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CAVES AND KARS AQUIFER DRAINAGE OF SUPRAMONE(SARDINIA, IALy): A REVIEW

JAME IN KRAKI ODOK V GOROVJU SUPRAMONE

(SARDINIJA, IALIJA): PREGLED

Salvatore CABRAS1,2, Jo DE WAELE2,3 & Laura SANNA2,4

Izvleek UDK 556.34450.88Salvatore Cabras, Jo De Waele & Laura Sanna: Jame in kraki

odtok v gorovju Supramonte (Sardinija, Italija): Pregled.Supramonte je eno najvejih in najzanimivejih krakih regijna Sardiniji. V zadnjih petdesetih letih so v gorovju raziskali

ve velikih jamskih sistemov. e prvi jamarji in raziskovalci sonaredili nekaj sledilnih poskusov z barvanjem, vendar takrat

vejih podzemnih tokov e niso poznali. V zadnjem desetletjuso odkrili veji podzemni vodni sstem, ki je omogoal iz-

vedbo novih sledilnih poskusov. V lanku pregledno opiemozgodovino speleolokih, morolokih in hidrolokih raziskavobmoja, posebno pozornost pa namenjamo rezultatom sledil-nih poskusov. Namen lanka je celostno prikazati razultatenovejih raziskav v tem pomembnem krakem masivu.Kljune besede: Speleologija, podzemni odtok, jamska mor-ologija in hidrologija, hidrogeologija, sledilni poskusi.

1 Gruppo Archeo Speleo Ambientale Urzulei2 Associazione Speleologica Progetto Supramonte3 Dipartimento di Scienze della erra e Geologico-Ambientali, Universit o Bologna, e-mail jo.dewaele@unibo it4 Gruppo Speleo Ambientale Sassari

Received/Prejeto: 19.8.2008

COBISS: 1.01

ACA CARSOLOGICA 37/2-3, 227-240, POSOJNA 2008

Abstract UDC 556.34450.88Salvatore Cabras, Jo De Waele & Laura Sanna: Caves and

karst aquifer drainage of Supramonte (Sardinia, Italy): A re-view.Supramonte is one o the biggest and interesting karst areas oSardinia Ital, hosting extensive cave sstems explored sincethe 50s. Earl cavers and scientists have carried out some detests, but hdrogeological research was hindered b lack o ac-cessible underground rivers. A complex subterranean river ss-tem has been discovered in the past decade enabling to organ-ise several new tracer tests. Te histor o cave explorations, themorpholog and hdrolog o the sstems and the de tracingexperiments are reviewed in this paper in order to give an up-dated view on hdrogeolog o this important karst area.Keywords: Speleolog, underground drainage, cave morphol-og and hdrolog, hdrogeolog, de tracer tests.

INRODUCION

Te understanding o karst hdrolog has improved alot in the past decades and several reviews Bakalowicz2005; Pulido Bosch 2001; White 2002 or state o the artpublications Andreo 2008; Goldscheider & Drew 2007have been printed recentl.

Karst aquiers show exceptional heterogeneous

permeabilit distribution with water moving along in-tergranular pores, more or less open ractures and con-

duits Gabroveket al. 2004. Tis makes karst aquiersextremel difcult to model Gabroveket al. 2005, and

vulnerabilit assessment can be a complicated task Dalet al. 2002; Perrin et al. 2004.

I underground drainage routes are not accessible,the karst aquier can be studied b monitoring at the

springs. Especiall the analsis o hdraulic Labat et al.2002 and phsico-chemical response o a spring to re-


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ACA CARSOLOGICA 37/2-3 2008228

charge events (Birket al. 2004; Desmarais and Rojstacz-er, 2002) is an extremel useul tool in characterising thekarst aquier. Tese investigations can give an idea o thestructure o a karst sstem, e.g. whether it is organisedin a well-developed underground drainage or rechargedb water owing in a ssure network. Te insight on h-

drodnamic behaviour o underground water ows canbe studied directl i caves with subterranean rivers areaccessible (Preloveket al. 2008).

Determining karst groundwater divides is not astraightorward task. Te boundaries between adjacentkarst groundwater basins can var in dierent hdrolog-ical conditions (e.g. oods) or because o piracies. Detracing experiments can determine connections betweenconcentrated inlets (e.g. swallow holes) or losing streams(Field 2006) and outlets (springs) (Goldscheider et al.2008; Kss 1998; Lerch et al. 2005) i groundwater isnot directl accessible through caves. A combination o

short- and long-term tracer tests enables to dene thoseow paths that are activated in varing hdrological con-ditions (Gppert & Goldscheider 2008). Especiall instudies on vulnerabilit assessment o karst aquiers itcan be extremel important to monitor potential outletsover at least one ear in order to determine possible owpaths o contaminants in dierent hdrological condi-tions (Kogovek and Petri 2004, 2006).

Cave exploration is a valuable aid in studing karstaquiers, since discoveries o active caves allow direct ob-servation o underground ow paths and enhance detracing experiments (Huselmann et al. 2003; Smart,1988; Staut & Auersperger 2006; White 2007). Wheresurace drainage is particularl ephemeral, such as in

South Mediterranean areas, the discover o streams incaves makes it possible to carr out de tracing tests dur-ing most o the ear.

Recent explorations in Supramonte karst massi(Sardinia, Ital) have enabled speleologists to access ac-tive caves and nd important underground rivers (Ca-bras et al. 2000; Crobu 2003; Crobu & De Waele 2007; DeWaele 2003). Tese ke discoveries have allowed to orga-nise several de tests with sodium uorescein (Uranine),placing charcoal bags deep in caves. Tis paper gives asummar o the present speleological and hdrologicalknowledge o this signicant karst aquier, describing all

the de tracing experiments in detail. Tis will help oth-er researchers and hdrogeologists to make more reliable

vulnerabilit maps based on updated speleological dataoen o difcult access to people not amiliar with cavepublications (Barrocu et al. 2007).

GEOGRAPHICAL, GEOLOGICAL AND HyDROLOGICAL SyNHESIS

Supramonte is a karst massi located in the Central-East-ern part o the island and occuping an area o approx-imatel 170 km2, almost 80% o which is composed ocarbonate rocks (Sanna et al. 2002) (Fig. 1). It is charac-terised b an almost 1 km thick Middle Jurassic-UpperCretaceous sequence composed o dolostones and lime-stones covering a crstalline Palaeozoic basement madeout o granites and metamorphic rocks. Te whole se-quence has been olded and aulted during ertiar dis-plaing main N-S and NE-SW directions (Pasci 1997).

Te overall structure o karst massis greatl inuencesthe hdrogeological asset (Goldscheider 2005), and Su-pramonte is no exception.

Allogenic surace waters owing rom the Palaeo-zoic basement (altitude around 1400 m a.s.l.) are di-rected underground as soon as the reach the racturedbasal dolostone ormation, in the Southern part o Su-pramonte. Underground drainage ollows the inclinationo the bedrock close to the contact with the carbonaterocks, along major aults and axes o olds (snclines oLanaitto, Flumineddu-Gorropu and Campu Oddeu-Or-

bisi) showing a general direction rom South to North.owards the East and the West the carbonate aquier islimited b the permeabilit threshold o the Palaeozoicbasement located at higher altitudes (Sanna et al. 2002)(Fig. 2).

Tus, main inlets o the sstem are located inSouth Supramonte (see Fig. 3 or locations). SEderacave drains several small allogenic streamlets comingrom the South and directs water underground towardsthe North. Tis cave represents the southernmost part

o the main hdrological sstem. Water is not com-pletel drained b SEdera cave sstem during impor-tant oods and ows urther to the North-East and iseventuall swallowed in the Orbisi sinkhole. Tis caveis part o a smaller independent karst sstem compris-ing the Luigi Donini cave and the Giuseppe Sardu shaand has its outlet probabl at Gorropu spring, in thecentral eastern part o Supramonte. Since no de trac-ing experiments have been carried out in this part oSupramonte, this smaller satellite sstem will not bediscussed in this paper.

SALVAORE CABRAS, JO DE WAELE & LAURA SANNA


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ACA CARSOLOGICA 37/2-3 2008 229

Fi. 1: geoloical sketch ma o Suramonte (modifed rom pasci, 1997).

Te biggest river o thearea, Riu Flumineddu, iscaptured along its upstreamcourse b several swallowholes, the most important owhich is known under the

name Sa Funga e SAbba. Fur-ther downstream man otherswallow holes are known andsome o these give access toimportant caves discussedlater in this article.

Te main outlets o thekarst sstem are located 20km to the North o SEderacave, along the northernborder o Supramonte. Herelithological and structural

constraints orce the subter-ranean water to fow out othe sstem though a series osprings. Te most importanto these are Su Gologone, Suippari and San Pantaleo,the rst being captured ordrinking water purposes, theother two almost permanent-l drowned b the articiallake caused b the Pedra eOthoni dam, built on Cedri-

no river De Waele 2008.Beore the discover-

ies o the last 10 ears, waterfowing in SEdera cave wasbelieved to exit at Gorropuspring Assorgia et al. 1973.Geological and structuralevidence does not rule outthis possibilit, but a connec-tion between SEdera caveand Lanaitto valle and thusthe northern springs was re-

tained highl probable San-na & Vernier 1993.

ACCESSIBLE UNDERGROUND DRAINAGE NEWORK

More than 400 caves are known in Supramonte but onlaround 2 % o these are characterised b the presenceo important groundwater bodies. Te most important

o these caves are described below and their location isshown in Fig. 3.

CAVES AND KARS AQUIFER DRAINAGE OF SUPRAMONE (SARDINIA, IALy): A REVIEW


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Fi. 2: geoloical schematic cross-sections (eoloical profles modifed rom Sanna et al. 2002); or location see Fi. 1.

SHOR HISORy OF EXPLORAIONSSstematic explorations started in Supramonte massionl relativel recentl, with the Su Bentu-Sa Oche cavesstem (North-Supramonte) in the 50s (Columbu 1955)and the discover and exploration o the rst 3 km o SaRutta e SEdera cave (South-Supramonte) in the nalears o the 60s (Assorgia et al. 1973). Man cave associa-tions o various nationalities have worked in the area, butwithout getting into the heart o the sstem. Te major

discoveries are related to: (a) Su Bentu-Sa Oche cave ss-tem, surveed or around 15 km b the Gruppo GrotteNuorese (Carta et al. 1988) and still object o explorationever ear; (b) SEdera cave, that doubled its development(rom 3 to 6 km) (Scano 2002); (c) the descent o mandeep shas, none o which however reached importantactive river parts (Fercia & Pappacoda 1992). Tese ear-lier researchers thought that Supramonte was composedo two independent karst aquiers: SEdera cave was be-lieved to drain the southern part o the massi with themajor spring at Gorropu gorge, while the bigger outletslocated along the northern border o Supramonte (SuGologone, San Pantaleo springs) had their recharge inthe surroundings o Lanaitto valle (Assorgiaet al. 1973).Tis dogma was abandoned when a de test carried outin 1999 (Bandiera 2000) unequivocall showed that Su-pramonte is a single karst aquier, in which an enormoussstem o galleries and tunnels could be discovered. Tishas lead to an escalation o speleological explorationsand surves.

Te rst discover o an underground river goesback to spring 1998, when cavers o the Gruppo ArcheoSpeleo Ambientale o Urzulei and Gruppo Speleo Am-

bientale Sassari discover Sa Rutta e Mandara e SUruManna, 2,000 m o ssures, small shas and gallerieswith an entrance 30 m above Flumineddu river bed, onthe right side o the canon (Cabras et al. 2000). Lessthan 1 km downstream, still on the right side o Flu-mineddu and 10 m above the river bed, another activecave, Su Colostrargiu, is discovered b independentcavers in 2000. Tis cave, aer urther exploration in2006, is 1,500 meters long and ends in a boulder choke

that abruptl blocks a river passage at a bit more than150 m depth (Crobu 2003).

In autumn 2001, 2 km downstream Su Colostrargiu,still at the right side o the canon but this time almoston the canon foor (subject to fooding during winters)another important, but this time 340 m deep and 1,500m long, cave is discovered and explored: SOrale e SuMudrecu (also called VPF) (Crobu 2003). During thewinter o 2002, 1 km downstream VPF and onl a ewmeters above the canon foor, the most important caveentrance is ound, Su Eni e Istettai, surveed during 2003up to a depth o 360 m. Here a small underground river

is ollowed up to a small sump, which is passed in apneabut gives access to a narrow galler that apparentl endsin a boulder choke (Crobu & De Waele 2007). In thesame summer several cavers operate inside SEdera cavesucceeding in passing the since 40 ears unviolated nalbreakdown, discovering over 500 m o underground gal-ler up to a nal sump that will later be explored b cavedivers o the Federazione Speleologica Sarda (De Waele2003; uveri & Moi 2006). At the end o the summer,together with the cavers o the Groupe Ulsse Splo oLon, other 2 km o new conduits are discovered behind



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Fig. 3: Supramonte karst area with major caves and springs.

the upstream Sa Funga e SAbba sump in SEdera cave.Cave divers Vincent Lignier and Slvestre Condaminexplore huge passages that are onl partiall surveeddue to lack o time. Tese passages will be thoroughlexplored and surveed the ollowing summer b 6 cav-ers o the Groupe Ulsse Splo and Gruppo Speleo-Ar-cheologico Giovanni Spano Cagliari, with other 2 km o

new passages making SEderalonger than 13 km De Waeleet al. 2006.

Also at Istettai the mainunderground river o Supra-monte is at last reached b

Vittorio Crobu and MarcelloMoi in September 2004, butanother food season obligesthe explorers to wait severalmonths again Cossu et al.2007. Te ollowing sum-mer the explorers are able todescend this main river up to450 m depth and during thesummer o 2006 all exploredpassages are surveed, total-ling a development o 4200 m

Crobu & De Waele 2007.Aer the December 2004exceptional fash food, inthe southern part o Lanaitto

valle a new temporar over-fow is discovered in alluvialboulders. Tis cave, exploredb cavers o the Speleo ClubOliena, consists in 200 mo phreatic galleries endingin a sump which could be ahpothetical access to an un-

derground tributar o the SuGologone spring. During theollowing ears cave diversDiego Vacca, Sandro uveriand Luca Sgualdini explore 5sumps surveing urther 250m o conduits and stoppingin ront o a boulder chokeCapra 2007.

Te past two sum-mers have been dedicated toSOrale e Su Mudrecu VPF

where, aer exploration inapnea o two small sumps, 2km o new and huge galleriesare discovered and partiall

surveed up to another sump, behind which the cavecontinues with similar dimensions. At present the cave isaround 4.6 km long Associazione Speleologica ProgettoSupramonte 2007; De Waele et al. 2008.



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CAVE MORPHOLOGy AND HyDROLOGyOnl some caves with a perennial subterranean waterow have been used or hdrological investigations usinguorescent des. Tese caves are here shortl described.

Sa Rutta e SEdera is the main cave sstem exploredor a total development o approximatel 13 km (De

Waele 2003; uveri & Moi 2006). It has an entrance at950 m a.s.l. and descends rapidl along enlarged ssuresin dolostones or 50 meters where a small river (1-3 l/sin average) is encountered (Fig. 4a). Tis small rivuletmeets a greater subterranean river at 760 m a.s.l. bringingwater rom the southeastern ank o Serra Lodunu andhaving an average ow o 20 l/s. Tree hundred metersdownstream o this conuence another major inlet is en-countered coming rom the West. Tis tributar conveswater rom the swallow holes in the Riu Flumineddu (SaFunga e SAbba, 892 m a.s.l.). From here on a uniqueriver having a ow rate o 50 l/s in average is ormed and

continues or another 1,5 km without receiving urthertributaries and orming several sumps, disappearing inthe nal sump at 740 m a.s.l.

Several entrances o active caves are located alongthe course o Riu Flumineddu. Sa Rutta e Mandara eSUru Manna cave is located at 870 m a.s.l., approximate-l 2 km downstream o Sa Funga e SAbba swallow holeand 500 metres downstream o Badu Ogotza, a series opermanent pools ed b some small perennial springsand a brook (Sas Venas). Tis cave is entirel developedalong ssures and bedding planes in dolostones. Water isound at 780 m a.s.l. on the contact with basal dolostones

along Ortorgo Trust and ows in a Southeast direction(Fig. 4b). Te active part ends in a tunnel at 750 m a.s.l.with a nal sump o difcult access and not et explored.Average ow rate is around 0.7 l/s (Cabras et al. 2000;Sanna & Cabras 2008).

Su Colostrargiu cave is located 700 m downstreamat 825 m a.s.l., a little beore the conuence between RiuFlumineddu and Badde ureddu. Tis cave, entirel de-

veloped in dolostones, reaches the Palaeozoic basementat an altitude o 740 m a.s.l. where an underground riveris ound with an average ow rate o 5 l/s (Fig. 4c). Tiswater comes rom several swallow holes present along

the course o Badde ureddu, less than a km to the West.Tis river can be ollowed, with difcult, or a length oaround 500 meters where it disappears into a nal boul-der choke, at 673 m a.s.l. (De Waele et al. 2007).

Another important underground stream is oundin the deep SOrale e Su Mudrecu cave, that has its en-trance two km downstream at 790 m a.s.l.. A river withan average ow rate o 4 l/s is encountered here at 470m a.s.l. (Fig. 4d). Tis river disappears in small passagesclose to the contact between dolostones and Palaeozoicbasement at 440 m a.s.l. and ows towards the North

where no active caves are known. Te water can also beollowed upstream, passing two small sumps in apnea,or a total length o about 2 km up to a nal sump, atan altitude o approximatel 630 m a.s.l. (Crobu 2003).Te provenance o this stream is still unknown. Recentlit has been demonstrated that at least part o this water

comes rom Mandara e SUru Manna.Su Eni e Istettai is the deepest cave o the region

(and o the Island), located 1 km downstream o SOralee Su Mudrecu. Here a perennial small rivulet is ound at460 m a.s.l., and this small tributar meets with the ma-

jor underground stream, aer a technicall difcult cavepart, at approximatel 400 m a.s.l. Te main river can beollowed or about 100 meters upstream, where it owsout o an impressive dolostone boulder choke. Tis wa-ter has been proved to come rom SEdera cave, located300 metres higher and at a distance o around 3 km. Teriver can be ollowed or 1.5 km downstream (Fig. 4e) up

to the nal boulder choke, at 310 m a.s.l. (Crobu & DeWaele 2007).

From this point northwards no active caves areknown and subterranean water ow appears to concen-trate at a depth rom surace o at least 400-500 metres.owards the North, the rst caves in which importantwater ow is encountered are located around the Lanait-to sncline valle, at a distance o approximatel 10 kmrom the nal part o Istettai cave.

Su Venadore de Corojos cave is the lowest cave en-trance in the Lanaitto valle (168 m a.s.l.). It is locatednear the important Su Bentu-Sa Oche karst sstem, on

the other side o the valle, and is characterised b asub-horizontal clindrical conduit interrupted b smallsumps with big scallops on the cave walls. It is 450 mlong developing in South direction and is completelooded or most o the ear. Tis cave could represent anoverow o SEdera Su Gologone underground drain-age sstem (Capra 2007).

Te Su Bentu-Sa Oche cave sstem has been exploredor more than 15 km (Carta et al. 1988; Murgia 2007) andis characterised b an underground canon and severaltunnels o considerable dimensions developed at approx-imatel 130-150 m a.s.l. reaching several sumps around

105 m a.s.l.. All these sumps, where explored, give accessto a network o phreatic passages (Murgia & Fancello2000). In normal conditions there is no water owing inthe sstem, but during oods the water level in the sumpsrises more than 30 meters and starts owing through thecanon leaving the sstem at the Sa Oche entrance, reach-ing ow rates exceeding 10 m3/s.

Te Su Gologone spring is the major and bestknown outlet o the Supramonte karst aquier (Fig. 4).wo other important springs (Su ippari and San Panta-leo) are unortunatel almost permanentl drowned b



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the water o the Pedra e Othoni dam built on the Ce-drino river some km downstream o Su Gologone. Tesame Su Gologone spring is subjected to fooding onceor twice a ear, when heav rainalls ll the reservoir toorapidl to allow water to fow out o it, rising the waterlevel in the articial lake De Waele 2008. Su Gologoneis located at 104 m a.s.l. and has been explored b Ol-

Fi. 4: Caes o hydrooica i-ortance: A. pothoe aon therst streaet encountered inSEdera cae (photo Riccardo Deluca); b. Injection o fuorescentdye in the sa underround

rier o mandara e SUru manna(photo laura Sanna); C. Water-a aon the strea in Su Co-ostrariu cae (photo vittorioCrou); D. Watera and ake inthe Atoo Roo in SOrae e Sumudrecu Cae (photo vittorioCrou); E. Wateras and raidsaon the ain coector streain SEni e Istettai cae (photovittorio Crou); F. Su gooonesrin showin reenish fuores-cent dye aer the tracin exeri-

ent carried out in Seteer2007 (photo laura Sanna).

ivier Isler up to a depth o 107 m, thus going 3 m belowsea level Fancello 1997. Its mean minimum outfow isaround 100 l/s with peak discharges during foods thatexceed 10 m3/s Sanna 1995.



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Fig. 5: map showing certain andpresued hydrological connec-tions between caves and springs.

Since the two rst de tracing experiments o 1967 and1969, in the past 10 ears a total o 8 more de injectionshave been carried out in recentl discovered caves withunderground streams. Tese experiments with theirinjections points and monitored caves and springs areshown in Fig. 5.

JULy 1967In the summer o 1967 the earliest cave explorers

o Sa Rutta e SEdera carried out a de trace experimentdissolving 3 kg o Methlene Blue in water disappear-ing in the Funga e SAbba swallow hole. In the westernbranch o SEdera cave rom which a large amount owater comes, pH analsis gave positive results aer 12hours, indicating a possible connection between thesetwo points (Assorgia et al. 1973).

AUGUS 1969o ascertain this connection, this time using a more

reliable method, two summers later the same tracingexperiment was repeated using 4 kg o fuorescent deUranine injected in Sa Funga e SAbba swallow hole andinstalling charcoal detectors at SEdera cave, Gorropuspring and Su Gologone spring. Onl SEdera cave waspositive aer 18 hours, while the de wasnt traced atboth springs also aer urther injection o other 5 kg ode (Assorgia et al. 1973).

JUNE-SEPEMBER 1999Aer 30 ears cavers o the Gruppo Archeo Spe-

leo Ambientale Urzulei and Gruppo Speleo AmbientaleSassari injected 10 kg o Uranine in SEdera cave, down-stream o the Funga e SAbba confuence. Flow rate at

time o release was estimatedin 60 l/s. Te charcoal detec-tors were placed at Gorropuand Su Gologone springsand in the nal lake o a cave1 km upstream Gorropu (Gi-useppe Sardu cave). Te dewas visible at Su Gologone atnaked ee approximatel 70das aer the injection, con-rmed also b positivit ocharcoal detectors, while allother monitored points werenegative or the ollowing 2months (Bandiera 2000).

NOVEMBER 2001In the earl winter o

2001 a de trace experimentwas carried out in the up-stream part o Fluminedduriver. One kg o Uranine wasdissolved at Badu Ogotzaswallow hole putting char-

coal detectors inside Manda-ra e SUru Manna cave andSEdera cave (downstreamconfuence with Funga eSAbba tributar). Te un-

DyE RACING EXPERIMENS



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derground stream o Mandara e SUru Manna was posi-tive aer 14 das, while SEdera cave remained negativeor two months Crobu & De Waele 2007.

MAy-JULy 2002

Te de tracing experiment o 1999 has been re-peated b the Sardinian Federation o Speleologists witha smaller quantit o Uranine 5 kg and monitoring SuGologone spring with a G-GUN uorimeter Politec-nico di orino rom the end o Ma to 7 Jul makingmeasurements ever 4 minutes almost 15,000 analsis.Te de was released the 1st o Ma in SEdera cave withan estimated river owrate o 120 l/s. In this experimentalso the nal sump o Su Bentu cave has been equippedwith charcoal detectors. Te de tracer has onl beenclearl registered at Su Gologone spring, the uorimeterrevealing uorescein on Ma 26th reaching maximum

value o 4.5 ppb one week later between June 2nd and4th ollowed b a slow decrease with concentration o 0.5ppb on Jul 7th, when the monitoring was ended Fig. 6.Minimum uorescein transit time can be estimated in26 das with an average ow velocit o 33 m/h, meantransit time instead is 34 das giving an average velocito 27 m/h. Te total amount o uorescein discharged atthe spring, estimated on the basis o the restitution graphand the ow rate during time o monitoring ranging be-tween 400-500 l/s, was 2.5 kg Cabras et al. 2002, dem-onstrating that part o the de was withheld in the aquier

or discharged in other springs, like the ones submergedb the articial lake o Cedrino De Waele 2008. Teslightl positive charcoal detector collected at Su Bentucould indicate arrival through difusion o Uranine, butthis result is retained not trul reliable.

SEPEMBER 2002Another small de tracing experiment has been

carried out with 1 kg o Uranine in the autumn betweensome swallow holes along Badde ureddu and Su Colos-trargiu and SOrale e Su Mudrecu caves. Te uorescentde was clearl visible at naked ee in Su Colostrargiucave 8 das aer injection Crobu & De Waele 2007 andwas also retraced in the charcoal detector taken romSOrale e Su Mudrecu several months later. Te connec-tion between Badde ureddu sinks and Su Colostrargiuis unmistakabl proved, but that between the two caves,

nevertheless, is unreliable since around 10 das aer deinjection the surace drainage network activated due toheav rainall, and remaining Uranine could probablhave been brought to SOrale e Su Mudrecu along RiuFlumineddu.

SEPEMBER 2004With the discover o the river at Su Eni e Istettai

in September 2004, a de tracing experiment was im-mediatel set up to ascertain that this river is efectivelthe same disappearing in the nal sump at SEdera cave.


Fi. 6: breakthrouh Curve reistered at Su goloone sprin durin the 2002 tracer test (modifed rom Caras et al. 2002).


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wo kg o Uranine de were injected downstream theFunga e SAbba tributar in SEdera cave and appearedonl twelve das later in Istettai, visible at naked ee.Tis result designates the main underground water owin South Supramonte (Crobu & De Waele 2007).

JULy 2006Te connection between SEdera and Istettai didnt

give an answer to the most important question about thedirection o rivers owing in Mandara e SUru Manna,Su Colostrargiu and SOrale e Su Mudrecu. Te rst in-dications arrived rom a de tracing experiment carriedout with 1 kg o Uranine at Mandara e SUru Manna cavein the summer o 2006. Charcoal detectors were placedinside Su Eni e Istettai, Su Colostrargiu and Su Venadorede Corojos caves. Aer 14 das charcoal detectors werepositive at Istettai, while the de has not been registeredinside Colostrargiu. At Su Venadore de Corojos, instead,

the charcoal detector sampled several months aer thetest also gave a positive result. Tus, water inltrating atBadu Ogotza pools transits in Mandara e SUru Mannacave and, ollowing unknown underground paths, ap-pears in Istettais river (Sanna & Cabras 2008). Su Vena-dore de Corojos cave seems to be located close to and incontact with at least one o the underground ow pathsrom Istettai to Su Gologone.

JULy-SEPEMBER 2007Te second answer arrived with the injection o

2 kg Uranine in Su Colostrargiu cave and the installa-

tion o charcoal detectors in SOrale e Su Mudrecu caveand at Su Gologone spring. Te charcoal bag in the caveremained negative or three months, while Su Golog-one spring, located 13 km South, started releasing theuorescent de approximatel 56 das aer injection.Tis resolves our doubts on the positive results obtained

during the September 2002 test and denitivel proosthat Su Colostrargiu and SOrale e Su Mudrecu streamsare independent and are tributaries o the main under-ground stream connecting SEdera and Istettai havingtheir conuence downstream, beond the nal boulderchoke o Su Eni e Istettai (De Waele et al. 2008; Sanna &Cabras 2008).

JULy-AUGUS 2008Te most recent de tracing test has been carried

out at Mandara e SUru Manna cave, with the injectiono 0.9 kg o Uranine and the monitoring o SOrale e Su

Mudrecu underground stream and Su Gologone spring.Aer about 20 das, the uorescent de was visible atnaked ee inside the cave and about one month lateralso in the charcoal detector placed at the spring. Tisresult, however, still doesnt clari the relationship be-tween SOrale e Su Mudrecu and Su Eni e Istettai cave.It is however clear that the small streamlet o Mandara eSUru Manna cave eeds both cave rivers (this is the rstcase o difuence in Sardinia). Water owing in SOralee Su Mudrecu cave, instead, reaches Su Gologone with-out passing Istettai, directing southwards through down-stream unknown passages.

SUMMARy AND DISCUSSION

Te discover o cave sstems with underground wa-ter ows has allowed to carr out a series o de tracingexperiments with the aim o dening the subterraneandrainage divides and the connections between caves andwater ows. Beore the discover o these caves water wasthought to ow rom SEdera cave to the nearest Gorropuspring, although tracing experiments carried out in 1967and 1969 did not give positive results. With the de trac-ing experiment o 1999 all doubts were cancelled, and asegment o this 20 km long underground route has beendiscovered in Istettai cave as demonstrated b the 2004de test.

All these de tracing experiments, especiall thosecarried out in several newl discovered caves, have en-abled to draw the ollowing conclusions (Fig. 7): (1)water o Riu Flumineddu entering in the upstream SaFunga e SAbba swallow hole enters SEdera cave and

conuences with the main underground river o SEderaat approximatel 1 km o the entrance; (2) water sink-ing at SEdera cave combines with the Sa Funga e SAbbatributar, disappears in the nal sump at 1.5 km romthe entrance, ows along unknown paths under MonteUnnoro, through Istettai cave and nall disappears inthe terminal boulder choke in northward direction; (3)the Badu Ogotza pools, 2 km downstream o Sa Fungae SAbba swallow hole, drain water towards Mandara eSUru Manna cave, disappearing in its nal sump at 500m rom entrance and joining, along unexplored under-ground paths, the rivers owing through Istettai andSOrale e Su Mudrecu caves; (4) the Badde ureddusinkholes carr water into Su Colostrargiu cave, whereit can be ollowed or 500 meters to the nal choke, romwhere it continues along unknown routes in northwarddirection reaching Su Gologone spring; (5) the river



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discovered inside SOrale e Su Mudrecu has partiallunknown origin rom the South, a minor part comingrom Mandara e SUru Manna cave and disappears in

northward direction withunknown destination to-wards Su Gologone spring;6 uorescent des can bedetected in the downstreamcaves around Lanaitto Valleonl through difusion, sinceall these caves reach the karstwater table but no importantcurrents are observed.

In the near uture a detracer experiment is pro-grammed in SOrale e SuMudrecu cave, and continu-ous monitoring o the SuEni e Istettai cave and theSu Gologone spring is beingcarried out. Further speleo-

logical explorations will also help us in understandingmore about this continuousl evolving undergroundlandscape.

Table 1: Tracing exeriments carried out in Suramonte since 1967.

Year Dye injection in Amount and name of

dye injected

Charcoal detector in Dye results Mean

transit

time

1967 Sa Funga e SAbba Sinkhole 3 Kg Methylene Blue Sa Rutta e SEdera Cave Positive 12 h

1969 Sa Funga e SAbba Sinkhole 4 Kg Na-Fluorescein Sa Rutta e SEdera Cave Positive 18 h

Sa Rutta e SEdera Cave 5 Kg Na-Fluorescein Su Gologone Spring Unknown

Gorropu Spring Unknown

1999 Sa Rutta e SEdera Cave 10 Kg Na-Fluorescein Su Gologone Spring Positive 70 days

Gorropu Spring Negative

G. Sardu Cave Negative

2001 Badu Ogotza Pools 1 Kg Na-Fluorescein Mandara e Suru Manna Cave Positive 14 days

Sa Rutta e SEdera Cave Negative

2002 Sa Rutta e SEdera Cave 5 Kg Na-Fluorescein Su Gologone Spring Positive 34 daysSu Bentu Cave Doubtful

2002 Badde Tureddu Sinkhole 1 Kg Na-Fluorescein Su Colostrargiu Cave Positive 8 days

SOrale e Su Mudrecu Cave Doubtful

2004 Sa Rutta e SEdera Cave 2 Kg Na-Fluorescein SEni e Istettai Cave Positive 12 days

2006 Mandara e Suru Manna Cave 1 Kg Na-Fluorescein SEni e Istettai Cave Positive 14 days

Su Venadore de Corojos Cave Positive Unknown

Su Colostrargiu Cave Negative

2007 Su Colostrargiu Cave 2 Kg Na-Fluorescein Su Gologone Spring Positive 56 days

SOrale e Su Mudrecu Cave Negative

2008 Mandara e Suru Manna Cave 0,9 Kg Na-Fluorescein SOrale e Su Mudrecu Cave Positive 20 days

Su Gologone Spring Positive 50 days

Fig. 7: pie diagram o the Sura-monte active conduit fow systembased on hydrological and directobservations (not to scale).

CAVES AND KARST AQUIFER DRAINAGE OF SUPRAMONTE (SARDINIA, ITALy): A REVIEW


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ACKNOWLEDGEMENTS

We would like to thank all cavers that have substantiallyhelped during all the phases o these 10 years, and es-pecially Silvia Arrica, Carla Corongiu, Vittorio Crobu,

Riccardo De Luca, Massimo Farris, Gianluca Melis, Mar-cello Moi, Antonio Saba, the French cavers o the GroupeUlysse Splo Lyon and many other cavers o the Sardin-ian Federation o Speleologists that have sporadically ac-companied us during our explorations. Special thanks toFranco Bandiera o Gruppo Speleo Ambientale Sassari

or the supply o fuorescein salt in several tracing ex-periments, to Pro. Bartolomeo Vigna o the PolytechnicUniversity o Turin or the borrowing o the fuorimeter

used in the 2002 dye tracing test and to Mauro Muceddao University o Sassari and Alessandro Uggeri o IdrogeaVarese or the charcoal detector analyses. Also commentso Nico Goldscheider and an anonymous reviewer havebeen greatly appreciated.

SALVATORE CABRAS, JO DE WAELE & LAURA SANNA

Andreo, B., ed., 2008: Karst hydrogeology in caves.- In-

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Bandiera, F., 2000: Colorazione con fuoresceina delsistema idrico sotterraneo di Sa Rutta e SEdera-SuGologone.- Sardegna Speleologica, 16, 2-8.

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vironmental Geology, 51, 701-706.Birk, S., R. Liedl & M. Sauter, 2004: Identication o

localised recharge and conduit fow by combinedanalysis o hydraulic and physico-chemical springresponses (Urenbrunnen, SW-Germany).- Journalo Hydrology, 286, 179-193.

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Cabras, S., F. Murgia & L. Sanna, 2002: ComplessoSEdera-Su Gologone: tracciamento geochimicosulle acque sotterranee del Supramonte.- SardegnaSpeleologica, 19, 18-24.

Capra, M., 2007: La grotta Su Venadore de Corojos:otoracconto.- III Radino Speleologico Regionaledella Sardegna, Urzulei 25-27 aprile 2008.

Carta, G., F. Murgia & F. Sanna, 1988: 4 Vento: nuovo

complesso di diramazioni nella Grotta di Su Ben-tu.- Gruttas e Nurras, 1-8.

Columbu, M., 1955: Note su alcune grotte della provin-cia di Nuoro.- Rassegna Speleologica Italiana, 7,139-149.

Cossu, A., J. De Waele & F. Di Gregorio, 2007: Coastalkarst geomorphosites at risk? A case study: thefoods o 6-11 December 2004 in Central-East Sar-dinia, in Parise, M. & J. Gunn, eds., Natural andAnthropogenic Hazards in Karst Areas: Recogni-tion, Analysis and Mitigation.- Geological Societyo London, Special Publication, 279: London, Geo-

logical Society o London, p. 85-95.Crobu, V., 2003: Supramonte verticale.- Speleologia, 48,

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De Waele, J., C. Corongiu, L. Sanna, V. Crobu, R. DeLuca, S. Arrica, G. Melis, P. Marcia, M. Moi, S. Ca-bras & A. Saba, 2007: Su Colostrargiu, un ume dipassione.- Antho 9, (in print).

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