Publicación: 22/03/2017_
- 22 March 2017 -
- Cesme- Izmir- TURKEY
- IWA-PPFW 2017.
2nd IWA Regional Symposium on Water , Wasterwater and Environment The Past, Present and Future of Word's Water Resources.
ASSESSMENT OF THE PRESENT STATE AND PERSPECTIVES OF_The old dam of Relleu ( Marina Baixa, Alacant, Spain.)
- Jose Francisco Climent Brotons.
- Miguel Salgado de Marcay.
- Manuel A. Soler Manuel.
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2nd IWA Regional Symposium, PPFW 2017, Izmir, Turkey, 22-24 th March
ASSESSMENT OF THE PRESENT STATE AND PERSPECTIVES OF THE OLD DAM OF RELLEU (MARINA BAIXA, ALACANT, SPAIN).
Theme D Ancient Water System, Oral presentation
J. F. Climent*, M. A. Soler**, M. Salgot***
* Geography Department, University of Alicante, Sant Vicent del Raspeig, Alicante, Spain
josefranciscorelleu@gmail.com
** Casa del Escrivà, Plaza Magistrado Soler 2, 03578, Relleu, Alicante, Spain
casadelescriva@gmail.com
***Soil Science Unit and Water Research Institute (IdRA), University of Barcelona, Joan XXIII s/n, 08028, Barcelona, Spain
salgot@ub.edu
ABSTRACT
The old arch dam of Relleu (Alacant, Spain) was during three centuries the slendest in Europe, with a height of 32 meters. Its walls upstream and downstream and its drain tower were built with ashlar and the nucleus was made from masonry. At the beginning of the 20th century, the dam was decommissioned and nowadays is quite entirely silted up and is being degraded. This infrastructure used to regulate the scarce flows of the Amadorio river and managed the floods of a Mediterranean regime catchment. At present, there is an increasing interest to declare the dam site of cultural interest and stop its degradation.
For this purpose, research has been performed on the history of the infrastructure, the hydrology and the capacity to manage floods of the basin. The geology and the geometry of the dam, the auxiliary dam which derives water from another basin, the water leakages, the needs of maintaining and repair the structure and where exactly are the fallen off ashlars were also being determined. Apart, the situation of the quarry which stones were used to build the dam has also been determined. It is also to value the landscape where the dam is located, including the spectacular gorge downstream the dam.
The reasons for this research are the desire of ensuring the survival of the dam and if possible recover part of its functionality. Finally, to preserve the hydraulic and constructive heritage values of the dam and its surrounding are necessary.
Main characteristics and history of the old dam of Relleu
The Relleu dam, a historic jewel of the hydraulic heritage of the Amadorio River, used to be the slendest dam of Europe during 300 years. This dam consists of an arched wall between the drain tower and the left abutment of the structure and is practically flat between the tower and the right abutment. The 60 m bend radius is constant along the wall. The wall thickness is 10 m up to the original 28 m height of the original construction, built to supply water to Villajoyosa town in the Mediterranean seaside. The heightening over the original fabric is a wall with thickness of 5 m up to the old
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dam crest, which is at 31.85 m high (Giménez 2003, Gómez 1958, Fernández 1984) while the measurement of the authors indicated 31.80 m. The heightening was needed because the loss of volume through the years due to silting. The location of the dam is perfect from the constructive point of view (Fig. 1). The vertical wall is covered upstream and downstream of the dam by an ashlar sheet. The material used is sandy limestone, from the Cenozoic, lower and medium Miocene from a neighbouring quarry series (Fig. 2). The nucleus is made from masonry. The drain tower is built using ashlar stones, 0.4 x 0.2 x 0.3 m.
Fig. 1. Geometry of the dam. A) Schematic view from downstream with the window of the scour outlet. B) Schematic view from upstream, showing details of the silting up (the changes of width of the wall are not shown). The reference axis appears in both figures.
The dam receives its water from the Amadorio basin upwards from its location. The surface of the draining basin is 10,453.2 ha and goes from the upper part, in the highest peak of the basin (1,217 m Rentonar range) to the bottom of the dam (275 masl).
The Relleu’s dam has an auxiliary dam (Fig. 3) which receives water from the Fasamai and Cortés basins and diverts it to the Relleu’s dam, recovering the water that should have been reaching the Amadorio below the dam. The auxiliary dam drives the water through a bypass channel (Fig. 4) partially carved into the rock. By this way, the draining basin surface is increased by 324.7 ha. This secondary basin has its maximum height at 565 m and its minimum at 285 m. Between the main and the auxiliary dam there is the guard house (Fig. 5) accessible by ladders built or excavated in the ground.
Fig. 2 El Brull quarry Fig.3 Auxiliary dam Fig. 4 Diversion canal Fig.5 Guard’s house
When performing the field works, an alignment, using a string, was installed, nearly in parallel with the dam, which was the basis for the measurements. The alignment was oriented at 175º W. Measures were taken every 5 m, along the string of the alignment and for 37.1 m, to help to perform the geometric characterization. The results appear in the Figure 1. The present irregular form of the dam crest is due to the loss of ashlars and
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results in the diverging data of height quoted by the authors that described this infrastructure (Giménez 2003, Gómez 1958). The overall view appears in the Figure 6.
Fig.6. Views of the dam. A) The Wall seen from downstream and the tower B) Section of the dam
The drain tower is 5.37 m high over the sediments, 2.20 to 2.63 m width and 31.85 m high. At present, the sediments are covering the tower quite entirely, and only the upper part of the tower can be seen (Figs. 2 and 6).
The climatic characteristics of the catchment are the typical of the southeast of the Iberian Peninsula. Temperatures are mild all the year round and equinox rains more usual during October, with irregular heavy rains in wintertime and quite no rain during summer because of the tropical subsidence related to Hadley cells. This subsidence is generating the persistent summer droughts in the area. The catchment is heavily dissymmetric in terms of climate, influenced by two key geographical factors, relief and orientation. Then, the average rainfall of the area is not homogeneous and several points of the catchment, located inland by the Amadorio’s source, receive a maximum rain, 800 mm/year, while in the meridional part of the basin the isohyet is around 350 mm/year. The temperatures are also dissymmetric, because of the same geographical factors which affect the rain. In the inland part of the catchment, frosts in winter time and there are mild temperatures in summertime, usually with cool nights. In the south of the catchment, frosts are really scarce and short and this area is warmer in summertime (Fig. 7).
The hydrological characteristics of the Amadorio river correspond to a river-ravine system, typical from the Spanish southeast, having irregular flows combined with equinox maximums (following the rain episodes) associated with sudden high flows in wintertime and a general minimal flow during summertime, when usually the river becomes dry. Nevertheless, there are other specific factors which make the area unique; after cool and humid winters, the Amadorio river regime can be nival, as well as the one of its main effluent, the Sella.
The catchment has an area of 10,543 ha, mainly in the municipality of Relleu. The southern part has a rounded shape, while in the north is rectangular (Fig. 7). The river flows, from the source to the dam, along 16,142 m and from the west to the east. Arriving at the old Rabós mill the Amadorio becomes encased until reaching the Palanquetes area, where water starts to be used for irrigation and in the past was also
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Fig.7 The Amadorio catchment
used to generate energy in several mills. The flows were derived using weirs until the river reached the dam. A really impressive set of storage and distribution canals was implemented and is still used for irrigation purposes.
The Climate Change previsions for the area describe the possibility to modify the pattern of rainfall, increasing the irregularity of rains and as a result the hydrology of the river. If predictions become reality, the drought episodes will increase being longer, and the flash floods more raging. In the last 20 years, an increase of 0.5 ºC (Fig. 8) in the Alcoleja weather station, near Relleu, has been observed (Soler, 2010) confirming the possible tendencies.
Figure 8 Temperatures in the Alcoleja (Alacant province, Spain) weather station
The dam revisited, its present state and restoration needs
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The authors have been visiting the dam several times between 2014 and 2016 in order to reconfirm measurements, revise the surrounding area and detect and confirm the degree of deterioration of the infrastructure and the possibility and origin of water losses inside the ponded area.
The downstream wall is partially collapsed as a consequence of overspills, the vegetation (Fig. 9) which is growing over it (partially removed nowadays), and the lack of maintenance. The vegetation (even trees of big size) includes a fully grown taray (Tamarix gallica). Is in this part of the wall where more ashlars have been collapsing, leaving the masonry of the dam nucleus exposed (Fig. 6).
Fig. 9 Vegetation in the walls and crest of the dam
Abundant vegetation is growing on the crest, which is helping to keep the spillway by the left margin of the dam, as it seems was intended when the dam was designed and is shown in old pictures (Soler, 1910) (Fig. 10). At present (2017), the water is spilling along the crest (Fig. 11) when there is a certain amount of water. At the same time this vegetation is deteriorating the structure. The old picture (Fig. 10) is showing that the crest was entirely covered by ashlars and used to have a tier nowadays disappeared and located downstream, not upstream (Fig. 6 B).
Fig. 10 The dam overflow, 1900 Fig. 11 The dam overflow, 2017
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The drain tower is apparently well preserved but partially silted and without the wooden cofferdams which allowed to choose the level of water extraction.
The auxiliary dam (Fig. 3) is just a stone wall, recovered with lime mortar with a maximum width in the crest of 0.5 m which at present is completely silted, but does not matter because it is acting as a derivation canal for the waters arriving from the Fasamai and Cortés catchments towards the Relleu dam. This canal (Fig. 4) is carved in the rock and has a changing depth with a width of 1 m until it reaches a small canyon, probably generated by the water after years of spillage, and as indicated before is draining to the Amadorio upstream the main dam.
The quarry, which supplied the ashlars used to recover the masonry works, is located in a neighbouring area at about 2,000 m from the dam, and is called “El Brull” (Fig. 2). The ashlars were transported downwards which made the process easier. The comparison of the materials from the dam and the quarry, as well as the oral tradition, confirm this statement. If the dam is to be rehabilitated, to know the place of the original material is important for several reasons, such as economy, facility of building, and homogeneity of materials, existing and new ones.
An examination of the foot of the dam was also performed following the riverbed downstream the facility, through the gorge of the Amadorio (Fig. 12). The gorge is following a fault which cuts the Orxeta range and is showing very weathered walls; smoothed by the passage of water though centuries. In the bed there are alternatively dry passages and pools requiring the passers-by being wetted to follow the path. The gorge scarcely receives sun in the bottom, only a few hours in summertime. The examination was performed from the base of the dam to an area downstream where the walls collapsed, thus creating a wide area where the vegetation, spontaneous and invasive, is growing without being disturbed due to the difficulty of reaching this site. Along the gorge, several ashlars can be found both in dry or inundated areas, all of them eroded because of having rolled away and due to the action of flowing water. The gorge has several meanders and because of this, and the other mentioned circumstances, it would be difficult to recover the fallen ashlars if desired. Additionally the installation of several zip lines, winches and cable cranes would damage the surrounding environment and the walls of the gorge; this solution is to be discarded. The use of aerial systems to recover the ashlars will also be dangerous due to the scarce width of the gorge. For the mentioned reasons, it was important to localise the quarry where ashlars from the same material than the original ones could be obtained. It is estimated that around 1,200 ashlar pieces would be necessary to fully restore the walls downstream the dam and the crest and for the reconstruction of the old tier. Just at the bottom of the dam, the width allows the implementation of a scaffold system to rebuild the walls downstream. The transportation of the ashlars from the identified quarry to the dam can be performed by using trucks.
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The restoration of the drain tower is not difficult indoors. For the moment this restoration is not necessary outdoors because the dam is quite fully silted. If it is desired to place cofferdams for controlling the drainage, it would be difficult to uncover the whole tower because it would mean some accommodation of the silting material near the dam wall which could affect the structure. Even if all the elements of the tower drainage systems were rebuilt, it could not be enough for using the dam as a regulating manageable infrastructure, considering that several water leakages were detected in 2015 in the walls of the reservoir but not in the walls of the dam.
Fig. 12 The gorge after the dam
Present state of the reservoir and the possibility of exploitation
The silting of the reservoir created a flat area located approximately at a height of 275 masl. This plain is absolutely filled with vegetation mainly in springtime with a huge amount of autochthonous plants such as the thistle (Fig. 13) or invasive, like the American reed (Arundo donax), flourishing at springtime (Marcos, 2003). Last years another invasive species appeared, like the saltmarsh aster (Aster squamatus). In the area several small mammals (rabbit mainly – Oryctolagus cuniculus), birds (goldfinches – Carduelis carduelis, turtle doves – Streptopelia turtur, and wood pigeons - Columba palumbus) and its predators (foxes - Vulpes vulpes, and eagles like Aquila crysaetos) are described. When pools are formed, are quickly colonized by anatidae species.
Geologically, the dam is located over a calcareous lithology, mainly formed by nummulites, dolomites, dolomitic breccias and marls; materials highly permeable. All of them are from the Mesozoic era, Cretaceous system of the upper series and Senonensic basin; like the Orxeta range, which includes green clays of medium permeability, from the same Mesozoic era and cenomanian-turonian stage, more than 100 million years old. The surrounding areas are not so old in geological terms, like Quaternary sediments. Additionally, the dam is located in a concordant contact near an inverse fault located north of the dam.
The leakage of water happens in the lateral areas of the dam, not in the wall. There the terrain presented cracks which were sealed in the past (Fig. 14) using cement mortar. The water leakage through the cracks (microfaults) is present especially in the Amadorio riverbed, but not in the bed of the Salat ravine, also named Cova ravine. 25 sinks where water infiltrates have been located in the surface of the sediments (field works of the authors, 2015); the sinks shift due to local changes of leaking capacity in the sediment’s cracks, which become sealed and thus water finds new ways down.
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Those leaking places are nearly aligned with the underlying faults, parallel to the Orxeta range. From this, can be deduced that the bottom and walls of the dam vessel are not impervious and the amount of water lost in this way can be important. This is an added difficulty to recover the original goals of the dam. It would be interesting to know the final destination of the water lost by infiltration which reaches the faults, because the leakage seems to be recharging certain aquifers of the area. The losses through the nummuliting calcareous stones have been calculated to be 80 L/s with the dam fully filled (Confederación Hidrográfica del Xúquer, 2016).
Fig. 13 Flowering thistle Fig. 14 Seals with mortar Fig. 15 Dam, vegetation and gorge
Landscape around the dam. Appealing places
The dam is located in a complex geographical location, a wild and rough landscape in the deepest part of the Relleu municipality, in the ideal place to be built, a narrow gorge eroded by the flowing water. It is a place where the efforts to build a dam would be minimal, with the maximum benefit in terms of water storage. The gorge is the natural outflow of the river-ravine Amadorio. The gorge or gully (estret, meaning narrow, in the local expression) has by itself a unique attractiveness. The gully has vertical walls of more than 200 m high, walls with slopes exceeding 100% in some places. The bottom of the river is located 225 masl, while the crest of the range is placed at 527 masl. This is a perfect place for extreme sports, like canyoning and climbing (Fig. 12) and bird watching in a natural reserve. This attractiveness is favoured by the presence of dolines, poljes, canyons, gorges… formed along millennia by the action of water.
From Relleu, looking west in direction to the dam, it is possible to see clearly the depressed area. This area is formed by a terraced landscape, cultivated for centuries and holding a lot of relics of the past; like a small aqueduct named the Arcà or the arcade (Fig. 15), in the middle of the orchard. A great number of canals and ditches form the complex hydraulic network of the Reg Major or great irrigation canal; as well as other weirs which manage the water of the Amadorio (Fig. 15) (Maquiegui, 2013, Soler 2015). All this terraced Mediterranean landscape merits a detailed visit. The system is immerged in a framework of a xeriscape, with schlerophyll and perennial vegetation. The Mediterranean maquis shrubland or the garrigue include esparto grass (Spartium junceum) and dwarf palm (Chamaerops humilis).
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Fig. 15 Part of the hydraulic heritage of the Amadorio basin
The hydrology of the Amadorio River and the influence of the dam
The hydrology of the Amadorio basin was performed by using conventional methods and coefficients that several authors counsel for this area (runoff coefficient 0.30, a little bit higher than the 0.25 indicated by Gil (1972), because persistent rains which overcome the field capacity of the soils and a k uniformity coefficient of 1.32 are being considered). The work performed has been tested applying the figures and calculations to a rain episode during January 2017. The amount of rain was 181 mm at Relleu (www.avamet.org) along 72 h in 4 days. At the 101,76 hours of the episode; 103,29 m3/sec were registered. During that period the runoff through the river and the losses in the crest of the dam were measured. The hydrogram obtained is being shown at the Figure 16. Once verified, the hydrograms for the return periods of 25, 50 and 100 years were calculated as indicated in the Fig. 17.
Fig. 16 Hydrograph January 2017 Fig. 17. Hydrographs for several return periods
Considering that the surface of the dam vessel is 517.6 m2 and the maximum height is 3 m (the rest of the volume is silted), the approximated holding capacity is 1.295.000 m3. The rainfall for 25 years return period is 135 mm, for 100 years 185 mm and for 500 years 251 mm; with a lapse of 3, 4 and 6 hours of duration respectively, being the rain torrential. The concentration time of the catchment is 1.18 h. The lamination of the flow which offers the dam is still interesting, even considering that the 1.3 Mm3 available
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will be reached in 13 h for a return period of 25 years, 11 h for 100 years and 2 h for 500 years.
CONCLUSIONS
The Relleu dam, an architectonical and engineering jewel of the 17th century needs, at present, immediate but simple fixing actuations in order to avoid that any eastern gale, such as the one of last January 2017, could destroy the dam wall due to the erosive activity of water when overflowing the crest.
A previous action should be the elimination of the vegetation growing on the dam structure.
The ashlars lost by the action of the floods should be replaced by using similar pieces and, additionally, the recovery of the drain tower must be performed to return the dam certain regulation and aquifer recharge capacity.
The necessary bureaucracy to qualify again the infrastructure as a Place of Cultural Interest would ensure the future of the dam (Melgarejo 2015, Soler 2015). It will become, as well, an ornithological reserve.
Bibliografía
Confederación Hidrográfica del Xúquer. http://www.chj.es/. Consulted Oct 2016.
Gil, A., Rico, A. M. (2015), Consorcio de aguas de la Marina Baja: gestión convenida, integral y sostenible del agua. Instituto interuniversitario de Geografía, Universidad de Alicante D.L. 2015; ISBN 978-84-697-1947-3; 327pp.
Marco, J. A.; Atles fitonómic d’Alacant. Publicaciones Universidad de Alicante.
Giménez, P. (2003); El pantano de Relleu y el riego de la huerta de Villajoyosa (1653-1879), investigaciones geográficas nº30 (2003) pp 97-118, ISSN: 0213-4619.
Soler, M.A. (2010); ¿Seguirá lloviendo en Relleu? III Centenial Book, 1710 El milagro de la lluvia. Asociación Cultural Benesit.
Soler Manuel, Manuel and Alt. (2015) Simposium La presa de Relleu (Sgl. XVII) Referencia del patrimonio hídrico. Associació Benesit.
Melgarejo, J. (2015) Los pantanos de la Epoca Moderna en la Provincia de Alicante. Editorial Diputacion de Alicante. ISBN 8415327633, 9788415327639
Marquiegui, A. (2013) El patrimonio hidráulico de la provincia de Alicante. Diputacion de Alicante.
Visores:
www.terrasit.gva.es , www.ign.es/iberpix2/visor/ www.avamet.org ; http://www.wetterzentrale.de
Fernández, J.A. (1984) Catalogo de noventa presas y azudes españoles anteriores a 1900. Ed. Comisión de Estudios Históricos de Obras Públicas y Urbanismo. Madrid 511 pp.
Gil, A. 1972, Embalses españoles de los siglos XVIII y XIX para riego. Estudios Geográficos, 129, Universidad Autónoma de Madrid, pp 557-596
Gómez, J. Juan-Aracil, J, 1958, Saltos de agua y presas de embalse. Escuela de Ingenieros de Caminos Canales y Puertos, Madrid, 2 volúmenes.
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PANTANO RELLEU = BIC. CHANGE.ORG
https://www.change.org/p/president-de-la-generalitat-valenciana-conceller%C3%ADa-de-cultura-declaración-de-bien-interes-cultural-bic-pantà-de-relleu-pantano-de-relleu-s-xvii-xviii?utm_source=embedded_petition_view
20171106-DIFUSION DEL BIC PANTANO DE RELLEU CICCP Valencia a 6 Noviembre 2017_5pags
20171106-RELLEU.PANTANO-Old mills hidraulics in the upper Amadorio River. Relleu_11pags.pdf
https://relleupantano.blogspot.com.es/2017/11/20171106-relleupantano-old-mills.html
20171106-RELLEU.PANTANO-_6 HYDRAULICS IN THE OLD MILLS VALLEY OF RELLEU_xM.Salgot I M.Soler_9pags
https://relleupantano.blogspot.com.es/2017/11/20171106-relleupantano-6-hydraulics-in.htmlAURORA ass. Relleu. The hydraulic mills in the upper Amadorio. October 2016
10170324-RELLEU.PANTÀ-_PaperID_58_Prevention of flood episodes al Relleu_22a24.03.2017xJFCliment-MASoler-MSalgot_10pags.
20170322-RELLEU.PANTANO._ASSESSMENT OF THE PRESENT STATE AND PERSPECTIVES OF_Turquia_xxJFCliment_MSalgado_MASoler_10pags
https://relleupantano.blogspot.com.es/2017/11/20170322-relleupantanoassessment-of.html
20170507-BIC Pantano de Relleu Colegio de Ingenieros de Caminos, Canales y Puertos de Alicante - Mayo 2017 x Manolo Soler.
https://relleupantano.blogspot.com.es/2017/07/20170507-bic-pantano-de-relleu-colegio.html
20171106-RELLEU- a VALENCIA en el salón de actos del * Colegio de Ingenieros de Caminos, Canales y Puertos de la Comunidad Valenciana*-
20171106-RELLEU- a VALENCIA en el salón de actos del * Colegio de Ingenieros de Caminos, Canales y Puertos de la Comunidad Valenciana*-
https://relleupantano.blogspot.com.es/2017/07/20170507-bic-pantano-de-relleu-colegio.html
20170417-RELLEU- PANTANO DE RELLEU: -PETICIÓN DE FIRMAS APOYANDO LA DECLARACIÓN DE BIEN DE INTERÉS CULTURAL DE LA COMUNIDAD VALENCIANA Y PATRIMONIO DE LA HUMANIDAD-
20171106-RELLEU-PRESA :.- a VALENCIA en el salón de actos del * Colegio de Ingenieros de Caminos, Canales y Puertos de la Comunidad Valenciana*- https://relleupantano.blogspot.com.es/2017/11/20171106-relleu-valencia-en-el-salon-de.html
PANTANO RELLEU = BIC. CHANGE.ORG
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