Hydrogeological Framework for Potential Groundwater Resources

1. Hydrogeological Framework for Potential Groundwater Resources in the Whole Red River Delta, Vietnam Akira Kawamura1 Duong Du Bui1 Thanh Ngoc Tong2 Hideo Amaguchi1 Naoko Nakagawa1 1 Tokyo Metropolitan University, Japan 2 Ministry of Natural Resources and Environment, Vietnam 26 May, BALWOIS 2010

2. Contents • Backgroundand Objective, inc. Study Area 2. “National Hydrogeological Database Project” and Data used 3. Results of Identified Hydrogeological Framework 4. Conclusions

3. Background e.g. in Hanoi • The Red River Delta is one of two biggest deltas in Vietnam • People living in the delta depend entirely on groundwater for their domestic water • Undue groundwater exploitation has caused serious problems such as: decline of groundwater level, land subsidence, and groundwater pollution in some cities Pumping rate (m3/day) Decline of groundwater level

4. Objective So far, no one has accomplished a comprehensive analysis of the aquifer system for the whole Red River Delta (RRD) due to the unavailability of basic data, while it is a prerequisite for other studies Quantitativelyidentify the hydrogeological framework (aquifer system) of the RRD, for potential groundwater resources using the best number of 778 borehole data provided by National Hydrogeological Database Project

5. Study area • the Red River Delta, the second biggest delta in Vietnam. • Area: • 13,000 km2 • Population: around 19million • -Topography • the RRD is mainly flood plain with an elevation is less than 12 m

6. Study area • Annual rainfall:1,600 mm (70% occurs in the rainy season from May to October). • Surface Water: water has a high level of suspended deposit & seriously polluted • Groundwater thus becomes a main source of water supply in the RRD

7. National Hydrogeological Database Project • - The reliability and validity of groundwater analysis strongly depend on data availability. • - In Vietnam, hydrogeological data are sparse, not well organized. • - A time-consuming and costly project named, “National Hydrogeological Database Project” was therefore initiated. • Lasted from 2002 to 2004 and cost around $600,000, • Hydrogeological, stratigraphical, borehole-structural, chemical data over Vietnam were managed.

8. Data used • Made the best use of all the 778 boreholes. • Focused on analyzing hydro-geological properties, such as: surface boundaries of aquifers, aquifer thicknesses and depths. Distribution of boreholes used in this study

9. Methods used • Hydrogeological mapping is an effective method to visually depict the hydrogeological characteristics • Hydrogeological map and cross-sections are techniques commonly used for depicting a hydrogeological system. • An isopach map is typically used to create a continuous picture from discrete sampling sites • In this study, we not only utilized a effective geostatistical gridding Kriging method, but also interpreted and compared to the observational data to get the realistic isopachs.

10. Geologic Age

11. Hydrogeological Framework HUA(Holocene Unconfined Aquifer) is the topmost aquifer and distributes widely about 88% of the RRD. HPA (Holocene-Pleistocene Aquitard) is mostly located under HUA, but exposed out on the surface about 5% of RRD. PCA (Pleistocene Confined Aquifer), placed under HUA and HPA, is distributed almost entirely the delta Aquifer system on the surface MB (Mesozoic Bedrocks) exposed on the surface create mountainous areas mainly outside of the delta

12. Hydrogeological Framework The RRD is composed of Quaternary-aged unconsolidated sediments (HUA, HPA, PCA) with a maximum thickness of 100 meters, lying directly over the bedrocks aging from the Neogene period to the Mesozoic era. Identified hydrostratigraphy of the Aquifer system of the RRD along the coastline from Hanoi to the sea

13. Hydrogeological Framework Groundwater of the Quaternary sediments mostly exists as porous water forming the topmost HUA andthe shallow PCA sandwichingHPA,while cleft and karst water exist in consolidated Neogene formations and Mesozoic rocks constituting NWL (Neogene Water bearing Layer) andMFZ (Mesozoic Fractured Zones) Identified hydrostratigraphy of the Aquifer system of the RRD along the coastline from Hanoi to the sea

14. Hydrogeological Framework Both HUA and PCA are thicker in the center than the edge of the delta and increasing downward to the sea. Identified hydrostratigraphy of the Aquifer system of the RRD along the Thaibinh River and the Red River

15. Findings of Hydrogeological Framework HUA thickness: Varies up to more than 60 m . -There is an increasing tendency from the northwest to the southeast of the delta -There exists a thin area less than 30m in the middle of the delta Isopach map of HUA’s Thickness

16. Findings of Hydrogeological Framework PCA thickness: - also fluctuates over a large range, up to 80 m - has also an increasing tendency from the northwest to the southeast of the delta - three areas of more than 60 m in thickness Similar tendency of thickness distribution between HUA and PCA. Isopach map of PCA’s Thickness

17. PCA is widely distributed almost entirely the delta. It serves as the highest groundwater potential. HUA is also widely distributed to about 88% of the delta and has a high groundwater potential. NWL and MFZ are minor sources for local domestic water supply only. These preliminary findings are worthy to note and can serve as the basis for further groundwater considerations in the Red River Delta. Conclusions

18. This study was carried out as part of the research project, “Solutions for the water related problems in Asian Metropolitan areas” supported by the Tokyo Metropolitan Government, Japan. ACKNOWLEDGMENT

19. Thank you for your kind attention!