José Bautista Reservoir
Background
The Guadalentín, a tributary of the Segura, is a river with an extremely irregular flow system, which can go from being completely dry to having an extremely large flow volume.
Over the last 130 years we should recall, amongst others, the following floods:
- October 1879 (Santa Teresa Flood): In Lorca it produced a peak flood flow of 1,510 m³/s, causing 13 deaths and substantial damage.
- September 1891 (San Jacinto Flood): Bigger than the previous one, and thanks to the existence of Puentes dam, located at the headwaters of the river basin, the region was saved from an unprecedented catastrophe.
- June 1900 (San Aniceto Flood): Bigger than the Santa Teresa flood, it flooded the San Cristóbal quarter in Lorca.
- October 1948: The estimated flow at the bridge on the Murcia to Granada road was over 800 m³/s.
- October 1973: According to a report by the Centre for Hydrographic Studies, the peak flood downriver from the Puentes reservoir reached 2,000 m³/s, whilst around 1,500 m³/s reached El Paretón canal (located in the mid-region of the river basin).
Another of the characteristics of this river is the large amount of suspended solids which it drags along, causing silting problems, reflected in its name in Arabic, meaning river of mud.
Bearing in mind these characteristics of the Guadalentín, many attempts have been made over the years to alleviate, as far as possible, the destructive effects of its floods. Amongst these we should mention:
- The Puentes Dams are located at the confluence of the Vélez and Luchena rivers, headwater rivers of the basin, and where the most intense rainfall is registered, the former having been the main cause of some big historical floods, such as that of October 1973. The old dam, located downriver from the new Puentes dam, was built at the end of the last century to cater for irrigation needs and has become redundant with the construction of the new dam.
The Puentes dams play an important role in protecting against floods. In 1973, before the new Puentes dam had been built, there was overspill from the crest in the old dam, which highlighted the need to heighten it, or as was the case, the need to build a new dam in this location which would create a reservoir with a bigger capacity. - Upriver from the Puentes reservoir, on the Luchena river, the Valdeinfierno reservoir is located, which in spite having been heightened, is at present almost completely silted up and has practically no regulation capacity.
- Downriver from the Puentes reservoir, there is El Paretón by-pass channel, developed to lead part of the River Guadalentín flood waters straight to the sea. It was planned at the start of the 20th Century with a capacity of approximately 200 m³/s, was subsequently expanded, and in 1973, after the flood, its capacity was increased to 600 m³/s.
- Finally, there is a very old artificial course (previous to 1651, the date of the historical San Calixto flood), to by-pass the water from the River Guadalentín, to avoid it passing through the city of Murcia. It is called El Reguerón. Its maximum capacity is estimated at around 250 m³/s, even though at certain points it may overflow with lesser flow rates.
The overflows of El Reguerón channel affect the fertile plains of Alcantarilla and Murcia.
With regards to the work on the José Bautista Reservoir, the most specific records come from the Flood Control Plan of the Segura river Basin.
In May 1977 the Flood Control Plan of the Segura river Basin was drawn up under the guidance of the Engineer Mr. José Bautista Martín. This document was finally approved on 12th November 1978, after a Public Information inquiry, ordaining the Segura Hydraulic Confederation to draw up the projects included in the Plan.
One of the most important works included in this Flood Control Plan was the Romeral Reservoir, for the abatement of the Guadalentín floods. This project was drafted in 1985 with a gravity dam as the preferred solution.
As a result of the floods in the regions of Murcia and Valencia in November 1987, emergency measures were taken, published in Royal Decree 4/1987 of 13 November, to repair the damage caused by the floods in the Autonomous Communities mentioned. In Annex I these included a list of the works to be carried out amongst which, once again, was that of El Romeral Reservoir.
In 1989 the point of closure was further investigated, and the conclusions served as the grounds for the Rules of Tender for the project and construction of El Romeral Reservoir. It was submitted to tender on the 13th July 1990, and, in the Additional Technical Clause, it was highlighted that the structural solution should be that of a loose material dam with lateral spillway.
On 30th January 1993 the works were finally allocated, with the Variation Order being signed on 17th June 1993.
Once the excavations had begun, and as had been projected in the chosen plan, the closure’s additional geological geotechnical tests were conducted. Once these tests had been analyzed it was concluded that the land conditions for the dam foundations were better than had been foreseen during the tendering stage.
Based on these conclusions, on the 19th May 1994 permission was requested from the Directorate-General for Hydraulic Works for authorization to draft Amendment I to the Project. This proposed a structural solution of a mixed reservoir with a spillway into the riverbed and a land closure dike on the left abutment without any increase in the budget.
On the 15th June 1994, the Directorate-General for Hydraulic Works authorised the drafting of Amendment I, under the conditions requested.
On the 19th December 1994 Amendment I to the PROJECT FOR THE ROMERAL RESERVOIR –MUNICIPALITY OF LIBRILLA (MURCIA) is technically and finally passed.
On the 9th October 1995 authorization was requested to draft the Project for Additional Works I, with its drafting being approved on 5th December 1995.
On the 2nd August 1996 the Directorate-General for Hydraulic Works requested authorization to draft Amendment II to the Project.
On the 20th September 1996 the Directorate-General for Hydraulic Works and Quality of Waters authorized the drafting of Amendment II to the Works, under the conditions requested, indicating in the document that the affected works should be temporarily suspended. The Partial Temporary Suspension Act was signed on the 4th October 1996.
The works were finished on 30th of December 1999, and their provisional acceptance took place on the 19th June 2000 with the definitive acceptance on the 22nd October 2002.
On the request of several institutions El Romeral Reservoir was renamed José Bautista Martín Reservoir, by decree of the Directorate for Hydraulic Works on 3rd April 1997.
Access
The access to the dam and reservoir formed part of its works. There are two tracks on both shores of the natural downstream boundary which help connect the reservoir to El Palmar road at Cuevas de Reyllo, on the right bank, and with the A 340 main road on the left bank.>
The location of the reservoir can be seen in the following map:
Characteristics
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LOCATION OF THE RESERVOIR
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Province
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Murcia |
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Municipality
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Librilla |
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River
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Guadalentín |
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Hydrographic basin
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Segura |
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DETAILS OF THE RIVER
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Length of the river
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- |
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DETAILS OF THE BASIN
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|
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Surface area of the reservoir basin
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31,42 km² |
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Maximum altitude of the reservoir basin
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2.045 m |
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DETAILS OF JOSÉ BAUTISTA RESERVOIR
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|---|---|
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Shore length
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- |
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Reservoir surface area
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80,00 ha |
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Reservoir volume
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5,55 hm³ |
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BODY OF THE DAM
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|---|---|
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Type
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Gravity |
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Materials
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Concrette mass |
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Upriver slope
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0,05/1 (h/v) |
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Downriver slope
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0,80/1 (h/v) |
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Height above course of river
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26,00 m |
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Level of crest (eje de calzada)
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137,00 m |
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Crest length
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265,00 m |
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Crest width
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5,50 m |
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Total volume of concrete
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- |
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Total Volume of materials
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- |
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SPILLWAY
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Number of Spillways
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1 |
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Type of spillway
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Fixed lip |
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Location
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Centre dam |
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Position relevant to flow direction
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Frontal |
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Situación
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On dam |
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Closure type
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- |
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Number of openings
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6 |
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Free length of each opening
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16,67 m |
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Total free length
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100,02 m |
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Floodgate type
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- |
Purpose
The José Bautista Martín Reservoir, then called the El Romeral Reservoir, is one of the most important works included in the Flood Control Plan of the Segura river Basin drawn up in 1977.
With its capacity of 5.55 million cubic metres this reservoir is essentially intended to abate the River Guadalentín floods.
The José Bautista Martín Reservoir is of a mixed type: gravity on the riverbed and loose material in the side closure dike on the left abutment. The section chosen for the main dam is based on a gravity design with a strong base and a conservative section, with an angle in the upriver wall which displaces the vertex and improves the pressure dissipation. It is a weir dam, - conventional concrete straight plan gravity dam. There is an overfall spillway in the central part of the main dam which flows into a stilling basin. The scour outlet which also flows into the stilling basin is situated on the central block.
Territorial and Administrative Context
Physical characteristics of the basin.
The River Guadalentín drainage area is located in the south-western part of the Region of Murcia, between the Sierras of Lavia, El Cambrón, Espuña and El Cura, to the North and those of Las Estancias, La Carrasquilla, Almenara and Carrascoy to the South and South-east. The basin’s watershed intercepted by the José Bautista Martín Reservoir, meets the watershed for the general basin of the Guadalentín in the Sierra del Cura to the North and the Sierra de Carrascoy to the South.
The reservoir’s drainage area covers an area of 3,142 km² and is at altitudes of between 111 metres above sea level at the dam and 2,045 metres above sea level at Cerro Poyo, in Sierra de María, at the headwaters of the Caramel or Alcaide River.
The reservoir has a capacity at maximum normal level (131.50 metres above sea level) of 5.55 million cubic metres and covers an area of 80 ha.
Librilla and Alhama in Murcia are the two Municipalities covered by the Reservoir’s surface.
In the basin we can find the three different subgroups of the Mediterranean climate- arid, semi-arid and subhumid-, due in particular to the presence of the Sierra de Espuña. The arid climate can be found in the lowest areas, particularly in the Guadalentín valley and up to altitudes of 600-700 metres in the mountains. It is characterized by mean annual temperatures of around 18 ºC and a rainfall of below 300 mm. The semiarid subgroup is only found over altitudes of 600-700 metres and is characterized by mean temperatures which range between 14 and 18 ºC and rainfall of between 300 and 500 mm. Above altitudes of 900-1000 metres we can find the subhumid subgroup with mean annual temperatures below 14 ºC and rainfall of more than 500 mm.
Geology.
Geology and geotechniques of the dam.
The area inundated by the reservoir essentially affects materials from the Quaternary epoch.
To a lesser extent, in the area near the reservoir, Miocene materials have also been inundated, made up of the same facies which form the ravines.
The Quaternary materials which make up the storage area are:
- Greyish-white and yellowish-white clays and loams; they correspond to the letters Qm in the geological map.
- These materials cover practically the entire surface affected by the storage area, as well as a large part of the Guadalentín valley floor.
- Present alluviums and terraces of the River Guadalentín (Qal and Qt) occupy the sunken areas formed by the river course and the areas adjacent to it.
Geometrically, they are always found below the Quaternary clays and loams (Qm) which fossilize them. When they appear, they tend to be small outcrops close to the natural downstream boundary, where the clays and loams (Qm), the main constituents of the reservoir area, have been eroded. There is also a small outcrop in the riverbed close to the bridge on the secondary road from Librilla to Casas Nuevas which has been affected by the reservoir.
From a tectonic point of view, no accidents, such as faults or folds, which affect the reservoir area, need to be reported. If anything, there is an accumulation of clays and loams (Qm) with horizontal stratigraphy.
From a geotechnical point of view there is one important factor to be considered which is how easily the loams (Qm) which form the reservoir area erode. In fact, the water courses formed during more or less torrential periods of rainfall, create deep furrows cut into these loams producing their immediate erosion. Similarly, landslides are produced in the areas where the river course touches one or other embankment of the hillside. These landslides are not significant, due mainly to the fact that the hills in the area upriver of the natural boundaries, where the reservoir storage area widens leading to a low altitude plain, (Guadalentín valley) are not particularly high, though superficially there are some substantial landslides.
Geology and Geotechniques of the Natural Downstream Boundary.
The area of the natural downstream boundary of José Bautista Martín Reservoir, on the River Guadalentín in the Municipality of Librilla (Murcia), has been studied in detail on several occasions.
The River Guadalentín enters the Miocene substratum in this area. From the aerial photograph and the geological map we cannot guarantee the existence or absence of more or less important faults dividing the Miocene substrate in the area where the reservoir is located. There are signs of some vertical faults following the river’s alignment, though this extreme has, until now, been difficult to confirm.
The last explorations carried out included three probings: one in the bed and another two in the hillsides, in order to provide certain information on supposed faults appearing in previous reports.
Test drilling of the river bed.
The materials which appear in the test drilling of the river bed are Miocene deposits (they have been dated in accordance with their microfossils). The lithology varies throughout the test drilling. The minerals range from clayey carbonated limes (which could be denominated loams) to poorly cemented conglomerates.
In the lithological column, only three different types of soils were distinguished:
- Conglomerates with a clayey cement
- Brown or reddish-brown clayey loams (or loamish clays)
- Microconglomerates and/or sandstones with calcareous cement
From the test drilling of the river bed, a particularly thick area was detected formed by conglomerates whose deformability is the lowest of those found in this test.
At greater depths, gravel appears less frequently and below the altitude of 70 metres above sea level they do not appear again in practically the next twenty metres examined in the drilling.
Test drilling of the left abutment.
The test drilling of the left abutment revealed a similar lithological formation, though, in the upper part, different layers were detected (whitish carbonated limestones, gravels and a layer of grey loamish clay) which are probably Quaternary deposits.
Conglomerates with a clayey cement are less frequent in this test drilling. The ground appears to be formed from finer materials.
At the end of the drilling the recovery of the loams is clearly better than in the shallower areas.
Test drilling of the right embankment.
This test drilling perforated the Miocene from its mouth. In the area located at the level of the riverbed (the first fifty metres) there are cemented conglomerates. Some complete samples have been recovered which have later been highly resistant in the laboratory. These conglomerates alternate with clayey loams similar to those found in the riverbed and the left abutment.
The deepest area of the test drilling indicates the predominance of poorly cemented sandstones which are recovered as sand from the test drilling.
The presence of sandstones in the left abutment and their absence in the other test drillings leads us to thinking that there is a discontinuity close to the foot of the right embankment.
The difference in the thickness of the clayey cement conglomerates found in the different drillings suggests that the presence of conglomerates is erratic.
In any case, the decrease in the abundance of the conglomerates from the riverbed to the left embankment, and, in particular within the area of the riverbed, at depth, is a fact already which other examinations have already highlighted and which is also hinted at in these studies.
(6 MB)Situation
The reservoir of José Bautista Martín (before called El Romeral reservoir) is located near the river Guadalentín, in the Segura basin, in the municipal district of Librilla (Murcia).
In nowadays the reservoir works and its access belongs to the Headquarter of Hydraulic Works and Quality of the Waters, of the Environment Department, but the Segura Hydraulic Confederation is incharge of its exploitation.
The coordinates of the point where the river meets the reservoir comes as follows:
X 1º 19' 92 " West
Y 37º 52' 60 " North
The meeting point mention before has the next U.T.M. coordinates :
Reference system ETRS89. Time zone= 30
X=648.051
Y=4.193.333
