The Crevillente reservoir is a reservoir in Spain that is located in the municipality of Crevillente, in the province of Alicante, Spain and whose function is to regulate part of the flow from the Tajo-Segura transfer. This reservoir belongs to the Segura Hydrographic Confederation and was built in 1985 in the bed of the Boch ravine.
It has a reservoir area of 108 hectares, with a maximum capacity of approx. 12.78 hm³ and a bank perimeter of about 14 km. It has a gravity dam 54 m high and 360 m long.
Situation
The Crevillente dam, also known as Crevillente Canal Regulatory Reservoir, is located in the Bosch ravine. This ravine has a discontinuous flow, with a strong low flow, so contributions from its own basin are practically non-existent, its main source of power being the Crevillente Canal. This Canal runs at lower levels than the reservoir, so the water can either continue directly to the distribution system of the irrigable area, or be diverted to a pumping station that lifts it to the reservoir for regulation. The pumping station is located on the left bank of the Canal, near the foot of the dam, and the pumped flow reaches the reservoir through a reversible intake that runs in a tunnel under the right abutment of the dam.
The Crevillente dam and its reservoir are located on sheet 893 (Elche) of the Army Geographic Service, at a scale of 1:50,000, in its 1997 edition. The dam closes the Bosch ravine, about 6 km upstream from its mouth into Laguna del Hondo.
Background
The Crevillente Canal runs downstream of the homonymous splitter located in the Left Bank Postrasvase Canal (CPMI), at the intersection of this infrastructure with the Salada or Abanilla boulevard. The flows it transports are assigned to the General Community of Irrigation Irrigators of Levante Izquierda del Segura, which is in turn integrated by communities of irrigators in the Júcar and Segura basins whose first intake is located at the San Antonio dam in the municipality of Guardamar del Segura. In the General Preliminary Project of the main conduction and regulation works in the Southeast of the Tajo-Segura Joint Use, 1st phase, approved on April 1, 1971, it had been planned that this Canal would end in a 2.5 km long siphon, to directly feed the head of the indicated irrigations, materialized with two 2 m pipes with a total capacity of 11.4 m³/s. But the need to irrigate for 18 hours a day and on demand led to consideration of the possibility of building a regulation tank at the tail of the Canal, around the siphon and at the height of the Bosch ravine, to store the difference between the arrival flow and that supplied for irrigation. The morphology of the territory where the deposit was to be implanted and the associated volume only left the possibility of materializing it by closing a natural channel with a dam. The viability of this dam was pending the geological-geotechnical report that the Geological Service of Public Works (SGOPU) had to prepare.
Regulating tank
Introduction
The Crevillente reservoir is a reservoir in Spain that is located in the municipality of Crevillente, in the province of Alicante, Spain and whose function is to regulate part of the flow from the Tajo-Segura transfer. This reservoir belongs to the Segura Hydrographic Confederation and was built in 1985 in the bed of the Boch ravine.
It has a reservoir area of 108 hectares, with a maximum capacity of approx. 12.78 hm³ and a bank perimeter of about 14 km. It has a gravity dam 54 m high and 360 m long.
Situation
The Crevillente dam, also known as Crevillente Canal Regulatory Reservoir, is located in the Bosch ravine. This ravine has a discontinuous flow, with a strong low flow, so contributions from its own basin are practically non-existent, its main source of power being the Crevillente Canal. This Canal runs at lower levels than the reservoir, so the water can either continue directly to the distribution system of the irrigable area, or be diverted to a pumping station that lifts it to the reservoir for regulation. The pumping station is located on the left bank of the Canal, near the foot of the dam, and the pumped flow reaches the reservoir through a reversible intake that runs in a tunnel under the right abutment of the dam.
The Crevillente dam and its reservoir are located on sheet 893 (Elche) of the Army Geographic Service, at a scale of 1:50,000, in its 1997 edition. The dam closes the Bosch ravine, about 6 km upstream from its mouth into Laguna del Hondo.
Background
The Crevillente Canal runs downstream of the homonymous splitter located in the Left Bank Postrasvase Canal (CPMI), at the intersection of this infrastructure with the Salada or Abanilla boulevard. The flows it transports are assigned to the General Community of Irrigation Irrigators of Levante Izquierda del Segura, which is in turn integrated by communities of irrigators in the Júcar and Segura basins whose first intake is located at the San Antonio dam in the municipality of Guardamar del Segura. In the General Preliminary Project of the main conduction and regulation works in the Southeast of the Tajo-Segura Joint Use, 1st phase, approved on April 1, 1971, it had been planned that this Canal would end in a 2.5 km long siphon, to directly feed the head of the indicated irrigations, materialized with two 2 m pipes with a total capacity of 11.4 m³/s. But the need to irrigate for 18 hours a day and on demand led to consideration of the possibility of building a regulation tank at the tail of the Canal, around the siphon and at the height of the Bosch ravine, to store the difference between the arrival flow and that supplied for irrigation. The morphology of the territory where the deposit was to be implanted and the associated volume only left the possibility of materializing it by closing a natural channel with a dam. The viability of this dam was pending the geological-geotechnical report that the Geological Service of Public Works (SGOPU) had to prepare.
On April 14, 1971, the technical director of the Segura Hydrographic Confederation requested this document from said Organization who, in December 1972, issued the Geological Report on the Crevillente reservoir, in the municipality of Crevillente (Alicante), in which it concluded the viability of building the aforementioned reservoir using a dam up to 45 m high, at the junction of the Bosch ravine with the highway. N-330. On March 13, 1973, the General Directorate of Hydraulic Works approved the drafting of the appropriate project.
The Regulatory Reservoir Project for the Crevillente Canal (Alicante) was drafted by the engineer of the Segura Hydrographic Confederation, Mr. Alfonso Botía Pantoja, dated September 1974, when the main conduction and regulation works of the Tajo-Segura Joint Use, within the Segura basin, were already being carried out and had a completion deadline of December 31, 1974. The project studied two Possible alternatives for the joint exploitation of the Crevillente Canal–Regulatory Depot system.
• - In Solution 1, which is the one that was finally chosen, the Crevillente Canal transported by gravity the instantaneous flow to the canals of the irrigable area, and the surpluses were derived by pumping to the regulating reservoir created by the Crevillente dam. The necessary height of the dam was 55 m above foundations and the volume of the reservoir created was about 14 hm³.
• - In Solution 2, the Crevillente Canal discharged by gravity to the Reservoir, where the daily differences between contributions and demands were regulated, which were supplied directly through the intake from the reservoir. This different conception of the hydraulic system led to a dam height of 29 m and a reservoir of 1.5 hm³ capacity.
The project was approved by the DGOH on August 12, 1977, for the purposes of public information. In the same letter from the DGOH, the Segura Hydrographic Confederation was ordered to proceed to break down the project for the CN-330 highway variant, for its independent processing, as well as to introduce into the dam project the recommendations and modifications advocated in the report of the Dam Surveillance Service. But this project was not going to be definitive since, during the course of the construction of the dam, it was necessary to draft two Modified projects and a Complementary project.
As a consequence of the previous procedure, the Modified Project 02/79 of the Regulatory Depot of the Crevillente Canal was drafted, signed by Mr. Alfonso Botía Pantoja, in which a complete response was already given to the instructions of the DGOH, by segregating the project from the road and processing it before the General Directorate of Highways, and incorporating all the modifications of the report of the Dam Surveillance service.
The stipulated execution period was 24 months from the date of signing the staking document. On May 4, 1982, the engineer directing the works reported favorably to the Superior Authority, the contractor's proposal to change the type section of the dam, from breakwater with an impermeable core, to a full one, which implied greater slopes and dam volumes, although the request did not mean an increase in the budget. The alleged cause was that the planned quarries could not provide sufficient volume of breakwater, so other more distant ones had to be used, which would increase the budget for the works. To avoid this, he proposed modifying the projected section, preserving the core, replacing the breakwaters on the shoulders with a whole from the vicinity of the closed one, protected with breakwater and extending the downstream filters to the outside.
On June 6, 1982, the DGOH authorized the drafting of Project 05/83 of Modification No. 1 of the Crevillente Canal Regulatory Deposit, with an extension of the period of three months, that is, until December 31, 1984. This project was approved on January 24, 1984. During the execution of the foundation excavation work, it was discovered that the loams at the base were very weathered, which made it necessary to increase the excavated depth and, at the same time, the necessary filling material.
To consider the increase in cost that the increase in the volume of excavations, core, shoulders and concrete lining of galleries implied, the DGOH authorized on May 21, 1984, the drafting of Project 09/84 of Modification No. 2 of the Regulatory Deposit of the Crevillente Canal. This project was technically and definitively approved on November 21, 1984, and the execution period was increased by six months.
Project 07/85 of Complementary Work No. 1 of the Crevillente Regulatory Depot was also drafted in order to carry out various additional actions that improved the operation and use of the Regulatory Depot.
The works were completed in March 1986, meeting the deadline finally stipulated. The provisional reception took place on July 15, 1986 and the final one on July 22, 1987.
Purpose
The Crevillente reservoir has the function of regulating a part of the flows transported by the Postrasvase Canal of the Left Bank to supply the irrigation demands of a part of the irrigation of the General Community of Irrigators of Levante Izquierda del Segura, in an area located in the Júcar basin. Its scarce drainage basin and its reduced contributions would never have justified the construction of this reservoir that acts practically as a regulation reservoir at the tail of the Canal. It is an important piece in the distribution of water from the Tajo-Segura Aqueduct through the Postrasvase, so practically all of its contributions come from the Tajo-Segura Joint Use.
The Crevillente dam is a gravity dam, with a straight plan -except in the area of the two abutments where it has a slight curvature-, made of loose materials with a clay core. The core constitutes the impermeable element, it develops from the foundation to one meter below the crown level. From the inside to the outside, the dam is made up of a core of clay loam, two layers of filter – fine and coarse – downstream of the core, two shoulders built with gravel from the area, an outer wedge of gravel, and a layer of protective breakwater. The plan length of the dam is 360 m, its height from the foundation rises to 58.00 m, while above the channel it is 54.50 m. The volume of earth with which the dam body was manufactured amounts to 100,000 m³.
The type section of the dam is trapezoidal with slopes of 2.35:1 on the upstream side and 2.60:1 on the downstream side. The crest of the dam is located at elevation 147.50 and is 12.50 m wide. To limit pore pressures during the construction of the dam and when discharges occur, it has a complex system of filters and drains built on both shoulders.
Territorial framework
Physical characteristics of the basin
The drainage basin to the Crevillente reservoir has an area of 11.80 km², its maximum altitude is 792 and it belongs entirely to the municipality of Crevillente. The Bosch ravine, in which the dam sits, barely flows during the days following significant rainfall. As a related fact, it should be noted that precipitation with a return period of 1000 years barely generates a peak flow of 85 m³/s. The Bosch ravine basin does not have developed tributaries as such. The slope surface has a clearly rectangular shape, except for a small appendage that protrudes to the NW, about 4 km perpendicular to the dam and about 3 km parallel. This territory receives an average annual rainfall of about 450 mm.
The Maximum Normal Reservoir Level (MNEN) was set in the original project at the threshold of the spillway, which has a fixed lip and is located on the right bank of the dam, has a rapid and buffer bowl and is located at a level of 145.00. The total reservoir volume for the normal maximum level rises to 12.78 hm³, while the useful one reduces it slightly to 12.28 hm³. For its part, the flooded surface for this level is 90.87 ha, the length of the coast is 14 km and the length of the reservoir goes back 0.9 km upstream.
For the project flood, calculated for a return period of 500 years, the flow rises to about 75 m³/s, the maximum level reached by the reservoir - Level for the Project Avenue (NAP) - turns out to be 145.52, which corresponds to a reservoir volume of 13.26 hm³ and a flooded surface of 93.03 ha.
Regional geology
The Crevillente dam is located on a set of post-alpidic sediments, deposited in a predominantly marine environment. These materials rest on the northeastern edge of the allochthonous subbetic zone and, more specifically, on the eastern end of the Crevillente mountain range, which is made up of an anticline of Triassic, Jurassic and Cretaceous materials, whose WSW-ENE direction axis sinks towards the East under a powerful Miocene series. The materials of the Mesozoic series that crop out in the Crevillente mountain range are gypsum marls of Keuper facies, limestones, dolomites and dolomitic limestones, marly limestones and marls.
The Tertiary series begins, discordantly, with levels of conglomerates and sandstones (molasses) and continues with marls, clays, poorly cemented sandstones, limestones and marls, ending with Ade conglomerate banks, sandstones and reddish marls from the Pliocene. The quaternary is a recent alluvial, which covers large areas, but already outside the area near the reservoir.
The compact calcareous nature of the Jurassic contrasts with the clayey-gypsum material of the Trías, which, morphologically, gives rise to a marked differential erosion that produces high peaks in the mountains, bordered by deep ravines with vertical walls. In the Aspe Valley, this aspect is attenuated by the filling of alluvial materials in the depressions. On either side of this core are the Tertiary ridges with much more moderate relief in their unevenness, but also quite broken by differential erosion, with valleys parallel to the structure and consequent collectors, frequently embedded in faults. These Tertiary materials (Middle Miocene to Upper Pliocene) present frequent lateral variations of lithofacies related, both to the immediate local contributions, and to the various depths of sedimentation.
Geology and geotechnics of the glass
Along the entire length of the channel there is an alluvial thickness that rapidly decreases downstream, as is natural given the morphology of the channel, since the drag is maximum at the narrowing. This thickness varies from a maximum of 4 m, to about 2 m and to less than one meter. During the initial construction project phase of 1972, seven mechanical boreholes were carried out, with a total drilled length of 600 m and distributed in 3 different profiles; two of them transverse to the ravine and the other longitudinal. The percentage of witnesses was quite variable within each survey, as some sections were found in which almost 100% was reached and others in which the recovery was practically zero. The results of the profiles indicated that the right slope, in its first meters, was in worse condition than the left.
In order to evaluate the permeability of the area, water admission tests were carried out. Taking as an admissible limit about 4 l/m/minute for an injection pressure of 10 atm. Total losses were infrequent, except in one survey, in which, in addition to the fact that the percentage of witness recovery was very irregular, the admissions were significantly higher than those of the rest of the surveys.
The entire basin is developed in Miocene terrain. It is impermeable, as it is in areas excavated by erosion in marls and clays. There are levels of sandstone and limestone that are not very permeable and are embedded in impermeable packages.
Geology and geotechnics of the closed
The terrain of the closed area where the dam is located corresponds to a series of levels of marl, limestone and sandstone, which dip 30° and 40° towards the South. All of these materials form the southern flank of a gentle anticline. During the initial construction project phase of 1972, seven mechanical boreholes were carried out, with a total drilled length of 600 m and distributed in 3 different profiles; two of them transverse to the ravine and the other longitudinal. Natural radioactivity was recorded in all surveys. In the final project, by changing the typology of the dam to loose materials with an impermeable clay core, the closure was moved forward slightly upstream, so the geological-geotechnical characterization of the terrain, as it dips downstream, was critically assumed and confirmed during the execution of the works.
The lithological column deduced from the drillings is quite similar in all of them since it begins with detrital limestone, which gradually passes to detrital sandstone and, subsequently, to progressively less detrital marl. There are levels of clay, sandstone or detrital limestone at various depths, which make the noA changes abrupt. These levels begin with a package of detrital limestone, which gradually transitions to detrital marl, distinguishing in some parts a level of sandstone. Afterwards there is a level of yellowish sandstone, in which one of light gray clay is interspersed. Below is a large package of marl and detrital marl, whose approximate depth is about 25 m, and in which some correlations of the levels of sandstone and limestone have been given although, in general, it does not seem that there is continuity between them. Further down there is a level of yellowish detrital limestone of varying strength, which gives way to a level of dark gray clays and marls. All the drillings end with a level of loam of various shades, which begin as detrital and become more clayey at depth.
Geologically, no problem was found for the implementation of the dam in the closed area chosen in the Modified Project 02/79 of the Crevillente Canal Regulatory Reservoir. Finally, the dam was advanced upstream with respect to the closed one initially planned to adjust the type of dam made of loose materials, with a central clay core, to the morphology of the narrowing. The core rests, at least in the central two-thirds, on impermeable materials formed by more or less clayey loams and, to a lesser extent, on calcareous and sandy loams in at least 250 m, which were crossed by the drillings. Its depth is greater than 4 m, its dip is towards downstream (concordant with the structure of the area) and its permeability is more than sufficient. In the abutments, the core rests on levels of sandstone and sandy detrital limestone which, being of doubtful impermeability, required cleaning and sealing of joints and joints.
Data
• - River data: length of the dammed river 0.90 kKm.
• - Basin data:.
• - Prey body:.
• - Spillway:.
Access
The dam is located at the intersection of the old CN-330 highway - which links Crevillente with Albacete (today CN-325) - with the Bosch ravine, in the municipality of Crevillente. From Murcia you reach the Crevillente dam via the Mediterranean highway A-7 (E-15), and then take the Crevillente exit, cross this town and take a detour to take the current N-325 road. Access to the dam is conveniently signposted at PK 19+000 of this last road. The dam's homes are located about two hundred meters away and are accessed via a paved road.
The area around the reservoir is very populated and the distance by road from the dam to the most important cities is 1.5 km to Crevillente, 11 km to Elche, 47 km to Murcia and 28 km to Alicante. The closest railway station and airport are in the city of Elche.
• - Segura Hydrographic Confederation Archived July 17, 2006 at the Wayback Machine.
On April 14, 1971, the technical director of the Segura Hydrographic Confederation requested this document from said Organization who, in December 1972, issued the Geological Report on the Crevillente reservoir, in the municipality of Crevillente (Alicante), in which it concluded the viability of building the aforementioned reservoir using a dam up to 45 m high, at the junction of the Bosch ravine with the highway. N-330. On March 13, 1973, the General Directorate of Hydraulic Works approved the drafting of the appropriate project.
The Regulatory Reservoir Project for the Crevillente Canal (Alicante) was drafted by the engineer of the Segura Hydrographic Confederation, Mr. Alfonso Botía Pantoja, dated September 1974, when the main conduction and regulation works of the Tajo-Segura Joint Use, within the Segura basin, were already being carried out and had a completion deadline of December 31, 1974. The project studied two Possible alternatives for the joint exploitation of the Crevillente Canal–Regulatory Depot system.
• - In Solution 1, which is the one that was finally chosen, the Crevillente Canal transported by gravity the instantaneous flow to the canals of the irrigable area, and the surpluses were derived by pumping to the regulating reservoir created by the Crevillente dam. The necessary height of the dam was 55 m above foundations and the volume of the reservoir created was about 14 hm³.
• - In Solution 2, the Crevillente Canal discharged by gravity to the Reservoir, where the daily differences between contributions and demands were regulated, which were supplied directly through the intake from the reservoir. This different conception of the hydraulic system led to a dam height of 29 m and a reservoir of 1.5 hm³ capacity.
The project was approved by the DGOH on August 12, 1977, for the purposes of public information. In the same letter from the DGOH, the Segura Hydrographic Confederation was ordered to proceed to break down the project for the CN-330 highway variant, for its independent processing, as well as to introduce into the dam project the recommendations and modifications advocated in the report of the Dam Surveillance Service. But this project was not going to be definitive since, during the course of the construction of the dam, it was necessary to draft two Modified projects and a Complementary project.
As a consequence of the previous procedure, the Modified Project 02/79 of the Regulatory Depot of the Crevillente Canal was drafted, signed by Mr. Alfonso Botía Pantoja, in which a complete response was already given to the instructions of the DGOH, by segregating the project from the road and processing it before the General Directorate of Highways, and incorporating all the modifications of the report of the Dam Surveillance service.
The stipulated execution period was 24 months from the date of signing the staking document. On May 4, 1982, the engineer directing the works reported favorably to the Superior Authority, the contractor's proposal to change the type section of the dam, from breakwater with an impermeable core, to a full one, which implied greater slopes and dam volumes, although the request did not mean an increase in the budget. The alleged cause was that the planned quarries could not provide sufficient volume of breakwater, so other more distant ones had to be used, which would increase the budget for the works. To avoid this, he proposed modifying the projected section, preserving the core, replacing the breakwaters on the shoulders with a whole from the vicinity of the closed one, protected with breakwater and extending the downstream filters to the outside.
On June 6, 1982, the DGOH authorized the drafting of Project 05/83 of Modification No. 1 of the Crevillente Canal Regulatory Deposit, with an extension of the period of three months, that is, until December 31, 1984. This project was approved on January 24, 1984. During the execution of the foundation excavation work, it was discovered that the loams at the base were very weathered, which made it necessary to increase the excavated depth and, at the same time, the necessary filling material.
To consider the increase in cost that the increase in the volume of excavations, core, shoulders and concrete lining of galleries implied, the DGOH authorized on May 21, 1984, the drafting of Project 09/84 of Modification No. 2 of the Regulatory Deposit of the Crevillente Canal. This project was technically and definitively approved on November 21, 1984, and the execution period was increased by six months.
Project 07/85 of Complementary Work No. 1 of the Crevillente Regulatory Depot was also drafted in order to carry out various additional actions that improved the operation and use of the Regulatory Depot.
The works were completed in March 1986, meeting the deadline finally stipulated. The provisional reception took place on July 15, 1986 and the final one on July 22, 1987.
Purpose
The Crevillente reservoir has the function of regulating a part of the flows transported by the Postrasvase Canal of the Left Bank to supply the irrigation demands of a part of the irrigation of the General Community of Irrigators of Levante Izquierda del Segura, in an area located in the Júcar basin. Its scarce drainage basin and its reduced contributions would never have justified the construction of this reservoir that acts practically as a regulation reservoir at the tail of the Canal. It is an important piece in the distribution of water from the Tajo-Segura Aqueduct through the Postrasvase, so practically all of its contributions come from the Tajo-Segura Joint Use.
The Crevillente dam is a gravity dam, with a straight plan -except in the area of the two abutments where it has a slight curvature-, made of loose materials with a clay core. The core constitutes the impermeable element, it develops from the foundation to one meter below the crown level. From the inside to the outside, the dam is made up of a core of clay loam, two layers of filter – fine and coarse – downstream of the core, two shoulders built with gravel from the area, an outer wedge of gravel, and a layer of protective breakwater. The plan length of the dam is 360 m, its height from the foundation rises to 58.00 m, while above the channel it is 54.50 m. The volume of earth with which the dam body was manufactured amounts to 100,000 m³.
The type section of the dam is trapezoidal with slopes of 2.35:1 on the upstream side and 2.60:1 on the downstream side. The crest of the dam is located at elevation 147.50 and is 12.50 m wide. To limit pore pressures during the construction of the dam and when discharges occur, it has a complex system of filters and drains built on both shoulders.
Territorial framework
Physical characteristics of the basin
The drainage basin to the Crevillente reservoir has an area of 11.80 km², its maximum altitude is 792 and it belongs entirely to the municipality of Crevillente. The Bosch ravine, in which the dam sits, barely flows during the days following significant rainfall. As a related fact, it should be noted that precipitation with a return period of 1000 years barely generates a peak flow of 85 m³/s. The Bosch ravine basin does not have developed tributaries as such. The slope surface has a clearly rectangular shape, except for a small appendage that protrudes to the NW, about 4 km perpendicular to the dam and about 3 km parallel. This territory receives an average annual rainfall of about 450 mm.
The Maximum Normal Reservoir Level (MNEN) was set in the original project at the threshold of the spillway, which has a fixed lip and is located on the right bank of the dam, has a rapid and buffer bowl and is located at a level of 145.00. The total reservoir volume for the normal maximum level rises to 12.78 hm³, while the useful one reduces it slightly to 12.28 hm³. For its part, the flooded surface for this level is 90.87 ha, the length of the coast is 14 km and the length of the reservoir goes back 0.9 km upstream.
For the project flood, calculated for a return period of 500 years, the flow rises to about 75 m³/s, the maximum level reached by the reservoir - Level for the Project Avenue (NAP) - turns out to be 145.52, which corresponds to a reservoir volume of 13.26 hm³ and a flooded surface of 93.03 ha.
Regional geology
The Crevillente dam is located on a set of post-alpidic sediments, deposited in a predominantly marine environment. These materials rest on the northeastern edge of the allochthonous subbetic zone and, more specifically, on the eastern end of the Crevillente mountain range, which is made up of an anticline of Triassic, Jurassic and Cretaceous materials, whose WSW-ENE direction axis sinks towards the East under a powerful Miocene series. The materials of the Mesozoic series that crop out in the Crevillente mountain range are gypsum marls of Keuper facies, limestones, dolomites and dolomitic limestones, marly limestones and marls.
The Tertiary series begins, discordantly, with levels of conglomerates and sandstones (molasses) and continues with marls, clays, poorly cemented sandstones, limestones and marls, ending with Ade conglomerate banks, sandstones and reddish marls from the Pliocene. The quaternary is a recent alluvial, which covers large areas, but already outside the area near the reservoir.
The compact calcareous nature of the Jurassic contrasts with the clayey-gypsum material of the Trías, which, morphologically, gives rise to a marked differential erosion that produces high peaks in the mountains, bordered by deep ravines with vertical walls. In the Aspe Valley, this aspect is attenuated by the filling of alluvial materials in the depressions. On either side of this core are the Tertiary ridges with much more moderate relief in their unevenness, but also quite broken by differential erosion, with valleys parallel to the structure and consequent collectors, frequently embedded in faults. These Tertiary materials (Middle Miocene to Upper Pliocene) present frequent lateral variations of lithofacies related, both to the immediate local contributions, and to the various depths of sedimentation.
Geology and geotechnics of the glass
Along the entire length of the channel there is an alluvial thickness that rapidly decreases downstream, as is natural given the morphology of the channel, since the drag is maximum at the narrowing. This thickness varies from a maximum of 4 m, to about 2 m and to less than one meter. During the initial construction project phase of 1972, seven mechanical boreholes were carried out, with a total drilled length of 600 m and distributed in 3 different profiles; two of them transverse to the ravine and the other longitudinal. The percentage of witnesses was quite variable within each survey, as some sections were found in which almost 100% was reached and others in which the recovery was practically zero. The results of the profiles indicated that the right slope, in its first meters, was in worse condition than the left.
In order to evaluate the permeability of the area, water admission tests were carried out. Taking as an admissible limit about 4 l/m/minute for an injection pressure of 10 atm. Total losses were infrequent, except in one survey, in which, in addition to the fact that the percentage of witness recovery was very irregular, the admissions were significantly higher than those of the rest of the surveys.
The entire basin is developed in Miocene terrain. It is impermeable, as it is in areas excavated by erosion in marls and clays. There are levels of sandstone and limestone that are not very permeable and are embedded in impermeable packages.
Geology and geotechnics of the closed
The terrain of the closed area where the dam is located corresponds to a series of levels of marl, limestone and sandstone, which dip 30° and 40° towards the South. All of these materials form the southern flank of a gentle anticline. During the initial construction project phase of 1972, seven mechanical boreholes were carried out, with a total drilled length of 600 m and distributed in 3 different profiles; two of them transverse to the ravine and the other longitudinal. Natural radioactivity was recorded in all surveys. In the final project, by changing the typology of the dam to loose materials with an impermeable clay core, the closure was moved forward slightly upstream, so the geological-geotechnical characterization of the terrain, as it dips downstream, was critically assumed and confirmed during the execution of the works.
The lithological column deduced from the drillings is quite similar in all of them since it begins with detrital limestone, which gradually passes to detrital sandstone and, subsequently, to progressively less detrital marl. There are levels of clay, sandstone or detrital limestone at various depths, which make the noA changes abrupt. These levels begin with a package of detrital limestone, which gradually transitions to detrital marl, distinguishing in some parts a level of sandstone. Afterwards there is a level of yellowish sandstone, in which one of light gray clay is interspersed. Below is a large package of marl and detrital marl, whose approximate depth is about 25 m, and in which some correlations of the levels of sandstone and limestone have been given although, in general, it does not seem that there is continuity between them. Further down there is a level of yellowish detrital limestone of varying strength, which gives way to a level of dark gray clays and marls. All the drillings end with a level of loam of various shades, which begin as detrital and become more clayey at depth.
Geologically, no problem was found for the implementation of the dam in the closed area chosen in the Modified Project 02/79 of the Crevillente Canal Regulatory Reservoir. Finally, the dam was advanced upstream with respect to the closed one initially planned to adjust the type of dam made of loose materials, with a central clay core, to the morphology of the narrowing. The core rests, at least in the central two-thirds, on impermeable materials formed by more or less clayey loams and, to a lesser extent, on calcareous and sandy loams in at least 250 m, which were crossed by the drillings. Its depth is greater than 4 m, its dip is towards downstream (concordant with the structure of the area) and its permeability is more than sufficient. In the abutments, the core rests on levels of sandstone and sandy detrital limestone which, being of doubtful impermeability, required cleaning and sealing of joints and joints.
Data
• - River data: length of the dammed river 0.90 kKm.
• - Basin data:.
• - Prey body:.
• - Spillway:.
Access
The dam is located at the intersection of the old CN-330 highway - which links Crevillente with Albacete (today CN-325) - with the Bosch ravine, in the municipality of Crevillente. From Murcia you reach the Crevillente dam via the Mediterranean highway A-7 (E-15), and then take the Crevillente exit, cross this town and take a detour to take the current N-325 road. Access to the dam is conveniently signposted at PK 19+000 of this last road. The dam's homes are located about two hundred meters away and are accessed via a paved road.
The area around the reservoir is very populated and the distance by road from the dam to the most important cities is 1.5 km to Crevillente, 11 km to Elche, 47 km to Murcia and 28 km to Alicante. The closest railway station and airport are in the city of Elche.
• - Segura Hydrographic Confederation Archived July 17, 2006 at the Wayback Machine.