Abstract

Shallow groundwater collecting systems byhorizontal galleries, known by the Arabicvoice qanats, have had a large developmentin Mediterranean Spanish areas (southernand eastern Iberian Peninsula). These sys-tems have been used in order to supply waterto cities or irrigated lands, from the 10th cen-tury to the beginning of 20th century, al-though there exist examples of possibleroman construction too, extended duringArabian domination and in medieval andmodern period.

Spanish name is “viaje de agua” (latin namedeformation “via aquae”), and there aremany examples of these constructions alongspanish geography: in Barcelona there weremany mines that start in Tibidabo base;Costa Brava (Gerona); Lorca (Murcia); Cre-villente (Valencia); Granada; Puebla deMontalbán (Toledo); Córdoba; Ocaña (Tole-do); Madrid and so on.

Madrid ones are the best studied of all ofthem, thanks to an exhaustive study carriedout in the eighties. Madrid springs were atypical feature on urban landscape, and werefeeder of “viajes de agua”.

During 17th and 18th century, and the firsthalf of the 19th century, the “viajes de agua”were the main water supply in the village,as, although private houses had wells, thesewaters only were used for irrigation. Totallength of “viajes de agua” was about 124

Km, 70 Km of which were collecting gal-leries and the other part conduction ones.Volume supplied was 3.600 m3/day, whichdecreased over the years mainly due to a badconservation service. In the middle of 19th

century, the volume didn’t exceed 2.000m3/day. Location of these “viajes de agua”was in the superficial saturated zone, induc-ing a high vulnerability of the system duringdraught periods, and also to pollution in acity where the sewer system wasn’t properlydeveloped yet.

Ocaña qanat, probably of roman age butwith arabian and medieval elements, repre-sents an incredible relic due to its 400 m ofgalleries and magnificent vaulted rooms.Qanat supplies the monumental “FuenteGrande”, herrerian style, declared nationalmonument. Nowadays, it’s an excellent ex-ample – still on use- of famous ”viajes deagua”, that supplied Madrid until the middleof 19th century.

This work shows its hydrogeological en-claves and the constructive elements, em-phasizing water management according toits chemist quality.

1. Introduction

Spanish Mediterranean areas (southern andeastern Iberian Peninsula) have highly de-veloped shallow groundwater systems thatcollect and conduct water through horizon-tal galleries.

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Some Examples of Spanish Qanats

Irene De Bustamante1; Juana Mª Sanz1, José A. Iglesias2, Bernardo López-Camacho2. 1 Universidad de Alcalá (Spain)2 Canal de Isabel II (Madrid Water Supply Organization, Spain)

These systems, or qanats (a Persian termtaken from the Arabic), have served to sup-ply cities or irrigate lands from the Xth tothe beginning of the XXth century. There arealso some examples of possible roman ori-gin that became extended during Arab ruleand in medieval and modern epochs.

The significance throughout history of thistype of water supply system is such that inMay 2002, the UNESCO recommended itsprotection as a monument of world heritage.

The name given in Spanish to the qanat is“viaje de agua”, or waterway (possible fromthe Mozarabic “via aquae”, Oliver Asín,1958). The many examples of these con-structions include: several channels, ormines, in Barcelona commencing theircourse at tributaries of the Tibidabo river;and the qanats of the Costa Brava (Gerona);Lorca (Murcia); Crevillente (Valencia);Granada; Puebla de Montalbán (Toledo);Córdoba; Ocaña (Toledo); and Madrid – toname but a few.

Among the many qanats throughout thepeninsula, those considered the most splen-did and those most extensively investigatedare the galleries found in Madrid. Investiga-tions to date have been undertaken mainlythrough the cooperation of several organisa-tions under the formal agreement of: “Tech-nical and cultural collaboration for investi-gating the soil and subsoil of the Madridmunicipal area“. This project was launchedin 1982 by the Madrid City Council in con-junction with the Complutense University,the Spanish Ministry of Public Works andUrbanism (MOPU), the Planning and Coor-dinating Commission of the Madrid Metro-politan Area (COPLACO) and the SpanishGeology and Mining Institute (IGME). Theproject's main objectives were to charac-terise the geological and hydrogeological

features of the area, to evaluate the watersystems' potential, qualities and associatedrisks (as a water supply or as a reserve re-source). A further aim was to select some ofthese geological-cultural resources on thegrounds of their scientific, pedagogic andlandscape features from a perspective ofpossible applications in conservation and/orteaching programmes (López-Camacho etal., 1986a).

2. Madrid´s “viajes de agua”

From the times of Arab domination until thewater company Canal de Isabel II (whichpresently supplies the city) was set up in1858, groundwater was the sole source ofwater in Madrid.

Madrid's first settlement arose around theMatrice stream as a small Visigoth village.In the second half of the IXth century,Muhammad Ibn al Rahman founded Mayrit,the northern fort of the Toledo kingdom, toward off invasions from the north of theIberian Peninsula. This led to a populationincrease such that the Matrice stream wasunable to meet the demands of the city's12.000 inhabitants. This deficiency wassoon resolved by the construction of qanats(collecting galleries) to capture groundwater

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Figure 1. The main qanats of Madrid and underlying hydrogeological units

and conduct it to the city, where it could bedistributed (via conducting galleries)through public fountains. Although therewere wells in private estates, these wereonly used for irrigation purposes (López-Camacho et al., 1986b).

Most qanats rest on a detrital hydrogeologi-cal unit comprised of sediments that corre-spond to several facies of alluvial fan devel-opment, infilling the Fosa del Tajo on whichMadrid is built. An upper and lower subunithave been identified (Figure 1):

The higher detrital unit is lithologicallycomposed of more or less clean arkoses,southwardly increasing in fine grain content.The lower detrital unit is characterised by al-ternating arkoses and brown clays, andshows a similar decrease in grain size to-wards the south, accompanied by an in-creased proportion of mud.

There was also a series of hard-water qanats(not shown in Figure 1) in a transition unitcomposed of a set of lithofacies made up ofcarbonates, clays with flints, green clays, se-piolite and micaceous sands.

These channels were constructed by sinkingwells until the saturated zone was reached.The wells were linked by galleries that also

captured water, and were lined or left un-lined depending on the consistency of theterrain. The starting points of these gallerieswere always to the north and east of the cityand were separated by some 7 to 12 Km of1% slope.

The galleries varied in shape and their sizewas such that a person could walk along thegallery. Depending on the terrain's condi-tions, the galleries were generally unlinedand the shape of a “lomo de caballo”, or“horse back”, in cross-section. Othersshowed an arched section and were bricklined (Figure 2).

Water entered the collection galleries underthe force of gravity, running either directlyalong the gallery floor (Figure 3) or along aside channel, or gutter (Figure 4). On arrivalat the city, the qanats branched out to form adistribution network of conducting galleries.These are similar to the collecting galleries,but are lined and fitted with several possible

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Figure 2. Fuente del Berro qanat. Horse-back gallery andlined, arched gallery

Figure 3. Horse-back gallery. Amaniel qanat

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Figure 5. Cast iron pipe. Bajo Abroñigal qanat

Figure 6. Breathing well. Fuente del Berro qanat

Figure 7. Breather cap. Amaniel qanat

Figure 8. Breather. Alto Abroñigal qanat

Figure 9. Course of the Villamalea qanat (Alcalá deHenares, Madrid) indicated by breather caps

Figure 4. Side gutter. Bajo Abroñigal qanat

types of gutter systems (closed gutters, mudor cast iron pipes, etc. Figure 5).

The galleries made contact with the outsideat certain points through aeration wells, orbreathers (Figure 6) capped with a stone orbrick cover (Figures 7 and 8). Often, the po-sitions of these structures allow the courseof the qanat to be mapped (Figures 9 and10).

If the gallery had to change direction duringits course, this was achieved by a “cambi-jas” or small box. Turbid water could be re-moved from the general flow at an “arca” ordrain, that also served to sample the waterin the qanat (Figure 11).

The course of the qanats came to an end atpublic fountains, where initially the waterwas collected by the people. This practicesubsequently gave way to the trade of water-carrier, which soon became an essential fea-ture of the water supply service, and wasdocumented as such in 1950. Besides deliv-ering water to each house, the water-carrier

also ran errands, took on the duties of a fire-man on rainy days when the streets becameimpassable and helped pedestrians cross thestreet (García Cortez, 1950).

The fountains of Madrid were a typical signof urban landscape and included the famousfountains of: San Isidro, Fuente de la Saludin the Parque del Oeste (West Park), LaMariblanca, Fuente de la Alcachofa inAtocha, Fuente de los Once Caños, Fuentede la Reina, etc. Even the monument foun-tains of the Salón del Prado such as that of“Cibeles” or “Neptuno” were fed by these“viajes de agua”.

The first gallery known, was one construct-ed along the course of the Matrice streamspring, which was made reference to in 1202(Oliver Asín, 1958). There are also reportsof an ancient, perhaps Roman, gallery thatwas discovered at an archaeological site in

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Figure 10. Course of the Rey qanat indicated by breathing wells

Figure 12. Roman (?) qanat. Plaza de los Carros

Figure 11. Registry drain. Fuente del Berro

As the Court was transferred to Madrid in1561, the population amounting then to14.000 inhabitants reached 46.000 in 1594(Canal de Isabel II, 1954). This promptedthe opening of several new galleries, whichbecame a constant source of concern for theMadrid government, who set up a “Junta deFuentes”, or “Fountain Committee” in 1617.It was the task of this committee to searchfor new galleries, maintain and repair the ex-isting system, and distribute the water andcontrol its flow (Madrid Moreno, 1896).

Although there is record of isolated meas-ures of the amount of water supplying theqanats since 1761, it was not until 1829 thatdischarge was systematically gauged on atwo yearly basis (Archivo de la Villa, 1761to 1880). Gauging was performed using theso-called “marcos de Madrid”. These weremetal boxes with one side perforated withholes of varying diameter (Figure 13). Theamount of water passing through the holesin 24 hours gave the measure “real de agua”.

This was defined by Ardemans (1724) as thewater that emerges from a tube of the diam-eter of a “real de vellón”, a copper coin pro-

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Figure 13. Discharge registry box (Ardemans, 1724)

Figure 14. Hydrogeological profile of the qanats of Madrid.

the “Plaza de los Carros” (Figure 12). How-ever, the first documented qanat is that of“La Alcubilla” (1399). From this date until1855, in which the Fuente de la Reina wasinaugurated, new conduits were openeduntil a length of 124 Km was attained, ofwhich 70 Km were collecting galleries andthe rest were conducting channels (GilClemente, 1911). Figure 1 shows the mostsignificant qanats of Madrid that are still inuse today.

duced in Spain in 1642. In 1727, Aznar dePolanco described the origin of the so-called“real de agua”, as the circle and area occu-pied by “un real de a ocho”, measured usingthe diameter of five silver coins. The meas-ure is of no significance whatsoever, sincethe water velocity was not taken into ac-count and thus its equivalence with the deci-mal metric system varies for each qanat(Aznar de Polanco, 1727). Madrid's watersystem supplied 3.600 m3/day, which de-creased over the years mainly due to poorconservation. By the middle of the XIXthcentury, discharge did not surpass 2.000m3/day (Canal de Isabel II, 1954). The depthat which the “viajes de agua” lay also posedrestrictions on the water supply; their close-ness to the surface of the saturated zonemaking them highly vulnerable to draught(Figure 14) (De Bustamante et al., 1986).

There is scarce information on water qualitysince it was not analysed on a routine basis.In some documents, there are references tothe “softness of its waters”. Indeed, differen-tiation was made according to this propertyand qanats were described as soft- or hardwater qanats. Aznar de Polanco (1727) madethis distinction as a function of the weight ofan “arroba” of water. On November 2nd1852, the Madrid gazette published the firstfigures derived from the analysis of qanatwater as concentrations in grams per poundof MgCl2, CaSO4, CaCo3, MgCo3, SiO2 andAl2(SO4)3. Water quality was related to thehydrogeological units crossed by the gal-leries. For example, the waters of qanats thatonly cut the higher detrital unit were de-scribed as soft, while those of the qanatscrossing the lower detrital unit were “aguasgordas” (hard), such as the water of theFuente del Berro qanat, still used today.

The Fuente del Berro, set in one of Madrid'smost beautiful parks, is of great historic

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value due to its renowned waters that wereconsumed by members of the royal familyand the inhabitants of Madrid since thetimes of Phillip IV (ca. 1631). Indeed, thepark's appearance has changed through timeaccording to the presence of the fountainand use of its waters.

The unique nature and fame of the watersupplied by the Fuente del Berro is attribut-able to its dissolved salts. This property wasconditioned by the presence of materialsfrom the lower detrital hydrogeological unit,which cuts the channels and enriches its wa-ters with magnesium and calcium salts, in-creasing hardness to around 100 ºF (Frenchdegrees).

The chemical composition of water samplestaken from the northern and southernbranches is shown below. It is of interest thattoday’s criteria for quality (e.g., the popularwater from Lozoya has a markedly lowersalt content and a hardness that does notreach 10 F) differ greatly from those defin-ing the water that was so highly regarded bythe people of Madrid for centuries (Table I,De Bustamante et al., 2001).

The water supply of the Fuente del Berro,which for centuries quenched the thirst ofthe “Madrileños”, was cut off in 1977 due tobacterial contamination. Its water was con-

Figure 15. Fuente del Berro

sequently diverted towards the duck pondwithin the park. On April 16th 1983, aftercleaning and repairing, the fountain wassupplied with water from Madrid's main net-work, the Canal de Isabel II (Figure 15).

3. The qanat of Ocaña

The qanat of Ocaña, an admirable work ofengineering of probable Roman origin withArabic and Medieval elements, is an impres-sive relic due to its 400 m of waterways andmagnificent domed chambers.

The fact that it is so well preserved is attrib-utable to a set of circumstances. The mainone is that it still constitutes a significantpart of the supply route to the town of Ocaña(around 6.000 inhabitants). Further con-tributing factors are careful maintenance onbehalf of the Town Council and perhaps, itsconnection to the spectacular Fuente Gran-de, declared a national monument in 1976.

Ocaña entered into the history of Spain asthe Courts were summoned in the town byJohn II in 1422 and by Henry IV in 1468.Queen Elizabeth “the Catholic” resided inOcaña for some time. Indeed, several re-nowned comedies by Lope de Vega andCalderón de la Barca are set in the town ofOcaña.

The town of Ocaña, or “Villa de Ocaña”, hassince the Middle Ages made use of itssprings emerging from the scarps of two gul-lies in the meseta on which it lies (Figure 16).

Other surrounding springs (Ocañuela,Aljibe, Aldehuela) of the Mesa de Ocaña it-self were captured to supply Aranjuez. Thespring in Aljibe has a gallery of over 300 min length, which in 1970, provided a dis-charge of 11 l/s. From 1745 onwards, allthese galleries and springs were conducted

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Figure 16. Location of the Fuente Grande and it captures(Aranjuez)

Table I. Chemical composition of the water feeding the fuente del berro

North South Branch Branch

Cl- mg/L 57 28

SO4= mg/L 837 595

COH3- mg/L 268 256

NO3- mg/L 86 81

Na+ mg/L 55 49

Mg++ mg/L 85 73

Ca++ mg/L 261 200

K+ mg/L 4 4

TSD mg/L 1652 1.278

pH 7,1 7,0

Hardness ºF 100 80

the quality of the water from the Tagus Riverclose to Aranjuez, which is much harder andsulphated. This explains its capture and tran-sport across a distance of over 10 km to sup-ply the Real Sitio Palace and Mansion sincethe mid 1980s.

The Mesa de Ocaña is a practically horizon-tal plain of around 1.000 km2 surface area,situated in the northeast of the Toledoprovince, some 60 km south of Madrid.Topographically, the meseta lies 100-150 mabove its surroundings and is of an invertedtrough shape. This morphologically charac-terises the geological formations of theparamos. Its highest points range from 700to 800 m.

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Figure 17. Main drain. Ocaña qanat

Figure 18. Geological cross-section indicating captures

towards Aranjuez. In 1757, Ferdinand VIimproved these conduits using glazed pipesfrom Madrid, and constructed many "arcas"or resting places for maintenance and clean-ing (Madoz, 1845-50), some of which maystill be seen (Figure 17). The hardness of thewater collected does not reach an “F” value(French degrees) of 40, and contrasts with

Figure 18 shows a diagram of a cross-sec-tion through the Mesa de Ocaña, in whichthe different lithologies are represented:

a) a series mainly composed of gypsumwith intercalated marls at the base (Mio-cene);

b) overlying this series are lithofaciesformed of marl-gypsiferous materials atthe base, that pass upwardly to marla-ceous, marly limestone and calcareousmaterials (Miocene); it is the upper partof this calcareous or limestone faciesthat is captured by the galleries(Miocene);

c) a packet of white-reddish paramo lime-stones located above the water table; andd) generally clayey covering materials(Pliocene).

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Figure 19. Fuente Grande de Ocaña qanat

Figure 20. Well excavated at the southern branch of theOcaña qanat

Figure 21. Conducting gallery with two channels carry-ing hard and soft water. Ocaña qanat

The Ocaña qanat ends its course at the Fuen-te Grande. The total length of the two maingalleries is some 340 m. The main transportchannel runs in an approximate W-E direc-tion. The collecting channels bear 90 degreejunctions (Figure 19); one that takes a southdirection and another running ENE. Otherbranches have not been fully identified. Themain gallery cross-section is 1.90 m high;its width ranges from 1.30 to 0.80 m. It iscovered with a half-barrel vault.

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Figure 22. Pumping station supplying Ocaña with waterfrom the qanat

The southern branch is the main collectinggallery, due to its greater water supply sinceit also captures water from an excavatedwell (of turquoise coloured waters, Figure20). Its waters are harder (around 70 ºF),since it crosses marly limestone materialsand some gypsum. In contrast, the highereastern branch captures calcareous stretchescarrying softer water, and its water does notsurpass a hardness of 40 ºF.

A peculiar feature of the Ocaña qanat is thatthe different types of water do not mix. Inthe main collecting drain (Figure 17), flowscross such that along the main gallery thatconducts the waters from this drain to theFuente Grande, the waters are delivered intwo channels separated by a central passage:the soft waters of the ENE branch are carriedby a lower channel, and along a parallelchannel further north, flow the hard watersof the southern branch (Figure 21).

In the main transport gallery, some 80 m be-fore reaching the Fuente Grande, the twosmall channels diverge and continue untilthey reach a 200 m3 deposit at a depth of 5m. Water is obtained by pumping upwardsfrom this deposit to supply the inhabitants(Figure 22). Mixing of the waters gives riseto a hardness of 50-60 F. This point consti-tutes the access to the waterway from a

group of houses built in the mid XIXth cen-tury to pump the water using steam-poweredmachines, which were subsequently re-placed by the current electric pumps. Meandischarge provided by collection is around500 m3/day, insufficient to meet the needs oftoday's population.

Over the last years, this supply has beencomplemented with water of inferior qualityobtained from a bore well close to the riverTagus, some 10 km away. Nevertheless, thefact that some supply from the qanat is stillmade use of has meant the survival of thissurprising work of engineering (López Ca-macho and Iglesias, 2001). It is documentedthat in the XVIth century, an engineer – per-haps Baltasar de San Juan- or architect ofHerreran formation, updated the old conduit(Madoz, 1845-50), which was probably ofArabic or perhaps Roman origin.

The main gallery of the qanat, with its twosmall channels transporting water of differ-ent quality, finishes its course at a fountainof Renaissance architecture, whose design isattributed to Juan de Herrera, the architect ofEl Escorial, and was constructed over theyears 1573 to 1578.

Figure 23. Channels for water of varying hardness in theFuente Grande

This impressive monument separately con-ducted soft and hard waters along pipes atdifferent altitudes (Figure 23) to a largedrinking trough used by livestock (Figure24) and two huge washing pools, whichcould be simultaneously used by 300 wash-er-women (Figure 25).

The fountain stands in a large stone plaza ofsome 2.000 m2 (Figure 26) and is accessedby a ramp and double masonry staircase. Itis closed in its eastern part by a portico of 20pillars that support a two-way roof. It is tothis point that the waters from the galleryflow via 20 copper pipes (Figure 27). The

central part of the portico has narrow passesor port holes that act as overflows for runofffrom storms, avoiding water accumulationbehind the portico. Further, to avoid floodsproduced by heavy rainfall affecting boththe land along which the qanat runs and thefountain itself, a millrace was built to divertthe rain around the washing trough towardsthe fountains (Figure 28).

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Figure 25. Washing pools. Fuente Grande

Figure 24. Livestock drinking trough. Fuente Grande Figure 26. Fuente Grande

Figure 27.Bronze pipes. Fuente Grande

The waters are channelled in such an order-ly, well-thought out manner, that the excesswaters from the channels, troughs and de-posits were collected and transported alonga tunnel to the outside of the fountain to irri-gate the neighbourhood crops.

References

Ardemans, T. (1724). Fluencia de la Tierra ycurso subterráneo de las aguas. Biblioteca Na-cional, pp 88-149. Madrid.Archivo de la Villa (1761-1880). Aforos de losviajes. (several documents).Aznar de Polanco, J.C. (1727). Aritmética ygeometría práctica y especulativa; origen de losnacimientos de aguas dulces y gordas de la Villade Madrid, sus viajes subterráneos, con las noti-cias de las fuentes públicas y secretas de las casasde los señores particulares. Biblioteca Nacional.Madrid.Canal de Isabel II (1954). Los primeros 100 añosdel canal de Isabel II. Memorias 1946-1950.COPLACO, 437 pp. Madrid.

De Bustamante, I.; López-Camacho, B.; Bas-cones, M. (2001). The Fuente del Berro (Madrid).Science and technology for the safeguard of cul-tural heritage in the Mediterranean Basin. 9 pp.CD-ROM. Serv. Pub. UA. Madrid.De Bustamante, I.; Bascones, M.; López-Cama-cho, B. (1986). El abastecimiento histórico deaguas subterráneas a Madrid. Publicaciones de laComunidad de Madrid. Vol. 12: 103-116. Madrid.García Cortez (1950). Madrid y su fisonomía ur-bana. Secc. Cult. Infor. Artes Gráficas Munici-pales. Madrid.Gil Clemente, J. (1911). Expediente instruidopara el saneamiento de las conducciones de aguasde los viajes antiguos a Madrid. Archivo de lavilla, legajo: 21-117-25. Madrid.Madrid Moreno, J. (1896). Las aguas potablesde la Villa de Madrid. Imp. Y Litogr. Municipal.Madrid.Madoz, P. (1845-1850). Diccionario geográfico-estadístico-histórico de España. 16 Vol. Madrid.López-Camacho, B.; Bascones, M.; De Busta-mante, I. (1986a). El agua subterránea en Madrid.Bol. Inf. Est. 128 pp. MOPU.López Camacho, B.; Bascones, M.; Bustamante,I. (1986b). Antecedentes del Canal de Isabel II:Viajes de Agua y Proyectos de Canales. Canal deIsabel II. Madrid. 199 pp.López-Camacho, B.; Iglesias, J.A. (2001). Theqanat of the Fuente Grande of Ocaña (Toledo).Science and technology for the safeguard of cul-tural heritage in the Mediterranean Basin. 7 pp.CD-ROM. Serv. Pub. UA. Madrid.Oliver Asín, J. (1958) Historia del nombre deMadrid.. Inst. Oliver Asín, CSIC, 412 pp. Madrid.

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Figure 28. Rain channel. Fuente Grande