Problem of Salinity in Coastal Aquifers of Tunisia

University of Hawaii, Manoa Honolulu, April 2, 2015

DR. MOHAMED FETHI BEN HAMOUDA

Fulbright Visiting Scholar Division of Earth and Ocean Sciences Duke University, NC, USA CNSTN, Isotope Hydrology and Geochemistry Unit, Tunisia 1 Kelibia Beach, Tunisia Coastal Zones

WR Strategic

variable Population availability growth Agriculture WR Industry And Tourism

Population Severe and irregular increasingly urban and Climate concentrated along the coast

Increasing water demand

OVEREXPOITATION

PIEZOMETRIC DROP

INCREASE OF WATER SALINITY 2 Causes of salinisation of aquifers?

Natural and anthropogenic

Water Air Pollution

Vapeur

Waste water Mines Drainage Acid Industrial dump rain

Evaporation Continental Evaporites Surface Water

Infiltration, Evaporation Pumping Water irrigation return Irrigation Seawater Groundwater Salinisation Geothermal Water

Dilution /mixing Magmatic Rocks Sedimentary brines Primary Secondary Dissolution of mines wastes

Marin Evaporites 3 What are the Consequences?

Economic and social

Loss of fresh water: water-quality degradation

Environment: Loss of biodiversity: replacement by halotolerant species

Human health: inorganic pollutants: Nitrates, Arsenic, Selenium, Boron and radioactivity

Loss of fertile soils

Collapse of agricultural

Immigration, exodus to the cities 4 Geochimical and et Isotopic tools Tracers of salinity

Cations (Ca, Mg, Na, K) Anions (Cl, SO4, Br, NO3)

stable and radioactive 18O, 2H, 13C, 3H, 14C Isotopes

5 Problem of salinity in four coastal aquifers

Sampling and Djeffara: 29 measurement Sousse: 30 Côte orientale: 47 El Haouaria :35 6 Climate and Hydrology Sub humid to Semi arid and arid climate Mediterranean Mild winter )16°C ( Hot summer ) 30°C( P= 570, 440, 320, 180 mm/a ETP = 1100, 1750, 1300 mm/a

• No perennials rivers

• Small rivers carry water

• Intense storm cause surface runoff

• O. Laya and wadi akarit major wadis reaching the coast

• The wadis discharge into Hydrographic network and salty lakes Isohyetes Map of Tunisia 7 Evolution of exploitation

La Nappe profonde de la Côte Orientale

6 120

Nb de forages 5 100 Exploitation

4 Eastern Coastal

80

3

60

(Mm3)

(Nbdeforage)

2

40

1

20

0 0

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

La Nappe profonde d'El Haouaria

6

60

5

50 4

40 El Haouaria plain

3

30

(Mm3)

(Nb de forage)

2 20

Nb de forages 1

10 Exploitation

0 0

1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004

Exploitation of Djeffara aquifer 4500 (1950-2003)

4000

3500

3000 Djeffara plain

2500 Expl-Djeffara 1950-2003 (l/s) Djeffara-Gabès

Débit(l/s) 2000

1950 1952 1954 1956 1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 8 Evolution of piezometry in El Haouaria plain

18 16 P41 Average: 3.38 m 14 P42 12 10 8 N.P (m) N.P 6 4 2 0 juin-72 juin-77 juin-82 juin-87 juin-92 juin-97 juin-02 juin-07 11 % Années This decrease ranges from 1 to more than 14 m according to the location of the well

4 average: 2.83 m 8862 2 8894 0 -2

N.P (m) N.P -4 -6 5 % -8 juin-72 juin-77 juin-82 juin-87 juin-92 juin-97 juin-02 juin-07 Années Continued decline of piezometry 1 to over 11m

Métouia 6 (N°IRH ) 26 Reducing artesian 25 pressure 24 Depletion wells 23

22 Springs dry NP(m) 21

20

1963 1966 1969 1972 1975 1978 1981 1984 1987 1990 1993 1996 1960 9 Consequences

6 8684 P19 9 892 8315

5

4

3

RS (mg/l) RS 2

1

0 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Années

Temporal evolution of the salinity (g / l) at the Eastern coastal aquifer

10 Geological and Hydrogeological setting

Geological block diagram at the Cap Bon (Ben Hamouda et al, 2011)

Miocene and Oligocene outcrop in Jebel Sidi Abderrahmane

Pliocene and Quaternary outcrop near the coast at the Eastern shallow aquifer Quaternary covers the plain of El Haouaria

11 Shallow unconfined Deep confined

Hydrogeologic cross section SW-NE (Ben Hamouda et al, 2013) 12 Djeffara Four aquifers levels

Shallow: Quaternary (Pontien)

Miocene sands

Senonian limestone

Continental Intercalaire

Hydrogeologic cross section in Djeffara aquifer (Ben Hamouda et al, 2013)

13 North-western Sahara Aquifer System NWSAS

Great Oriental Erg

2.5 billion 3m in 2000 to 7,8 billion 3m in 2050 14 15 The « Continental Intercalaire » (C.I.) aquifer

1200 km

0 m

-1 km

-2 km

16 17 Piezometric Maps

Kelibia

El Haouaria Mer Méditerranée

Sidi Daoud Dar Allouch

Korba Km Azmour Mer 0 2 4 Méditerranée

Quaternary aquifer Nabeu l Characterized by a grounwater divide Plio-quaternary aquifer Flow south and north Main flow: O-E toward the center of the plain and Alongside wadis moves towards the east and west and towards the sea 18 Oued Laya Aquifer Djeffara aquifer

Groundwater flow Groundwater flow towards the sea towards the sea Groundwater is recharged by rain and runoff and from a vertical leakage (up flow) from Djeffara

19 Continental intercalaire

Main flowpaths under the Great Oriental Erg

20 Salinity map : Eastern Coast El Haouaria plain

Kelibia

Kelibia Mer Méditerranée El Haouaria Menzel Temime

Sidi Menzel Horr Daoud

10 Dar Allouch Tafelloune

8

Korba Mer Méditerranée Mer Méditerranée Azmour Korba

Quaternary aquifer Béni Khiar Nabeul High salinity level at Haouaria (depression area) 5-6 g/l Nabeul Plio-quaternary aquifer Near the coast, Salinity 2 to 3 g/l, littoral High salinity in Korba Tafelloune barrier 6-8 g/l, 20 to 30 g/l 21 Salinity map O. Laya Salinity map nothern Djeffara

Salinity varies from 2 to 10 g/l Salinity varies from 3 to 8 g/l

22 Estimation of the mixing with seawater

using chloride as a conservative tracer (Barbecot, 1999)

Cl  Cl F  sample fresh Clsea  Cl fresh

F sea is fraction of Seawater (0

23 Kelibia

the % SW 1 à 30 %

Max of SW is 70 % (13143/2)

66 % in the 11186/2 3 % in the 11829/2

Heterogeneity of

Mer Méditerranée processus Of salinisation H: P 31 & P34, F< 1 % Korba Confirmation absence of Seawater intrusion

Nabeul

Map of Estimation of mixing with seawater (%)

24 Piper Diagram

Mixted chemical profile

Na-Cl and Ca-Cl water type

Anions: Cl> SO4 et HCO3

Cations: Na> Mg et Ca

Wells whose waters are contaminated by seawater are turning into Ca-chloride water, different from seawater (NaCl water type).

25 The [Na+]/[Cl-] relationship

Indicates contribution of Halite dissolution to the mineralisation GW 140 marine ratio Halite Djeffara

120 Sousse Haouaria Côte Orientale 2 parallel trends

100 Na/Cl > 1 reflecting 80 Income of Na to GW

system Na Na (meq/l)

60 WRI

40 Ion exchange

20 Na –Ca Clay minerals 0 0 20 40 60 80 100 + O.M Seawater intrusion: Chloride (meq/l) Na/Cl

Na is retained and Ca is released

26 The [Br-]/[Cl-] relationship

A distinctive geochemical fingerprint

1.0E-02 Seawater Br/Cl=sw

8.0E-03 Haouaria Seawater intrusion

Côte Orientale

6.0E-03 Sousse Relationship not distinctive 4.0E-03 Br/Cl Br/Cl (molar)

2.0E-03 Sea spray Influence on the infiltrated 0.0E+00 0 10 20 30 40 50 60 70 80 90 100 rain water

Chloride (meq/l)

Brine contamination

27 The SI gypsum / SO4 relationship

Precipitation,

1 disolution and 0.8 Ion exchange

0.6

0.4

0.2

0 0 10 20 30 40 50 60 70 80 90 100 Water is -0.2 unsaturated -0.4

Gypsum Djeffara

-0.6 Vs. gypsum SI SI -0.8 Sousse and anydrite

-1 Haouaria

-1.2 Côte Orientale Progressive -1.4 Saturation Vs -1.6 increase in -1.8

-2 SO4 SO4 (meq/l)

28 High salinity linked to the geology : presence of gypsum

XRD Spectrum of gypsum found in the geologic formations

29 2 18 Isotopes Stables ( H, O) 1st group: -1 ‰ < 18O < -4 ‰ -8 -7 -6 -5 -4 -3 -2 -1 0 0 Probable seawater Mixing line with sea water intrusion -10

nd -20 2 group: Recent Water 18

SMOW -4 ‰ < O< -5 ‰ -

Old water Recharge from -30

H (‰) H V 2

rainwater d Shallow Eastern Coast Global meteoric water line GMWL -40 rd Local meteoric line of Tunis Carthage 3 group Deep Eastern Coast : -4.9 < 18O< -6 Djeffara Shallow Haouaria -50 Fingerprint of old Deep Haouaria water. Sousse Paleowater

-60 th d18O (‰) V-SMOW 4 group: Paleowater from CI and Djeffara 2 18 Plot of d H ‰ Vs. d O ‰ (V-SMOW)

30 Relation 18O/[Cl-]

100000 Marine pole Seawater (SMOW, 19500) 10000 Paleowater

Recent water Sal: SWI + Evap.

1000 Rain water (mg/l) (-4.4 ‰,10)

Shallow Eastern Coast Recent water (300, Chlorides 100 Old water Deep Eastern Cost 2000 mg/l) Sea water

Tunis-Carthage rain 10 Shallow Haouaria Sal: WRI + C. Exch Deep Haouaria

Tunis-Carthage Sousse rain pole Djeffara Old water 1 -8 -7 -6 -5 -4 -3 -2 -1 0 (100, 400 mg/l)

d18O (V-SMOW) Paleowater (1000, 3000 mg/l) Relation entre Cl- et d18O ‰ (V-SMOW) Diss. Halite

31 12,0 Plio quaternaire Miocène 10,0 Plot of Tritium Vs Chlorides Oligocène Eau post-nucléaire 8,0

3 6,0 Le H identify differents water types : Eau récente

4,0 Tritium (U.T)

2,0 Group post-nuclear Eau ancienne

0,0 Low content in Cl 0 500 1000 1500 2000 2500 3000 3500 4000 Fast infiltration in the rivers Chlorures (mg/l)

12.0 Group recent water Recharge durind last 10.0 Quaternaire decade Eau post-nucléaire Pliocène 8.0 High salinity

6.0 Group Old water

Tritium (UT) Tritium Eau récente 4.0 3H (<1 UT) 2.0 Eau ancienne 0.0 0 500 1000 1500 2000 2500 3000 Chlorures (mg/l) 32 (3H et 14C)

6.0 1000 GAB 4 GAB 10a 5.0 100 GAB 14

GAB 15 MRT (years) MRT 4.0 10 GAB 21 0.1 1 10 all others Tritium (TU)

3.0

H(TU) 3

2.0

1.0

0.0 -8.00 -7.00 -6.00 -5.00 -4.00 -3.00 -2.00 Oxygen-18 )‰(

Correlation between tritium and δ18O in Djeffara aquifer Map of distribution corrected ages in Oued Laya aquifer

indicator of recent recharge The coastal zone is an area of recent and renewable water. While the area located in S.O is that of older waters that exceeds 5000 years

33 Isotope contents in “deep” groundwaters – Northern Africa  mapping fossil groundwater

34 Radioactive isotopes (3H et 14C) modeling of renewal rate

Leduc, (1996, 2000), Favreau, (2000, 2002), Le Gal La Salle, (2001) et Cartwright, (2007)

Rr (%)

3H et 14C Discharge Recharge (Ani) (Api) (Ani)

Variation of reservoir (∑ Hn) (-5 to -11 %)

Conceptual schema of estimating of renewal rate is a simple model of vertical mixing. The model assumes an uniform isotopic facies throughout the thickness of the aquifer and a constant water storage, that is to say a discharge of water exactly compensated by infiltration of rain

35 (3H et 14C): Renewal rate estimation

(1) ln2/ Pe (Leduc, 1996) Ani  1 Rr  Ani1 e  (Rr  Api )

with :

An i: Activity in groundwater for the year i

Rr: Annual renewal rate of groundwater,

An i-1 : Activity in groundwater for the year i -1,

Pe : Period of radioisotope (14C or 3H),

Api : Activity in rain for the year i.

i1 i1  ln2/ Pe      Ani  1 Rr  Ani1 e 1  Hn   (Rr  Api ) /1  Hn    n1    n1 

36

Tritium (UT) 300 10000

Tritium mediane 250

1000 14C

100 200

C Troposphèrique C (PMC)Troposphèrique

10

150

14

1

Tritium Pluies Tunis Carthage(UT)

100

1950 1960 1970 1980 1990 2000

Chronic reconstructed and extrapolated from annual levels of 3H in rain and from annual tropospheric levels for 14C since 1950

14C: (Nydal et al, 1996)

37 Annuel Renewal rate estimated from Tritium

1000 3H= 4.4 TU (2001) et 20 TU (1980)

2001 100 Lassoued, (1980) 1980

10

1 Tritiumnappe dans la (U.T)

0,1 Rr = 0.2 % (2001) et 0.3 % (1980) 0,01 0,1 1 10 100 Taux de renouvellement annuel Tr (%)

100

10

1 2001

Tritiumnappe dans la (U.T) 1980

0,1 0,01 0,1 1 38 Taux de renouvellement annuel Tr (%) The determination of renewal rate of the aquifer to estimate the recharge rate

R = T . p . Rr Leduc, (1996, 2000) et Cartwright, (2007)

Avec:

R : Recharge in mm/year Rr : renewal rate P : Porosity T : Thikness of the aquifer in m

H: T= 30 m, P= 14% R= 12 mm/y

C.O: T= 43 m, P= 12% R= 10 en mm/an

39

Dissolution Recharge (rain) Of salts WRI Salinisation (Halite+Gypsum) Cations exchange

Semi Arid Hydrochemical •Irrigation Coastal zone isotopic Data return flow Prevailing wind • Sea spray Mediterranean Sea Origin of salinity

Hydrogeologic Near the information Evaporation salty lake

•Piezo drop Seawater • Salinity map Intrusion •Na/Cl Ratio 1-70 % (CO) •Br/Cl Ratio < 1% (H) •isotopes 18O,2H

40 Thank you !

41 Evolution of the Tunisian population (1000.hab) source : Prévisions Démographiques Nationales, Institut National des Statistiques, Août 2005 13000

12000

11000

10000

9000

8000

7000

6000

5000

4000

3000

42 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 2055 2060 2065 Drinking Water: 300 Mm3 (30 m3/Cap/year)

Industrial Water: 100 Mm3 ≈ (10 m3/Cap/year)

Tourist Water: 20 Mm3 ≈ (2 m3/Cap/year)

Agriculture : 2100 Mm3 ≈ (210 m3/Cap/year)

43 • is limited ~ 400 m3 /Cap/year

• is non uniformly distributed In space & In time

• is largely exploited (~ 80 %)

44 In Tunisia, from 600 to 1400 m3/year/hab

m3/an/hab 1500

1300

1100

900

700

500 1960 1970 1980 1990 2000

45 données : FAO www.fao.org/countryprofiles & INS Tunisie Overexploited Aquifers in red (in 2000) 46 source: Annuaires d’exploitation des nappes profondes & phréatiques, DGRE < 1.5 g/L

1.5 to 3 g/L

> 3 g/L

Salinity of shallow aquifers (< 1.5 g/L; 1.5 to 3; > 3 g/L) 47