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Vietnam-Netherlands Mekong Delta Masterplan project MEKONG DELTA WATER RESOURCES ASSESSMENT STUDIES January 2011 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com TABLE OF CONTENTS TABLE OF CONTENTS LIST OF FIGURES LIST OF TABLES ABBREVIATIONS AND ACRONYMS CHAPTER DESCRIPTION OF THE MEKONG DELTA OF VIETNAM 1.1 ADMINISTRATIVE OVERVIEW 1.2 TOPOGRAPHY 1.3 RIVER SYSTEM CHAPTER HYDROLOGY AND SURFACE WATER RESOURCES 10 2.1 CLIMATE AND EXPECTED CLIMATE CHANGE 10 2.1.1 Air temperature 10 2.1.2 Evaporation 10 2.1.3 Air humidity 10 2.1.4 Wind 10 2.1.5 Rain 12 2.1.6 Climate change 13 2.2 HYDROLOGICAL REGIMES 15 2.3 SURFACE WATER QUANTITY 16 2.4 FLOODING 17 2.5 SALTWATER INTRUSION 19 2.6 IMPACTS OF UPSTREAM DEVELOPMENTS 21 2.6.1 Current upstream flow 21 2.6.2 Further data on the upstream flow of the Mekong river 23 2.7 POSSIBLE MEASURES TO IMPROVE THE SITUATION 24 2.7.1 Integrated water resources planning for MDV and Decision No.84/2006/Q -TTg 24 2.7.2 Adaptation measures for climate change and sea level rise 24 CHAPTER WATER QUALITY 26 CHAPTER HYDROGEOLOGY AND GROUNDWATER RESOURCES 36 4.1 GEOLOGY 36 4.1.1 Tectonics and faulting 36 4.1.2 Stratigraphy 36 4.2 HYDROGEOLOGY AND GROUNDWATER RESOURCES 36 4.2.1 The aquifer system in the Mekong Delta 36 4.2.2 Groundwater quality 39 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com 4.2.3 Groundwater reserves 42 4.2.4 Present Groundwater utilization 43 CHAPTER WATER DEMAND AND WATER BALANCE 45 5.1 METHODOLOGY 45 5.2 RURAL, URBAN AND INDUSTRIAL WATER DEMAND 45 5.3 WATER FOR NAVIGATION 48 5.4 PRESENT WATER BALANCE 48 CHAPTER ISSUES TO BE SOLVED 51 CHAPTER _Toc283708758CONCLUSIVE REMARKS 53 References 55 APPENDIX 1;Water demand assessment source materials 56 APPENDIX 2; Description of aquifer systems in the Mekong Delta 59 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com LIST OF FIGURES Figure 1: Administrative map of the Mekong Delta of Vietnam Figure 2: Topographic map of the Mekong Delta .7 Figure 3: Map of existing river/canal system of the Mekong Delta in Vietnam Figure 4: Map of hydro-meteorological stations .11 Figure 5: Spatial distribution of annual rainfall 12 Figure 6: Flooding extent in the Mekong Delta with sea level rise 75cm 15 Figure 7: Variation of flood levels 2000 at Tân Châu and Châu c 17 Figure 8: Spatial distribution of maximum flood flow and total volume of the flood 2000 (using VRSAP model simulation) 18 Figure 9: Salinity intrusion isolines in some dry years .20 Figure 10: Water works development plan for Mekong Delta 25 Figure 11: Water quality monitoring network 27 Figure 12: pH in 2008 at some stations 30 Figure 13: pH in different water resources in 2002-2008 30 Figure 14: EC in fields and main streams in 2008 31 Figure 15: Salinity at M Tho, 2002-2008 31 Figure 16: TSS in fields and rivers in 2008 (right) and TSS in rivers in 2002- 2008 (left) 32 Figure 17: T-N in river courses and canals in (data for 2008) 32 Figure 18: NH4+ and NO2&3- (data for 2002-2008) 33 Figure 19: T-N in 2002-2008 & T-P in 2002-2008 33 Figure 20: BOD5 and COD (data for 2008) 34 Figure 21: BOD5 in 2002-2008 & COD in 2002-2008 .34 Figure 22 Cross –section III-III 37 Figure 23: Map of 120 sub-irrigation areas 47 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com LIST OF TABLES Table 1: Rainfall frequency all the Mekong Delta 13 Table The change of climate and sea level in southern Vietnam up to 2100 by an average emission scenario (B2) 14 Table Level of monthly temperature change (°C) in southern Vietnam up to 2100 by an average emission scenario (B2) 14 Table Average monthly rainfall change (%) in southern Vietnam up to 2100 by an average emission scenario (B2) 14 Table 5: Total flow volumes in the Mekong Delta at Tan Chau and Chau Doc stations (unit: Million m3) 16 Table The Mekong river flow at some locations 22 Table Comparision of recent flow with previous flow at Pakse (unit: m3/s) 22 Table Comparision of recent flow with previous flow at Kratie (unit: m3/s) 22 Table List of hydropower projects upstream Mekong basin 23 Table 10: List the standard method of testing water quality 28 Table 11: Coliform in 2008 (MPN/100 ml) 35 Table 14 Results of calculation of static reserves (m3/day) 42 Table 15 Results of calculation of dynamic reserves (m3/day) 42 Table 16: Groundwater utilization in the Mekong Delta 44 Table 17: Monthly water flow demand 46 Table 18: Monthly water volume demand 46 Table 19: Water requirements for navigation/waterway transportation 48 Table 20: Present water balance 49 ABBREVIATIONS AND ACRONYMS POR Plain of Reeds LXQ Long Xuyen Quadrant CMP Ca Mau Peninsula MD Mekong Delta of Vietnam TCVN Vietnamese Standard LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com CHAPTER DESCRIPTION OF THE MEKONG DELTA OF VIETNAM 1.1 ADMINISTRATIVE OVERVIEW The Mekong Delta of Vietnam (MD) is formed by the lower part of the Mekong river delta, and includes 13 cities and provinces of Long An, Tien Giang, Dong Thap, Vinh Long, Tra Vinh, Can Tho, Hau Giang, Soc Trang, Ben Tre, An Giang, Kien Giang, Bac Lieu and Ca Mau The total natural area comprises approximately 3.96 million hectares (excluding Duc Hoa District Long An Province and Phu Quoc island province Kien Giang), accounting for 79% of the whole MD and forming 5% of the Mekong River basin The Mekong Delta of Vietnam is surrounded by: (a) Vietnam-Cambodia border in the North; (b) Pacific ocean / South China Sea to the East (the so-called East sea), (c) Gulf of Thailand in the West (the so-called West sea), and (c) Vam Co Dong River and Ho Chi Minh City in the North-West (Figure 1) Figure 1: Administrative map of the Mekong Delta of Vietnam 1.2 TOPOGRAPHY The Mekong Delta of Vietnam consists of flat terrain, mostly of average height of 0.7 to 1.2 m, except for some high hills in the northern delta province of An Giang (Map 1/25000, Ministry of Water Resources, 1984 and also in the 2003 Digital Terrain Model of the Mekong delta) Along the Cambodian border, the terrain is highest, from 2.0 to 4.0 m above sea level, then lower to the central plains, from 1.0 to 1.5 m high, and only 0.3 to 0.7 m in the tidal and coastal areas LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com Figure 2: Topographic elevation map of the Mekong Delta 1.3 RIVER SYSTEM The Mekong Delta river system comprises a relatively dense network of river courses and canals, including the natural river systems and canals: - The main natural river branches and canals in the Mekong delta are formed by the two systems of the Tien River and Hau River (respectively the lower branches of the Mekong and Bassac rivers) These rivers flow to the sea in estuaries via nine river mouths as Tieu, Dai, Ba Lai, Ham Luong, Co Chien , Cung Hau, Dinh An, Ba Thac and Tranh De (river mouths in the territory of Ba Thac in Soc Trang province have been covered in the 1970’s) and a short river Vam Nao river linking the Tien and Hau LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com main branches Vam Co River (including the Vam Co Dong-Vam Co Tay) runs parallel to the east of the Tien River, Cai Lon-Cai Be River, My Thanh, Ganh Hao, Ong Doc, Bay Hap rivers flow to the West and East Sea The Tien and Hau rivers transfer the largest amounts of water with a total annual flow of 325.41 billion m3 observed at station Tan Chau (on the Tien river) and 82.43 billion m3 in station Chau Doc (on the Hau river); the flow rate on the Tien River / Hau River is 80/20 Both the Tien river and Hau river are wide and deep, with the average width of about 1000-1500 m and an average depth of 10-20 m (and locations where the depth is over 40 m) However, near the mouth, the river widens and the riverbed is raised by siltation Within the two rivers courses many elongate islands have formed River processes cause shore erosion and sedimentation and complex flow patterns cause instability of river banks Vam Co River system consists of two branches (Vam Co Dong and Vam Co Tay), that originate in Cambodia, and flow east through the Mekong Delta - The Cai Lon-Cai Be are tidal rivers, derived from the center of the Ca Mau peninsula and flow to the sea through the Cai Lon river mouth The estuary is very wide but not deep - The system of manmade canals in the Mekong delta was constructed primarily during the past century, with the primary purpose to develop agriculture and transportation Until now, the canal system has developed into a dense network with levels of major, primary and secondary canals The primary and secondary canal systems have a high density, with some 80-10 m / ha, and a total of 30,000-40,000 km of canals in all the Mekong Delta Figure below illustrates the density of the irrigation systems LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com Figure 3: Map of existing river/canal system of the Mekong Delta in Vietnam LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com CHAPTER HYDROLOGY AND SURFACE WATER RESOURCES 2.1 CLIMATE AND EXPECTED CLIMATE CHANGE The Mekong Delta, being located in a tropical monsoon region, is hot year-round and has a seasonal distribution of dry-wet months depending on the operation of the monsoon The dry season usually coincides with the period of control of the NorthEast monsoon that lasts from November to April, and the weather is characterized by dry heat and little rain The wet season coincides with the period of control of the South-West monsoon that lasts from May to October, and the climate is characterized by hot, humid, and (high) rainfall Specific features are as follows: 2.1.1 Air temperature The average temperature in January varies from about 27-28oC May is the month with the lowest temperature (an average of 25.5oC) and the hottest month is IV (28oC) There is a relative equal distribution of temperatures across the delta region 2.1.2 Evaporation The evaporation regime also changes little over time and space In terms of time in the year evaporation is highest in the months III, IV and V The highest amounts for these months vary around 180-220 mm As soon as the rain starts in months VIII to IX, lower evaporation is reached, from 100-150 mm 2.1.3 Air humidity Relative humidity reaches high values in May and decreases towards the dry season Average humidity in months VIII, IX and X ranges from 84-89%, while in months II and III it ranges from 67-81% 2.1.4 Wind The winds in the north-east of the Mekong delta are prevalent during the dry season, from months XII-IV and in the south-west prevalent during the rainy season, (months V-X) Average wind speeds are about 2.0 m/s General, closer to the sea, wind speeds often increase in months I, II and III Wind speeds in low-pressure periods and storms can reach 15-18 m/s (with a storm number of in 1997) Sunshine hours are on average hours per day (approximately 2,000-2,500 hours per year) Months II, III have the highest number of sunshine hours, with 8-9 hours a day, while months VIII, IX have less hours of sunshine, with an average 4.6 to 5.3 hours per day 10 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com years time series data are available In addition, SIWRP have carried out 2-week flow monitoring at all Mekong river mouths to assess dry flow distribution in main streams Overland flood flow in the upper parts of the Plain of Reeds and the Long Xuyen Quadrant is observed in recent years Flood and dry flow in canals can be simulated using existing calibrated hydraulic model VRSAP by SIWRP 54 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com REFERENCES [1] MRCs-DSF (2004), WUP-A Decision support framework Version 1.0.0; Modeler’s grant access for Dang Thanh Lam of SIWRP [2] SIWRP (2002), Study on water balance for MD for sustainable development strategy of the Mekong water resource, Main report [3] SIWRP (2005), Integrated water resources planning for MD [4] SIWRP (2008), Annual report on water quality monitoring for the lower Mekong basin [5] To Van Truong (2005), Research study on Flood analysis, flood forecasting and flood control for ‘living with flood’ on demand in the MD [6] www.mcdvietnam.org (2010), ‘Climate change and sea level rise scenarios for Vietnam’ issued in 2009 by MONRE in PDF format [7] State government (2006), Decision No.84/2006/Q -TTG [8] GROUND WATER STUDY MEKONG DELTA, FINAL REPORT 2001 [9] NGUYÊN HUY DUNG, Research geological structure and classification of N-Q stratigraphy in MD, 2004 55 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com APPENDIX 1: Water demand assessment source materials Document/ Database/ Model/ Material Author/ Owner/ User MRC-DSF Owner: MRC and Three line agencies VNMC, SIWRP, IMHR Contents/ Descriptions The MRC Decision Support Framework, or DSF, is a tool for managing and sharing observed and modelled datasets for the Mekong river basin These data can be time series, spatial or other miscellaneous data The datasets are contained with the DSF Knowledge Base database, which is packaged with the DSF software All of these data can then be utilised to investigate the behaviour of the river basin and, thus, facilitate the decisionmaking process over how to react to future impacts on and changes to the basin The Decision Support Framework contains a Main Interface and a series of associated tools These applications are as follows: Main DSF Interface Impact Analysis Tools Time-Series Plotting Tool Probability Exceedence Tool Event Analysis Tool Low Flow Analysis Tool MQUAD DSF Model Interfaces DSF SWAT Interface DSF IQQM Interface Study on water balance for MD for sustainable development strategy of the Mekong water resource Owner: MARD DSF ISIS Interface The main report contains information as follows Author: SIWRP - Assessment of existing water utilization in the MD Computing water demand by 2010 Computing upstream impacts on monthly flow with development of hydropower and irrigation Computing existing and future water balance 56 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com Integrated water resources planning for MD Owner: MARD Author: SIWRP The content of main report consists of: - - - - Research study on Flood analysis, flood forecasting and flood control for ‘living with flood’ on demand in the MD Owner: MOST Author: Dr To Van Truong, SIWRP Analysis of characteristics of MKD meteorology, hydrogeology and water resources Assessment of welfare of the people, social and economical situation of the Mekong Delta to 2004 Assessment the opportunities and demand for development of MKD, consisting of development orientation of agriculture, forestry, aquaculture, transportation, and construction Calculation of water demand for agriculture, aquaculture, transportation and domestic water supply at present 2005 and to 2010 Formulation of water resources development projects Analysis of hydrology, hydraulic, cost estimation of construction of water resources works according to the planned development projects Choice of the list of water resources works for investment for the periods of 2006-2010 and 2011-2020 The content of main report consists of: - - - Investigation of control flood and living with flood models; of production model in flood areas; Assessment of impacts of infrastructure development to the flow of MKD Analysis of basic data on topography, meteo-hydrology of MKD; Building the methodology on recognition of flood in MKD and the methodology to control, manage and live with floods in MKD; Calculation of parameters to recognise river floods; building the technology to recognise river floods in MKD and 57 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com - - Climate change and sea level rise scenarios for Vietnam Owner Author: MONRE application of the technology to recognise the level of flood peak in 2003-2004; Upgrading the data on topography, boundary conditions and building a hydraulic model to simulate the floods in 2000, 2001 in MKD; Building the technology to recognise floods in MKD and its application to forecast; Building the series of maps of floods in MKD according to frequencies using GIS technology; Researching of measures to control floods, to construct infrastructure, to develop economy, to protect environment, and to control floods for living with flood in MKD; & Report of MONRE on Climate change and sea level rise scenarios for Vietnam 58 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com Appendix 2: Description of Aquifer systems in the Mekong Delta 59 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com Holocene aquifer (qh) The Holocene aquifer occurs at the surface of almost the whole delta with an area of 40,000km2 (see Figure 33), and consists of the following sediments: - Lower – middle Holocene sediments (qh1-2), consisting of clayed silt, fine sand and organic matters - Alluvial and coastal sediments (qh2-3), consisting of silt, clay, fine to medium sand to form sandy dunes ( indicative of ancient sea shores) - Sediments (qh3), consisting of clayed silt and fine sand, accumulated in river valley Figure 25 Hydrogeological map of the Holocene aquifer Sediments formulated in the period of sea regression (qh2-3) are characterized by sand dunes bearing fresh groundwater These sand dunes are located in Mo Cay, Ba Tri, Tra Cu, Long Toan districts of Tra Vinh province Its lithology consists of fine to medium sand, having a thickness of to 10m 60 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com The boreholes placed in this aquifer are mainly shallow boreholes, with depths from several meters to 30 m, having yields from 0.1 to 2.0 l/s and groundwater levels from 0.5 to 3.0m Fresh groundwater (TDS
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