In The Name Of GODIn The Name Of GOD

SEFIDRUD DAM DESILTATION OPERATIONSEFIDRUD DAM DESILTATION OPERATION

byby

M.H.Ranjbar Taklimy & E. TolouieM.H.Ranjbar Taklimy & E. Tolouie

Sefidrud Reservoir desiltation committee, Gilan Sefidrud Reservoir desiltation committee, Gilan regional water board, Iranregional water board, Iran

August 8-15,2005, Yichang,Hubei Province, ChinaAugust 8-15,2005, Yichang,Hubei Province, China

LOCATION OF SEFIDRUD DAM AND CATCHMENTLOCATION OF SEFIDRUD DAM AND CATCHMENTLOCATION OF SEFIDRUD DAM AND CATCHMENTLOCATION OF SEFIDRUD DAM AND CATCHMENT

SEFIDRUD RIVER SYSTEMSEFIDRUD RIVER SYSTEMSEFIDRUD RIVER SYSTEMSEFIDRUD RIVER SYSTEM

Feature Qezelowzan ShahrudSefidrud *

(at dam site)

Total Catchment(km2) 49,300 5,070 56,200

Length of main channel(km) 500 80 -

Annual erosion(t/km2/yr) 745 1,550 855

* Including intermediate tributaries

Sefidrud Dam

Tarik Diversion Dam

Guelerud Diversion Dam

Sangar Diversion Dam

Evap. + Infilt.

Tutkabon River

Fuman Tunnel

Guelerud Canal

Left CanalRight CanalTo Caspian Sea

4835 MCM

4770 MCM

4970 MCM200 MCM

4580 MCM390 MCM

4360 MCM

220 MCM

2780 MCM

900 MCM680 MCM

65 MCM

Sefidrud Dam

Tarik Diversion Dam

Guelerud Diversion Dam

Sangar Diversion Dam

Evap. + Infilt.

Tutkabon River

Fuman Tunnel

Guelerud Canal

Left CanalRight CanalTo Caspian Sea

4835 MCM

4770 MCM

4970 MCM200 MCM

4580 MCM390 MCM

4360 MCM

220 MCM

2780 MCM

900 MCM680 MCM

65 MCM

SEFIDRUD DAMSEFIDRUD DAMSEFIDRUD DAMSEFIDRUD DAM

Evacuating system:

. 2 morning glory spillways, 3,000 m3/s

. 2 auxiliary spillways, 2,000 m3/s

. 5 power intakes, 160 m3/s

. 5 bottom outlets, 980 m3/s

. Total capacity, 6000 m3/s

Construction period, 1959-1962

Year of commissioning, 1963

Year of starting desiltation, 1980

Main Purpose, Irrigation

Other purposes,

* Power generation, flood control

* Installed cap. = 87.5 mw (5*17.5)

SEFIDRUD DAMSEFIDRUD DAMSEFIDRUD DAMSEFIDRUD DAM

Location, 250 km north west of Tehran

• Type, Buttress-gravity

• Max height, 106 m

• Crest length, 425 m

• Crest elevation, 276.95 masl (metre above sea leavel)

• Main purpose, Irrigation (Mostly rice field)

SEFIDRUD DAMSEFIDRUD DAMSEFIDRUD DAMSEFIDRUD DAM

Original storage capacity at NWL, 1760mcm

Original surface area at NWL, 54 km2

Length along Qezelowzan at NWL, 25 km

Length along Shahrud at NWL, 13 km

Capacity/Inflow ratio, C/I = .36

SEFIDRUD RESERVOIRSEFIDRUD RESERVOIRSEFIDRUD RESERVOIRSEFIDRUD RESERVOIR

Long-term ave. water inflow, 4835 mcm/yr

Long-term ave. sediment inflow, 48 mt/yr

Long-term ave. water outflow, 4615 mcm/yr

RESERVOIR SEDIMENTATION DATARESERVOIR SEDIMENTATION DATARESERVOIR SEDIMENTATION DATARESERVOIR SEDIMENTATION DATA

Emptying the reservoir:

Provision of suitable evacuating facilities in order to

empty the reservoir within reasonable time period. In

Sefidrud a volume of about 300 mcm is being

evacuated during 15 days.

FEASIBILITY OF FLUSHING OPERATIONFEASIBILITY OF FLUSHING OPERATION

Changing the rule curve

FEASIBILITY OF FLUSHING OPERATIONFEASIBILITY OF FLUSHING OPERATION

Changing the rule curve

Flushing season:

In normal years, river flow is established in Sefidrud Reservoir

for 3.5 months. However, the maximum desiltation efficiency

occurs during the first 15 days or so, during river flow the

desiltation efficiency very much depends on inflow water

discharg.

FEASIBILITY OF FLUSHING OPERATIONFEASIBILITY OF FLUSHING OPERATION

Changing the rule curve

FEASIBILITY OF FLUSHING OPERATIONFEASIBILITY OF FLUSHING OPERATION

Changing the rule curve

Refilling the reservoir:

feasibility of filling the reservoir after flushing season

means taking a suitable volume of inflow water for

flushing operation. This criterion is defined as capacity

inflow ratio(C/I), in Sefidrud C/I = 0.36

FEASIBILITY OF FLUSHING OPERATIONFEASIBILITY OF FLUSHING OPERATION

Changing the rule curve

FEASIBILITY OF FLUSHING OPERATIONFEASIBILITY OF FLUSHING OPERATION

Changing the rule curve

Dam safety considerations during rapid drawdown and

refilling of the reservoir:

This parameter is especially important in fill type of dams

particularly during the first 5-10 years of operations.

FEASIBILITY OF FLUSHING OPERATIONFEASIBILITY OF FLUSHING OPERATION

Changing the rule curve

FEASIBILITY OF FLUSHING OPERATIONFEASIBILITY OF FLUSHING OPERATION

Changing the rule curve

Sediment deposition in irrigation system

Sediment deposition along downstream river channel

Sediment deposition in Sefidrud Delta

Fish life

FEASIBILITY OF FLUSHING OPERATIONFEASIBILITY OF FLUSHING OPERATION

Environmental impacts

FEASIBILITY OF FLUSHING OPERATIONFEASIBILITY OF FLUSHING OPERATION

Environmental impacts

MITIGATION OF NEGATIVE EFFECTSMITIGATION OF NEGATIVE EFFECTS

In order to mitigate negative environmental impacts,

comprehensive studies on environmental aspects of sedimentation

and desiltaion is carried out since 2003, we hope that the result

of the studies will help us to achieve sustainable development in

sefidrud river system.

Ave. outflow sediment:

In normal operation, 14 mt/yr

In flushing operation, 44 mt/yr

In total period, 28.4 mt/yr

Annual loss of reservoir capacity in normal operation, 2.3%

RESERVOIR SEDIMENTATION DATARESERVOIR SEDIMENTATION DATARESERVOIR SEDIMENTATION DATARESERVOIR SEDIMENTATION DATA

FLUSHING WITH FLOW DIVERSIONFLUSHING WITH FLOW DIVERSION

Diversion scheme

FLUSHING WITH FLOW DIVERSIONFLUSHING WITH FLOW DIVERSION

Diversion scheme

Main featuresMain features

Features Siahpush Shahrud Qezelowzan

(pilot plan) (empty reservoir) (partial drawdown)

Length of diversion canal(km) 5 7.6 5.5

Constrution period Sep.-Dec. 1987 Nov. 88 - Jan. 89 Sep. - Nov. 2001

Operation period Jan. & Feb 1988 Jan. & Feb. 1989 Dec. 2001- Jan. 2002

Range of diverted discharg(m3/s) 1.2-3.8 4 - 24.5 2 - 80

Volume of deposited sediment removed(mcm) 0.45 4.2 3

Diversion scheme

Features Siahpush Shahrud Qezelowzan

(pilot plan) (empty reservoir) (partial drawdown)

Length of diversion canal(km) 5 7.6 5.5

Constrution period Sep.-Dec. 1987 Nov. 88 - Jan. 89 Sep. - Nov. 2001

Operation period Jan. & Feb 1988 Jan. & Feb. 1989 Dec. 2001- Jan. 2002

Range of diverted discharg(m3/s) 1.2-3.8 4 - 24.5 2 - 80

Volume of deposited sediment removed(mcm) 0.45 4.2 3

Diversion scheme

FLUSHING WITH FLOW DIVERSIONFLUSHING WITH FLOW DIVERSION

Diversion scheme

FLUSHING WITH FLOW DIVERSIONFLUSHING WITH FLOW DIVERSION

Diversion scheme

Layout

FLUSHING WITH FLOW DIVERSIONFLUSHING WITH FLOW DIVERSION

Diversion scheme

FLUSHING WITH FLOW DIVERSIONFLUSHING WITH FLOW DIVERSION

Diversion scheme

ComponentsComponents

(a) diversion dam

(b) diversion(pilot)canal

FIELD OBSERVATIONSFIELD OBSERVATIONS

Types of erosion occurred along diversion canal

FIELD OBSERVATIONSFIELD OBSERVATIONS

Types of erosion occurred along diversion canal

Outflow water vs outflow sediment

0

2000

4000

6000

8000

10000

12000

14000

16000

1963

-64

65-6

6

67-6

8

69-7

0

71-7

2

73-7

4

75-7

6

77-7

8

79-8

0

81-8

2

83-8

4

85-8

6

87-8

8

89-9

0

year

An

nu

al o

utf

low

wat

er

(10

6 m

3 )

An

nu

al o

utf

low

se

dim

en

t(10

4 t

)outflow water outflow sediment

normal operation desiltation operation

1:

900

1000

1100

1200

1300

1400

1500

1600

1700

1800

63-6

4

65-6

6

67-6

8

69-7

0

71-7

2

73-7

4

75-7

6

77-7

8

79-8

0

81-8

2

83-8

4

85-8

6

87-8

8

89-9

0

91-9

2

93-9

4

95-9

6

97-9

8

99-0

0

Operational year

Re

se

rvo

ir v

olu

me

(m

cm

)

Normal operation Desiltation

1244mcm

1040mcm

Note: Reservoir original capacity = 1760 mcm

Calculated based on inflow/outflow sediment data, taking 25% as bed and unmeasured load as well as sediment inflow from intermediate catchment

Capacity Survey

Recovery of storage capacity

Rehabilitation of reservoir capacity

CONCLUSION:

1- Flushing operation is a suitable tool to conserve and rehabilitatereservoir capacity, provided suitable outlet system is avilable.

2- Flow diversion to the flood plain is an effective and practical method to increase desiltation efficiency in flushing operation.3- In sefidrud reservoir, flow diversion as a supplementary measure to

flushing operation was proved to be very efficient in reducing trap efficiency of the reservoir, as presented below:

• trap efficiency (inflow sed.- outflow sed.) Inflow sed.during 17 years of normal operation=79%.

• trap efficiency during 3 years of flushing operation=37%

• trap efficiency during 7 years of flushingoperation + flow diversion = - 96%.

PHOTOSPHOTOS

SEFID - RUD RESERVOIR DESILTATION

Note: Foreset of deposited sediment is above power intake levelNote: Foreset of deposited sediment is above power intake level

Different views of deposited sediment U/S of damDifferent views of deposited sediment U/S of dam

Different views of deposited sediment U/S of damDifferent views of deposited sediment U/S of dam

Different views of deposited sediment U/S of damDifferent views of deposited sediment U/S of dam

Formation of main thalweg with in reservoir areaFormation of main thalweg with in reservoir area

Sampling of suspended sedimentSampling of suspended sediment

Qezel Owzan Diversion Dam during constructionQezel Owzan Diversion Dam during construction

View of Diversion Dam after completionView of Diversion Dam after completion

Digging pilot canalDigging pilot canalDigging pilot canalDigging pilot canal

Initial stage of diversionInitial stage of diversionInitial stage of diversionInitial stage of diversion

Retrogressive erosion along pilot canalRetrogressive erosion along pilot canalRetrogressive erosion along pilot canalRetrogressive erosion along pilot canal

Massive slide in unconsolidated depositMassive slide in unconsolidated depositMassive slide in unconsolidated depositMassive slide in unconsolidated deposit

Constructing fuse Plugg to create Hydraulic shockConstructing fuse Plugg to create Hydraulic shock

Constructing fuse Plugg to create Hydraulic shockConstructing fuse Plugg to create Hydraulic shock

Extensive erosion of new thalweg due to Hydraulic shock (dam break)Extensive erosion of new thalweg due to Hydraulic shock (dam break)

Extensive erosion of new thalweg due to Hydraulic shock (dam break)Extensive erosion of new thalweg due to Hydraulic shock (dam break)

The EndThe End