Evaluation of groundwater and surface water resources in quality and quantity at Binh Chanh district in Ho Chi Minh city, Vietnam

Transcription

1 JDS International Seminar 29 th November, 2013 UNIVERSITY OF TSUKUBA GRADUATE SCHOOL OF LIFE AND ENVIRONMENTAL SCIENCES Evaluation of groundwater and surface water resources in quality and quantity at Binh Chanh district in Ho Chi Minh city, Vietnam CONTENT 1. Introduction 2. Objectives 3. Methodology Name : Bui Thi Tuyet Van Supervisor : Prof. Maki Tsujimura 4. Results 5. Conclusion 6. Future Work

2 Introduction Groundwater is a reliable source of water for drinking and production both in quantity and quality if the resource is properly managed. However, this resource is now under stress in some Asian cities because of unregulated and excessive abstraction. (IGES, 2007) Population growth Industrialization Urbanization 2 Increase in water demand Surface water polluted Overexploitation of GW Sustainable water management Drawdown of GW table Land subsidence Saltwater intrusion GW quality deterioration It is important to clarify GW flow system and the interaction between surface water and GW.

3 Introduction 3 (Source: Southern Institute for Water Resources Planning)

4 No Previous researches on groundwater in Ho Chi Minh city Recharge sources The flow component (m 3 /day) Pleistocene aquifer Upper Pliocene aquifer (2-3-4 th aquifers) 5 th 6 th 1 Flow recharged from rainwater 309,530 2 Flow recharged from Dong Canal 156,750 3 Flow recharged from Sai Gon river 67,500 (HCMC) Lower Pliocene aquifer 4 Flows from northern and western 22, ,170 94,030 boundaries of HCMC 5 Static flow 239, , ,970 Total 796, , ,000 Source: Department of Industry, 2002

5 Distribution of fresh water of aquifers 2 nd aquifer 3 th aquifer 4 th aquifer Source: Division for water resources Planning and Investigation, th aquifer 6 th aquifer 7 th aquifer Dissolved salts Fresh water Brackish water Saline water (ppt) < > 10

6 Drawdown of water table at monitoring stations in high well density area Change of GW exploitation rate in HCMC Source: Dan et al.,2007 The total recharge volume is only one-third of the extraction rate due to accelerated growth of impermeable urban surfaces and hydrological changes associate with rapid urbanization (Vo, 2007)

7 Study area: Binh Chanh district Area: 253 sq. km Population: 447,291 people Annual precipitation: mm Groundwater 90% (Source: IGES) 7 Source: MRC

8 Hydrogeological cross section Binh Chanh district 8 qp 3 qp 2-3 qp 1 n 2 1 n 2 2 n 1 3 qh : Holocene qp 3 : upper Pleistocene qp 2-3 : mid-upper Pleistocene qp 1 : lower Pleistocene n aquifers : upper Pliocene n 1 2 : lower Pliocene n 3 1 : Miocene Shallow groundwater (0 140 m) Deeper groundwater (>140 m) Aquitard (Researches of the Union No.8)

9 Objectives 9 To investigate the GW flow system of Binh Chanh district. To consider the stable isotopic compositions and ion concentrations in surface water and groundwater in both the dry and rainy season (March and August, 2013). To clarify the interaction between surface water and groundwater as well as among aquifers.

10 Methodology 10 Sampling: Dry season (March 2013): 39 samples Rainy season (Aug. 2013): 54 samples Field measurement: Air and Water temperature, ph, EC. GW level (the depth of GW table from ground surface) Location of samples: using GPS meter. Analysis in laboratory: Inorganic ions: Na +, K +, Mg 2+, Ca 2+ and HCO 3-, Cl -, NO 3-, SO 4 2- Stable isotope: 18 O, D

11 Location of sampling points 11 March 2013 August samples 9 RW 11 shallow GW 19 deeper GW. 54 samples 11 RW 23 shallow GW 20 deeper GW. 11

12 Result Groundwater table of shallow aquifers in dry and rainy seasons (2013) 12 1 st aquifer (4 25 m) Dry: ~ 3.28 m Rainy: ~ 4.54 m March 1 st aquifer August Water flow direction March th aquifer August th aquifers ( m) Dry: ~ 0.78 m Rainy: ~ 4.86 m

13 Result Groundwater table of deep aquifers in dry and rainy seasons (2013) 13 5 th aquifer Water flow direction March August 5 th aquifer ( m) Dry: ~ m Rainy: ~ m 6 th aquifer 6 th aquifer ( m) Dry: ~ m Rainy: ~ m March August

14 14 Result - Spatial distribution of geochemical composition and 18 O, March 2013 The north: exploited GW from shallow aquifers because of good quality. The south: exploited GW mainly from deep aquifers 18 O ( ) Na+K Ca Mg Na+K Ca Mg Cl HCO 3 SO 4 Cl HCO 3 SO 4

15 Result - Spatial distribution of geochemical composition and 18 O, August Na+K Ca Mg Cl HCO 3 SO 4 Na+K Cl Ca HCO 3 Mg SO 4 In the rainy season: Ion concentration and stable isotopic values of river water decreased. 18 O ( ) Ion concentration of deeper GW located in the south changes a little, while 18 O ( ) remained in dry and rainy season. Ion concentration of sample GW1.2 &7.3 (deeper GW) is too high an effect of saltwater intrusion

16 Result - Piper diagram of inorganic ions in rainy season (August) 16 River water Holocene Pleistocene Upper Pliocene Lower Pliocene Miocene fresh groundwater Ca-Mg-HCO 3 Shallow GW: Na-HCO3, Na-K-Cl (similar to river water) Saline water Ca 2+ Cl -

17 Result - Distribution of geochemical composition and 18 O in August Hydraulic head contour line Water flow direction

18 18 O ( VSMOW) 18 O ( VSMOW) Result - 18 O and Cl - concentration in March Cl (mg/l) Z August Cl (mg/l) 18

19 D ( ) Relationship between 18 O and D of samples in March -24 August River water Holocene Pleistocene -54 Upper Pliocene Lower Pliocene Miocene O ( ) GMWL LMWL (Bangkok)

20 Conclusion Almost river water samples are influenced by seawater intrusion. Some groundwater samples show high Cl - and Na + concentrations in both shallow and deep aquifers, suggesting an effect of salinized water intrusion to the fresh groundwater. Stable isotope value changes significantly between dry and rainy seasons. It is necessary to compare the data in dry and rainy seasons. 20 Future work Literature review Interpret deeply all results.

21 Thank you for your attention!