El Judío Reservoir
Background
The first existing record of a dam construction in the Judío riverbed was the result of the extraordinary floods that took place in October 1948, which prompted the study of whether it was advisable to build a dam in the Judío riverbed in order to control its floods.
On November 12, 1948, and according to the Plan of Works proposed by the Segura Hydrographic Confederation to regulate the Segura river from its head waters to the boundary between the provinces of Murcia and Alicante, the Ministry for Public Works authorized the drawing up of the ”preliminary draft of the flood barrage in the Judío riverbed in Cieza”.
Therefore, the “Preliminary Draft for the Regulating Reservoir for the Judío Riverbed” was drafted.
This preliminary draft, drawn up by José Sancho-Tello Báquena, was finished and presented to the authorities in August 1951, although the final draft was not subsequently authorized.
It must be pointed out that the anticipated dam construction site in 1951 was practically the same as the current site given that they share the same goals: the reduction of the dam body to be built because of the riverbed narrowing at that point. The dam was located in a gorge, immediately upstream from where the watercourse and the Madrid– Cartagena railways intersect. Here, the reservoir volume was about 3.5 hm³.
In the “General Flood Defense Plan of the Segura” Basin, the dam was located at about 400 meters upstream from the current intersection of the N-301 and the watercourse, where the reservoir volume reaches 4 hm³ for a dam with a height of 30 m and a crest length of 340 m. Furthermore, as in the Preliminary Draft dated 1951, a solution involving loose materials and limestone breakwaters with a marly impermeable core, with bottom drainage without sluices – a hole-formed dam where the whole volume of the reservoir would be used to control floods.
Later, a new dam design was drafted, based on more detailed information, mostly geological and geotechnical, modifying the location and the kind of dam included in the Plan, a concrete gravity dam, although at first it maintained the “hole shape” (the final location is downstream from the mouth of the Ramblilla ravine.
Parallel to these actions and before the drafting of the final Project, there have been other different directives for the dam of the Judío riverbed, among which two geological reports must be pointed out:
- Preliminary geological study of the Judio riverbed reservoir C.E.H.O.P. Center for Hydrographic Studies. Madrid, February 1967”,
- Preliminary report of the flood controlling reservoir in the Judío water bed. Public Works Geological Services S.G.O.P.U. Madrid, December 1986”,
both favorable to locating the dam in the riverbed after performing the necessary field work and detailed studies, developed by S.G.O.P.U. and collected in the “Study 03/88. Reservoir of the Judío” riverbed.
The “Project of the Judío” dam was drafted in June 1988 while Julio Munoz Bravo was the director.
The document verifying readiness for construction was signed on December 18, 1989, and the works began the following day; the project execution term was established at three years.
During the execution of the works, it became necessary to modify some ideas established in the original project with the purpose of improving and adapting the dam to the current needs.
This is the reason why the General Directorate of Hydraulic Works was asked for the authorization to draft the Modified Project N&Odom;1. This authorization was issued by the General Directorate on July 9, 1991, and finally approved on July 10, 1992.
Changes to this Modified Project N&Odom;1 include the corrections briefly listed hereunder:
- Removal of the side sluices, improving instead the central sloping sheet, which would force to extend the stilling basin around 15 metres.
- Change of slope stabilization treatment by means of reforestation of the reservoir surroundings with indigenous flora.
- Removal of levees.
- Building of levees with compacted fill in the embankments near the dam abutments in order to improve soil stabilization in the surrounding areas of reforestation.
- Increase ventilation in the drainage galleries and wells, as well as removal of certain segments for the purpose of improving control, access and ventilation for the rest.
- Removal the waterproof, riprap covered embankment in order to prevent seepage due to cracking marle.
- Enlargement of the floodgates chamber, as well as immediate accesses to it, making it possible for small vehicles to enter, and improving access to the gear, as well as general ventilation.
- Replacement of access to the galleries through existing manhole steps and stairs by paved roads in order to allow vehicles to reach the entrance.
- Replacement of the concrete handrail by a metal rail, so that it may be folded in the event of crest overflow, and change of the lighting system, both at the crest and on the strong wall in order for both technical and aesthetic improvement.
- Change of location and improvement of the Administration Area, placing it near left bank abutment, so as to improve access to it.
- Restoration of certain services affected by the aforementioned change of access.
On June 23, 1992, authorization for the drafting of Modified Project N&Odom;2 was requested, motivated by a number of ideas not previously considered, and it was granted on July 22 of that same year
This Modified Project N&Odom;2 includes the following changes which had not been previously considered:
- Replacement of two Ø 500 mm fiber cement pipes in wells on the left margin of the dam.
- Addition to the budget of the actual quantities obtained when work was completed by the digging and concrete unit operations for the dam body and stilling basin foundation, as well as the necessary units for river diversion.
- Increase in the quantity of drilling and cement grout units in the required operations for building waterproofing, consolidation and drainage walls, caused by existing contact planes between solid blocks of different marl thickness.
- Outfit the dam with lightning arresters, a sound data collection and process system, a power generator strong enough to operate over the sluices autonomously and independently to prevent any power outage, as well as installing a phone line in the Administration House.
- Building and improvement of required drainage works, both longitudinally and across, to allow proper access to the limited area in case of floods due to severe storms in the area.
On July 26, 1993, the Modified Project N&Odom;2 was finally approved.
On September 6, 1993, authorization for drafting the Supplementary Works Project N&Odom;1 at the Judío Dam, based on a number of considerations aimed at improving and supporting the main works.
The works completed included the following:
- Reforestation.
Anti-erosion treatment by means of plants on the existing surface between the lip of the spillway and its boundary with the basin. - Conditioning of the dam's surroundings.
These works were developed in two different locations: one one hand, landscaping of the left wall of the dam, and on the other, creating a recreational area in the old firing range. - Archaeological consolidation and heritage conservation.
These works included a properly fenced access to the area which occupies an Iberian archaeological site.
The General Directorate of Hydraulic Works authorized the drafting of this Supplementary Works Project on October 29, 1993, which was completed in November 1993, and finally and technically approved on April 4, 1994; the works contract was signed on October 11 of the same year.
The date of completion of the works subject to different contracts was April 13, 1995, proceeding then to the Provisional Acceptance of the Works on June 28, 1995.
In March 1997, the classification according to potential risk of its break or malfunctioning proposal was performed, obtaining category A rating for the dam. Such a proposal was eventually settled by the General Directorate of the Hydraulic Works and Water Quality on July 28, 1998.
In 2001, the Final Settlement Project for the works subject to the construction project of the Judio river dam was drafted .
During its first phase, and before concrete was poured on the low part of the dam blocks, the river diversion was projected by means of pumping and through the existing saddle dam on the right margin of the watercourse, together with the construction of a coffer dam and a 2 m wide secondary with a height of 6 and 4 m above the bed, respectively.
The pumping system of the first phase was kept during the entire works with the purpose of reducing the level of the provisional reservoir, if necessary, by pumping water through the bottom drainage pipes.
In a second phase, diversion was done over the top of one of the central blocks and the spilling basin while the construction of the bottom drainage pipes was not finished. Once the drainage pipes were ready, the block could be lifted, and water flowed downstream through its own dam bottom drainage.
The Building Project of the Judío dam deemed it necessary to dig a volume of about 115,000 m³ of material for the dam body, spilling basin and drilling of galleries; this last plan had not been executed so that the underground marl would suffer as little damage as possible (the volume drilled, including the supplementary works, amounts to 260,000 m³).
The materials used in the construction of the dam were mass concrete for the dam body and reinforced concrete for the spillway structure, the bottom drainage and the spilling basin.
Aggregates were crushed limestone from an open quarry near the town of Jumilla.
The binder used was a mix of 55% type I-45 concrete, and 45% fly ash from the thermal power plant.
Access
The access to the dam of the ravine of the Jew from Murcia is realized across the highway A-30 up to the exit of "Cieza". In this point the N-301 takes (that passes parallel to the previous highway) up to a way that leads to the " Club of tennis Cieza ", placed approximately in the P.K. 343+400 of the indicated road (N-301)..
The tracing of this way that leads finally to the dam passes, in his first 625 meters, for the access to the mentioned sports club, in 300 following m it is realized coinciding sensitively with the esplanade of the line Cieza-Gandía of left railroad, being the rest, up to his total length of 2365 meters, again planned..
The section type adopted for the access to the dam consists of a causeway of 5 m and borders in both sides of 0,50 m with gutters. The road surface is formed by a base of zahorra artificial of 20 cm of thickness, a sub-base to granulate also of 20 cm, an irrigation of priming and a cap of bituminous mixture(mixing) in warms of 5 cm. In the initial section, in which takes advantage of the way of entry to the club of tennis, the cap of tread is formed only by means of the extension of the bituminous mixture on an irrigation and the existing road surface before treated by means of cleanliness of the same one..
The location of the reservoir can be seen in the following map:
Characteristics
| SITUATION OF THE DAM | |
|---|---|
|
Province
|
Murcia |
|
Municipal Territory
|
Cieza |
|
River
|
Judío watercourse |
|
Hydrographic basin
|
Segura |
|
DAM DATA
|
|
|
Surface of the reservoir dam
|
603.54 km² |
|
Maximum height of the reservoir basin
|
|
|
Surface of the reservoir at the maximum normal level (ancient)
|
98.84 ha |
|---|---|
| Reservoir volume at the maximum normal level ( ancient) | 11.44 hm³ |
| DAM BODY | |
|---|---|
| Type | Gravity |
| Materials | Vibrated mass concrete |
|
Slope above the water
|
0.05H/1V |
|
Slope under the water
|
0.76H/1V |
|
Height from the bed
|
48.50 m |
| Top spot height (spindle width) | 246 m |
|
Top length
|
610.00 m |
|
Top width
|
5.00 m |
|
Total volume of concrete
|
|
|
Total factory volume
|
|
| CHUTE | |
|
Nº of chutes
|
1 |
|
Kind of chute
|
Fixed lip |
|
location
|
Centre of the dam |
|
Position in comparison with the current one
|
Front |
|
Situation
|
In the dam |
|
Kind of closure
|
|
|
Number of spans
|
3 |
|
Free length of each span
|
22.53 m |
|
Total free length
|
67.60 m |
|
Kind of gate
|
|
Purpose
The purpose of the dam is to laminate the floods in the basin, characterised by a high intensity of rainfalls and a very shor concentration periods.
Through the construction of this dam, it is possible to avoid flows which would be added to the ones of the Segura river in case of a heavy rain in the Segura basin and, on the other hand, it will be reduced the risk of flooding the Cieza area, in case of a heavy rain in the basin of the Judío watercourse.
The dam of the Judío watercourse is made up of vibrated concrete, with a maximum height above the cement of 48.5 metres and a top length of 610 m. The plant is straight apart from the left wall, where it is round with a ray of 160 m with the object of adjusting the dam body to the existing topography.
The block above the water has a slope of 1(V):0.05(H), while the one under the water presents a slope of 1(V):0.76(H). Both are cut in the vertex of the section.
The top bridge above the chute is made up of three spans formed by five pre-tensioned beams with an edge of 0.8 m, above which there is a concrete slab with a thickness of 0.2 m. The beams support on the walls and the columns with a neoprene ring.
The dam body is made up of 41 blocks without longitudinal joints, among which 14 form the left abutment, 13 the central area and 14 the right abutment. Its lengths are 15 m by the walls and 14 m by the central body.
The chute has a fixed lip with the dumping on the dam body transferring the flows to the energy dissipation system constituted by a stilling pool.
The dumping has a fixed lip with a total width of 70 metres divided into 3 spans, which sum of net width is 67.6 metres (22.53 per area).
To dissipate the energy before the entry of the flows to the bed of the Judío watercourse, there is a spilling basin type II from the Bureau of Reclamation. It has a length of 55 m, a width of 70 m, bering the height of the walls 10 m.
Territorial and Administrative Context
Physical Characteristics of the Basin
The Judío watercourse is born at a site called “El Calderoncillo” north of the municipality of Jumilla.
Sub-basins of the Judío watercourse
At first, and up to near the town of Jumilla, the Judío watercourse is insignificant, and the drainage network is made up of the Jimena, Alquería, Cingla, Agüeros, Calderoncillo and Campana watercourses.
Once it leaves Jumilla behind, and after the confluence of all the aforementioned watercourses, the Judío watercourse appears as such, and after crossing road to Cieza, it enters into an area of terraces where it is difficult to notice its presence, except for the sand deposits in low areas or recent flood debris. In this segment, it receives the waters of the Carche, Santa Ana and los Álamos watercourses on its left margin, and from the Rodalizas and Gargantones on the right, and it is flanked by the Larga, Sopalmo and Carche mountains on the left margin, and by the Picarcho and Molar mountains on the right.
After it goes through the municipalities of Jumilla and Cieza, the watercourse acquires the typical look of the large southeastern riverbeds. In this third and last segment, it receives the Larguerón and Ramblilla ravines, both on the left margin just upstream from dam. Downstream, and after crossing road N-301 and the Madrid-Cartagena railway, it empties into the Segura river on its left, about 3 km upstream from Cieza. This final segment limits on the left side with the Benís and Ascoy ranges, and on the right side with the Fonseca range; however, close to the riverbed, there are low hills shaping the landscape.
The longitudinal profile of the Judío watercourse, whose basin has a total surface of 612 km², is divided into three totally different segments: the upper basin collects the runoffs from the Carche mountains and the La Alquería riverbed; the second segment is called the Judío ravine, which basically ends when entering the municipality of Cieza; the third and last segment is the actual riverbed, going from the last point up to its mouth in the Segura river.
Catchment basin of the Judío dam
Environmental information
The “Environmental Impact Assessment” of the Judío Dam Construction Project, established the environmental impact of building the dam, and pointed out the necessary measures to prevent and reduce the negative effects derived from the execution of the works.
A series of corrective measures in reference to the impact of filling the dam basin, building the dam, exploiting the quarry and building the access roads:
- Landscape improvement of the banks through appropriate plant species .
- Reforestation of the building areas through shrub species.
- Slope correction by reforestation.
- Correction of areas affected by exploitation of the quarry, integrating it into the landscape and offering a series of recommendations for its use.
With the aim and purpose of minimizing environmental impact of the works, a series of reforestation and improvement actions of the surroundings was included in the Complementary Works Project Nº1 of the Judío dam.
Geology and seismology.
Regional geology.
The Judio dam reservoir is located in the northernmost part of the Baetic System, which at the same time is the Peri-Mediterranean Alpine Orogen (alignment of mountain chains with an overriding structure created during the Cretaceous and Tertiary centrifugally arranged in reference to the sea; Martín Algarra, 1987).
Within the Baetic System, the area under consideration is framed within the External Areas or South-Iberian Domain. Materials in this domain occupy an extensive area in the system and represent a time period from the Triassic to the Miocene. Their structure is characterized by a detachment between the base (Hercynian Paleozoic) and the deformed cover (Mesozoic and Cenozoic folds, faults and buckled layers), where the clayey-evaporite Triassic act as detachment material, and the buckled layers have a general vergence towards the W and NW. The Paleozoic base does not surface, and remains at a depth of 5-8 km, and it is made up of the same materials as the Iberian Mountains.
General geological map of the Baetic System
Geology and geotechnics of the basin.
The area where the Judio reservoir and dam are located is mainly characterized by the presence of Tortonian marl which gives the area the typical badlands landscape.
In the basin, marl is the typical material, although it is possible to distinguish some Quaternary deposits, such as the sedimentary deposits at the bottom of the riverbed of low-consolidated marly-limey materials with alternating and discontinuous layering of gravel and sand.
Other deposits in the reservoir are glacis and alluvial, used intensively in agriculture by filling up their soft beds and building terraces on the margins which are currently stepped.
From a geotechnical point of view, the basin has the following characteristics:
- Waterproof:
The basin is waterproof, as it is made up exclusively of Tortonian marls. - Stability:
Due to the high erodibility of marl, soil runoffs and falling blocks are no unusual, although such runoff is not very significant. - Physical-chemical stability:
Many soluble salts in the materials of the basin give stored water high conductivity. - Erodibility:
Tortonian marl is highly erodible and has created the typical morphology of the basin, a type of landscape known as “badlands”. Such erodibility has given birth to the project involving specific operations aimed at reducing basin filling through the deposit of these materials.
Geology and Geotechnics of the Natural Downstream Boundary.
In the enclosure where the dam of the Judío watercourse is located, it is possible to distinguish two areas: on one side, the left riverbed and left abutment, and on the other, a depression on the right side of the talweg of the current watercourse, which is geologically identified as a stoned bed.
The dam, as previously indicated, lays on Tortonian marl which, which if it is good and freshly cut, it appears compacted and really uniform and shows a dark grey colour with light green or blue tones. Through rapid weatherization and alteration, it becomes light grey, but keeping their lytic aspect, while they changed to a grayish-ochre colour when such an alteration is particularly intense.
In the natural surroundings of the marl, it is possible to observe a double geomorphological evolution. On the sides of the valley, blocks of rocky marl fall frequently and quickly crack onion-like to finally disaggregate through weatherization. The disappearance of the lytic structure causes color changes in the material, which appears grey when the cut is recent.
The thickness of the weathered layer is usually less than 5 meters in the Judío dam's enclosure, followed by an alteration layer between 5-10 meters thick, up to the healthy layer, where many discontinuities are evident.
The post-orogenic nature of these marls determines an arrangement that is not so much structurally affected even though they have been subject to neotectonic readjustments still happening nowadays in this region. This fact has caused micro-cracking of all its mass, probably due to the aforementioned post-orogenic adjustments.
These processes cause tension inside the block, which, consequently, cause significant cracking. Thus, marl appears heavily fractured, producing crushed-looking blocks and outcrops, in addition to been affected by further fracturing after diaclasing, although sparely and of little relevance.
Furthermore, there are deep crevices, in general with 45º slope, as well as sub-vertical. In some segments, they are lightly mineralized with calcite or small clayey filling, although it is normal to find them clean. In some cases, they have friction striations, revealing a certain lip movement. The gap of these discontinuities under the decompression/alteration zone is usually sporadic, meaning with a frequency of at least one meter, although there are segments, generally connected to more clayey sequences, where the frequency is higher.
Terrace-like alluvial deposits were also found on the right margin, topping the jetty between the neutral talweg (stone bed) and the Judío riverbed.
From a geotechnical point of view, the substrate of the enclosure is made up of calcareous-clayey materials with a carbonate content which makes it possible to classify them as marl (40-60%). They appear strongly over-consolidated, so they have soft rock features. They are Miocene formations (Tortonian), created by the filling up of an internal depression. They appear intermittently covered by granular sediments of recent geological age.
Depending to the weatherization of the materials, it is possible to distinguish two marly sets: one on the surface and a deeper one, whose separation follows approximately the topographic profile.
Seismology
Seismic hazard is different from one place to another, and it has been common practice to classify areas according to it. Taking into account the recommendation criteria included in the "Dam Safety Technical Guidelines. Geological and Material Prospecting Studies” published by the Spanish National Committee on Large Dams (SNCLD), paragraph 3.3., there are three large groups:
- Low seismicity areas. Coefficient ab < 0,04 g
- Medium seismicity areas. 0,04 g < ab < 0,13g.
- High seismicity areas. 0,13 g < ab
where ab is the basic acceleration of the zone.
According to this classification, the Judío reservoir is located in area of medium seismicity given that the basic acceleration of the municipality of Cieza is 0.09 g (data taken from the Seismic Resistance Regulation NCSE-02).
According to the the Dam Safety Technical Guidelines. Geological and Material Prospecting Studies, and taking into account the land factor (applying Seismic Resistance Regulation NCSE-2002 and by analogy with the previous instruction), the Project's calculated earthquake acceleration is 0.095•g and 0.146•g for extreme earthquake.
(1.08 MB)Situation
The reservoir associated with the dam of the Ravine of the Jew and his(her,your) environment they are inside the basin of Sure, in the Region of Murcia, to the north of the Autonomous Community. Concretly they are located in the leaves 891 (CIEZA), from the IGN to scale 1:50.000. The territory corresponds to the province of Murcia, Cieza´s municipal area..
The dam of the Ravine of the Jew is located on the ravine of the same name, approximately to 5 kilometres of his river mouth in the river Segura for the left margen of this one. On the other hand, downstream from this point and to approximately 3 kilometres of distance for the river, Cieza´s city is located, existing therefore a distance of 8 kilometres between the prey and the first significant core of population for which the wealths dedicated to the riverbed happen from the reservoir..
The intersection of the dam axis with the course of the river is at the following coordinates:
X 1º 25' 56" West
Y 38º 17' 00" North
The meeting point mention before has the next U.T.M. coordinates:
Reference system ETRS89. Time zone= 30
X=637021
Y=4238291
