Origin and Assessment of Deep Groundwater Inflow in the Ca' Lita

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) with 1 − Sciences 1 Discussions Earth System Hydrology and , and A. Corsini 2 ). The deep water inflow recharges 1 − water (more than 9500 µS cm 4 7700 7699 , T. A. Bogaard 3 , G. Martinelli 1 ). It also partly recharges the landslide body, where the hydro- 1 − yr 3 , F. Ronchetti 1 This paper aims to assess the origin of groundwater in the Ca’ Lita landslide (north- Results show that the groundwater balance in the Ca’ Lita landslide must take into This discussion paper is/has been under review for the journal Hydrology and Earth System Sciences (HESS). Please refer to the corresponding final paper in HESS if available. Department of Earth Sciences, UniversityDepartment of of Modena Water and Management, Reggio Delft Emilia,Regional University Italy Agency of for Technology, The the Netherlands Protection of the Environment (ARPA), Emilia Romagna, Italy Instability of hillslopes istors generally governing triggered infiltration, by increase hydrological of pore and water hydrogeological pressure, fac- and resulting decreases in 7800–17 500 m chemical imprint of deepThis water mixed points with to rainfall a and probablelandslide, snowmelt a influence finding water of that was deep could observed. watertectonized be inflow applicable areas to on in other the the large northern mobility landslides of Apennines occurring or the in in highly Ca’ other Lita mountain chains. 1 Introduction also carried out. account an inflow of highlynon-negligible amounts mineralized of Na-SO Chloride (up tothe 800 mg aquifer l hosted in the bedrock underlying the sliding surface (at a rate of about influence long-term pore-pressure regimes and play a role onern local slope Italian instability. Apennines) andter to inflow. qualify The and research quantifyanalyses. is the It essentially involved aliquot 5 based yr attributable of on toductivity continuous in deep and monitoring temperature, situ of wa- and groundwater monitoring with levels, electrical and groundwatermajor con- sampling hydrochemical ions, followed tracers by (such determination of asTritium). Boron Leaching and experiments Strontium), on and isotopes soil (Oxygen, samples Deuterium, and water recharge estimation were Changes in soil water content,well-known groundwater causal flow and or a triggeringare rise generally factors in assumed pore for as water hillslope the pressureneglects only instability. are sources the Rainfall of and role groundwater snowmelt recharge. of This assumption deep water inflow in highly tectonized areas, a factor that can Abstract Hydrol. Earth Syst. Sci. Discuss.,www.hydrol-earth-syst-sci-discuss.net/9/7699/2012/ 9, 7699–7738, 2012 doi:10.5194/hessd-9-7699-2012 © Author(s) 2012. CC Attribution 3.0 License. 1 2 3 Received: 9 May 2012 – Accepted: 26Correspondence May to: 2012 F. – Cervi Published: ([email protected]) 14 June 2012 Published by Copernicus Publications on behalf of the European Geosciences Union. Origin and assessment of deep groundwater inflow in the Ca’landslide Lita using hydrochemistry and in situ monitoring F. Cervi 5 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (point no. 7) 4 ect groundwater balance on erent water types (Freeze and ff ff 7702 7701 ecting highly tectonized flysch rock masses in the ff erentiation of water types in hillslope hydrology is not often ff ) moves from the upper NA chain toward the Po Plain. Sup- 1 − (point no. 5 in Fig. 1a, b) and pass through SO ms 3 14 − ´ oth, 1999). The presence of deep water into landslide deposits was ´ oth, 1999) has recently been identified by Gargini et al. (2008): it slowly ective groundwater infiltration on a slope scale over long periods of time ff to 10 12 − ective stress in the soil (Wieczorek, 1996; van Asch et al., 1999). In deep-seated Systematic changes in the anion facies have been reported: fresh infiltrated wa- This paper deals with the analysis of groundwater in the Ca’ Lita landslide, a large Deep water can easily be detected by hydrochemical surveying (Bogaard et al., However, the activation/reactivation of deep-seated landslides is a complex issue ff ters start from HCO widely distributed. The unconfinedwhich aquifers discharge where feed the a groundwaterity table large crosses contrast number the occurs. land of A surface low-yield deep– or BRS a regional springs permeabil- sensu groundwater T flow system(from (Base 10 Regional System plied by rainfall andis driven snowmelt by water regional infiltratingconcentrate gradients, discharge near but in the in isolated springs some watershed or cases divide, directly tectonic into the lineaments stream BRS beds. or topography The main hydrogeological characteristics ofimprint these of units hosted and groundwater are the described typical below. hydrochemical 2.1 Tuscan Units (TU) Groundwater circuits developing within TU flysch rock masses are mostly shallow and of the accretionary wedge,stratigraphic units the of northern marine sedimentary Apenninesurian rocks are (Fig. Unit made 1). (LU), The up Tuscan andand of Unit (TU), the several highly the tectono- Sestola Lig- tectonized Vidiciaticodeposits turbidite Unit (clayshales). sequences Within (SV) (flysch these arefound. units, The rock mainly Triassic Epiligurian masses) composed evaporites Unit (EL) (TUG of andThe is gypsum) thick mainly clayey Messinian are composed and chaotic of also Post turbiditestain (flysch Messinian chain, rock units, are masses). outcropping made up only of at evaporites the (MME front gypsum) of and the marine moun- clayey rocks (QM). The northern Apenninesclosure (NA) of are the aAdria Ligure-Piemontese fold-and-thrust and mountain Ocean European belt basin continentaltelli generated and plates and by the Vannucchi, (Boccaletti 2003; the subsequent et Molli, al., collision 2008). 1971; As of a Klingfield, the consequence 1979; of Bet- the polyphasic evolution 2 Hydrogeological and hydrochemical context of the northern Apennines rotational rock slide-earthnorthern flow a Italian Apennines.through The which deep landslide water inflow occursgroundwater is below believed along to and occur. a inside Thegroundwater the aim major from is landslide, deep regional to and water assess to fault inflow. the Theter qualify origin line, research monitoring of and makes and quantify combined chemical/isotopic the use analyses.contribution of aliquot The of groundwa- results of deep allow water an to assessmentinvolved the in of hydrological the the processes landslide. and development of instability 2007) due to itspressure very conditions, distinct the mineral chemical composition imprint ofaction hosting depending between rocks on water or and depth, deposits, aquifer, time temperature,Cherry, and of 1979). and inter- However, the di mixing ofconducted di (Guglielmi et al., 2000; Cappa et al., 2004). and groundwater recharge is notwater always due upflow to along precipitation alone.a regional For slope instance, tectonic scale deep structures (T reported can in several a cases ingoni, the 2001; northern Ciancabilla Apennines (Baraldi, et2009) 2008; al., as Bertolini 2004; well and as Gor- Colombetti2007). in and other Nicolodi, mountain 1998; chains Ronchetti (Bonzanigo et et al., al., 2001; de Montety et al., landslides, e can increase hydrostatic levels and determinetant groundwater role flow, thus in playing the an reactivation impor- 1987; of van slope Asch movements et (Hutchinson, al., 1970; 1999). Iverson and Major, e 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 ). H) 2 CO p O and and and low 18 ) together 1 75: Cervi, 18 1 − 75: Gargini O between − − − 18 (Duchi et al., δ 1 (Boschetti et al., − 1 (White, 1965) while ranging from 0.6 to − 55 and 1 2 − − CO H can reach p 2 H equal to 0) while 2 δ while Sr and B contents are δ 1 with − ). Their water isotopes are posi- water (point no. 5 in Fig. 1a, b). 1 H between values and, if the aquifer consists 1 − 3 2 − 4 δ 5 and 11 while 1gl + − ÷ ) flushing out particles of clay and en- 11, 1 − − 7704 7703 10.5 to 75) (Minissale et al., 2000; Cremaschi, 2009). O up to stays around 1 kPa (Conti et al., 2000; Capozzi − − 2 18 http://unmig.sviluppoeconomico.gov.it/videpi/en/ δ 8.5 and while B doesn’t exceed 0.05 mgl CO − 1 (Conti et al., 2000; Capozzi and Picotti, 2010). , respectively (Chiesi et al., 2010; Duchi et al., 2005; p − 1 1 − 55 and O up to − − 18 is between 0.03–0.3 kPa. Isotope composition reflects the δ 2 6) while CO + O between p ÷ and 2 mgl 18 5 1 δ + − H between 2 δ constantly increases up to 2.0 kPa. Water stable isotopes (O 2 11, − CO p O around . 18 1 and EL) − δ ect the impermeable QM. These phenomena, which are widely observed along com- EL flysch acts as an aquifer and stores Ca-HCO In the longer and deeper flow paths (main anion: Cl), accumulation of trace ions, 8.5 and ff H) are sometimes highly positive ( pressive margins around the world2005), (Martinelli consist and Judd, of 2004; Na-Cltrapped Martinelli connate and waters water Dadomo, (up of to theburied old QM-TU 90 gl pliocenic contact sea (located (Bonini, atstart 2007). a to depth They of originate rise2 more from up than the towards 2000 m) the whereas surface oilfield following fluids varies inverse widely faults. (0.03–0.9 Stable kPa). isotopes B2010). ( and Sr can be as high as 300 mgl 2.4 Post Messinian Units (QM) Along the boundary with the Poa plain, several mud volcanoes (points 3a, b in Fig. 1a, b) In gypsum formations belonging toin the Fig. TUG 1a, and b) MME, can freshof originate. water springs halite, This (point also water no. has Cl. 6 high Salinitylower SO is than normally 15 mgl higher thanToscani 2–3 et gl al., 2001). recharge altitude ( 2003). 1.9 kPa). The isotopic imprint− corresponds to theSr local is recharge area normally ( 2005; lower Toscani et than al., 1 2001). mgl 2.3 Triassic (TUG) and Messinian (MME) evaporites During the warm seasonion springs content (salinity provide is discharge normally in lower the than order 0.8 of few ls Many oil wells (Viano, Baiso,mations Serramazzoni found in impregnation Fig. (even 1a) salience)with passing of oil through salt and the water gas (Na-Cl clayey emissionspontaneous for- up (methane, to emissions superior 9 hydrocarbon, (point gl nitrogen). no. Likesimilar 3c these, chemical in other characteristics Fig. (salinity 1a)tive up flowing ( to out 11 from gl theand same Picotti, 2010). unit show Moving towards the middle-frontconsidered portion impermeable. Starting of from theeral the wedge, 1950s, drilling the the campaigns LU SV for hasinside intensive and been the hydrocarbon subjected LU national investigations to units (results sev- VIDEPI can are Project: be collected such as Bwere and noted Sr (point no. and 4Heinicke in transported et Fig. hydrocarbons al., 1a, 2010). b: and/orbe Minissale In immiscible mobilized et several from al., cases fluids the 2000; organic their (oil, Capozzi matterassociated content buried and with gas) is during oilfield Picotti, sedimentary water strongly 2002; if processes, related; itsSr is B, value normally ranges is which from in can 100 the to order 500 of mgl 100 mgl 2.2 Sestola-Vidiciatico Unit, Ligurian Units and Epiligurian Units (SV, LU 10 gl range within precipitation values,the shifted higher towards recharge negative areas values, ( et which al., characterize 2008). finally reaching Cl (point no. 4), while TDS (Total Dissolved Solids) increases up to 9– 5 5 20 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ). Pre- http://www.arpa.emr.it C( ◦ with two peaks: a main one in autumn erent locations in the slope (Fig. 2a, b). 1 ff − 7706 7705 ects a hillslope composed of formations belonging to the Lig- ff and the mean air temperature was 11.7 1 − More specifically, the groundwater chemistry and stable isotope contents were char- The aliquot of deep water was estimated by coupling radioactive isotopes content After the 2004 event, an extensive geological investigation and monitoring campaign Later, inclinometers and 5 standpipe piezometers were installed and equipped with The Ca’ Lita landslide a The landslide can be classified as a reactivated complex landslide (WP/WLI, 1993; validation, to check ifogy the of peculiar the water site, chemistrytwo consisted outcropping could in be geological leaching due formations. experimentsPHREEQC only In with (Parkhurst to soil addition, and the samples another Appelo,term mineral- belonging 2004) equilibrium-based chemical to was interaction model the between defined rainfall in water and order host to rocks. simulatewith groundwater the balance. long- drochemical (groundwater conductivity monitoring,cal analyses, groundwater leaching isotopic experiments, hydrochemical andcomposition) modelling), surveys. chemi- and mineralogical (soil acterized in order to assess end-members and mixing phenomena. An independent same area, a set ofbedrock sub-horizontal below drains the of length sliding from surface 50–100 and m convey drain it water to from drainage the point A (DrA4 in Fig. 2a, Methods b). With reference to theconsisted case of study, an severalmonitoring, interdisciplinary steps estimation investigation involving was of hydrological performed. the (groundwater It groundwater level balance for and several discharge hydrologic years), hy- drains constructed during mitigation workDeep at drainage di wells inconvey the it to rock well slide A drain (WAof in groundwater the Fig. frontal from 2a, scarp the b), of from landslide thefrom where rock body the it slide superficial and is zone, a removed debris by shield and pumping. of convey At shallow it drainage the wells to base drain drainage water point B (DrB in Fig. 2a, b). In the points. Other monitoring and sampling points were drainage wells and sub-horizontal these. Piezometers were used in the research as groundwater monitoring and sampling preceding months combined with the rapid melting of aboutwas 80 cm set of up snow. in orderinclinometers to design showed mitigation that structures (Corsini the44–48 et active m al., while rock 2009). the Boreholes slide active and depositgatti earth had et flow al., deposit a 2006). had maximum ahave Since thickness been mean summer of recorded thickness 2006, and of no only about further shallow 10 m slides deep (Bor- have seated occurred rock closepressure slide to movements the transducers. main Electrical scarps. conductivity probes were also fitted inside two of Cruden and Varnes, 1996),zones associating (in rotational the rock MOHformation). slides formation) It in with was the reactivated earth crownCorsini several and et flows times al., head in in 2009). thephases Recently, the lower it in last winter resumed main century 2003 activity body and (Borgatti in spring (in 2002 et 2004 the and al., due underwent MVR to 2006; paroxysmal 200 mm of cumulated rainfall in the two (October–November) and a secondaryport one an in average spring annual (April). snowfall of Fazlagic about et 42 al. cm (2004) fromurian 1830 re- Units to (LU). 1998. One formationanother consists is of composed of poorly clayshales cemented (MVR)lation sandstone (Fig. between flysch 2a, MOH (MOH), b). and In MVR thefault is slope, (Papani complicated the et by stratigraphic al., the re- 2002). presence of a high angle regional The Ca’ Lita landslidenorthern is located Apennines. between Over 640 the810 and mmyr last 230 m 40 yr, a.s.l. the incipitation the is average distributed NE annual over slope rainfall 70 of in to the the 100 daysyr area was 3 Ca’ Lita landslide context 5 5 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | H ratio 1 H value 3 H/ multimeter 2 (Table 3). + 1 − O or the 16 -notation as per mil (‰) O/ δ 18 hydrogen atoms). Analysis 18 H) were carried out by mass 2 and groundwater temperatures O, EC 18 Suprapur Merck. H ratio of the SMOW. 3 1 erent depths and monitor groundwater ff H/ 2 7708 7707 represents either the S O or the R 16 O/ were measured seasonally from 2006 to August 2010. 1000; 18 T · is 1] ) after removing the standing water in the piezometer. Water ) with an acquisition frequency of 1 h. Electrical Conductivity 1 L − − ) SMOW R SMOW and the GW ) as well as the B and Sr contents. Cation contents were assessed by /R 3 S EC R [( = ) was measured from June 2009 to March 2010, with an acquisition frequency δ ) were measured periodically from 2006 to 2009 and from 2010 to date. and HCO EC T 4 erences between the sample and the standard (Vienna Standard Mean Oceanic In August 2010 (sampling campaign F; green diamond in Fig. 3b), Tritium analysis Five sampling campaigns scattered over 3 yr were conducted starting from 2007 Analyses were conducted to establish major ion concentrations (K, Na, Cl, Ca, Mg, The discharge of groundwater drained by the wells from inside the rock slide body They have been equipped with pressure transducers since 2005 in order to monitor H) was carried out on water collected from DrA in order to determine Tritium Units ff 3 (T.U. in which onewas T.U. performed equals using the one electrolytic enrichment tritium(Thatcher and liquid atom et scintillation al., per counting 1977). method 10 Duetive to of the the chemical deepest content,while and DrA stream was longest water selected circulation as flowing path representa- Romagna-ARPA, a developed 2009) few through was km the used north landslide asfor of area local a Ca’ rainfall. “benchmark” Lita representing (Secchia the river; mean Regione Emilia- Water: V-SMOW). This deviation is presentedwhere in the standard of the sample, and ( 4.3 Groundwater isotopic analyses Stable oxygen andspectrometry hydrogen on isotope water analyses samples collected ( from all the piezometers(sampling and campaigns DrA. B, C, D, E,the F; summer yellow (B, diamond D, in F), Fig.di 3b). winter The (C), samples and represent spring (E) periods. The results are reported as SO atomic absorption spectrometry (Spectr AA-640,ing an Varian). HPLC Anions (high were performance determined liquidwas us- chromatography, Dionex assessed DX-120). by Total alkalinity Gran titration (Gran, 1952). Data are reported in mgl for cation analysis was acidified with 65 % HNO 4.2 Groundwater chemical analyses Groundwater sampling was conducted in 2006(sampling (sampling campaigns campaign B A), and 2007 D; andand red 2009 both square DrA in and Fig. DrBsamples 3b). were collected All sampled. the during All 5 summer samples standpipea 2009 were piezometers low-flow from collected pump DrA using (0.1 and bailers ls P1,for except laboratory which study were was collected filtered through using 0.45-µm cellulose membranes, and the aliquot drains from the bedrock underneath2006 the to main 2009 rock sliding byDrA, surface means the was of monitored GW a from The graduated weir physical-chemical located parameters at wereequipped the checked with outlet a using Ross of a glass DrA. Crison electrode In for MM40 pH. WA and groundwater levels (GW (GW of 6 h in P3(GW and P4. In the other piezometers, GW was monitored from 2007of to the 2010 by WA means pumping of system. a The graduated discharge weir of located groundwater at drained the by outlet sub-horizontal The 5 standpipe piezometersin are the slotted at bedrock di atrock the slide crown body (P3), and andcharacteristics along across of the the the side deepest boreholes sliding are of surface reported the (P4, in rock P5) Table 1. (Fig. slide 2a, (P1, b). P2), The inside the 4.1 Groundwater level, conductivity and discharge monitoring 5 5 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | L http: , has L erently. ff ractometry ff peaks then dis- L cial databases ( ffi 5.8) until equilibrium is reached. = 7710 7709 observed inside the main landslide body (P3). L C and pH ◦ erent geological formations (MVR and MOH) were ff 2 µm fraction was conducted using X-ray di < ected by the high-frequency pumping in WA; as a result, they can increase by more than 5 m. These GW ff L are a ) for the nearest weather station (Baiso), located 4.5 km northwest of L patterns are reported in Fig. 3a. In the crown area (P1), the groundwa- L ective rainfall is available. Similarly to the rainfall pattern, the GW ff record (total head increased by 1 m after 1 month) while seasonal peaks are L variations for each event are modulated or even absent (as the consequence of L In the deepest piezometers, which monitor deep multi-compartmented horizons (P4, H data as described by Mazor (1997). modulated (2–4 m) and shifted by some months compared to the rainfall records. increase of more thansurface (P3), 10 m GW was detected.are In stabilized at the about head 29 m zone, from above the the ground surface. mainP5: since sliding the records areare overlapping, only about the 20 second m isOnly higher represented the in than most Fig. intense the 3a), precipitations GW GW the (such GW as 150 mm on 10 June 2008) can influence of days, while thecharge GW completely within 5–10The days. flysch The rock maximum mass seasonal inGW amplitude the is crown is about intensively 7 fractured m. high (P2) hydraulic and conductivity). behaves di However, during an intensive rainfall-recharge period, an 5.1 Groundwater monitoring The main groundwater rechargewhen into the the e slope takestwo place peaks in (Table 2) the onemally autumn in and followed November/December spring and by another groundwaterOctober. in GW regression April. periods; These are theter nor- response main delay one after between rainfall May events and is in the order of a few hours up to a couple estimated by solving3 a simplified annual water-balance equation and processing the 5 Results recharge area. The mean annual groundwater recharge from deep water inflow was mula was used to assesswater the recharge potential volume mean was annual calculated evapotranspiration. Total by ground- multiplying the water surplus for the slope Ca’ Lita with the same elevation and aspect. The Thornthwaite and Mather (1957) for- air temperature of the site, i.e. 11.7 4.6 Groundwater balance The mean annual groundwater rechargetemperature from data rainfall was over estimated the//www.arpa.emr.it using last rainfall and 40 yr derived from available o The mineralogy was investigatedMVRa). using The 2 analysis of soilon the samples oriented paste. collected Starting at frommodel these Ca’ simulates two Lita the mineralogical interaction assemblages, (MOHa, (precipitation theous and PHREEQC solution dissolution (specifically: of rain water phases) with with a an mean aque- temperature equal to the mean annual terial for each samplewater, continuously was shaken sieved by less200 a than rpm). magnetic The 2 agitator mm experiments (with extendedductivity and a over probe leached a constant was maximum into rotation of used 11 speed l 10 m, to h of of 2 while monitor m, an deionised water 5 electricalinteraction m, mineralization to con- 10 on determine m, the a 30 major m, fixed ion time-table contents. 1 h, (30 s, 4.5 10 h). Each Mineralogical water analyses sample and PHREEQC was modelling collected after 1 h of Four soil samples fromcollected the from two in-situ outcrops di (about 7and km south regolith of Ca’ (i.e. Lita, Fig.MVRa weathered 1a: and material MVRb MOHa). and According still MOHb) to in the USGS its Field original Leach Test location (2005), at 50 g Ca’ of dried Lita, ma- Fig. 1a: 4.4 Leaching analyses 5 5 20 25 15 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . 1 L 1 O in − − 1 18 − . For δ 1 − O did not ) while the 18 1 from DrA. measured in − δ ). This fact is 3 1 content. 1 − − 3 with a maximum 1 − ). The piezometers in- 1 − ). In summer 2011, due with substantial amounts 1 , it fell to a final value of − 4 800–1000 mgl 1 − 4 on 22 October 2009. This drop 1 − , respectively. in November 2010. The latter was 9.5. In one case (P5), 1 − 1 and SO − − 1 − 8.5 to tripled (more than 3000 mgl − measured in the lower part of the slope (DrA, 4 7712 7711 1 (P1); Sr varied from 6.8 (DrA) to 3.3 (P1) mgl was drained from WA and 6000 m − 1 3 − and 1000 mgl 9.23). These mean values are more negative than 1 − − H are reported in Table 3. Several samples from the 2 reached a new minimum value of 1247 µScm while SO measured in P4 increased from 5500 to 5800 µScm δ 1 − EC 9.13; EC ective rainfall over 3 months, which provided slight GW ) and a significant content of chlorides (up to 787 mgl − ff 1 − O and 8 for an elevation between 600 and 650 m a.s.l.; Longinelli and GW-type). This hydrofacies characterizes all water sampled at with a minimum of 4570 µScm 18 − is evident. Starting from 5450 µScm 4 1 δ O which ranged from − (DrA) and 6.4 mgl continuous monitoring only being available for the head zone, dif- 18 1 EC δ − 7.8 to EC − in DrA. ranged from about 6 kPa (P4) to 1.4 kPa (DrA), while pH fluctuated around 1 2 − (up to 1100 mgl 3 CO p slightly increased. The most pronounced increase involved DrA: in this case, Na 4 A comparison between sampling campaigns A, B and D was only possible for P1 Trace ion levels are available only for the last sampling campaign: B concentrations Regarding the main ion contents (reported in Table 3), P3, P5 and DrB had the lower Marked discrepancies were detected in the Chloride contents. The head zone (P3, The most mineralized water collected at Ca’ Lita during sampling campaign A (DrA) The discharge monitoring network started to collect data in 2006–2007 and was Despite GW The isotopic values landslide body (P4, P5)pleted or values the of lateral unstablechange crown over the (P2) seasons were ( the characterized isotopic by signal de- which characterizedranging the from mean annual rainfallSelmo, for 2003). this That is altitude consistent ( window with (see the Sect. water-balances calculated 7). for In the fact, same it time- can be expected that recharging is concentrated in the (Fig. 5b). reached 8.2 mgl 5.3 Groundwater isotopic analyses P4, P5) is characterized byserted lower levels inside of the Cl flysch (less rock masses thanof (P1, 90 790 mgl P2) mgl reached 300–400 mgl and DrA. In 2009SO (sampling campaign D) theincreased Cl to contents about were 1600 mgl halved,responsible while of Na the and upward displacement of the last DrA sample in the Piper diagram Ca’ Lita (Fig. 5b), with P4 shifted downwards owing tovalues the for higher both HCO ions (Naother of samples about exceeded 500–600 800 mgl mgl right corner (Na-SO mon shallow GW falls on the left side of the diamond, the Ca’ Lita sample plots in the the upper part of thesampling slope campaign (P1), to F). 6 According gl to(brackish) Drever water. (1977), These the waters latter areof can enriched HCO be in classified Na as andDrA). salt SO 7 (slightly acid in the upper part of theis slope: reported 6.6–6.9 observed in in a P1). Piper diagram together with other GW of NA (Fig. 5a). Whereas com- comparison, when a total of 30 000 m 5.2 Groundwater chemical analyses Groundwater salinity ranged between a minimum value of about 1.5 gl equilibrium was reached onlyto after continuous 3 pumping, GW monthsthe (5100 same µScm time window, GW with a smoothed peakpreceded of by more than 300 mm 6000increases µScm of even in e the deepest piezometers (P2). stopped in 2009 (WA) and so only the hydrologic year 2007–2008 is available for further ferent trends can bedecrease observed in (Fig. GW 4). Abovearound the 5100 µScm sliding surfacewas (P3), the a result of continuous automaticof pumping switching-on less in mineralized WA and water the coming consequent downflow from the shallow part of the landslide body. A new 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | H 2 up to 4 ) was no- 1 − O in P1 and erences were 18 ff δ 53.54). The other − of Cl were detected 1 water with similar min- − 3 GW. 7.90 in June 2009 while the ) while Ca was assessed as 1 4 49.23 to − − − 5.33, respectively, in July 2007). As 0.1 mgl − equal to 0.03 kPa). In both cases, some < 2 H graph (Fig. 6). Several points (DrA, P1, water of the former, the samples leached 2 ) could be produced by these assemblages 3 CO 1 δ − p 7714 7713 O- 6.51 and 18 erent scenarios were tested according to the state − δ ff after 1 h). Otherwise, appreciable di 1 − was detected. 4 was guaranteed ( O values are even less depleted than those characterizing the 2 (more than 100 mgl 18 3 , respectively. These results are only partially in agreement with the δ 1 . Sodium content was increased through albite dissolution, reaching 1 − 6.93 in summer 2010). − − while the furthest sample MVRb remained around 180 µScm 1 (closed system) and some thousands in the second case. Regarding anion − 1 H content in GW flowing out of DrA during summer 2010 was significantly − reached values of 2.5 kPa and 3 kPa, respectively), while in the second a fixed 3 2 In the landslide body (head zone), the aquifer hosted above the main sliding sur- In the PHREEQC modeling two di Once leached, all the MOHa and MOHb provided Ca-HCO All the samples were plotted in a The In P1 and DrA, CO p face (P3) exhibits an unconfined behaviour (Fig. 2b). Its response to rainfall events 100 mgl contents, only HCO of minerals while no SO 6 Discussion: origin of groundwater and conceptualResults model of suggest deep the water inflow existencelapping of aquifers a characterized complex by hydrogeological the system presence comprising of Na-SO over- ( partial pressure of CO ions showed discrepancies evenment. with Mg was the not results presentaround in obtained 2–4 the mgl from final solution the ( leaching experi- The composition of the flyschsmectites, rock 25 mass % (MOH) chlorites, was8.6 established 41 % % as feldspar. 33.6 illites, % MVR 8 clay %kaolinite, (25 is % kaolinite), and mainly 55.8 % some composed1.2 quartz, traces % of 2 feldspar. of % clay illites) calcite, (about and together 78 %: with 89 % 7.8 %of smectites, the quartz, 8 hydrogeological % 13.3 system: % in calcite the and first, it was considered as closed to the surface 160 and 175 mgl chemical characteristics of theIn water this hosted case, in unlike theduring the the deepest water leaching aquifer collected experiment. of from Ca’ DrA, Lita only few (DrA). 5.5 mgl PHREEQC modelling with MVRa soil collected along the main fault were enriched with Na and SO the final concentration wastotal chemical generally content short was achieved forsamples within are 10 all min, representative and the of 90 the % samples: lixiviation within at interactions 1 h. between least Clearly, soil the 70 and 1eralization % water. h (close of to the 200detected µScm between MVR930 samples. µScm In particular,ticed an in increase MVRa. of Starting mineralization from the (up Ca-HCO to respectively; the latter was obtained fromyear a monthly 2009). dataset that includes the hydrologic 5.4 Leaching analysis Table 4 summarizes the results of the leaching experiments. The time required to reach other reached P2) are clearly shifted downwardsline from by the local Longinelli meteoricisotope and line (northern which Selmo, Italy 2003); becomes meteoric piezometers this highly-depleted lie is in on the due DrA local to (from meteoric line. a slightlower negativization than of the the mean isotopic value characterizing the rainfall in NA (3.5 and 10 T.U., values (Iacumin et al., 2009). meteorological observations (up to soon as the mitigationDrA system started began to to become drain more GW negative (the in first the reached head zone, late autumn to early spring when rainfall and snowmelt provide more depleted isotopic 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | of up 9.5 5.33 18 − EC at the − δ 1 ected by − ff H together 2 δ (stabilized at about 8.7 compared to decreased from EC − values and ion contents, 18 O–Cl graph (Conti et al., δ 18 EC δ 8.5 and values measured in mud volca- : values range between 1000 to − 18 (P3). Due to the continuous pump- EC δ 1 − H measured in DrA and of the recon- 3 (as described in further detail in Sect. 7, record. In DrA, 3 18 ). The latter reaches about 800 mgl O (between 7716 7715 δ 1 − 18 δ 5.5 can be estimated by considering an aliquot of variations in P1 are higher than those detected in as reported by Duchi et al., 2005; Toscani et al., 9.5) can be assumed to be strongly linked to infil- ). + L 1 − 1 − − for shallow groundwater can be obtained from P5, which 9.13. On the other hand, an indicative value for the mean 18 − δ = 18 O (close to δ 18 δ 6.93 in August 2010. This can be interpreted as the result of an − ). 1 at 20 m below the water table). The other aquifers were also a − . 1 1 erently. Depending on the denser and more persistent fracturing pattern − − of deep groundwater of ff 18 δ have no direct relationships with rainfall as only modulated (changes less than L Other evidence supports the hypothesis of mixing between deep water inflow and If mud volcanoes and oil field waters are plotted in a This change was also observed in the A sharp decline in chemical parameters occurred during November 2009: EC in the However, in both cases the chemical imprints are quite similarAll and the characterized by water samples taken lie on the local meteoric isotopic line,The and aquifer hosted the in the most undisturbed flysch (P1 and DrA) and in the side crown (P2) Below the sliding surface (P4 and P5), in the thick deformation band made up of dis- 5.5 for deep water inflow is also consistent with 2000), they represent one of the end-members of a hypothetical mixing line connecting and Sr in DrAshallow is springs three of orders NA2001). of (a Considering magnitude few greater µgl the thanwater data and the reported host value rocks in normally (suchsured as Sect. found flysch B in and/or 2, values. evaporites) Mud the cannotdetected volcanoes in long-term at and itself Ca’ justify oilfield interaction Lita, the waters while between mea- Srlike are is Sr, consistent B much with behaves higher in than the a expected.(Grew B It more and should conservative contents Anovitz, be way 1996; and noted Walker, hardly that, 1975). precipitates un- from the solution flowing out of TU flysch formationsLU-TU (i.e. formations Well Salsmag1 in in the Boschettipoint et middle-frontal 3c al., part 2010) in or of Fig. from the 1a; Capozzi Apennine and chain Picotti, (i.e. 2010). Regnanorainfall-recharge site, water inside the bedrock underneath the landslide. The content of B value for the mean annual is constantly close to annual deep water inflow in thethis order value of can 500 000 bestructed m geometry estimated and on storativity the+ of basis the MOH of reservoir).noes An located estimated 15 value km to of the north (points no. 3a, b in Fig. 1a) as well as in other springs halved. in July 2007increased to contribution of lighter rainslide water infiltrating body, into thus bedrock producing from the a upper mixture land- of shallow and deep groundwater. A reference the hydrological changes in the head zone: in some cases (P1 and DrA) Cl levels were 4000 µScm bottom of the aquifer (DrA). Dischargedto water 9500 is µScm the most highly mineralized (GW landslide body repositioned at abouting 1500 in µScm WA, the unconfinedby aquifer the hosted inflow in of the moreThis head zone fresh presence was and was progressively less confirmed renewed P1: mineralized by water Ronchetti the from et authors the al. upper detected (2009) landslide a after body. conductivity rapid loggings increase in with depth of GW behaves di characterizing the crown zone, GW P2. However, both piezometerswith are high characterized contents by of water Cl depleted (300–400 in mgl together with less depleted valuesobserved of for P5). low Cl contents (less than 88 mgl depleted values of tration processes, representing natural rain gaugescontent. for the mean annual isotopic rainfall 5000 µScm arranged flysch, the sameGW aquifer becomes semi-confined (or5 m) multi-compartmented). seasonal variations are observed. P4 had higher GW is brief. The same patterns can be noticed in GW 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | - L ffi (1) (2) ec- ) at ff dw V ) in the dw 5.33) and, ective rain V ff − = f O 18 δ cannot be reached. 4 9.13; − plus deep inflow = . Considering annual water r 2 3 O 18 δ variations and the total and e , depending on the infiltration coe L 3 5.5; =+ (Fig. 9). Each component can be linked to 3 dw 7718 7717 O OUT 30000–68 000 m represents about the 26 % of the e V 18 = δ ). The annual deep water volume inflow ( r f dw f V V V O ( cient used (0.4 and 1, respectively). 18 3 ffi H result according to Mazor (1997). The 3.5 T.U. de- δ by Ronchetti et al., 2009), the amount of water hosted ) 3 2 7800–17 500m dw − (rainfall was calculated, which is concentrated between December V = I 1 + V ) − r f ) r V O ( O = 18 18 δ dw δ − O − f dw 18 O than MVRb leading to the supposition that these clayey outcrops were O δ 18 4 18 ected by drainage. Before the drainage network was set-up, the chemical dw δ ff V ( δ ( ) involves a confined unit and it could influence the long term groundwater · + 1 O–B graph (Fig. 8) makes it possible to separate these two components. Ca’ r r − V in each piezometer. Conversely, 2009–2010 was very wet and the maximum GW 18 cient (quantified as 10 O δ L = ffi landslide 18 The supplemental annual inflow A simple chemical equilibrium analysis was conducted coupling the mineralogical Leaching experiments on soil samples strengthen this conclusion. In particular, water δ dw r times smaller than the0.56 volume ls stored in the deepest aquifer, its constant influx (0.25– where: V depending on the infiltration coe which can infiltrate annually through the surface. Although this amount of water is forty flysch is assumed equal tothe the respective outflow oxygen isotope value ( in this way, the steady-state budget can be expressedV as follow: equation and processing the tected in DrA was duewater to characterized a by mixing long ofrespectively time can two paths be members, (about i.e. assumed. rain Itthe O sampling water should T.U.), campaign (10 aliquots be F T.U.) noted (August of with 2010), thatbecome about deep when these the a 1/3 hydrogeological proportions system and are had 2/3 already relatedand isotopic to analyses suggest a majorwater. influence Considering of the the deep unmodified water conditions componentthe before than annual the rain input drainage volume network (pre-2006), be estimated in thecients range used of (0.4 30 000 andcoe to 1, 68 respectively). 000 m Considering aquiferin geometry the and flysch its storativity isthe about bottom 750 of 000 m the aquifer was estimated by solving a simplified annual water-balance flysch rock outcroppingsurplus area, and which infiltration is area, about the mean 340 000 annual m groundwater recharge in the slope can thwaite and Mather (1957) formulater and 40 surplus yr of records of 200 mmyr rainfalland and April temperature. A (Table wa- 2).tive A rainfall comparison calculated for betweenpresented each GW in hydrological Table 2. year A (Thornthwaitelogical direct year and was relation Mather, characterized can 1957) by easilyGW the is be lowest recharge observed: value the andwas 2006–2007 consequent recorded hydro- minimum at all points. On the slope scale, the recharge area corresponds to the 7 Discussion: influence of deep water inflow on the groundwater balance ofThe the mean annual groundwater recharge from rainfall was estimated using the Thorn- which interacted with MVRaNa samples and collected SO atimpregnated Ca’ with Lita deep became water. The moredid interactions enriched not with produce MOH in samples any (MOHa changes and in MOHb) water chemistry andcompositions ion contents. of the soillined samples that, using even PHREEQC at software. equilibrium,Moreover, The the there investigation are observed under- no levels of local mineralogical Ca phases and that SO could provide Chloride. the Lita water is completely left-shiftedan from extra the source mud volcano of points,foredeep B which origin are contained (oilfield polluted waters) in by for the the connate Ca’ waters Lita GW. of QM. This suggests a purely them with shallow GW. GW from Ca’ Lita falls on this line (Fig. 7). At the same time, 5 5 25 20 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | from 1 − yr 3 ective rainfall) was ff deriving from deep water and rain- I V elli, G., Caputo, G., and Puglisi, C.: Large ff scraped Ligurian oceanic sequences of the ff erent sources in slope-scale water budget es- 7720 7719 ff of discharge from DrA, and around 30 000 m 1 − yr 3 of deep water (i.e. 26 % of the annual mean e 3 from the external northern Apennines2007. (Emilia-Romagna, Italy), J. Geophys. Res., 112, 1–21, Campo Vallemaggia landslide, in: Proceedingmeasures, Davos, of Switzerland, Landslides-Causes, 13–22, Impacts 2001. and Counter- igation of landslide risk(Italy), via Georisk, numerical 2, modelling: 141–160, a 2008. case study from the northern Apennines reactivated landslides in(Italy), weak Landslides, rock 3, 115–124, masses: 2006. a case study from the Northern Apennines istry in landslide research: a review, B. Soc. Geol. Fr., 178, 113–126, 2007. di Reggio Emilia), Quad. Geolog. Appl., 8, 1–21, 2001. northern Apennines: new hypothesismatrix concerning fabric, the J. Struct. development Geol., of 25, the 371–388, melange 2003. block-in- Western Alps and northern Apennines, Nature, 234, 108–111, 1971. dell’Appennino Emiliano. CasiRomagna, di 18, studio: 19–36, 2008. Vedriano, Ca’ Lita e Silla, Il Geologo dell’Emilia On the other hand, monitoring data from the weirs at the drainage system outlets Bonzanigo, L., Eberhardt, E., and Loew, S.: Hydromechanical factors controlling the creeping Bonini, M.: Interrelations of mud volcanism, fluid venting, and thrust-anticline folding: examples Borgatti, L., Corsini, A., Marcato, G., Ronchetti F., and Zabuski, L.: Appraise the structural mit- Borgatti, L., Corsini, A., Barbieri, M., Sartini, G., Tru Bogaard, T., Guglielmi, Y., Marc, V., Emblanch, C., Bertrand, C., and Mudry, J.: Hydrogeochem- Bettelli, G. and Vannucchi, P.: Structural style of o Boccaletti, M., Elter, P., and Guazzone, G.: Plate tectonics models for the development of the Bertolini, G. and Gorgoni, C.: La lavina di Roncovetro (Vedriano, Comune di Canossa, Provincia Baraldi, S.: Caratterizzazione idrogeologica, idrochimica e radiometrica di alcuni corpi di frana and this study clearly demonstrateswhenever the that presence hydrochemistry of should other be groundwater taken sources into is account suspected. 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N.: A coastal mudflow on the London Clay cli 5 5 30 25 20 30 15 25 10 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 7726 7725 (m) (m a.s.l.) surface (m) monitoring monitoring 50–5955–60 52050–59 525 521 44 48 X 44 X X X from–to Altitude main sliding level/discharge conductivity- about 55 465 44 X slide surface slide surface slide surface slide surface Characteristics of piezometers, wells and drainage systems in the Ca’ Lita landslide. Name LocationP1P2P3 Rock slide SlottedP4 Rock slide Rock slide bodyP5 Below the main WA Below the 9–50 main 3–44 Depth of the 4–59 BelowDrA the main Continuous 631 520 BelowDrB the main 539 Continuous Superficial debris about 13 17–35 44 6 455 X X X 13 X ety, Multilingual Landslide Glossary,Columbia, edited Canada, by: 59 Richmond, pp., B. 1993. C., BiTech Publishers, British Table 1. Depth of the main slip and filters are also reported. WP/WLI: Working Party on the World Landslide Inventory and Canadian Geotechnical Soci- Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | O 18 7.71 9.17 5.33 6.51 8.05 9.13 5.33 7.73 8.51 9.13 6.80 7.90 8.58 8.73 9.22 9.88 8.60 6.93 9.65 9.90 9.33 δ − − − − − − − − − − − − − − − − − − − − − H 2 δ 49.23 52.47 59.03 63.77 47.99 56.28 60.56 63.88 52.38 54.98 58.66 57.78 61.35 66.00 58.53 53.54 62.28 63.64 60.78 − − − − − − − − − − − − − − − − − − − ) 4 1 − ective ff ) (mgl 1 Cl SO − ) (mgl 3 1 − ) (mgl 1 − C) (mm) rainfall (mm) ◦ ) (mgl 1 − air temp rainfall e ) (mgl L 1 − ) (mgl 1 − min GW max- Mean Mean Mean Mean L ) (mgl L 1 − 7728 7727 ective rainfall. Data are distinguished by hydrologic ff GW ) (mgl 1 − Ca Mg Na K Sr B HCO L 2 GW CO p ) C 1 ◦ − 25 L − Electrical (µScm T C) Conduct. (kPa) (mgl (m a.s.l.) (m a.s.l.) (m) ( ◦ year max min GW Petrolio Gibbio mazzoni Groundwater chemical (sampling campaign A, B, D) and isotopic (sampling campaign Piezometer monitoring and total-e P1 2007–2008P2P3 623.33P4P5 616.24P1 7.09P2 2008–2009P3 519.19 624.47 618.14P4 517.99P5 513.65 616.18 – 12.7 512.21P1 502.43 1.2 8.29P2 2009–2010 507.89 845P3 526.93 11.22 – 624.90 619.37P4 518.41 4.32P5 518.10 – 508.96 299 12.7 – 513.56 – 510.97 508.21 – 511.60 893 – 9.89 – – 488.73 2.15 – 518.26 – 447 512.33 514.17 512.27 – – – – – – – 488.5 12.5 – – – – 1152 – 488.50 – 347 – P1P2 2005–2006P3 623.62P4P5 616.16P1 8.71P2 2006–2007P3 523.35 621.19 618.39P4 520.70P5 513.77 614.33 – 12.3 508.98 2.65 – 6.86 880 520.7 – 4.79 522.22 616.03 508.47 509.75 – 518.42 273 510.16 14.5 510.79 508.33 – – 2.28 509.72 763 – 1.42 519.46 491.76 1.07 – 49 508.5 510.4 – 490.19 Pz Hydrologic GW campaign ( Group Sampling Name1 pH 11 A1 A1 A1 A1 B DrB1 B P11 B P31 B P51 n.a. B DrA1 n.a. 6.6 B P11 7.4 15.0 C P2 7.5 16.0 C P3 2641 7.6 15.0 C P4 4015 n.a. n.a. P5 2.0 2767 7.1 n.a. DrA 2.6 2243 n.a. 16.0 P3 67.1 5088 1.6 7.0 n.a. P4 1.8 n.a. 13.2 15.0 n.a. n.a. 4.7 47.3 3818 n.a. 5.5 n.a. n.a. 23.1 n.a. 16.0 n.a. 3.0 4362 n.a. 12.8 464 7.9 12.5 1.6 n.a. 13.2 n.a. n.a. 885 9.1 n.a. 13.8 3300 9.0 6.2 n.a. 619 n.a. 462 4390 n.a. n.a. 14.3 3.0 n.a. 8.8 1155 n.a. n.a. n.a. n.a. n.a. 9.9 2.4 n.a. n.a. 7.9 n.a. 858 3.0 n.a. n.a. n.a. n.a. n.a. n.a. n.a. 1045 n.a. n.a. n.a. 3.2 n.a. 195 n.a. n.a. n.a. n.a. n.a. n.a. n.a. 4.2 292 n.a. n.a. n.a. n.a. n.a. 53 n.a. n.a. 171 195 n.a. n.a. 425 n.a. n.a. 525 1110 n.a. n.a. n.a. n.a. 1140 n.a. n.a. 71 88 n.a. 348 n.a. 787 n.a. n.a. n.a. 1050 n.a. n.a. 1095 n.a. 795 n.a. n.a. 313 980 n.a. n.a. n.a. n.a. n.a. n.a. n.a. 35 n.a. n.a. 1160 n.a. n.a. n.a. n.a. 1400 n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. 3b D Monte 7.6 n.a. 33 739 0.7 163.0 160.0 7500 63.0 28.7 66.5 584 12 690 2 n.a. 5.00 8 D Rio 8.1 n.a. 6619 13.6 13.0 20.0 1445 27.0 1.5 11.9 1534 1480 4 n.a. 111 C1 D1 D1 D1 D P51 D DrA1 E P15 E P25 n.a. F P4 7.4 11.7 D P55 n.a. 7.1 D P25 6.9 18.0 P4 3770 n.a. 14.3 D DrA 7577 15.0 7.6 D Pavullo n.a. 4575 n.a. 15.0 Serra- 4.1 7.1 n.a. n.a. n.a. n.a. 7.3 9.1 n.a. 13.1 Lusino 146.0 n.a. n.a. 2330 n.a. n.a. Nismozza n.a. n.a. 98.0 n.a. n.a. 67.0 7.8 n.a. 7.1 5730 n.a. n.a. 16.0 n.a. 9540 n.a. 37.0 n.a. 1660 n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. 970 22.0 n.a. n.a. 681 n.a. 274 n.a. n.a. n.a. n.a. n.a. n.a. 14.0 n.a. 1.5 n.a. 6.8 n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. 41.0 n.a. 3.4 n.a. n.a. n.a. 8.2 n.a. n.a. n.a. n.a. n.a. n.a. n.a. 6.0 n.a. 6.4 n.a. n.a. 529 n.a. n.a. n.a. n.a. n.a. n.a. 1129 n.a. n.a. n.a. n.a. 13 416 n.a. n.a. n.a. n.a. n.a. n.a. 189 n.a. 3130 n.a. n.a. n.a. n.a. 1.1 n.a. n.a. n.a. 1280 n.a. n.a. n.a. n.a. n.a. n.a. n.a. 0.6 n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. 0.0 n.a. n.a. n.a. n.a. n.a. n.a. 152 n.a. n.a. n.a. n.a. 5 n.a. 31 n.a. B, C, D, E,parison: F) mud analyses volcanoes of (point: theseep 3b), Ca’ (point: common 8). Lita shallow samples. groundwater Other (point: samples 5) and are hydrocarbon reported for further com- Table 3. year. Table 2. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Geological cross- (b)

4 3 ) 1 − Cl HCO C (µScm ◦ no Regnano; 4: Quara baths; 5: ). Water springs, water samples, 4 25 s; 2: Salvarola baths; 3a: Mud volcano gend. Geologic units (TU: Tuscan Units; Northern Apennines. b: Geological cross- − piligurian Units; SV: Sestola-Vidiciatico unit; 7730 7729 Chemical data Electrical conductivity . 1 − Fig. 1. a: Simplified map of geologic units of the section (modified after Vannucchi et al., 2008). Le TUG: Triassic Evaporites; LU: Ligurian units; EL: E MME: Messinian Evaporites; hydrocarbon seeps QM: and oil Post wells (1: Messinian Ca’ Nirano; Lita sample 3b: Units Mud volcano Monte Gibbio; 3c: Mud volca

MOHaMVRa 68MOHb 460 106MVRb 615 133 78 694 107 157 81 817 135 193 96sample 924 192 112 196 855 198 123 206 205 140 861 222 754 148 244 228 928 249 179 251 194 199 SoilMOHa NaMVRa Mg 40MOHb 160 CaMVRb 2 25 4 K 10 5 3 SO 8 2 20 1 3 18 2 12 175 1 16 0 5 10 0 113 210 0 120 107 Soilsample 30 s 1 m 2 m 5 m 10 m 30 m 1 h 5 h 10 h Simpliﬁed map of geologic units of the northern Apennines. Leaching results for the 4 soil samples collected. Chemical analyses for the 1h samples section (modiﬁed after Vannucchi et al.,Triassic Evaporites; 2008). LU: Legend: Ligurian geologic units; units EL: (TU:Messinian Epiligurian Tuscan Evaporites; Units; Units; QM: TUG: SV: Post Sestola-Vidiciatico Messinian unit;seeps Units). MME: and Water oil springs, wells water samples, (1:volcano hydrocarbon Monte Ca’ Gibbio; Lita 3c: samples; Mud 2: volcanowater; Regnano; Salvarola 6: 4: baths; Poiano Quara spring; 3a: baths; 7: Mud 5:leaching Morsiano volcano Common experiments spring; Nirano; shallow (A: 8: ground- 3b: weathered Rio Mud Ca’ Petrolio Lita hydrocarbon seep) material; Soil B: samples in for situ rock outcrop). Fig. 1. (a) Table 4. are also reported in mgl Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

Cumulative rainfall lative rainfall for

8 (b) in WAand P5. L

wer wer part of the slope (DrA, sampling of about 1.5 g/l measured in the upper topic (yellow diamond: stable isotopes; rted. Litawith drainage and monitoring works. Location of the monitoring points: DrA, DrB 7732 7731 monitoring for piezometers P1, P2, P3, P5. monitoring for piezometers P1, P2, P3, P5. b: cumu L L monitoring piezometersfor P3and P4and GW EC Geological cross-section of Ca’ Lita with drainage and monitoring works. Fig. 2. a: Geological sketch of Ca’ Lita landslide. andpiezometers. b: Geological cross-section ofCa’ (b) Geological sketch of Ca’ Lita landslide. Location of the monitoring points: DrA, DrB Continuous GW each hydrologic year. Chemical (red square) and iso greendiamond: tritium) sampling campaigns are repo Fig. 3. a: Continuous GW Fig.4: Continuous GW

5.2)Groundwater chemicalanalyses Groundwater salinity ranged between a minimum value part of the slope (P1), to 6 g/l measured in the lo Fig. 3. (a) for each hydrologic year. Chemicalgreen (red diamond: square) tritium) and sampling isotopic campaigns (yellow are diamond: reported. stable isotopes; Fig. 2. (a) and piezometers.

L O 17

18 landslide in WA and P5. L rizing the meteorological wer wer part of the slope (DrA, sampling han the isotopic signal which of about 1.5 g/l measured in the upper O O ranging from -7.8 to -8 for an topic (yellow diamond: stable isotopes; 18 rted. with common shallow groundwater O O did not change over the seasons (- 18 dow (see paragraph 7). In fact, it can be n July 2007). As soon as the mitigation and Selmo, 2003). That is consistent with umin et al., 2009). uminal., et oint: 2, 4 - Boschetti et al., 2010), and e e autumn to early spring when rainfall and re characterized by depleted values of δ O O in P1 and DrA started to become more itude (δ b: Ca’ Lita watersamples fromthe andB D 7 - Venturelli et al., 2003), mud volcanoes e the other e reached -6.93in 2010).summer 18 7734 7733 Ca’ Lita water samples from the B and D campaigns. H H are reported in Table 3. Several samples from the 2 (b) O O and δ Water sample DrA compared with common shallow groundwater 18 monitoring for piezometers P3 and P4 and GW (a) O O values are even less depleted than those characte EC 18

monitoring for piezometers P1, P2, P3, P5. b: cumu L characterized the mean annual rainfall for this alt 9.13; -9.23). These mean values are more negative t which ranged from -8.5 to -9.5. In one case (P5), δ negative(the first reached-7.90 in June 2009 whil observations (up to -6.51 and -5.33 respectively, i system began to drain GW in the head zone, δ the water-balances calculated for the same time-win expected that recharging be concentrated in the lat elevation between 600 and 650 m a.s.l.; Longinelli snowmeltmore provide depletedisotopic values(Iac In P1 and DrA, δ body (P4, P5) or the lateral unstable crown (P2) we (point: 5), other springs (point: 6 - Cervi, 2003; (point: 3a, 3c - Martinelli et al., 1989), baths (p Fig. 5: Piper diagram. a: water sample DrA compared hydrocarbonseep (point: 8) described as in Fig.1A. campaigns. 5.3)Groundwater isotopic analyses The isotopic values δ

Piper diagram. Continuous GW monitoring piezometersfor P3and P4and GW EC Fig. 5. (point: 5), other springs (point: 63a, – c Cervi, – 2003; Martinelli 7 – et(point: Venturelli al., et 8) 1989), al., baths as 2003), mud (point: described volcanoes 2, in (point: 4 Fig. – 1a. Boschetti et al., 2010), and hydrocarbon seep Fig. 4.

each hydrologic year. Chemical (red square) and iso greendiamond: tritium) sampling campaigns are repo

Fig. 3. a: Continuous GW

Fig.4: Continuous GW

Groundwater salinity ranged between a minimum value part of the slope (P1), to 6 g/l measured in the lo

5.2)Groundwater chemicalanalyses

21 O O values 18

3 18 with δ

H H isotope which 2 are only partially of the total chemical d. Point: 2, 4 (Boschetti )-baths; 3a (Conti et al., 2000), O-Cl graph (Conti et al. 2000), they 18 water with similar mineralization 10 was significantly lower than the tween deep water inflow and rainfall- 3 an extra source of B contained in the h (points n°3a, 3b in Fig. 1a) as well as in MVRa. Starting from the Ca-HCO H H depleted samples at Ca’ Lita. Black Ca’ Lita water is completely left-shifted cani et al., 2001). Considering the data 2 rmally found in shallow springs of NA (a mixing line connecting them with shallow ep ep origin (oilfield waters) for the Ca' Lita -common shallow groundwater; 6 (Cervi, ine (Northern Italy meteoric line by H depleted samples at Ca’ Lita. Black s s (i.e. Well Salsmag1 in Boschetti et al. at Ca’ Lita, while Sr is much higher than ndslide. The content of B and Sr in DrA is l part of the Apennine chain (i.e. Regnano as obtained from 5-common shallow 54). The other piezometers lie on the 2 soil collected along the main fault were riments. The time required to reach the δ t the same time, the δ t negativization of the sured B values. Mud volcanoes and oilfield tween water and host rocks (such as flysch n a δ le differences were detected between MVR aves aves in a more conservative way and hardly on (up to 930 µS/cm while the furthest he water hosted in the deepest aquifer of hehydrologic year 2009). the δ within 1 Clearly hour. the 1h samples are arbon seep. Black line: evaporation line from ected ected from DrA, only few mg/l of Cl were apozzi and Picotti, 2010)-mud volcanoes; 7 NA (3.5 and 10 respectively; T.U. the latter samples: at least 70% 0). een soil and water. eensoil and water. 7736 7735 O-δ2H graph (Fig. 6). Several points (DrA, P1, P2) 18 up to 160 and 175 These mg/l resultsrespectively. 4 (Grew and Anovitz, 1996; Walker, 1975). and (Grew Anovitz, 1996; Walker, H diagram. DrA point sampling campaigns are reported. Point: 2, 4 (Boschetti

2 δ O–Cl diagram. Point: 2, 4 (Boschetti et al., 2010) – baths; 3a (Conti et al., 2000), H H diagram. DrA point sampling campaigns are reporte O– 2 18 18 δ δ O O of +5.5 for deep water inflow is also consistent O O - δ 18 18 Fig. 7. 3b,c (Capozzi and Picotti,2003), 2010) 7 – (Venturelli mud et al., volcanoes;seawater. 2003) 5-common – shallow spring; groundwater; 8-hydrocarbon seep. 6 Black (Cervi, line: evaporation line from dashed line is the2003). mean isotopic relation for rainfalls in northern Italy (Longinelli and Selmo, et al., 2010) –7 baths; 3a (Venturelli (Conti et et al., al.,groundwater. Blue 2000), 2003) line 3c represents – (Capozzi the spring. alignment and of Picotti, Red the 2010) dashed – line mud volcanoes; was obtained from 5-common shallow Fig. 6. H H content in GW flowing out of DrA during summer 20 3

enriched with Na and SO water water of the theformer, samples leached with MVRa dashedline (Longinelli and Selmo, 2003). The clearly shifted downwards from the Longinelli local and Selmo, meteoric 2003); this l is due to a sligh in agreement with the chemical characteristics of t Ca’ Lita (DrA). In this case, unlike the water coll (close to 200 µS/cm after 1h). Otherwise, appreciab samples. In particular, an increase of mineralizati sample MVRb remained around 180 µS/cm) was noticed representative the of lixiviation interactions betw mean isotopic value characterizing the rainfall in obtainedwas from amonthly dataset that includes t content was achieved within 10 minutes, and 90% Once leached, all the MOHa and MOHb provided Ca-HCO 5.4)Leaching analysis Table 4 summarizes the results of the leaching expe final concentration was generally short for all the et et al., 2010)-baths; 3a (Conti et al., 2000), 3c (C (Venturelli et al., 2003)-spring. Red dashed line w groundwater. Blue line represents the alignment of Fig. 6: δ

All the samples were plotted in a δ becomes highly-depleted in DrA (from -49,23 to -53, localline.meteoric

O O - Cl diagram. Point: 2, 4 (Boschetti et al., 2010 18

3b, 3c (Capozzi and Picotti, 2010)-mud volcanoes; 5 2003), 7 (Venturelli et al., 2003)-spring; 8-hydroc seawater.

represent one of the end-members of a hypothetical GW. GW from Ca’ Lita falls on this line (Fig. 7). A

measured in mud volcanoes located 15 km to the nort in other springs flowing out of TU flysch formation 2010) or from formationsLU-TU in the middle-fronta site,point in3c Fig. Capozzi 1a; and Picotti, 201 Other evidence supports the hypothesis of mixing be recharge water inside the bedrock underneath the la three orders of magnitude greater than the value no few µg/l, as reported by Duchi et al., 2005 and Tos reported in chapter 2, the long-term interaction be and/or evaporites) cannot in itself justify the mea waters are consistent with the B contents detected expected. It should be noted B that, beh unlike Sr, precipitatesfrom the solution

If If mud volcanoes and oil field waters are plotted i

makes makes it possible to separate these two components. from the mud volcano points, which are polluted by connate waters of QM. This suggests a purely forede GW.

Fig. 7: δ

estimated value of δ

22 wet ted in the . . Considering 2 e e recharge area

dw 24 V

-baths; 3b-mud volcanoes; 5- of of deep water (i.e. 3 3 groundwater balance of the , , depending on the infiltration turelli et al., 2003)-spring; 8- 3 : annual rainfall volume; r estigation underlined that, even at V was was estimated using the Thornthwaite ich is about 340,000 m became became more enriched in sodium and s s conclusion. In particular, water which (MOHa (MOHa and MOHb) did not produce any etween December and April 2). (Table A these clayey outcrops are impregnated infall and temperature. A water surplus of ring aquifer geometry and its storativity d coupling the mineralogical compositions was characterized by the lowest recharge ogy ogy with hydrochemical surveys for d. This aliquot represents an additional al investigation and could contribute to sources in slope-scale water budget s presented in Table 2. Adirect relation can presented s in Table Ca’ Ca’ Lita e Silla, Il Geologo dell’Emilia stablished the inflow of deep water into cannotthere beare noreached. Moreover, sourcesis suspected. seawater. es es of the system do not correspond with n annual groundwater recharge in the slope that hydrochemistry should be taken into ing of the hydrological limits of a hillslope oncovetro oncovetro (Vedriano, Comune di Canossa, ydrological balances and performing long- ide. around 7,800-17500 m iginates from an oilfield reservoir hosted at pplicata,8(2), 1-21, 2001. himica e radiometrica di alcuni corpi di frana 7738 7737 ) at the bottom of the aquifer was estimated by dw : mean annual volume of water hosted inside the ﬂysch; f V in each piezometer. Conversely, 2009-2010in Conversely, each was piezometer. very L by Ronchetti et al., 2009) the amount of water hos -2

. . O–B diagram. Point: 2, 4 (Boschetti et al., 2010) – baths; 3b – mud volcanoes; variations and the total and effective rainfall ca 3 L 18 δ was recorded at all points. On the slope scale, th Reservoir-concept model of the slope. Water volumes ( of the annual mean effective rainfall) was assesse L : annual water outﬂow volume) and their corresponding isotopic signals. 26% Fig.9: reservoir-concept model of the slope. inflow that cannot be detected by common hydrologic the destabilization of the slope. A good understand term modelling, and this study clearly demonstrates accountwhenever the presence ofother groundwater site is essential when calculating representative h

References Baraldi, S.: Caratterizzazione idrogeologica, idroc Conclusion 8) The paper underlined the utility of coupling hydrol dell’Appennino Emiliano. Casi di studio: 18, Romagna, 19-36, 2008. Vedriano, Bertolini, G. and Gorgoni, C., 2001: La lavina di R ProvinciaEmilia), di Reggio Quaderni di Geologia A quantifying the relative contributionestimation. A comprehensive hydrogeological of study e different the hydrological system of Ca’ Lita. This inflow or depth, demonstrating that the hydrological boundari the catchment area of the site. An annual inflow of OUT Fig. 9. V annual deep water volume inﬂow; Fig. 8. 5-common shallow groundwater;hydrocarbon seep. 6 Black line: (Cervi, evaporation line from 2003), seawater. 7 (Venturelli et al., 2003) – spring; 8-

O O - B diagram. Point: 2, 4 (Boschetti et al., 2010) 18

flyschis about 750,000 m

The The annual deep water volume inflow (V

hydrological year (Thornthwaite and Mather, 1957) i hydrological(Thornthwaite year and Mather, easily be observed: the 2006-2007 hydrological year value and consequent minimum GW

and the maximum GW

annual water surplus and infiltration area, the mea can be estimated in the range of 30,000 to 68,000 m

coefficients used (0.4 and 1 respectively). Conside coefficient (quantified as 10 Fig. 8: δ

The The mean annual groundwater recharge from rainfall Leaching experiments on soil samples strengthen thi A simple chemical equilibrium analysis was conducte 7) Discussion: influence of deep water inflow on the

common shallow groundwater; hydrocarbonseep. Black line: evaporation line from 6 (Cervi, 2003), 7 (Ven interacted with MVRa samples collected at Ca’ sulphate Lita than MVRb, leading to the supposition that with deep The water. interactions with MOH samples changesin chemistry water and ion contents. of the soil samples using equilibrium, the observed levels of Ca and Sulphate Phreeqc software. The inv localmineralogical phasesthat couldprovide chlor landslide and Mather (1957) formula and 40 year records of ra 200 mm/year was calculated, which is concentrated b comparison between GW corresponds to the flysch rock outcropping area, wh