dự Án thuỷ Điện trung sơn thiết kế kỹ thuật

8/11/2019 D n Thu in Trung Sn Thit K K Thut

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ISO 9001:2000

VIETNAM ELECTRICITY

POWER ENGINEERING CONSULTINGJOINT STOCK COMPANY 4

Project: T.02.04

D N THY IN TRUNG SN

TRUNG SON HYDROPOWER PROJECT

THIT K K THUT

TECHNICAL DESIGN

M HNH VN HNH H CHA

OPERATION MODEL OF RESERVOIR

Nha Trang City, July 2010

59895


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Trung Son hydropower project Technical design

Contributor i

CONTRIBUTORS

No. Full name Task Signature1 Vuong Anh Dung Preparing chapter 3

2 Nguyen Van De Preparing chapter 1

3 Nguyen Tien Phong Preparing chapter 2

4 Truong Hoai The Tuyen Preparing chapter 4

5 Phung Ngoc Tam Preparing chapter 4

6 Tran Minh Kha Checking


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Contents ii

CONTENTSThe document is established in below volume Operation model of reservoir


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Table of contents iii

TABLE OF CONTENTS

CHAPTER 1: ANNUAL FLOW SPECIFIC CALCULATION 11.1 FLOWCONDITIONCALCULATIONONBASIN11.2 CALCULATIONOFANNUALAVERAGEFLOWINLONG-TERMPERIODATTRUNGSON

HYDROLOGICAL51.3 DESIGNANNUALFLOWDISTRIBUTIONANDANNUALFREQUENCY10

1.4 DAILYFLOWRANGETOTRUNGSONHYDROPOWERDAMSITE11CHAPTER 2: RESERVOIR ANALYSIS AND SIMULATION 122.1 PLANNING HYDROPOWERPROJECTSCASCADES ONMARIVER122.2 ADDITIONALPLANNINGHYDROPOWERPROJECTSCASCADESONMARIVER132.3 MAIN PARAMETERS OF TRUNG SON HYDROPOWER PROJECT TECHNICAL DESIGN

STAGE142.4 DATAFORCALCULATION162.5 CALCULATION,SIMULATIONOFRESERVOIR182.6 WITHOUTTHANHSONRESERVOIRINDOWNSTREAMOFTRUNGSONHYDROPOWER

PLANT(CASE1)182.7 DOWNSTREAMWITHTHANHSONRESERVOIR(CASE2)37

CHAPTER 3: WATER SUPPLY DEMAND FOR DOWNSTREAM 403.1 WATERDEMANDATDOWNSTREAM403.2 ENVIRONMENTFLOWRELEASEMEASURES423.3 DISCHARGEOFWATERDURINGOPERATIONPROCESS423.4 DISCHARGEOFMUDANDSAND433.5 RESERVOIRDEWATERING433.6 CONCLUSION43

CHAPTER 4: RESERVOIR AND DOWNSTREAM LANDSLIDEPOSSIBILITY FORECAST 44

4.1 RESERVOIRBANKLANDSIDEPOSSIBILITY444.2 EROSIONRIVERBEDOFRESERVOIRDOWNSTREAM474.3 SLIDINGATBANKSOFDOWNSTREAM48

APPENDIX .............................................................................................................. 48- Appendix calculation of hydrographical- Location chart of section calculation stability- Appendix calculation of reservoir bank stability- Appendix calculation reservoir downstream stability


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Flow data chaining advent barrage calculation 1

Chapter 1: ANNUAL FLOW SPECIFIC CALCULATION

1.1 FLOWCONDITIONCALCULATIONONBASIN

Trung Son Hydrological station has been built and put into operation since Oct

2004, it is located about 400m downstream of Trung Son dam site. It measures all the

factors: precipitation, water level, discharge, flood.. The difference between the basinareas of the damsites and Trung Son station is not remarkable, we can consider the

flow to Trung Son hydrological station is equal to the flow to the damsite. Thus, the

calculation result at the Trung Son hydrological station is equal to the calculation

result at the damsites. There are hydrological stations at the upstream of Ma river:

Muong Lat (water level, precipitation), Xa La (precipitation, water level, temperature,

discharge..); at the downstream of the river, there are hydrological stations such as:Hoi

Xuan (discharge, 1965 1970, water level, 1962 2008), Cam Thuy (water level,

1957 2008; discharge 1957 1976, 1995 2008) besides, there are other

hydrological stations at the tributaries such as Nam Ty, Nam Cong, Cua Dat, LangChanh...

Due to the non-sychronous data and lack of data continuity observed at those

stations, the flow calculation of Trung Son hydrological station mainly depends on the

analysis method of flow correlation, co-ordinating with precipitation distribution and

flow module analysis. The method is carried out between Trung Son hydrological

station and 3 other hydrological stations that measure the discharge namely Cam Thuy,

Hoi Xuan, Xa La.

1.1.1. Recovering the flow data at Cam Thuy Hydrological Station

Cam Thuy hydrological station measured the water level and discharge from

1957 to 1976 with the standard of Level 1 hydrological station. From 1977 to 1994, it

moved some kilometers downstream and downgraded, only measured water level.

From 1995 up until now (2008), it moved to the old location and continued observing

according to the station of level 1 station.

Now, the water level data at Cam Thuy from 1977 to 1994 has been correlatively

calculated by Hydro-meteorological General Bureau and brought back to waterelevation of the old Cam Thuy hydrological station (it is also the location now) to

unify the elevation.

The relationship curve Q=F(H) is synthetized at Cam Thuy hydrological station

in 1973, 1975, 1995. Then the discharge is interpolated from the relation Q=F(H) and

daily water level data in 19771994


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After the calculation, we have the daily flow at Cam Thuy hydrological station

from 1957 to 2008, average long-term flow is Q tb=346 m3/s. Summarization of

monthly observed flow and calculated flow from 1957 to 2008 at Cam Thuy

hydrological station are shown in Table 1 of the Appendices.

1.1.2. Recovering data at Hoi Xuan hydrological Station

Hoi Xuan hydrological station has been measuring the water level from 1962 up

until now (2008), it measured the discharge from 1965 to 1970. The recovering and

addition to this flow data at Hoi Xuan hydrological station is carried out through 3

methods:

1) Calculation according to monthly average discharge in correlation with Cam

Thuy hydrological station:

The monthly average discharge correlation between Cam Thuy and Hoi Xuan

hydrological stations from 1965 to 1970

Flood season: Correlation coefficient =0.989; Correlation equation:

QHoi Xuan= 0.861*QCam Thuy 5.14 (m3/s)

Dry season: Correlation coefficient =0.984; Correlation equation:

QHoi Xuan= 0.823*QCam Thuy+ 4.864 (m3/s)

From this equation and the monthly average discharge at Cam Thuy hydrological

station, we can calculate the data chain at Hoi Xuan hydrological station from 1957

1964, 1971 2008. According to that, the average annual discharge in long-termperiod at Hoi Xuan is 295 m3/s.

2) Calculation according to daily average discharge in correlation with Cam

Thuy hydrological station:

The daily average discharge correlation between Cam Thuy and Hoi Xuan

hydrological stations from 1965 to 1970

January: the coefficient of =0.890. Correlation equation:


February: the coefficient of =0.900. Correlation equation:


March: the coefficient of =0.933. Correlation equation:


April: the coefficient of =0.927. Correlation equation:


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May: the coefficient of =0,895. Correlation equation:


June: the coefficient of =0.942. Correlation equation:


July: the coefficient of =0.890. Correlation equation:


August: the coefficient of =0,965. Correlation equation:


September: the coefficient of =0.952. Correlation equation:

QHoi Xuan= 0.740*QCam Thuy+ 55.17 (m

3

/s)October: the coefficient of =0.956. Correlation equation:


November: the coefficient of =0.936. Correlation equation:


December: the coefficient of =0.902. Correlation equation:

QHoi Xuan= 0.936*QCam Thuy 8.29 (m3/s)

Based on these equations and the daily average discharge at Cam Thuy

hydrological station can calculate data chain at Hoi Xuan hydrological station from

1957 1964, 1971 2008. Thence, the long-term average discharge at Hoi Xuan is

289 m3/s.

3) Calculation according to water level data and the relation Q=F(H)

Water level data at Hoi Xuan hydrological station from 1957-1961 was recovered

from water level data at Cam Thuy hydrological station by correlation method.

Cam Thuy hydrological station measured discharge and level water from 1957 -1976. After, its displaced to downstream and measured level water only. In 1995, its

displaced again to return the initial location, and upgraded to measure both discharge

and level water. The level water data at Cam Thuy hydrological station from 1977 -

1994 is calculated and converted. Hence, daily average level water in every month in

correlation between Cam Thuy hydrological station and Hoi Xuan hydrological station

is carried out from 1962 - 1976.


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HHoi Xuan= 1.56*HCam Thuy+ 3,386 (cm)


HHoi Xuan= 1.15*HCam Thuy+ 3863 (cm)



April: the coefficient of =0.927. Correlation equation:


May: the coefficient of =0.840. Correlation equation:


June: the coefficient of =0.957. Correlation equation:HHoi Xuan= 1.08*HCam Thuy+ 3960 (cm)


HHoi Xuan= 0.922*HCam Thuy+4167 (cm)

August: the coefficient of =0.936. Correlation equation:




October: the coefficient of =0.954. Correlation equation:





HHoi Xuan= 1.61*HCam Thuy+ 3332 (cm)Based on these equations and daily average level water at Cam Thuy hydrological

station can calculate data chain at Hoi Xuan hydrological station from 1957 - 1961

The relation curve Q=F(H) is synthesized from Hoi Xuans observed data in

1965-1970. Then, the daily flow data chain at Hoi Xuan hydrological station from

1957 1964 and 1971- 2008 is calculated based on the over relation curve Q=F(H)

and water level data. Hence, the long-term average discharge at Hoi Xuan is 290 m3/s


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Over results (calculated by three methods) are not different much. The daily

average discharge correlation method with Cam Thuy hydrological station (Method 2)

reflects the reality of the river flow, having high coefficient, giving values close to

values calculated by water level and the relation curve Q=F(H) method, and reducing

the errors due to the changes of river bed through many years. Thus, it is chosen.

Hence, the long-term average flow at Hoi Xuan hydrological station is 289 m3

/s. Thesynthesized results of monthly flow data chain at Hoi Xuan hydrological station is in

Table 2 in the appendices.

1.2 CALCULATIONOFANNUALAVERAGEFLOWINLONG-TERMPERIODATTRUNGSONHYDROLOGICAL

1.2.1. Daily average water level data recovery method

Create the correlation relationship of daily average water level between Trung

Son and Hoi Xuan hydrological stations from 01 January 2005 to 31 December 2008,

the achieved correlation coefficient is =0,949 and correlation equation is as follows:

HTrung Son = 0.707*HHoi Xuan+ 5131 (cm)





July: the coefficient of =0.958. Correlation equation:HTrung Son = 0.820*HHoi Xuan+ 4525 (cm)












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The coefficient of Jan, Mar, Apr, May months is smaller than 0.8. Thus,

correlation equation of this are taken general correlation equation:


With these equations and the water level data at Hoi Xuan can recover the water

level data at Trung Son in the period of 1957-2004.

The correlation curve Q=F(H) at Trung Son station is synthetized from observed

data in the period 2005 2008. Then, calculating the daily flow data chain at Trung

Son station in the period of 1957 2004 from the water level data and the synthetized

relationship Q=F(H). Hence, the long-term average discharge is 216 m3/s.

1.2.2. Flow correlation method with Cam Thuy hydrological station

- Creating the monthly average discharge correlation between Cam Thuy and Trung

Son stations from January 2005 to December 2008

Flood season: Correlation coefficient is =0.954. Correlation equation:

QTrung Son= 0.636*QCam Thuy- 3,27 (m3/s)

Dry season: Correlation coefficient is =0.941. Correlation equation:

QTrung Son= 0.506*QCam Thuy + 20,45 (m3/s)

With these equations and discharge at Cam Thuy hydrological station can

calculate the flow data chain at Trung Son station from 1957- 2004. Hence, the

average discharge in long-term period (1957-2008) is 218 m3/s.

- Creating the daily average discharge correlation between Cam Thuy and Trung

Son stations from January 2005 to December 2008

Average calculation result from 01 January 2005 to 31 December 2008,

correlation coefficient is =0,922.

Correlation equation is as below:

QTrung Son= 0.545*QCam Thuy+ 30.6 (m3/s)


QTrung Son= 0.654*QCam Thuy 1.04 (m3/s)






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April: The coefficient of April is smaller than 0.8. Thus, the correlation equation

of this is taken genera correlation equation:


May: The coefficient of May is smaller than 0.8. Thus, the correlation equation of

this is taken genera correlation equation:













QTrung Son= 0.341*QCam Thuy+ 95.14 (m3

/s)December: the coefficient of =0.971. Correlation equation:


Calculate the daily discharge data chain at Trung Son station in the period of

1957 2004 based on these correlation equations and daily average discharge at Cam

Thuy hydrological station. Hence, average annual discharge in long-term period is 229

m3/s.

1.2.3. Flow correlation method with Xa La stationCreating the monthly average discharge correlation between Xa La and Trung

Son station from January 2005 to December 2008

In flood season, the coefficient is =0.758. It is too small to calculate and recover

flow data at Trung Son station. So, data in flood months is recovered and calculated by

correlation relation among months in the whole year. The synthesized coefficient of


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months from 2005 to 2008 between Xa La and Trung Son stations is =0.875. The

correlation equation is as below:

QTrung Son= 1.638*QXa La+ 45.61 (m3/s)

In dry season, the coefficient =0.893. The correlation equation:

QTrung Son= 1.75*QXa La+ 26.17 (m3

/s)Based on these equations and discharge at Xa La station can calculate flow data

chain at Trung Son station from 1961- 2004. Hence, average annual discharge in long-

term period at Trung Son is 235 m3/s.

1.2.4. Flow correlation method with Hoi Xuan hydrological station

Creating the monthly average discharge in correlation between Hoi Xuan and

Trung Son station from I/2005 to XII/2008.

In flood season, the coefficient =0.968. The correlation equation:QTrung Son= 0.836*QHoi Xuan 34.78 (m

3/s)

In dry season, the coefficient (=0.692) is too small to correspond with

calculating and recovering flow data at Trung Son station. So, data in dry months is

recovered by correlative relation among months in the whole year. The synthesized

coefficient of months from 2005 to 2008 between Hoi Xuan and Trung Son is

=0.964. The correlation equation:

QTrung Son= 0.801*QHoi Xuan 20.01 (m3/s)

From these equations and discharge at Hoi Xuan hydrological station, we can

flow data chain at Trung Son station from 1957 to 2004. According to that, average

annual discharge in long-term period at Trung Son is 213 m3/s.

1.2.5. Flow module analysis method

The flow module distribution on Ma river is as follows:

Table 1.1: The flow module at some stations in Ma river basin

Station Area (km2) Period Qaver(m3/s) M (l/s/km2)

Cam Thuy 18,879 19572008 346 18.3

Hoi Xuan 16,850 19572008 289 17.2

Xa La 6,430 19612008 120 18.7


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Trung Son station is located between Hoi Xuan and Xa La stations, the flow

module of Trung Son station is M= 17.5 l/s/km2,calculated by interpolation method.

Thus, can calculate the annual average discharge at Trung Son station Q= 257 m3/s.

The flow data at Hoi Xuan hydrological station is recovered mainly; data at Cam

Thuy and Xa La stations is more adequate. Use interpolation method to calculate flow

module to Trung Son station from relation between area and flow module of CamThuy and Xa La stations. According to this method, the flow module to Trung Son

station will be M= 18.4 l/s/km2. Thus, the long-term average discharge at Trung Son

station can calculated Q= 270 m3/s.

The analysis of precipitation changes in the mid-areas from Cam Thuy to Hoi

Xuan and from Hoi Xuan to Trung Son shows that the average annual rainfall in long-

term period from Cam Thuy to Hoi Xuan is about 1850 mm; from Hoi Xuan to Trung

Son is about 1600 mm. The application of area rate method plus basin average rainfall

rate method due to mid-basin from Cam Thuy to Hoi Xuan. The average annualdischarge at Trung Son will be equal to the average annual discharge in long-term

period at Hoi Xuan minus the mid-area. QTrung Son= 236 m3/s.

1.2.6. Analyse, choose the results of flow calculation to Trung Son dam site

Table 1.2: Synthesized results of annual average flow in long-term period at Trung

Son station according to different methods

Method 0 M0

1. Inter olatin Water data and the relationshi =F H 216 14.72. Monthly average discharge correlation with Cam Thuy

hydrological station218 14.9

2. Daily average discharge correlation with Cam Thuy

h drolo ical station229 15.6

3. Dischar e correlation with Xa La station 235 16.0

4. Dischar e correlation with Hoi Xuan h drolo ical station 213 14.5

5. Inter olatin flow module Hoi Xuan Xa La 257 17.5

6. Inter olatin flow module Cam Thu Xa La 270 18.47. Mid-area dischar e deduction from Hoi Xuan to Trun 236 16.1

Avera e 234 16.0

Due to the complexity of the precipitation and flow distribution on Ma river the

part on Laos territory has less rainfall than on Vietnam, so the calculation results by

the different methods will be different as well. Each method has its own advantages

and disadvantages. The water level data retrieval method at Trung Son station from


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Hoi Xuan hydrological station is easy to cause errors because the parallel measured

water level data chain is short, the water level in serious flood years isnt measured

sufficiently and the cross sections are changed after years. The data chain from 1977

1994 at Cam Thuy hydrological station is achieved through calculation and recovery

from the water level and relationship Q=F(H), the parallel measured data chain

between Cam Thuy and Trung Son is still short, thus the monthly average flowcorrelation method between Trung Son and Cam Thuy is not fully trusted. It is similar

to above mention, the correlation method between Trung Son and Xa La also have a

short parallel observed data chain; their correlation coefficient is not much great; Ma

river, after flowing cross Laos territory where rainfall is small, flow amplitude changes

a little bit, thus results achieved by this method isnt completely trusted. The method

considering flow module progress based on the measured data at the hydrological

stations on Ma river basin, considering the effect of rainfall distribution on the basin,

can determine quite exactly the long-term average flow but determining exactly the

average annual precipitation in the basin is difficult, so it is difficult to determine

exactly the annual flow.

The average flow value achieved from these above methods are QTrung Son= 234

m3/s, MTrung Son = 16,0 l/s/km2, these values are equal to the discharge depreation

method at mid-area with the mean rain fall (QTrung Sn = 236 m3/s), nearly the same

with the result of discharge correlation with Xa La station method (QTrung Sn= 235

m3/s). As change a number of calculating years, the average annual runoff value at

Trung Son station fluctuates around at 235 m3/s, recommend to choose this result

Q0Trung Son= 235 m3/s

1.3 DESIGNANNUALFLOWDISTRIBUTIONANDANNUALFREQUENCY

1.3.1. Monthy average flow range

To achieve a nearly correct flow distribution at Trung Son station, the flow

distribution following the daily average flow correlation wih Cam Thuy hydrological

station has been used, with the modification according to the chosen average flow in

the long-term period. The results are as in table 3, Appendixes.

1.3.2. Seasonal flow rate

Based on the observed and calculated flow data at Trung Son station (1957

2007) carry out the seasonal flow classification according to the over-average

standard, the results achieved are: flood season starts from June, ends in October; dry


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season starts from November, ends in next May. The results are in table 4 in the

appendices.

1.4 DAILYFLOWRANGETOTRUNGSONHYDROPOWERDAMSITE

By correlation relation analysis, the flow correlation in Ma river at Trung Son

with Hoi Xuan and Cam Thuy is better than with Xa La. This difference shows that the

natural condition in Ma river is: heavy rain in the upstream, small rain in Laos territory

and gradually heavier from Trung Son to Cam Thuy, the area difference between

Trung Son and Hoi Xuan, Cam Thuy is smaller than between Trung Son and Xa La.

Hoi Xuan hydrological station has an short observed daily discharge data chain

(1965-1970), the data of the remaining years (1957 1964, 1971 2008) are achieved

by recovering calculation, the old relation Q=F(H) (synthetized from 1965 - 1970) is

not measured to check the changes in the following years, thus it is easily to cause

errors.

Cam Thuy hydrological station has a longer observed data chain (1957 1976,

1995 2008), the calculated recovering flow data chain (1977 1994) has a close base,

the relation Q= F(H) is synthetized according to the years before 1977 and after 1994.

Thus, flow distribution reflects the reality, can trust well, and choose to calculate flow

distribution at Trung Son hydrological station.

The daily discharge chain (1957-2004) at Trung Son station is chosen according

to daily average discharge correlation calculation results with Cam Thuy hydrological

station, in which: using separate correlation equations for each month and calculatingis in the adjustment to get average annual discharge at Trung Son, Qaver=235 m3/s.

The synthetized results of daily average discharge at Trung Son station are

summarized in the report of Reservoir operation process.


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Analysis and simulation of reservoir 12

Chapter 2: RESERVOIR ANALYSIS AND SIMULATION

2.1 PLANNING HYDROPOWERPROJECTSCASCADES ONMARIVER

On March 31, 2005, Ministry of Industry (presently called as Ministry ofIndustry and Trade) issued decision No.1195/Q-NLDK, concerningapproval on planning of hydropower cascades on Ma river, main contents as

below:- Exploiting scheme of hydropower cascades projects and main task ofhydropower projects on Ma river:

+ On Ma river tributary, there are 05 multi-purposes hydropower reservoirsprojects

Pa Ma hydropower project, with normal water level at 455m, installedcapacity of 80MW; main tasks are water supply and flood control;combined with electric power generation.

Huoi Tao hydropower project: normal water level at 380m, installed

capacity of 180MW; main task are water supply and flood control;combined with electric power generation.

Trung Son hydropower project: normal water level at 160m, installedcapacity of 280MW; main task are electric power generation andflood control.

Hoi Xuan hydropower project: normal water level at 80m, installedcapacity of 92MW; main task are electric power generation and watersupply.

Cam Ngoc hydropower project: normal water level at 50m, installedcapacity of 145MW; main tasks are water supply, combined with

electric power generation.+ In Chu River tributary, there are 02 hydropower projects

Hua Na hydropower project, normal water level at 240m, installedcapacity of 180MW; main tasks are electric power generation andflood control.

Cua Dat hydropower project, normal water level at 119m, installedcapacity of 97MW. This project is under operation. Main tasks arewater supply and flood control, combined with electric powergeneration.

- Flood control storage capacity at respective reservoirs

+ Total flood control storage capacity on Ma River is estimated approximately700 million m3respectively at Pa Ma reservoir (about 200 million m3), HuoiTao (about 300 million m3), Trung Son reservoir (maximum 200 millionm3). It is required to substantiate presisely in details the distribution floodcontrol storage capacity between cascades in Ma River when establishingFeasibility Study, with consideration of all actual topographical, geologicalcondition of the project as well as in the downstream area, proposed other


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reservoirs in Ma River construction time according to water resourcedevelopment program, to ensure economical and technical requirements.

+ Total flood control storage capacity on Chu River is estimatedapproximately at 400 million m3, respectively at Cua Dat hydropowerreservoir at 300 million m3and Hua Na hydropower reservoir at 100 millionm3

- Priority sequence construction of projects:+ Hydropower projects to be constructed in the first stage: Cua Dat and Hua

Na projects on Chu River, Trung Son project in Ma River

+ Hydropower projects to be studied as multipurpose: Hoi Xuan, Cam Ngoc,Pa Ma, Huoi Tao projects on Ma river

(detail at appendix: attachment legal documents)

2.2 ADDITIONALPLANNINGHYDROPOWERPROJECTSCASCADESONMARIVER

On April 18, 2008, Ministry of Industry and Trade issued decisionNo.2383/Q-BCT converning approval on additional planning hydropowerproject cascades on Ma River, with main contents, as below:

- Additional planning Thanh Son hydropower project on Ma river cascades wasapproved by Ministry of Industry (presently called as Ministry of Industry andTrade) at decision No. 1195/Q-NLDK dated on March 31, 2005 with maincontents, as below:

+ Construction site: On the main stream of Ma river at the Thanh Son andTrung Thanh communes, Quan Hoa district, Thanh Hoa Province, withcoordinates (VN-2000 system): X= 2 277 459.6 and Y= 490 006.9

+ Task and exploiting scheme of project: Project has main task is powergeneration. The hyro energy exploiting scheme consisting of main dam andspillway with dam-toe hydropower plant type.

+ Main parameters of project: Catchment basin area calculated to damsite Flv= 13.275Km2, annual average discharge Q0= 246 m

3/s, normal water level =89m, tailrace water level MNHLmin= 78.5m, rated water head Htt= 8.8m andinstalled capacity Nlm= 37MW

- Investment of Thanh Son hydropower project must be complied with socio-economic development plans, land and water resource use plans, electric powerdevelopment plan in the Thanh Hoa province; synchronously with power load

development situation as well as investment of electric power transmissionnetwork in region as planned by Vietnam Electricity.

- In feasibility study stage of Thanh Son hydropower project, Thanh HoaProvincial Peoples Committee shall be responsible to give directives,inspection and consideration of below issues:

+ Additional investigation, survey on natural conditions (topographical,geological, hydrological conditions, etc,..) for project area, precisely


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calculate relation curve between water level and discharge at tailrace ofpowerhouse.

+ Precisely calculate normal water level of hydropower reservoir based oncalculation of surge water level to the end of reservoir caused by flood, toensure no influence on electric energy efficiency and safety operation ofTrung Son hydropower plant at upstream.

+ The spillway of Thanh Son hydropower project shall be designed in such amanner to ensure release safely checked flood discharge from Trung Sonhydropower project in accordance with regulation specified in designstandards and codes..

+ Updating parameters such as upstream and downstream water level andpower generation discharge of Trung Son and Hoi Xuan hydropowercascade projects (downstream side). Analysis, comparison to make accuracyof main parameters of project, especially installed capacity to ensureeffective exploitation of project as well as electric power transmissionnetwork

+ Investigate, survey and establish compensation and resettlement plan forproject, to ensure compliance with current relevant State regulation.

2.3 MAINPARAMETERSOFTRUNGSONHYDROPOWERPROJECTTECHNICAL DESIGN STAGE

In the technical design stage, the main tasks of project are defined as below:- With regards of electric power generation, installed capacity is Nlm = 260MW,

annual electric energy Eo=1018.61 million kWh.- In terms of flood control, the reservoir flood control storage capacity is 150

million m3in which regular flood control storage capacity of 112 million m3 .Flood control period is 02 consecutive months of main flood season from 15 thJuly to 15thSeptember annually.

Table 2-1: Main parameters of Trung Son hydropower project

No. Description Unit Value

I Basin characteristics1 Catchment area Km2 14660

2 Average long-term rainfalls X0 mm 1 4203 Average long-term flow (Qo) m3/s 2354 Total annual flow Wo 106m3 7411II Reservoir1 Normal water level (NWL) m 1602 Dead water level m 1503 Water level before flood m 1504 Flood storage volume Wpl 106m3 1125 Reservoir storage volume corresponding to normal 106m3 348.53


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water level Wbt

6Effective storage volume, flood storage volumeWpl

106m3 112.13

7 Dead storage volume Wc 106m3 236.40

8 Reservoir surface area corresponding to normalwater level km2 13.13

9 Flood peak discharge corresponding to frequencies- P= 0.1 % m3/s 13 400

- P= 0.5 % m3/s 10 400 - P= 1 % m3/s 9 100 - P= 5 % m3/s 6 200

III RCC dam1 Dam crest elevation m 162.82 Dam crest length (L) m 513.0

3 Max. dam height m 84.54 Dam crest width (b) m 85 Upstream slope (m) 0.356 Downstream slope (m) 0.65

IV Spillway1 Spillway sill elevation m 1452 Number of spillway cells 63 Spillway span BxH m 14x154 Orifice dimension of radial gate BxH m 14x15.55 Design flood released discharge P=0.5% m3/s 9 900

6 Checked flood released discharge P=0.1% m3

/s 12 5347 Dissipation structure Flip bucketV WaterwayA Power intake gate

1 Power intake gate sill elevation m 1352 Orifice dimension of trash rack nxBxH m 8x5.5x113 Orifice dimension of maintenance stop logs nxBxH m 1x5.5x5.54 Orifice dimension of operation gate nxBxH m 4x5.5x5.5

B Penstock

1 Penstock diameter m 5.5

2 Total length of one penstock m 229.573 Gradient slope of penstock % 13.95; 46.634 Penstock shell thickness mm 16-18C Powerhouse characteristics

1 Turbine type Francis2 Number of units 43 Installed capacity Nlm MW 2604 Firmed capacity Nb MW 41.805 Max. head Hmax m 72.02


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6 Min. head Hmin m 51.327 Average head Htb m 66.308 Rated head Htt m 56.509 Max. discharge Qmaxthrough turbine m

3/s 522

10 Average annual generated electricity E0 106 KWh 1018.6111

Number of power generated hours at installedcapacity

hour 3918

D Tailrace channel

1 Bottom width (b) m 79.72 Slope factor (m) 0.5 1.53 Gradient slope of channel bottom (i) 0.00014 Tailrace channel length (L) m 80

2.4 DATAFORCALCULATION

- Reservoir regulation curve: Coordinate on regulation curves of Trung Sonhydropower project are shown in below table:

Table 2-2: Water level on regulation curves of Trung Son hydropower project

No. Month NWL(m) CXT PPH HCCN MWL(m)

1 June 160.0 160.00 160.00 150.00 150.0

2 July 160.0 150.00 150.00 150.00 150.0

3 Aug 160.0 150.00 150.00 150.00 150.0

4 Sept 160.0 160.00 160.00 150.00 150.0

5 Oct 160.0 160.00 160.00 157.00 150.06 Nov 160.0 160.00 160.00 156.60 150.0

7 Dec 160.0 160.00 160.00 155.50 150.0

8 Jan 160.0 160.00 160.00 154.30 150.0

9 Feb 160.0 160.00 160.00 153.10 150.0

10 Mar 160.0 160.00 160.00 152.50 150.0

11 Apr 160.0 159.00 158.20 151.70 150.0

12 May 160.0 158.00 155.40 150.50 150.0

Remark:+ NWL: Normal water level.+ CXT: Redundant discharge control regulation curve+ PPH: Critical reservoir water level regulation curve+ HCCN: Limit water supply regulation curve+ MNC: Minimum water level.

- 24 hours average flow to damsite of Trung Son hydropower project: see inchapter 1


21/110



- Reservoir characteristic curve: reservoir characteristic curve is set up on themap of 1/10,000 scale, established in 2003 by Power Engineering ConsultingJoint Stock Company 4 with aerial photograph method. The results are as

below:

Table 2-3: Reservoir characteristic curve of Trung Son hydropower project

No.Elevation

Z (m)Area

F (km2)Storage volume

V (106m3) Remarks1 85.0 0.0 0.02 90.0 0.3 0.63 95.0 0.5 2.64 100.0 1.1 6.45 105.0 1.7 13.26 110.0 2.2 22.77 115.0 2.8 35.18 120.0 3.5 50.9

9 125.0 4.4 70.610 130.0 5.1 94.111 135.0 5.9 121.612 140.0 7.0 153.913 145.0 8.2 191.914 150.0 9.6 236.4 MWL15 155.0 11.1 288.116 160.0 13.1 348.5 NWL17 165.0 15.2 419.318 170.0 17.6 501.2

- Relation curve between discharge and tailrace water level of Trung Sonhydropower plant was set up based on hydraulic calculation formulas and rivercross section, river bed longitudinal profile, investigation historical flood,Theresults are as below:

Table 2-4:Relation curve between discharge and tailrace water level of Trung Son

hydropower plant

No.DischargeQ (m3/s)

Water levelZ (m)


Water levelZ (m)

1 0 85.90 17 300 90.512 10 86.71 18 350 90.76

3 20 87.27 19 400 90.98

4 30 87.82 20 500 91.39

5 40 88.37 21 600 91.78

6 50 88.67 22 700 92.14

7 60 88.81 23 800 92.48


22/110




Water levelZ (m)


Water levelZ (m)

8 80 89.05 24 1000 93.12

9 100 89.25 25 1500 94.48

10 120 89.42 26 2000 95.66

11 150 89.66 27 3000 97.6312 180 89.86 28 4000 99.41

13 200 89.98 29 5000 100.90

14 220 90.10 30 7000 103.82

15 250 90.26 31 8000 105.06

16 280 90.42 32 10000 107.38

- Efficiency of hydropower plant: Efficiency of unit at the calculation timedepends on rated water head and discharge through turbine. In the calculation ofdaily hydro-energy operation of reservoir simulation, average efficiency of

powerhouse is selected at 0.88.

2.5 CALCULATION,SIMULATIONOFRESERVOIR

The process of reservoir simulation calculation is executed accordinghydrological years, with hydrological calculation data obtaned in 50 yearsstarting from June 1, 1975 to May 31, 2007.

On the basic of the data calculation as mentioned above, calculating hydro-energy simulation in two cases:

- Without Thanh Son reservoir in downstream of Trung Son hydropower plant- With Thanh Son reservoir in downstream of Trung Son hydropower plant

2.6 WITHOUTTHANHSONRESERVOIRINDOWNSTREAMOFTRUNGSONHYDROPOWERPLANT(CASE1)

2.6.1. Electric energy (Case 1)

- The results of hydro energy calculation shown that the Energy differencebetween daily flow and monthy flow for calculation is about -4.6%. The results

of calculation reflected variation in simulation operation of reservoir accordingto average daily flow and average monthy flow. Trung Son reservoir has small

regulation coefficient = 0.015. Furthermore, the reservoir uses 2 monthsperiod as flood control for lowlands (from 15thJuly to 15thSeptember annualy,reservoir water level at 150.0m elevation) hence regulation capacity of thereservoir in such period is not well enough. During flood control period, whennatural inflow to reservoir is greater than maximum discharge for powergeneration, the redundant discharge will be released through the spillway (such


23/110



redundant discharge shall not be considered as reservoir storage volume). Themonthy average flow covers the average flow of incoming floods to reservoir,so, the redundant discharge through spillway of about 9% was calculated inreservoir discharge simulation. The daily average flow shown the incomingfloods to the reservoir, so, the redundant discharge through spillway of 14%was calculated in reservoir discharge simulation. (greater than simulation ofmonthy average flow). According evaluation made by Design Consultant, thehydro energy simulation calculation results by daily average flow are morereliable than the hydro energy simulation calculation results by monthy averageflow.

Table 2-5: Results of hydro-energy calculation of Trung Son HPP using daily flowdata, without Thanh Son reservoir in downstream of powerhouse-----------------------------------------------------------------

| No | Qs | Qtbin | Qx | Htt | N | E |

-----------------------------------------------------------------

1. 112.70 112.17 .00 65.31 63.78 558.68

2. 184.43 165.79 14.50 67.44 93.59 819.86

3. 193.34 172.10 23.60 66.49 96.13 842.10

4. 290.12 225.92 60.81 66.89 125.47 1099.11

5. 234.88 200.85 33.33 67.35 114.49 1002.94

6. 225.50 198.62 26.29 67.42 112.92 989.14

7. 285.93 232.26 53.08 67.02 130.67 1144.65

8. 265.17 222.07 42.51 67.15 125.65 1100.689. 196.35 188.96 7.71 67.35 107.41 940.95

10. 259.87 211.02 47.38 67.16 117.19 1026.60

11. 205.69 183.57 21.52 67.59 103.84 909.67

12. 154.83 143.59 14.07 66.23 81.86 717.09

13. 186.31 168.94 13.41 66.88 94.47 827.54

14. 232.57 212.00 19.99 67.17 118.57 1038.68

15. 253.44 200.21 52.65 67.28 111.19 974.03

16. 249.88 206.54 42.76 67.27 116.24 1018.25

17. 341.71 233.54 107.58 66.94 130.34 1141.74

18. 228.45 212.48 15.39 67.32 121.21 1061.83

19. 274.81 214.58 59.65 67.19 121.91 1067.91

20. 233.28 199.87 32.82 67.40 113.95 998.16

21. 221.72 209.59 11.55 67.37 119.18 1043.98

22. 314.56 272.84 41.13 66.71 154.54 1353.73

23. 238.89 220.43 17.92 67.31 124.91 1094.21

24. 255.04 208.25 46.16 67.35 118.06 1034.22

25. 255.54 237.42 17.54 67.05 134.30 1176.43

26. 292.48 246.29 45.60 66.94 139.44 1221.46

27. 203.34 186.93 15.83 67.61 107.85 944.7728. 228.78 214.81 13.38 67.31 122.77 1075.48

29. 249.90 218.34 30.97 67.31 125.13 1096.15

30. 207.13 200.24 6.31 67.48 114.14 999.85

31. 175.81 161.98 13.23 67.84 93.08 815.42

32. 175.43 158.94 15.91 67.84 91.86 804.68

33. 229.75 205.65 23.51 67.37 118.08 1034.39

34. 275.91 234.00 41.32 66.99 131.43 1151.34

35. 206.27 181.01 24.68 67.58 101.18 886.35

36. 155.24 149.25 5.40 67.94 85.82 751.76

37. 172.08 164.69 6.80 67.83 94.78 830.31

38. 340.05 250.28 90.25 66.27 138.95 1217.23

39. 263.38 208.67 53.06 67.16 116.12 1017.22

40. 354.29 243.20 110.50 66.72 136.92 1199.39

41. 277.88 206.47 70.81 67.32 116.53 1020.81

42. 136.77 135.86 3.59 65.87 77.28 676.99


24/110



43. 226.20 203.78 18.60 67.30 115.69 1013.43

44. 249.11 221.13 27.39 67.29 124.98 1094.86

45. 292.05 248.47 42.99 66.86 139.14 1218.85

46. 333.96 269.39 63.98 66.56 151.24 1324.91

47. 242.04 223.27 18.18 67.27 128.20 1123.05

48. 248.41 218.69 29.38 67.29 123.05 1077.94

49. 264.07 206.05 57.20 67.24 116.84 1023.55

50. 161.65 146.66 17.94 67.84 82.89 726.09

-----------------------------------------------------------------

---------------------------------------------------------------------------------------------------

|TT| NWL | MWL | Vtb | Vc | Vhi | Vplu | Q0 | Qtbin | Qxa | Qdb | Qmax | Hmax |

---------------------------------------------------------------------------------------------------

1. 160.00 150.00 348.53 236.40 112.13 112.13 237.14 203.15 33.40 66.53 504.0 71.07---------------------------------------------------------------------------------------------------

|TT| Hmin | Htb | Nlm | Ndb | Ntb | E0 | Elu | Eki | Emua | Ekho | Hsd | Beta |

---------------------------------------------------------------------------------------------------

1. 48.05 64.85 260.00 41.75 114.91 1006.57 649.00 357.57 549.13 457.44 3871. .0150

---------------------------------------------------------------------------------------------------

In which:- Qs: Incoming discharge to Trung Son dam site (m

3/s)- Qtbin: Discharge through turbine (m

3/s)- Qx: Redundant discharge through spillway (m

3/s)- Htt: Water head (m)- N: Capacity (MW)- E: Electric energy (million kWh)- NWL: Normal water level (m)

- MWL: Minimum water level (m)- Vtb: Total storage volume (million m

3)- Vc: Dead storage (million m

3)- Q0: Annual average discharge to dam site (m

3/s)- Qdb: Firm discharge (m

3/s)- Qmax: Design discharge through turbine (m

3/s)- Hmax: Maximum water head (m)- Hmin: Minimum water head(m)- Htb: Average water head (m)- Nlm: Installed capacity (MW)- Nb: Firm capacity (MW)- E0: Long-term average electric energy (million kWh)- Eflood season: Long-term average electric energy in flood season (million kWh)- Edry flow season: Long-term average electric energy in dry flow season (million kWh)- Ewet season: Long-term average electric energy in raining season (million kWh)- Edry season: Long-term average electric energy in dry season (million kWh)

2.6.2. Trung Son hydropower plant tailrace water level (case 1)

- During the dry season days, the powerhouse is always operated with oneturbine to ensure the release discharge to downstream to avoid great fluctuationin water level at downstream. The process of fluctuation in water level at

downstream is considered as the most dangerous case when the power plantincreases from 40% 50% capacity of one unit to installed capacity (N lm=260MW), equivalent to discharge increasing from minimum discharge of oneunit (about 63m3/s) to powerhouse design discharge of 522m3/s. During theoperating process, it is not permitted to increase discharge to level which isgreater than natural increase discharge before existence of reservoir. Themaximum natural increased discharge taken place in range of < 700m3/s in

period from 1957 to 2007 as shown in below statistical table:


25/110



Table 2-6: Process of maximum natural increased discharge (


26/110



2.6.3. Specific characteristics of flow at power plant tailrace in daily period

The plant tailrace daily average water level, natural daily average water level atriver across section in powerhouse area, daily average discharge at tailrace of

power plant, natural daily average discharge at river cross-section inpowerhouse area are shown in below figures:


27/110

TrungSonhydropowerproject

FeasibilityStudy

Analysisandsimulationofreservoir

23

Averagewaterlevelandnaturalwaterlevela

tTrungSonhydropowerplant(PlanttailracewithoutThanhSonreservoir)

88.5

0

89.0

0

89.5

0

90.0

0

90.5

0

91.0

0

91.5

0

92.0

0

92.5

00

25

50

75

100

125

150

175

200

225

250

275

300

325

350

37

5

400

Time(day)

Waterlevel(m)

Planttailracewaterlevel

Naturaltailracewaterlevel


28/110


FeasibilityStudy


24

Waterlevelinlittlewateryearwithfrequen

cyP=90%

andnaturalwaterlevelatTrungSonhydropowerplant(plant

tailracewithoutThanhSonreservoir)

88.5

0

89.0

0

89.5

0

90.0

0

90.5

0

91.0

0

91.5

0

92.0

0

92.5

0

93.0

0

93.5

0

94.0

00

25

50

75

100

125

150

175

200

225

250

275

300

325

350

3

75

400

Time(day)

Waterlevel(m)


Naturalwaterlevel


29/110


FeasibilityStudy


25

Waterlevelinmuchwateryearwithfrequen

cyP=10%

andnaturalwaterlevelatT

rungSonhydropowerplant(Incase

plantt

ailracewithoutThanhSonreservoir)

88.0

0

89.0

0

90.0

0

91.0

0

92.0

0

93.0

0

94.0

0

95.0

00

25

50

75

100

125

150

175

200

225

250

275

300

325

350

3

75

400

Time(day)

Waterlevel(m)


Naturalwaterlevel


30/110


FeasibilityStudy


26

AveragedischargeandnaturaldischargeatT

rungSonplanttailrace(IncasePlant


0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

800.0

0

2

5

50

75

100

125

150

175

200

225

250

275

300

325

350

37

5

400

Time(day)

Discharge(m3

/s)

Discha

rgeatplanttailrace

Natura

ldischargeatplanttailrace


31/110


FeasibilityStudy


27

Disch

argeinlittlewateryearwithfrequency

P=90%

andnaturaldischargeatTrungSonplanttailrace(Incaseplant


0200

400

600

800

1000

1200

0

25

50

75

100

125

150

175

200

225

250

275

300

325

350

3

75

400

Time(day)

Discharge(m3

/s)

Dischargeatplanttailrace

Naturaldischargeatplanttailrace


32/110


FeasibilityStudy


28

Discha

rgeinmuchwateryearwithP=10%a

ndnaturaldischargeatTrungSonhydropowerplanttailrace(Incaseplant


0200

400

600

800

1000

1200

1400

1600

0

25

50

75

100

125

150

175

200

225

250

275

300

325

350

3

75

400

Time(day)

Discharge(m3

/s)

Disc

hargeatplanttailrace

Natu

raldischargeatplanttailrace


33/110

Trung Son hydropower project Feasibility Study


2.6.4. Specific characteristics of flow at power plant tailrace in hourly period

For estimation of flow specific characteristics fluctuation level (water level,discharge) in hourly period at river cross-section at powerhouse area, theDesign Consultant calculated some operation cases, particularly as below:

Table 2-7:Operation of Trung Son hydropower plant in case daily average discharge of 234 m3/s

released to downstream

Hour

Discharge(m3/s)

Unit 1 Unit 2 Unit 3 Unit 4 Total Increasing

1 63 63

2 63 63

3 63 63

4 63 63

5 63 63

6 63 63

7 63 63

8 126 126 63

9 126 126

10 126 126

11 126 63 189 6312 126 63 63 252 63

13 126 126 63 315 63

14 126 126 126 378 63

15 126 126 126 378

16 126 126 126 378

17 126 126 126 63 441 63

18 126 126 126 126 504 63

19 126 126 126 126 504

20 126 126 126 126 504

21 126 126 126 126 504

22 126 63 63 63 315 -189

23 63 63 -252

24 63 63

Average 102 55 50 26 234


34/110



Table 2-8: Operation of Trung Son hydropower plant in case daily average discharge of 200 m3/s


Hour

Discharge(m3/s)


1 63 63

2 63 633 63 63

4 63 63

5 63 63

6 63 63

7 63 63

8 63 63

9 126 126 63

10 126 126

11 126 126

12 126 126

13 126 126

14 126 63 189 63

15 126 63 63 252 6316 126 126 63 315 63

17 126 126 63 63 378 63

18 126 126 126 63 441 63

19 126 126 126 126 504 63

20 126 126 126 126 504

21 126 126 126 126 504

22 126 63 63 63 315 -189

23 63 63 63 189 -126

24 63 63 -126

Average 100 42 34 24 200


35/110





Hour

Discharge(m3/s)


1 63 63

2 63 63

3 63 63

4 63 63

5 63 63

6 63 63

7 63 63

8 63 63

9 63 63

10 63 63

11 63 63

12 126 126 63

13 126 126

14 126 126

15 126 63 189 63

16 126 126 252 63

17 126 126 63 315 63

18 126 126 126 378 63

19 126 126 126 378

20 126 126 126 378

21 126 126 126 378

22 126 63 63 252 -126

23 63 63 -189

24 63 63

Average 92 37 26 155


36/110





Hour

Discharge(m3/s)


1 63 63

2 63 63

3 63 63

4 63 63

5 63 63

6 63 63

7 63 63

8 63 63

9 63 63

10 63 63

11 63 63

12 63 63

13 63 63

14 126 126 63

15 126 126

16 126 126

17 126 63 189 63

18 126 126 252 63

19 126 126 252

20 126 126 252

21 63 63 126 -126

22 63 63 -63

23 63 63

24 63 63

Average 81 21 102


37/110



2.6.5. Trung Son hydropower reservoir water level fluctuation (case1)

- Regulation on maximum water level of reservoir: from 15th July to 15thSeptember annually, maximum water level of reservoir is regulated at minimumwater level of 150.0m to control flood for lowlands (according regulation onwater level of reservoir specified in Trung Son hydropower reservoir operation

rules which was approved by Ministry of Industry and Trade). Accordingstability calculation of the reservoir banks (in some areas with possibility ofreservoir banks collapse and sliding), it is shown that the requirement on

process of draining water level in reservoir should not be greater than 0.7m/dayand night, therefore in the hydro energy calculation, the time requested fordraining water level in reservoir from NWL=160.0m down MWL=150.0mshould be over 15 days. In the actual reservoir operation process, depending onincoming flow discharge in initial flood season, reservoir draining to lowerwater level should be made suitably, to ensure minimum redundant discharge

and increase electricity generation output. The actual process of drainingreservoir water level can be twenty days to drain water level from 160.0m downto water level at 150.0m.

- The generation discharge include natural incoming discharge to reservoir anddischarge supplied from reservoir. The reservoir discharge supply potential isshown in below table:

Table 2-11: Discharge supply potential from Trung Son hydropower reservoir

No.Elevation

Z (m)

Surface areaof reservoir F

(km2

)

Storage capacityof reservoir V

(106

m3

)

Discharge supplyfrom the reservoir

Qcp(m3

/s)

Remarks

1 160.0 13.13 348.52 159.0 12.72 336.4 140.03 158.0 12.31 324.3 140.04 157.0 11.90 312.2 140.05 156.0 11.49 300.2 140.06 155.0 11.08 288.1 140.07 154.0 10.78 277.7 119.68 153.0 10.49 267.4 119.69 152.0 10.19 257.1 119.6

10 151.0 9.90 246.7 119.611 150.0 9.60 236.4 119.6

- The process of reservoir impounding shall begin from 15thSeptember annually. Thereservoir impounding is allowable to full water level from time to time as possible

because the erosion to reservoir banks shall not be taken place during process ofimpounding water


38/110


FeasibilityStudy


34

Thewa

terlevelcurveprocesswithfrequency

90%

ofTrungSonhydropowerreservoir(DownstreamwithoutThanhSon

reservoir)

149.0

150.0

151.0

152.0

153.0

154.0

155.0

156.0

157.0

158.0

159.0

160.0

161.0

0

2

5

50

75

100

125

150

175

200

225

250

275

300

325

350

375

400

Time(day)

Waterlevel(m)


39/110


FeasibilityStudy


35

Thewa

terlevelcurveprocesswithfrequency

10%

ofTrungSonhydropowerreservoir(DownstreamwithoutThanhSon

reservoir)

149.0

150.0

151.0

152.0

153.0

154.0

155.0

156.0

157.0

158.0

159.0

160.0

161.0

0

2

5

50

75

100

125

150

175

200

225

250

275

300

325

350

375

400

Time(day)

Waterlevel(m)


40/110


FeasibilityStudy


36

Thea

veargewaterlevelcurveprocessofTrungSonhydropowerreservoir(Downs

treamwithoutThanhSonreservoir)

149.0

150.0

151.0

152.0

153.0

154.0

155.0

156.0

157.0

158.0

159.0

160.0

161.0

0

2

5

50

75

100

125

150

175

200

225

25

0

275

300

325

350

375

400

Time(day)

Waterlevel(m)


41/110



2.7 DOWNSTREAMWITHTHANHSONRESERVOIR(CASE2)

2.7.1. Electric energy (case 2)

- In case with Thanh Son Hydropower reservoir (Normal Water Level = 89.0m)located downstream of Trung Son hydro powerhouse, the toe of Trung Son

hydro powerhouse is submerged. The hydro energy calculation results showthat the energy decreases inconsiderable in compared with the case ofinsubmerged powerhouse toe (0.08 million KWh). See details as below:

Table 2-12: Hydro energy calculation results of Trung Son using daily flow data, with Thanh Son

reservoir dowstream of Trung Son HPP

-----------------------------------------------------------------

| No | Qs | Qtbin | Qx | Htt | N | E |

-----------------------------------------------------------------

1. 112.70 112.17 .00 65.13 63.71 558.07

2. 184.43 165.79 14.50 67.39 93.57 819.64

3. 193.34 172.10 23.59 66.44 96.11 841.90

4. 290.12 225.93 60.81 66.87 125.46 1099.06

5. 234.88 200.84 33.32 67.34 114.48 1002.84

6. 225.50 198.62 26.29 67.40 112.91 989.06

7. 285.93 232.26 53.07 67.01 130.67 1144.658. 265.17 222.08 42.50 67.14 125.64 1100.61

9. 196.35 188.98 7.71 67.32 107.41 940.89

10. 259.87 211.01 47.38 67.14 117.17 1026.42

11. 205.69 183.58 21.52 67.58 103.84 909.60

12. 154.83 143.59 14.06 66.19 81.84 716.88

13. 186.31 168.94 13.40 66.84 94.45 827.34

14. 232.57 212.00 19.99 67.14 118.56 1038.55

15. 253.44 200.22 52.64 67.26 111.18 973.95

16. 249.88 206.55 42.75 67.26 116.24 1018.22

17. 341.71 233.54 107.57 66.93 130.34 1141.75

18. 228.45 212.48 15.38 67.31 121.21 1061.81

19. 274.81 214.58 59.64 67.18 121.90 1067.88

20. 233.28 199.87 32.82 67.40 113.95 998.18

21. 221.72 209.59 11.55 67.36 119.18 1043.98

22. 314.56 272.85 41.13 66.71 154.54 1353.75

23. 238.89 220.43 17.92 67.29 124.90 1094.15

24. 255.04 208.25 46.15 67.33 118.05 1034.14

25. 255.54 237.42 17.54 67.04 134.29 1176.39

26. 292.48 246.30 45.59 66.94 139.44 1221.4727. 203.34 186.93 15.82 67.60 107.85 944.73

28. 228.78 214.82 13.38 67.31 122.77 1075.49

29. 249.90 218.34 30.96 67.31 125.13 1096.15

30. 207.13 200.24 6.31 67.48 114.13 999.81

31. 175.81 161.99 13.22 67.83 93.08 815.37

32. 175.43 158.94 15.91 67.82 91.85 804.58

33. 229.75 205.66 23.51 67.36 118.08 1034.38

34. 275.91 234.01 41.31 66.99 131.43 1151.34

35. 206.27 181.01 24.68 67.56 101.17 886.29

36. 155.24 149.25 5.40 67.91 85.80 751.62

37. 172.08 164.70 6.80 67.81 94.77 830.22

38. 340.05 250.32 90.25 66.24 138.95 1217.24

39. 263.38 208.65 53.05 67.13 116.09 1016.92

40. 354.29 243.20 110.50 66.72 136.92 1199.41

41. 277.88 206.48 70.81 67.30 116.52 1020.74

42. 136.77 135.86 3.59 65.79 77.24 676.64

43. 226.20 203.79 18.60 67.29 115.68 1013.37

44. 249.11 221.14 27.39 67.29 124.98 1094.83

45. 292.05 248.48 42.98 66.85 139.14 1218.8346. 333.96 269.40 63.97 66.56 151.25 1324.94

47. 242.04 223.27 18.18 67.27 128.20 1123.06

48. 248.41 218.70 29.38 67.27 123.04 1077.86

49. 264.07 206.06 57.19 67.22 116.83 1023.43

50. 161.65 146.67 17.93 67.80 82.87 725.91

-----------------------------------------------------------------

---------------------------------------------------------------------------------------------------

|TT| NWL | MNL | Vtb | Vc | Vhi | Vplu | Q0 | Qtbin | Qxa | Qdb | Qmax | Hmax |

---------------------------------------------------------------------------------------------------

1. 160.00 150.00 348.53 236.40 112.13 112.13 237.14 203.16 33.40 65.84 504.0 70.95

---------------------------------------------------------------------------------------------------

|TT| Hmin | Htb | Nlm | Ndb | Ntb | E0 | Elu | Eki | Emua | Ekho | Hsd | Beta |

---------------------------------------------------------------------------------------------------

1. 48.05 64.85 260.00 41.25 114.90 1006.49 649.01 357.48 549.15 457.34 3871. .0150

---------------------------------------------------------------------------------------------------


42/110



In which:- Qs: Discharge coming to dam site of Trung Son (m

3/s)- Qtbin: Discharge through turbine (m

3/s)- Qx: Redundant discharge release to spillway(m

3/s)- Htt: Water head calculation (m)- N: Capacity (MW)

- E: Electric energy (million kWh)- NWL: Normal water level (m)- MWL: Minimum water level (m)- Vtb: Total storage capacity (million m

3)- Vc: Dead storage (million m

3)- Q0: Annual average discharge to dam site(m

3/s)- Qdb: Firm discharge (m

3/s)- Qmax: Design discharge through powerhouse(m

3/s)- Hmax: Maximum water head (m)- Hmin: Minimum water head (m)

- Htb: Average water head (m)- Nlm: Installed capacity (MW)- Nb: Firm capacity(MW)- E0: Long-term average electric energy (million kWh)- Eflood season: Long-term average electric energy in flood season (million kWh)- Edry flow season: Long-term average electric energy in dry flow season (million kWh)- Ewet season: Long-term average electric energy in raining season (million kWh)- Edry season: Long-term average electric energy in dry season (million kWh)

2.7.2. Trung Son hydropower Plant tailrace water level(Case 2)

- The catchment basin area calculate to damsite of Trung Son HPP is 14660km2, to damsite of Thanh Son HPP is 14760 km2, middle catchment basin areais 100 km2

- Downstream of Trung Son hydropower plant is Thanh Son hydropower plant,so Trung Son Hydropower Plant tailrace water level is always higher thanminimum water level of Thanh Son hydropower plant. The Thanh Son HPP isdesign with dam combined with spillway in Ma river and dam toe type

powerhouse, so the water level fluctuation in reservoir is at small range. The

Thanh Son HPP shall be operated synchronously with Trung Son HPP. As ofpresent time, Thanh Son hydropower project is in feasibility study stage, thereservoir parameters such as NWL; MWL; Nlmhave not yet been defined

presisely. In case the reservoir of Thanh Son HPP has 24 hours regulationstorage volume, it is allowable to release discharge from 63m3/s up to 522m3/sin short time from Trung Son HPP (as allowable condition of equipment of

powerhouse)


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2.7.3. Trung Son HPP reservoir water level fluctuation (case 2)

- In case with Thanh Son reservoir downstream of Trung Son HPP reservoirwater levels fluctuation shall be same as in case without Thanh Son reservoir.The possibility of reservoir impounding to maximum water level is allowable.The reservoir water level drawn-down allowable condition should not be more

than 0.7m/24 hours. In the process of operation, depending on hydrologicalcondition (incoming flow to damsite) water draining capacity shall becalculated in such a manner to ensure minimum discharge released throughspillway and maximum electric energy generation output.


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Appendix 41

July) and flood season. Environmental flow is always secured on Ma river after Luongtributary.

Hence, only environmental flow within river section from downstream of damroute to confluence with Xia stream is considered.

3.1.2.

3.1.3. Water demand for Industry and daily uses.

Water demand for Industry and daily uses is considered up to 2020. Accordingto report named General updating Irrigation planning of cascades to developeconomy at downstream of Ma river basin, water demand for these fields as below:

Table 3-3: Water demand for Industry and daily uses

No Location Demand (m3/s) Note

1 Trung Sn town 0.052 Quan Ho town 0.05

3 B Thc town 0.10

4 Cm Thy town 0.10

Total 0.30

Ma River

Xia Catchment AreaF=249 km2

Trung Son HPP

Xia Stream

Interstream AreaF=209 km2


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Appendix 42

3.1.4. Water demand to secure environmental and ecological system.

In order to mitigate effects on environment of Ma river reach, time to setblocking of diversion culvert is flood season. Tentative blocking time is on July whenit often rains and flow is approximate to annual value (418m3/s) on catchment fromTrung Son dam route to Xia stream. Impounding time is 4 days to raise reservoir water

level reach to spillway crest elevation.During impounding period, flow within river reach from dam route to

confluence with Xia stream is runoff and groundwater. This 290 km2 catchment hasaverage monthly flow in July with Qo= 5.14 m3/s, equivalent to 14.12% of naturalflow of Ma River at the dam site. Minimum observed monthly flow at the dam sitefrom 1957 to 2002 is 36.4m3/s occurred in May 1957.

According to Tenant method, environmental flow to secure ecological systemin flood season is about 10-30% of annual flow. Therefore, flow on Ma river reachfrom dam site to Xia stream which is 5.14m3/s (14.12% of minimum monthly flow) isenough to supply all demands and environment along the river reach in 04 days ofdiversion culvert blocking. Then, environmental flow will be supplied by dischargethrough spillway after these 4 days.

3.1.5. Conclusion

With selected method for diversion culvert blocking and time to raise reservoirwater level to spillway crest in 4 days in July, flow on 20km-Ma river reach atdownstream of Trung Son dam will supply from runoff and groundwater. Hence, thereis no any structure that need be built in order to release discharge to downstream

during 4 days of culvert blocking. Cost of project, then, will be saved.

3.2 ENVIRONMENTFLOWRELEASEMEASURES

In order to release flow discharge at 15 m3/s during reservoir impoundingperiod, it is required to install released culvert with dimension BxH=1.2x1.2m forTrung Son HPP. The position of this released culvert is next to diversion culvert.

The hydraulic cylinders operated maintenance gate and operation gate withdimensions 1.2x1.2m are arranged at upstream of this culvert.

Design of environment flow released culvert are shown in drawings ofappendices.

3.3 DISCHARGEOFWATERDURINGOPERATIONPROCESS

During operation process, water will be discharged to downstream through theturbines of powerhouse. During operation of powerhouse, if there is any failureencountered or ceases operation due to different causes, water will be dischargedthrough spillway to maintain environment flow and water supply demand fordownstream without needing any other discharge structures, because the spillway weir


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Appendix 43

elevation is set at 145m and minimum water level is set at 150m (5m higher thanspillway crest elevation).

3.4 DISCHARGEOFMUDANDSAND

According to the calculation about sedimentation in reservoir of Trung SonHPP, after 100 years, the quantity of mud and sand still do not reach to the intake gate

elevation. Mud and sand will be mainly accumulated in the end part and middle part ofreservoir, so it is not necessary to install discharge outlet for mud and sand. The resultsof calculation in 2.2 Subject calculation sediment backwater Trung Son HPP, after100 years operation, sediment elevation at section near the dam at 97.0m

3.5 RESERVOIRDEWATERING

According to the ruling standards of Vietnam as well as many other countries inthe world, there is no obligation for installation of drainage system for reservoirdewatering.

3.6 CONCLUSION

Installation of a culvert to release water to downstream at 15m3/s discharge tomaintain ecological environment during reservoir impounding period is necessary.

When the reservoir impounding is up to the full supply water level, thedischarge culvert ceases its role, and according to the relevant regulations, there is noneed to install culvert for reservoir dewatering. Specific calculations on sedimentationconfirmed that it is not required to arrange culvert for discharging mud and sand.


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Appendix 44

Chapter 4: RESERVOIR AND DOWNSTREAM LANDSLIDEPOSSIBILITY FORECAST

4.1 RESERVOIRBANKLANDSIDEPOSSIBILITY

4.1.1. CALCULATION DATA

4.1.1.1 Table of physical mechanical properties indices stability calculationbank of reservoir

Table 4-1: Physical-mechical properties indices stability calculation bank of reservoir

Material layer (T/m3)

(natural/saturated)

(natural/saturated)

C (KG/cm2)

(natural/saturated)

edQ 1.72/1.79 0.18/0.16

IA1 1.65/1.77 25/18 0.24/0.18

IA2 1.68/1.79 25 0.22

IB 2.66/2.68 29 2.00

IIA 2.77/2.79 37 2.50

4.1.1.2 Project grade: grade II

Stability safe factor allowable of project: According Vietnamese constructionstandard TCXD V 285: 2002 with project grade II, natural slope, safety factor iscalculated according to the formula as follow:

k nc.kn/m

In which:

nc: Load combination factor. For basic load combination: nc=1, forspecial load combination: nc=0.9.

kn: Guarantee factor calculated according to project scale and tasks.Project grade II. Guarantee factor is taken as kn=1.2.

m: Operating condition factor. For natural and artificial slope m=1.

with parameters as above, safety factor is calculated as follow:

- Basic load combination : k = 1.20

- Special load combination : k= 1.08

4.1.1.3 Location of section calculationAccording topographical, geological condition at reservoir foundation area

studied in technical design stage to choose reservoir bank section easy to slidingSpecifically are 5 typical sections with features as below: sloping topographical,

thick weak geological zone and thin covering vegetation layer to calculate and checkstability

See location of calculation sections in drawing chart location of sectionstability calculation see in appendix


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Appendix 45

4.1.2. CALCULATION CASE

atural slope of reservoir foundation area is stability through time when

reservoir is not impounding and more stability after impounding at regular

water level exploit. So that it needs to check for two danger cases as follow:

- Fast drain reservoil water level frome WL=160.0m down to MWL=150.0mfollow different time step . (Special load combination)- Fast drain reservoil water level frome WL=160.0m down to MWL=150.0m

follow different time step and underground water level is raised to surface of slope.(Special load combination according to WB recommend)

From calculation results for two cases as above to recommend reasonable timeperiod to drain water of reservoir in operation process.

4.1.3. SOFTWARE CALCULATION

The program use to calculate stability: Slope/w software of Canada. Analysismethod: Bishop and Janbu, these are two methods applicable worldwide forslope stability analysis.

4.1.4. CALCULATION RESULTS

Table 4-2: Calculation result table according to recommend case of Consultant

Sectioncalculation

Case CaseKmin min

[K]Bishop Janbu

Section 1Drain water in 5 days Case 1 1.41 1.35

1.08Drain water in 10 days Case 2 1.50 1.45Drain water in 15 days Case 3 1.55 1.49





Section 4 at leftbank

Drain water in 5 days Case 1 1.01 0.981.08Drain water in 10 days Case 2 1.09 1.08

Drain water in 15 days Case 3 1.11 1.09

Section 4 atright bank

Drain water in 5 days Case 1 1.02 0.991.08Drain water in 10 days Case 2 1.09 1.06

Drain water in 15 days Case 3 1.12 1.09



(Detail see in appendix)


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Appendix 46

Table 4-3: Calculation result table according to recommend case of WB

Sectioncalculation

CaseKmin min

[K]Bishop Janbu

Section1Underground water level is raised tothe surface of the slope

0.80 0.79 1.08

Section2 Underground water level is raised tothe surface of the slope

0.40 0.37 1.08


0.70 0.68 1.08

Section 4 at leftbank

Underground water level is raised tothe surface of the slope

0.44 0.42 1.08

Section 4 atright bank

Underground water level is raised tothe surface of the slope

0.55 0.54 1.08


0.40 0.37 1.08

(See details in appendix)

4.1.5. CONCLUSION AND RECOMMENDATION FROM CALCULATIONCOMBINATION DONE BY CONSULTANT

According to calculation result mentioned in Table 4-2, recommendation can bemade, as follow:

- The banks of reservoir shall be instable in case water level draining from WL=160m down to MWL=150m in period time 5 days for Bishop method and 10days for Janbu method. However in practical operation reservoir, water level draining

from WL=160m down to MWL=150m shall be taken place in 20 days period.- In the process of operation reservoir, the reservoir drawn-down water level in

24 hours period should not be over 0.7m to protect environment and stable reservoirbanks.

4.1.6. ANALYSIS RECOMMEND CASE OF WB

For Consultancy, WB has recommended a case which is a extreme case, in factit cannot occur because of the following reasons:

- The formation process of underground water level is happened in a long timeand stabilized versus time. The fluctuation of underground water level is just occuredat the location water level adjacent of river bank. Therefore, the case undergroundwater level is raised to the surface of the slope which cannot occur. In fact it ischecked in process exploratory drilling geologic for many.

- The natural rive bank slope of Trung Son HPP area is heavy gradient (from 300

to450). Therefore the water shall be discharged follow subsurface flow down naturalwater-course when it has heavy rain, only a small part of the rain-water percolation


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Appendix 47

into underground. The part of leakage water just enough to do water-saturated soil sub-grade lap on surface of the slope and it cannot raise to the slope surface.

- Consultancy has checked realistic condition that: the slopes when HPP doesntbuild yet which is stabilized before age-old with reputed that underground water levelis raised to the surface of the slope by heavy rain, results show all the slopes in shearwith safe factors are very low, that fact indicate calculation case as above never occur.(Results have shown at table 4-3 and in appendix).

4.2 EROSIONRIVERBEDOFRESERVOIRDOWNSTREAM

The river bed erosion is a part of the process of moving sediment cause flow.This phenomena is happening continuous in the time. To estimate erode ability river

bed for specific river. measurement data and study about sediment moving flowinclude suspended load and bed load in a necessary period time. In addition. factorseffect to the sediment moving process as form of river bed. covering vegetation bed.geological structure of river bed and banks. ..etc.

owadays. there are studies in the world about erosion and moving layers atriver bed cause by flow for different grain component types. The method calculationsusually application so much and was mention in Handbook of Hydrology. Chapter 12of David R.Maidment author. McGraw-Hill publisher. Inc.. 1992 include: Mayer-Peter and Muller (1948). Einstein (1950). Bagnold (1956.1966. 1973). andPaker (1990). In which. Mayer-Peter method and Muller method was application forriver bed has coarse grain component. grain size from 0.4mm to 30mm. The Bagnoldmethod using for flow has much content sediment. The Einstein method is nearlycomplete and the most suitable. The other methods are necessary to estimation muchmore.

Out of Mayer-Peter and Muller method as mentioned above. other methods as

Acker and White (1973). England-Hansen (1967). Laursen-Copeland (1968.1989).Toffeleti (1968). Yang (1973.1984). Wilcock (2001. 2003) was introduction in HEC-RAS 4.0 (HEC-6) software to calculate moving sediment ability by flow.

Downstream riverbed erosion assessment for Trung Son HPP is a complicatedstudy which requires a lot of data, including accuracy measured and observed data, toapply for a specific erosion modeling. However, based on the current data, theconsultant can give the overview about erodibility of riverbed as follows:

Riverbed geological formation at downstream of the dam: the riverbed wasformed mainly by medium to slightly weathered rock with medium hardness. Itscompressive strength and shearing resistance are about 10 MPa and 0.36MPa

respectively. The erodible velocity (critical velocity) for such kind of riverbed is foundat 8 m/s. Moreover, only some location along the river was found that havingdeposition with small scale. Further to downstream of project, there is no officiallymeasured or investigated data of riverbed geological formation. However, based onobserved of our geological engineers observation during the time period for siteinvestigation, most of riverbed was found medium to slightly weathered rock (see theFigure below).

In order to assess, a narrow river cross section, of which section, geologicalcondition, and water level data are available, was selected. The consultant checked for


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Appendix 48

different discharge rate from a half of unit discharge to check flood discharge throughpowerhouse and spillway. Result of hydraulic calculation is shown in table below:

Discharge (m3/s) Water level (m) Wet area (m2) Velocity (m/s)63 (0.5 unit) 87.9 283.7 0.2126 (1 unit) 88.4 322.0 0.4

252 (2 units) 89.1 378.3 0.7378 (3 units) 89.6 429.0 0.9504 (4 units) 90.1 463.9 1.1

10400 (design flood) 103.8 2009.4 5.213400 (check flood) 106.3 2328.1 5.8

The result stated that water speed is always less than the critical speed. Ingeneral, with such geology condition of the riverbed mentioned, additional study onriverbed erosion should not take account.

4.3 SLIDINGATBANKSOFDOWNSTREAM

4.3.1. CALCULATION DATA4.3.1.1 Table of physical mechanical properties indices stability calculation

bank of downstream

Table 4-4: Physical-mechical properties indices stability calculation bank of

downstream

Material layer (T/m3) atural/Saturated

atural/Saturated

C (KG/cm2) atural/Saturated

edQ 1.72/1.79 0.18/0.16IA1 1.65/1.77 25/18 0.24/0.18

IA2 1.68/1.79 25 0.22IB 2.66/2.68 29 2.00IIA 2.77/2.79 37 2.50

4.3.1.2 Project grade: grade II

Stability safe factor allowable of project: According Vietnamese constructionstandard TCXD V 285: 2002 with project grade II. natural slope. safe factor iscalculated according to the formula as follow:

k nc.kn/m

In which:

nc: Load combination factor. For basic load combination: nc=1. forspecial load combination: nc=0.9.

kn: Guarantee factor calculated according to project size and tasks.Project grade II. Guarantee factor is taken as kn=1.2.

m: Operating condition factor. For natural and artificial slope m=1.

with parameters as above. safe factor is calculated as follow:

- Basic load combination : k = 1.20


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Appendix 49

- Special load combination : k= 1.08

4.3.1.3 Location of section calculation

Acoording topographical. geological condition at reservoir foundation areastudied in technical design stage to choose reservoir bank section prone to sliding

possibility.Specifically are 4 typical sections with features as below: sloping topographical,

thick weak geological zone and thin covering vegetation bed layer to calculate andcheck stability

Location of section calculation see in drawing chart location of sectionstability calculation attached to this report.

4.3.2. CALCULATION CASE

atural slope at downstream reservoir after exist project. Water level is onlyfluctuation mainly in range from 107m elevation to 90.2m elevation. In this

range belong river bed area so geological is rather good. mainly IB rock layerand IIA rock layer so fast drain water process is not effect more to slopestability of banks at downstream. In this appendix it is only checking for themost dangerous case. in the operation reservoir process water level atdownstream is draining fast from 104.5m (corresponding to release designflood P=0.5%) down to 90.2m (corresponding to Q=504m3/s through

powerhouse) in 5 days period of time.

4.3.3. SOFTWARE CALCULATION

The program use to calculate stability: Slope/w software of Canada. Analysismethod: Bishop and Janbu, these are two methods applicale worldwide forslope stability analysis.

4.3.4. RESULTS C

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