
Background
The first mention we have about the possibility of building a retarding basin in the Rambla del Moro basin goes back to the year 1930, when the engineer Mr. José Muso Blanch drafted the "Project for the Rambla del Moro Regulating Reservoir".
Later the Geological Advisory services issued a report on the geological conditions of the downstream boundary for the storage area, ordering probings to be carried out. Once the probing campaign was over, the results were published in the “Report on probings made in the Rambla del Moro, to study the siting of a dam to form a reservoir for flood control and projected by the Confederación Hidrográfica del Segura” issued in 1954 by the Supervisory Authority for Probings.
In October 1973 there was great flooding in the province of Murcia that led to the proposal to adopt a series of technical measures in order to eliminate, or at least mitigate, the harmful effects caused by very heavy showers in the area.
On 11th September 1974 a Coordination Plan was approved to carry out works and actions in the province of Murcia, which included those of the "Rambla del Moro Reservoir".
On 20th November 1974, the “Tender Specifications for the Contracting and Drafting of the Flood Protection Works General Plan in the Segura river Basin” was presented. It was approved on 9th December 1974. The drafting of the Plan was completed in 1977. Rambla del Moro Reservoir was included in this Plan as a basic hydraulic infrastructure required in that sub-basin for flood control.
The floods which occurred in the Segura River basin in October 1982 meant that the works included in the above-mentioned General Plan were given top priority and the procedure for the award of the Rambla del Moro reservoir and dam project was initiated.
Chronologically, the first document found that bears a direct relationship with the current Rambla del Moro reservoir dates from the year 1983. It is the Tender Specifications issued on the occasion of the contracting of the Technical Assistance for carrying out the necessary studies for drafting the Dam Project.
The Confederación Hidrográfica del Segura published the Project for the Construction of the Rambla del Moro Reservoir, in March 1984, directed by Mr. José Bautista Martín and Mr. Julio Bravo Muñoz.
This Project was given a favourable report on 13th June the same year by the Dam Surveillance Service with several conditional proposals (regarding the terracing of the land to support the foundations, the making of transversal galleries, the waterproofing of the calcareous land of the foundations, the detailed study of the seismicity in the area and the extension of the dam drainage network). The Project was approved technically and definitively on the part of the Directorate General for Hydraulic Works on 20th July 1984.
The Project, which was basically based on the suitability of the location due to its reduced cost (narrowing of the bed) and to the safety of the foundations (limestones), had its maximum level limited because of the Madrid - Cartagena railway, whose embankments and bridge would be affected by the reservoir. Therefore the maximum flood level established was 235.50 m.
The document verifying readiness for construction of the "Project of the Rambla del Moro Reservoir" works was signed on 5th December 1984.
On 6th May 1985, RENFE (the Spanish Railways Company) wrote to the then Directorate General for Hydraulic Works, expressing the problem of the above-mentioned railway line (RENFE’s refusal to accept the lining of the embankments of the Chinchilla-Cartagena railway line), proposing its total diversion. This facilitated the raising of the height of the dam, an Amended Project being proposed with the initial idea that the railway line would run along the dam crest, and so a crest pass had to be built.
On 18th November 1986 the drafting of Amendment Project I was authorized on the part of the Directorate General for Hydraulic Works, a report on the partial temporary suspension of the works being issued.
In January 1987 Mr. José Bautista Martín issued Amendment Project I for Rambla del Moro Reservoir. This removed the items related to the lining of the embankments, a crest pass was designed and the height was increased 2.5 m in the centre and 4.8 m in the abutments.
In the Dam Surveillance Service Report of 27th December 1988, the approval of Amendment Project I was proposed, some recommendations being added. The confirmation of the stability of the dam was among them. In October 1989 the justificatory documentation of the stability of the dam was received for this increase in height.
On 15th January 1991 the Provisional acceptance of the works that include those of Amendment Project I was made.
Additional Projects
Additional Works Project I:
When the works were being carried out, the need arose for undertaking other additional ones, the corresponding project dated January 1987 being drafted by Mr. José Bautista Martín. The project consisted of equipping the dam with certain services.
- Administration building.
- Electricity supply
- Drinking water supply
- Telephone line
Additional Works Project II:
This project was drafted, just as in the previous project, with the same dates and author, and its purpose was the consolidation of the abutments by means of injections.
Additional Works Project III:
Additional Works Project III was drawn up in July 1990 and approved on 3rd June 1991. In this project various works were proposed for improvement of the accesses, adaptation of the abutments, development of the area, illumination, etc. The following actions were considered:
- Access to the dam from the CN-301 main road (before the A-30 road was built), by making an intersection to facilitate change of direction.
- Paving of the road from the CN-301 as far as the junction where the fork of the access to the Administration building, access to the crest and of the access to the hollow.
- Development of the surroundings of the Administration building.
- Structure for accessing the right abutment.
- Closing wall on the right abutment.
- Bund wall on the left abutment.
- Consolidation of the left abutment following the landslides occurred between 20th and 22nd September 1989.
- Illumination of accesses and dam, exterior and galleries.
- Extension of the spillway basin wall on the right bank, by means of bolsters that would protect the dam access footpath (which was finally not carried out).
- Environmental improvements by means of plantations and gardening works.
Other Projects
In June 1991 the Project for the supply and installation of undersluices was drawn up.
In 1992 the works included in the Project for the supply and installation of the undersluices for the Rambla del Moro Reservoir were adjudicated to the dam constructor. The works of this project consisted of the installation of 4 “Bureau”- type floodgates of 2.00 x 1.70 m² (width x height), placed in twos, one for safety and another for closing and regulation, in each of the conduits of the scour outlets, as well as the necessary mechanical elements for their electrical and manual operation as well as the metallic elements for flow control and piping.
On 14th January 1993, the Dam Surveillance Unit issued the mandatory Report prior to the final acceptance of the work. In this Report, it is recommended that the dam monitoring equipment be installed as soon as possible.
In December 1993, the Engineer of the Confederación Hidrográfica del Segura, Mr. Carlos Marco García drew up the Project for the installation of the monitoring equipment in the dam.
At the end of 1995 the drafting and later implementation of the "Project of Urgent Conditioning in the Rambla del Moro Reservoir, Municipal Districts of Cieza and Abarán (Murcia)". took place. The works of this project consisted of:
- Consolidation injections and waterproofing of the abutments of the dam and opening of the chimney drain.
- Extension of the dimensions of the stilling pool.
- Elimination of the gypsiferous loam outcrop located downstream from the hollow.
- Installation of monitoring equipment.
- Conditioning of the scour outlet.
- Installation of an Alarm and CCTV System.
- Construction of a jetty and acquisition of a motorboat for the inspection of the reservoir and scour outlet.
Access
The main access to the dam from Murcia is by the A-30 main road, in the direction of Madrid. Approximately 5 km before reaching Cieza at turn-off number 358, a diversion for a change of direction must be taken and one connects with the N-301 main road, in the direction of Abarán. Then, after about 500 m, a turn to the left is to be taken to get to the dam service road that crosses the A-30 by means of an underpass. After about 700 m, you will reach the dam crest.
Secondary access to the dam can be made in the same way on the A-30, taking the turn-off for the MU-402 in the direction of Blanca railway station. About 200 m from the junction, take the A-22 minor road to the left. Continuing along this road, you will come across a junction on the left which goes to Casa de Ricote. This road takes you directly to the left abutment of the dam.
On the main access road to the dam, just as you reach the right abutment, there is a road junction, the first on the left leading to the Administration building. If you follow the road, you will find the access road to the dam crest and, on the right, an access road to the stilling pool
The location of the reservoir can be seen in the following map:
Characteristics
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LOCATION OF THE RESERVOIR
|
|
|---|---|
| Province | Murcia |
| Municipality | Cieza y Abarán |
| River | Rambla del Moro |
| Hydrographic basin | Segura |
|
DETAILS OF THE RIVER
|
|
| Length of the river | 2,489 Km |
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DETAILS OF THE BASIN
|
|
| Surface area of the reservoir basin | 379,78 km² |
| Shore length | 10,307 km |
|---|---|
| Reservoir surface area | 74,33 ha |
| Reservoir volume | 7,07 hm³ |
|
BODY OF THE DAM
|
|
|---|---|
| Type | Gravity |
| Materials | Mass concrete |
| Upriver slope | 0,05/1 (h/v) |
| Downriver slope | 0,76/1 (h/v) |
| Height above course of river | 32,15 m |
| Level crest | 234,82 m |
| Crest length | 104,00 m |
| Crest width | 8,30 m |
| Total fabric volume | 43.890 m³ |
|
SPILLWAY
|
|
| Number of spillway | 2 |
| Type of spillway | Fixed lip |
| Location | Central / Lateral |
| Position relevant to flow direction | Frontal |
| Situation | On dam |
| Number of openings | 3 / 2 |
| Total free length | 33,30 m / 32,00 m |
Imágenes
Presa de la Rambla de Moro
Purpose
Phenomena such as torrential rains or floods are well known in the Segura River Basin. The damages caused by water have been a historic concern for the inhabitants of the area from the point of view of economic and human losses.
In response to this situation, in 1977, and under the direction of the Chief Engineer of the Operations Department at the time, Mr. José Bautista Martín, the General Flood Protection Plan was drawn up, in which, amongst other works, a retarding basin was included in the Rambla del Moro.
Rambla del Moro forms part of a system of wadis that end in the Segura river on the left bank in its middle stretch. They are basically characterized by their zero flows all year round except for specific occasions when they evacuate significant volumes.
The function of the dam is that of preventing floods in the basin, characterized by some episodes of very intense rainfall during very short periods of time.
With the construction of this dam peak flows are avoided, which would be added to those of the Segura river in the event of a generalized heavy rainfall in this river basin, and, on the other hand, the risk of floods in the huerta area of Abarán would also be reduced, in the event of heavy rainfall in the Rambla del Moro basin.
The Rambla del Moro Reservoir has a height of about 32.15 m on the bed and 43.30 m on foundations, and a crest length of about 104 m. It is a gravity dam with an irregular ground plan, and its abutments face slightly upstream. The orientation is different for each of them, being 7º for the right abutment and 17º for the left one (measured with regard to the normal one of the bed). The slopes of the downstream and upstream faces are, respectively, 0.05H/1V and 0.76H/1V.
The irregular layout of the dam ground plan is because it was designed meaning the whole base of the dam foundations had to be built on the narrow layer of folded dolomites that crosses the ravine with a dip of about 45º downstream, caused by the overthrusting of the Miocene by the Triassic.
The transversal joints that make up the twelve dam blocks are not laid out in a regular way, i.e., the blocks have different widths, the largest being the two central ones measuring 14 m each, while the remaining ones are of various measurements of between 7 and 9.25 m.
Cross-section showing the cut-off and consolidation wall, consolidation mesh and chimney drain.
Territorial and Administrative Context
Physical Characteristics of the Basin
The surface of the reservoir basin catchment area is 379.77 km². The volume of the reservoir at the height of the threshold of the lower spillway, hereinafter, NAI, is 4.36 million cubic metres and the surface at the same height is 47.41 hectares. Below a picture of the catchment basin can be seen.
Volume of the Basin
Here is a summary of the main characteristics of Rambla del Moro reservoir and catchment basin:
Surface area of the catchment basin : 379,775 km²
Height of lower spillway (N.A.I.) 226,52 m.s.n.m.
Reservoir volume (N.A.I.) 4,36 hm³
Reservoir surface area (N.A.I.) 47,41 ha
Height of upper spillway (N.A.S.) 230,52 m.s.n.m.
Reservoir volume (N.A.S.) 6,70 hm³
Reservoir surface area (N.A.S.) 71,31 ha
Max. inflow standard project flood level 726,95 m³/s (T- 1.000 años)
Max. inflow maximum flood level 1.236,2 m³/s (T- 10.000 años)
Standard project flood level (N.A.P.) 231,04 m.s.n.m.
Reservoir volume (N.A.P.) 7,07 hm³
Reservoir surface area (N.A.P.) 74,33 ha
Maximum flood level (N.A.E.) 232,39 m.s.n.m.
Reservoir volume (N.A.E.) 8,13 hm³
Reservoir surface area (N.A.E.) 81,91 ha
Dead storage level 202,67 m.s.n.m.
Maximum daily rainfall registered (April 1946) 118,5 mm
In the initial project for the Rambla del Moro Reservoir dated 3/84, there is no environmental impact assessment or annex related with this issue.
However, an environmental impact assessment is included in the project "Urgent Conditioning of the Rambla del Moro Reservoir". The actions contained in this project which were potentially harmful for the environment were:
- Elimination of the Keuper clay and loam outcrop downstream from the dam
- Extension of the spillway basin
- Construction of the jetty
- Waterproofing injections, consolidation of foundations and opening of the chimney drain
Although it does not directly affect the dam, an environmental impact assessment was also made regarding the works carried out in the project for the hydrological correction of El Moro basin.
As for its use, the Regulations for the environmental integration of the dam are included in the Regulations for the Use of the Rambla del Moro reservoir published in this Technical Assistance.
In these integration regulations, the current environmental legislation that may affect its use is analyzed, there not being any measure worth mentioning basically due to the fact that the normal mode of use is an empty reservoir.
On the other hand, the dam and reservoir are not situated in any area of environmental protection.
Geology and Seismology
Regional Geology
Rambla del Moro reservoir is located in the north-eastern area of the Baetic Mountains, which, in turn, form the north-western segment of the peri-Mediterranean Alpine Orogenic belt (alignment of mountain ridges with structure on shifting strata formed during the Cretaceous and Tertiary periods and which present a centrifugal layout regarding the area occupied by the sea; Martín Algarra, 1987).
Within the Baetic Mountains, the area in question forms part of the external zones, right on the boundary between the Internal Pre-Baetic and the Internal Sub-Baetic.
The environment of the reservoir is located between the Geological Unit known as Frontal Internal Sub-Baetic and its Tertiary post-mantle materials. These materials are discordant in this area over the Geological Unit known as Internal Pre-Baetic.
The reservoir ravine is located on Mesozoic material corresponding to the Frontal Internal Sub-Baetic, whereas the reservoir basin area is located on Tertiary post-mantle material. The contact between both types of rock is due to the overthrusting belt, made up of the northern line of the advancing overthrusting event formed by the Frontal Internal Sub-Baetic on the materials of the Internal Pre-Baetic. For this overthrusting, originated with a horizontal anticline, the Internal Sub-Baetic unit would have run over the External Sub-Baetic (Jurassic to Tertiary). This overthrusting belt is located 30 m upstream from the dam.
General Geological Map of the Baetic Mountains
The materials of the Internal Sub-Baetic Front that appear in the ravine make up the allochthonous unit that is formed by a sequence going from the Triassic period, in its Germanic facies, to the Lower Cretaceous one, made up of dolomitic limestones from the Muschelkalk (on which the dam foundations are directly built) and of loams with gypsum from the Keuper.
The overthrusting belt puts the Triassic material in contact with a detritic formation, made up of conglomerates and sandstones with calcareous cement that form the base of the post-mantle materials (Lower Tortonian age). These materials are visible 40 metres upstream from the ravine. On the right bank of the wadi there is a very characteristic outcrop.
Between the Muschelkalk and the Tortonian (substratum of the overthrusting) there is another Keuper layer in an inverse order to that of normal stratification.
Downstream from the dam, there is an olitostromic unit that was formed as a result of several stages in which movement took place toward the North of the Internal Sub-Baetic Front, and it became interstratified between layers dated as belonging to the Upper Tortonian age. Due to the tilting of the Neogene basin, there is no concordance of the olitostrome with the Miocene covering material. The olitostrome was formed during this movement and it was checked by the Miocene substratum related with the overthrusting belt of the Triassic on the Neogene.
Geology and Geotechniques of the Storage Area Upstream of the Dam.
The bottom of the reservoir and the areas near the bed are made up of alluvial deposits, recent or old. In the upper parts, there are post-mantle Miocene soils corresponding to the Tortonian age in the intermediate area (conglomerates and sandstones with calcareous cement in the area nearest to the ravine, and loams and loamy limestones in the most distant part), and to the Andaluciense age (yellowish-white loams) in the upper part, both from the Upper Miocene. Most of the reservoir basin is made up of loams and loamy limestones from the Upper Tortonian.
It is formed by impervious soils (except for an area of limestone) in its entire visible surface or concealed beneath the wadi sediments.
The hillsides formed by the Miocene materials do not seem prone to landslides, but they are easily eroded.
However, the left hillside of dolomitic limestones, in the area of the left abutment, did show some signs of instability when the dam was being built.
Geology and Geotechniques of the downstream boundary for the storage area.
The dam is built on the Muschelkalk limestones that form part of the overthrusting belt. These limestones lie on in a layer of approximately 10 m of Keuper that has been a plastic support over which the limestones have slidden on the Miocene sandstones.
Beneath this layer of Keuper are conglomerates with carbonated cement and rounded stones from the Upper Tortonian age (Miocene). These conglomerates are folded next to the overthrusting belt (to the north of the dam), there being here a stratification dipping 40-50º to the south, and passing sub-horizontally to the north, far from the overthrusting belt.
Both the left and the right dam abutments are formed by Muschelkalk limestones.
This area is highly tectonized, as a result of which some faults can be detected in the two abutments, at the same time as the limestone is much brecciated, being fractured into blocks whose spacing can be a few centimetres and whose discontinuities are occupied by yellowish clay-silts and fragments of dolomites whose opening can sometimes be centimetres.
The dip in the right abutment is the same as the one that the rocky massif follows (except for the abutment on the left riverbank), which in this area specifically has an E-W dip 25º to the south.
Seismology
Seismic hazard varies depending on the place and it has been a habitual practice to grade territories in accordance with that hazard. Taking into account the recommended guidelines contained in the Technical Guide on Dam Safety. Technical Guide on Dam Safety. Material Prospecting and Geological Studies (published by the Spanish National Committee on Large Dams, CNEGP), in Section 3.3., a classification is made in three groups:
a) Areas of low seismicity: ab < 0,04g
b) Areas of medium seismicity 0,04g < ab < 0,13g
c) Areas of high seismicity 0,13g < ab
ba: basic acceleration
In accordance with this classification, the Rambla del Moro Reservoir is located in an area that we could classify as being of medium seismicity, since the “basic acceleration” for the municipal district of Abarán is 0.1 g.
In accordance with the Technical Guide on Dam Safety. Material Prospecting and Geological Studies, and bearing in mind the land factor (using the seismo-resistant regulations NCSE-2002), the acceleration calculated for the design earthquake would be 0.13·g, and for the maximum considered earthquake it would be 0.21·g.
(3,6 MB)Situation
Rambla del Moro reservoir and surroundings are located on Map 891, CIEZA, of IGN (or 26-35 of the Servicio Geográfico del Ejército) on a scale of 1:50,000. The territory corresponds to the province of Murcia, municipal districts of Cieza and Abarán.
The coordinates of the point where the dam meets the reservoir comes as follows:
Reference system ETRS89. Time zone= 30
X=642.975
Y=4.232.697
Geographical coordinates (based on the Greenwich meridian):
38º 13' 55'' Y North
1º 21' 54'' X East
The dam is situated in the natural course called Rambla del Moro, at a point where the valley narrows about 4 km upstream from its confluence with the Segura river.
The towns of Cieza and Abarán line the above-mentioned mouth, both being about 5 km away from the dam by road.
