Application of Isotope Hydrology in Groundwater Resources Management in Tunisia

Transcription

1 Application of Isotope Hydrology in Groundwater Resources Management in Tunisia University of Hawaii, Manoa Honolulu, April 1, 2015 DR. MOHAMED FETHI BEN HAMOUDA Fulbright Visiting Scholar Division of Earth and Ocean Sciences Duke University CNSTN, Isotope Hydrology and Geochemistry Unit, Tunisia 1

2 Situation 2

3 Tunisia is considered as a freshwater scarcity country Most experts consider a m per capita per year is water shortage warning line. Tunisia is 393 cubic meters in 2011!!! 3

4 Tunisia is a country of physical water scarcity, which means water resources development is approaching sustainable limits 4

5 Global Water Stress Indicator (WSI) for major water basins The water basins in Tunisia are considered Over Exploited 5

6 393* 6

7 1850 mm Humid Pluvial water resources 36 Billions 3 m 225 mm/y 1000 mm 750 mm Sub humid 500 mm Semi arid 300 mm Upper Arid 200 mm Under Arid mm Desertic

8 Topography 8

9 Water resources 4850 Mm 3 Surface water : 2700 Mm 3 which Mm 3 can be mobilized Groundwater resources 2125 Mm Mm 3 shallow aquifers 1380 Mm 3 confined aquifers 650 Mm 3 are non renewable 9

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11 Water resources mobilization and transfer 11

12 COMBINED USE OF ISOTOPES AND CHEMISTRY Piezometric Salinity Nitrates maps Na/Cl Br/Cl Ratios Time series PL +TDS GW.R.M Localisation of vulnerable zones to the overexploitation, to salinisation and pollution Seawater fresh water mixing Origin and mechanism of salinisation Estimation of seawater fraction Localisation vulnerable zones to SW intrusion Isotopes 18 O, 2 H 18 O/Cl Ratio Groundwater recharge and origin Interconnexion between Aquifers Preferential zones of recharge and SW intrusion radioactive Isotopes 3 H, 14 C Groundwater Age dating, Infiltation velocity Estimation of renewal and recharge rate 12

13 Stable Isotopes In Hydrology take advantage of natural variations of isotopes in water to study hydrological systems Isotope fractionation 13

14 IAEA-WMO Global Network for Isotopes in Precipitation (GNIP)

15 d 2 H ( ) Vs SMOW Stables isotopes ( 18 O, 2 H) P.Q Shallow aquifer: Mixing line with sea water st group: Contribution of rain recent recharge 2 nd group: influence of SW intrusion and evaporation Recent water Evaporation line -20 M & O deep aquifers: Plio quaternaire 2001" Droite météorique mondiale DMM -30 Isotopic fingerprint Caracteristic of old water Droite météorique locale Tunis Carthage Old water Miocène 2001" Oligocène d 18 O ( ) Vs SMOW Plot of 18 O- 2 H in the Eastern Coast aquifer 15

16 Tritium 3 H indicator of recent rechage TRITIUM [TU] Undergo a Radioactive decay 10,000 Tritium in Precipitation 1, KAITOKE, NEW ZEALAND VIENNA, AUSTRIA TU = Bq/l YEAR

17 Tritium distribution map Kelibia El Haouaria Mer Méditerranée Sidi Daoud Dar Allouch Mer Méditerranée Korba Km Km Azmour Nabeul PQ (CO), Q (H) : High 3 H content recent water + Post nuclear water Low content : Up flow High content 3 H near the rivers Recharge from rain water Low content in 3 H Deep aquifer Fingerprint of Old water 17

18 14 C Groundwater Dating

19 30 14 C gorundwater age (ka) unconfined (phreatic) conditions Flow velocity = 2.2 m/a confined (artesian) conditions Distance (km) After Vogel et al. (1982)

20 Distribution map of 14 C in the Eastern cost aquifer 14 C dating ages confirm hydrogeologic information Kelibia High activities in 14 C PQ aquifer Near the rivers confirmation stable isotopes results High recent recharge Low activities Miocene et Oligocene: Old water fingertprint Mer Méditerranée Flow velocity: 0.3 to 2 m/year Korba Km Nabeul 20

21 Distribution map of 14 C in El Haouaria aquifer Mer Méditerranée Shallow aquifer: recent water (High 14 C activities) El Haouaria Pliocene confined aquifer: Corrected Ages from 100 to years according to the depth and undergroud route Sidi Daoud Dar Allouch Low water velocity 0.2 to 2.5 m/year Azmour 21

22 Pizometric data with ( 18 O + 2 H), 3 H, 14 C R : Recharge Kelibia PL > 0 ; rise in PL (time series) ( 18 O + 2 H) close to WA isotope composition TC 3 H: 14 C: E : Overexploitation : Mer Méditerranée PL < 0 ; Continious decrease (time series) Korba R : Recharge Nabeul Km E : Exploitation CO: The inertia zone is located in the south of O. Boulidine (interconnexion between aquifers). Map of localisation de recharge and overexploitation zones 22

23 Mer Méditerranée Sidi Daoud El Haouaria H: the inertia zone is very limited due to the small surface and the thikness of the aquifer Dar Allouch R : Recharge E : Exploitation Map of localisation de recharge and overexploitation zones 23

24 Conclusion for these 2 aquifers in term of Groundwater recharge Management Monitoring Pizometry Hydrogeologic informations stable Isotopes 18 O, 2 H PQ, Q Aquifers recharged Rain water Post Nuclear Last decades Up flow Fast Infiltration Seawater Intrusion Tritium 3 H 14 C GW Dating PQ, Q: High Act. O,M,P: Low Act Ages 0 to years Tr= 0.3 % Recharge 12 mm/an in the preferential zones of recharge authorize exploitation Zones of overexploitation Establish a save and forbidden areas 24

25 In Tunisia we have Forbidden & Save areas: 32 Save : 23 (green) Forbidden: 9 (red) 25

26 Use of geochemical and isotope tracers for the characterization of water leakage at the Joumine dam, Tunisia Upstream watershed: 418 km 2 Capacity: m 3 After its construction Leakage of 500 l/s observed: D1 and D tons of mining residues in the sinkhole Leak: 500 l/s to 120 l/s reduction of 75% of leakage 26

27 5/6/84 5/6/86 5/6/88 5/6/90 5/6/92 5/6/94 5/6/96 5/6/98 5/6/00 5/6/02 5/6/04 5/6/06 5/6/08 5/6/10 Salinity in (mg/l) Water reservoir level in (m) Average Reseroir D 1 D 2 P 26 P 57 Water Level Construction of the dam Injection of material Decrease of the flow rate was accompained by an increase of the Salinity in D Which was interpreted as a risk of stability of the dam 0 40 Date Evolution of salinity and water level in reservoir from 1985 to

28 The two pillars integrated Cretaceous limestone, based on Triassic formations Geologic map of the Joumine dam (2013) 28

29 Water level, Temperature and EC at boreholes Water samples geochemical and isotopes Determination of origin and paths of leaks Quantify leakage Corrective action to minimize losses Reduce the risk of security and stability of dam 29

30 Upstream downstream 30

31 Valuable information on the local groundwater flow and hydraulic connections in the dam and in the surrounding areas The leakage emerging in D1 and D2 is related to infiltaration occuring near the uptake tower were the sinkhole was found Piezometric map at Joumine dam (2013) The arrows show the preferential pathway of water escarping from Reservoir 31

32 Similar EC in R & D1 D2: EC 2.34 ms/cm It was not clear high salinity Dissolution of material used for the dam construction Consequence of GW discharging from the underling Triassic formations The 2 nd hypothesis was the valid one Distribution of EC values at the Joumine dam expressed in ms/cm at 25 C 32

33 Temp C best traceur for leaks Temp R= 14.5 C The samples which are located on the paths of leaks have a T emperature close to the R Distribution of temperature in C values at the Joumine dam 33

34 Concentration (ppb) Concentration (ppb) Drain I 700 Drain II Rhodamine Uranine Uranine Rhodamine Time since injection Time in hour after injection Breakthrough curves obtained in drain D1 and D2 Q A C( t) dt V were C( t) dt Q A C( t) dt C Injection A t Where A indicate the surface of the curve, Q represent the flow rate C: concentration T: time QD l / s et QD l / s 34

35 Piper Diagramm The SI gypsum / SO 4 relationship Various chemical water types The reservoir & D1 same facies Water is unsaturated Vs. gypsum and anydrite Progressive Saturation Vs increase in SO 4 35

36 d 2 H ( ) st group: -4,4< 18 O<-3,7 Old water P42 P2 P41 P24 P12 P49 P22 recent water P55 P57 P57-14 D2 P57-2 D1 R P21 P57-1 Global meteoric water line Tunis Carthage meteoric local line Joumine Evaporation Line Proximity to the reservoir: same origin :water leakage 2 nd group: -5,6< 18 O<-4,9 Water depleeted: Local groundwater d 18 O ( ) Correlation ( 2 H, 18 O) in Joumine dam -40 confirming the above fact that the reservoir water is the main source of water leakage 36

37 Determine the pathways of water leaks and estimate any recent recharge to the aquifer from the reservoir 1st group 1,2 UT <Tritium<5UT Recent water coming from reservoir. 2nd group: 1,2 UT < Tritium Old water mixing with water coming deep aquifer. Map of distribution of Tritium in Joumine dam (2013) 37

38 Determination of suspended elements in Medjerda river by using nuclear probe 20 to 25 Mm 3 sediments / year Loss of 0,5 % of storage capacity Clogging of hydraulic infrastructure Watershed of Medjerda river, NW Tunisia Sedimentation of wadi s beds 38

39 Panneau solaire Pluviomètre Rotation vers deux Armoire de directions commande Translation verticale de la colonne Manivelle de manutention Porte source et détecteur Socle en béton SCHEMA GENERAL DE LA STATION AVEC LES STRUCTURES METALLIQUES General outline of measuring station with the metallic structures I I 0 exp C 1 C m s w I: intensity of radiation through a thickness of water with a concentration C. I 0 : intensity of the emitted radiation. µ s : sediment mass attenuation coefficient µ w : :Water mass attenuation coefficient ρ m : density of the water-sediment mixture Tige de manipulation de la protection de la source Connexion électrique du détecteur NaI Emplacement du détecteur NaI Bouchon métallique Joint Cale en plastique Source radioactive Support en plastique de la source Conteneur métallique m s w C s ρ s : density of sediments ρ w : density of water s w Détecteur NaI Implementation of the radioactive source and the NaI detector in the probe 39

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43 Determination of level of water in river H(m) ma Level of water in river depending on the pressure y = 0,1517x 1,849 R 2 = 0,99 Determination of flow rate in river 800 Q(m 3 s -1 ) ,5 1,5 2,9 4,3 5,3 6,4 7,4 8,4 9,4 10,4 11,4 H(m) Gauging Curve at Slouguia station 43

44 Comptage (CPM) Determination of the concentration of suspended elements y = -3919x R 2 = NaI detector converts into electrical impulses recorded radioactivity in CPM C(g/l) C( g / l) CPM 3919 Counting & concentration of SE Relationship 44

45 Determination of solid flow Gs of suspended elements Crossing the section of the river Débit (Q) Pluviométrie Transport des Sed. Cencentration des sed.susp C Gs( Kg / s) Q C with Q : flow rate (m 3 s -1 ) C : concentration of suspended elements (kg m -3 ) mm m 3 /s Volume total d eau m 3 Kg/m 3 Gs Kg/m 3 Poids total (Kg Temp (s 45

46 Big fluctuation of the sediment concentration concentrations varies from 0.1 to 6 g/l The amount of sediment during this period was estimated at T. Example of hydrological parameters over 2005 at Slouguia Station 46

47 Profondeur (cm) profil 2003 profil 2001 profil 1996 profil R.D R.G Continuous sedimentation of Medjerda since entry into service of the Sidi Salem dam Distance (m) Profile across the wadi Medjerda at Slouguia station 47

48 Activities with IAEA: RAF/0/038: Promoting Technical Cooperation Among Developing Countries (TCDC) in Africa through Triangular Partnerships: Use of geochemical and isotope techniques to improve water resources management of coastal aquifers in Senegal and Tunisia. ( ) Participation in the TC project TUN/7/001: Assessing the Impact of Uses and Management Practices on Water Resources Using Isotopic Techniques to Improve Water Resource Management ( ). IAEA Project Counterpart TUN/8/017 IAEA Project Counterpart TUN/8/014: Evaluation of erosiont and sedimentation in the Medjerda River, ( ). IAEA Project Counterpart TUN/8/015: Assessment of marine intrusion in coastal aquifer systems of Cap bon, ( ) *Course Director of IAEA training in Isotope Hydrology with particular emphasis on Dam Safety, April 2002, Tunisia * IAEA Project Counterpart: INT/5/144: Sustainable Utilization of Saline Groundwater and Waste Lands, ( ). *Project Counterpart RAF/8/028 Investigating Dam and Reservoir Leakage and Safety in Africa, ( ) *Participation in the TC project TUN/5/017: Nuclear Techniques to improve Water and Soil Management of Kairouan plain. 48

49 Visit of IAEA Director General Yukiya Amano to the Isotope Hydrology Laboratory CNSTN, Tunisia, 25 June

50 Isotope Ratio Mass spectrometry Lab 50

51 Carbon 14 for Groundwater Dating Lab 51

52 GEOCHEMISTRY LABORATORY 52

53 ATLAS - Presents summary information of about 10,500 water samples - 26 countries and 79 IAEA projects

54 Thank you! 54