12/10/2013 JDS International Seminar 2013 Research Topic Groundwater flows system at Cu Lao Dung Island, Soc Trang Province, Vietnam Student: Tran Dang An, M2 Supervisor: Prof. Tsujimura Contents 1. Background 2. Objectives 3. Study Area 4. Methodologies East Sea 5. Results and Discussion 6. Conclusions 7. Future works 1
12/10/2013 Introduction: Mekong Delta (MD) Mekong river Basin: The biggest river and the richest biodiversities in the world (WWF, 2012). Mekong Delta: • Very important role for food security, accounting for over 50% national food production of Vietnam (Anh et al., 2010) • • Many issues due to hydropower plants Many issues due to hydropower plants (Tyson R. Roberts, 2000; R. Edward Grumbine et. at, 2011; Jennifer Sills, 2012; Claudia Kuenzer et. Al, 2012). 1.Social issues: East Sea Serious impacts on livelihoods (18 mil.) 2.Environmental issues: Mekong Delta Lost biodiversities; water contaminations, seawater intrusion => Water scarcity Fig.1.1 Mekong Basin Hydropower plant s (R. Edward Grumbine et. al, 2011) 2
12/10/2013 Introduction: Current problems in MD 1. Surface water and soil pollution: � POPs: DDT, PCBs affected seriously on Mekong river and its aquatic environments (Carvalho et al., 2008; Ikemoto et al., 2008; Minh et al., 2007; Sudaryanto et al., 2011; Toan et al., 2013) � � Heavy mental and chemical fertilized: Pb, Mo, Rb Heavy mental and chemical fertilized: Pb, Mo, Rb and As influenced seriously on aquatic environment, particularly fish production (Yamaguchi et al., 2007). Chemical fertilizers also discharged into agricultural soil, river water and sediments (Toan et al., 2013). 3
12/10/2013 Introduction: Previous researchs 2. Groundwater contamination: � Urban areas: Holocene aquifer is heavily polluted with microbial and inorganic pollutants and considered unfit for drinking water purposes (Tuan, 2004; Danh, 2008). � Arsenic pollution causing severe health problems (S. Fendorf et al.,2010; Erban et.al, 2013). Fendorf et al.,2010; Erban et.al, 2013). 3. Seawater intrusion: � Serious issues in Mekong delta (Ho et al., 1991; Buschmann et al., 2007). 4
12/10/2013 Objectives Serious seawater � The questions : Severe pollution intrusion Chemical pollution River water Sea water Arsenic Ho et al (1991) contamination Over groundwater exploitation （ Inappropriate management ） （ Inappropriate management ） Shallow ? ? Groundwater Seawater intrusion Deep Groundwater � To answer : It is necessary to know Groundwater flow system in coastal aquifers (Hydro-geochemical processes) 5
12/10/2013 Study site: Cu Lao Dung Island Groundwater 80% 80% Private Wells (80-140m) Fig.4. Location of Water Samples in CLD Island 6
12/10/2013 Study site: Soc Trang province Groundwater: 54 samples River and canal water : 19 samples Fig.5.4. Samples locations of water samples at Soc Trang Province, Vietnam 7
12/10/2013 Methodology Approaches Field survey Lab Analysis I N � GWL, DO, ORP, T 0 C � Na, K, Mg, Ca,SiO2 T T � EC (Salinity) � EC (Salinity) � Cl, HCO3, NO3, SO4 � Cl, HCO3, NO3, SO4 E � Water Flow path � Mixing processes R � Seawater effects � Ion exchanges P R � Taking water � Stable Isotopes: E � (δO18 and δD) samples T � 54 Groundwater � Original water � 19 River water � Recharged areas Groundwater flow system, Interaction process 8
12/10/2013 Results and Discussion Water types and relationship among water sources Legend I - Calcium Magnesium Sulphate Chloride; II –Sodium Chloride Sulphate III –Sodium Bicarbonate; I IV –Calcium Magnesium Bicarbonate T10 A –Mixed Zone; B –Magnesium; C –Sodium Potassium; D –Calcium GW1.19 E –Mixed Zone; F –Sulphate; G –Chloride; H -Bicarbonate MX5 IV II T16 G2: Mixing with saline water G2: Mixing with saline water G4: Mixed water? B F Hot water III G1: Freshwater A E G3 Freshening D H C G aquifer ? Fig.5.1. Piper diagram of water samples at Soc Trang Province, August . 2013. 9
12/10/2013 Result and Discussion T 0 C > 40 0 C, EC > 1500 µS/cm 100.0 Effects of Silicate Mineral T11-S T9-S (Hot rocks dissolution) Seawater 10.0 T12-S T8-S intrusion? Ca 2+ / Mg 2+ > 2 a/Mg(mmol/ MX5 T7-S T16 T10, CAI >0 Dissolution of Dolomite Ca 2+ / Mg 2+ =1 1.0 Ca/M Ca 2+ / Mg 2+ < 1 GW-CLD L) GW1.19, CAI > 0 S-GW-ST 0.1 D-GW-ST Precipitation of Ca 2+ as CaCO 3 RW-CLD RW-ST 0.0 0.01 0.1 1 10 100 1000 Cl (mmol/L) Most of samples: CAI <0 , Mg, Ca of water exchanged with Na, K of Rock S-VC1, S-VC2, CTD1, T10,GW1.19 : CAI >0 , Na, K of water exchanged with Mg, Ca of Rocks Seawater intrusion ? Fig.5.2. Ratio of Ca/Mg versus Cl (mmol/L) 10
12/10/2013 Results and Discussion Whether seawater intrusion occurred or not? 100.0 S-VC2 S-VC1 2- (mmol/L) >6.5: strongly affected RW1.5 CW1.3 10.0 T10N - +CO 3 T9N slightly and moderately T16 T8-S T12N 1.0 Groundwater at qp23 Groundwater at qp23 T14 T14 Cl - /HCO 3 3 T9-S T9-S auifer in CLD Groundwater at qp23 aquifer in ST Deep groundwater at n13 aquifer in ST 0.1 Groundwater at qp1 GW1.19 aquifer in ST River water in CLD <0.5: Not affected River water in ST 0.0 0.01 0.1 1 10 100 1000 Cl - (mmol/L) Fig.5.3. The Cl - /HCO 3- +CO 32- versus Cl - 11
12/10/2013 Results and Discussion Fig.5.4. Groundwater flow paths at Soc Trang Province, August, 2013. 12
12/10/2013 Result and Discussion Seawater CDT1-T9N 80-130m intrusion here? 400-500m 400-500m Fig.5.5. Spatial distribution of Hexa diagram and δ O 18 of water samples at Soc Trang Province, August, 2013. 13
12/10/2013 Results and Discussion δ O 18 (per mil.) ����� ����� ����� ����� ����� ����� ����� ����� ������ δD = 8δO 18 + 10 S�VC2 ������ S�VC1 ������ T14 T5 T12N ������ r mil.) VC1.3 qp23�CLD δ D (per m qp23�ST T9N CTD1 ������ S�MX1 qp1�ST δD = 7.35δO 18 + 6.11 n12�n13� ST MX2 ������ River Water � CLD River water � ST ������ CW1.3 Linear (qp23�CLD) Linear (MWL) RW1.5 ������ Linear (Bangkok MWL) Linear (qp23�ST) ������ Fig.5.6 .Groundwater flow paths at Soc Trang Province, August, 2013. 14
12/10/2013 Results and Discussion Fig.5.7. Hydro-geological cross section, Soc Trang Province, Vietnam. 15
12/10/2013 Results and Discussion Soc Trang City Fig.5.8. Profile Hexa diagram and of water samples following depth of wells in Soc Trang, August, 2013 Cross section B-B 16
12/10/2013 Results and Discussion Fig.5.9. Profile Hexa diagram and of water samples following depth of wells in Soc Trang, August, 2013 Cross section F-F 17
12/10/2013 Results and Discussion Either seawater intrusion or mineral dissolution or both? Cl (mg/L) 1.00 10.00 100.00 1000.00 10000.00 �3.00 S�VC1 S�VC2 T14 T12N �4.00 T15 T10 T9N S�MX1 T16 SMOW �5.00 CDT1 GW1.19 δ O 18 ‰ SM Seawater intrusion Seawater intrusion ? ? �6.00 ? �7.00 RW1.5 GW�CLD qp1�ST CW1.3 qp23�ST �8.00 Deep GW� ST RW�CLD RW�ST �9.00 Rain water dilution Same recharged sources Fig.5.10. Chloride concentration versus δ O 18 18
12/10/2013 Results and Discussion CAI 1 = (Cl - - [Na + + K + ] )/ Cl - -20.00 -15.00 -10.00 -5.00 0.00 5.00 10.00 0.00 Groundwater at qp23 aquifer Cu Lao Dung Island Seawater intrusion ？ ？ ？ ？ Groundwater at qp23 aquifer , Soc Trang -1.00 Mineral dissolution Groundwater at qp1 Aquifer, Soc Trang Deep groundwater at n13 aquifer, Soc Trang -2.00 Mineral dissolution River water at Cu Lao Dung Island River water at Soc TrangT -3.00 SMOW T14 S-VC1 S-VC2 T5 T12N T12N -4.00 -4.00 δ O 18 ‰ S T6 T10 T16 T15 CTD1 -5.00 S-MX1 -6.00 Mineral dissolution -7.00 CW1.3 Mineral materials dilution RW1.5 -8.00 -9.00 Fig.5.11. CAI 1 index versus δ O 18 19
12/10/2013 Results and Discussion ∆ Cl = C Cl sample - C Cl mix (meq/L) -20 -19 -18 -17 -16 -15 -14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 0.00 Groundwater at qp23 aquifer in Cu Lao Dung Island -1.00 Groundwater qp23 aqu ỉ fer in Soc Trang Seawater intrusion >> Groundwater at qp1 Aquifer in Soc Trang Mineral dissolution Mineral dissolution >> -2.00 Deep Groundwater at n13 aquifer in Soc Trang Seawater intrusion trend River water at Cu Lao Dung Island River water at Soc Trang -3.00 MOW T14 δ O 18 ‰ SMO T6 T5 -4.00 T12N T15 T10 T16 CTD1 VC1.3 T9N -5.00 -6.00 -7.00 << Mineral dissolution CW1.3 RW1.5 <<< Mineral materials dilution -8.00 -9.00 Fig.5.12. Chloride concentration versus δ O 18 20
12/10/2013 Conclusions 1- Water types: a. Groundwater, 3 group: � qp23 Aquifer: Ca-Mg(CO3)2, � qp1 and n13 Aquifers: Na-HCO3, most of samples at n13 aquifer is hot water b. River and canal water: � Na-Cl, Ca-Mg(CO3)2 2. Interaction between Surface water and Groundwater: � River water (CTD1) and Groundwater (T9N) mixing together � Groundwater: some parts of ST may be affected by seawater 21
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