1. General

Garzan Dam located in Kozluk, Besri District on Batman Province and Kurtalan District on Siirt Province South East Region of The Turkey. Garzan Dam settle in Dicle River Basin. Garzan HEPP settle on foothill of the dam body, Binek HEPP settle on 800 meters from downstream. Access for Kozluk District possible from Diyarbakır – Silvan – Kozluk Highway everyday of a year. 13 km stabilized road from Kozluk District to Valley of Garzan Creek make possible to access project field.

Garzan Dam and HEPP Project structures follows:

  • Clay Core Rock fill dam

  • Free Flow Spillway (Right Bank)

  • Diversion Tunnel (Left Bank)

  • Upstream and Downstream Cofferdams

  • Power Tunnel (Left Bank)

  • Bottom outlet (Left Bank)

  • Plant with 2 units

  • Dam Reservoir

  • Transmission Line Connection

  • Access Roads and Site Buildings

These structures defined in details one by one chapter as follows.

2. Garzan Dam

Dam made of clay core and rock fill body. Upstream cofferdam placed inside the main Dam body. Crest length is 404.79 m and places 800 m altitude.

3. Spillway

Spillway has a free flow lip wall, concrete lining spillway and a ski-jump spillway. Spillway, which places on the right bank of the dam, crest elevation 788.30 m and prevent catastrophic flood.

4. Diversion Tunnel and Cofferdam

Diversion tunnel located on left bank of the dam and in the river bed altitude. Diversion tunnel design compatible to the cofferdam design flood discharge which is 50 years period peak flow. After the construction diversion tunnel become bottom outlet for the dam.

Upstream cofferdam type is rock fill type and compatible to the diversion tunnel design.

5. Power Tunnel and Water Intake

Water intake gate set to near of the tunnel entrance for maintenance purpose and closing for prevent any dangerous situation. Circular power tunnel made of both concrete and steel materials.

6. Bottom Outlet

Inside the diversion tunnel for tapping an 1100 mm diameter butterfly valve located. To fill and empty dam reservoir obtain from bottom outlet. Exit of the tunnel a quadratic valve placed in a valve chamber. At the end of the chamber an energy dissipater placed. Ensure access to bottom outlet valve chamber via field road.

7. Power Plant

Plant contains two Francis turbine and two generator. Plant’s infrastructure made of reinforced concrete. Plant building contains suction pipe, drainage pit, steel volute structure, generator socket, galleries, turbine, generator and main floor. Reinforced concrete upper structure is going around the plant and supports plant crane deck. Plant building mainly contains two unit blocks.

8. Dam Reservoir

Reservoir useful storage volume is nearly 110 hm³. This volume is less than half of yearly annual flow (877.21 hm³). Maximum water elevation 798.80 m reaches maximum volume that is 181 hm³. Reservoir area on minimum water elevation is 1.86 km², on maximum water elevation is4.60 km².

9. Transmission Line Connection

To maintain Garzan HEPP connection to the main network a transmission line and a switchyard project has been made.

10. Access Roads and Site Buildings

Diyarbakır-Silvan-Kozluk highway maintain access to the construction site. 13 km stabilized road from Kozluk District to Valley of Garzan Creek make possible to access project field.


1. River Data

Mean Discharge =37.26 m³/s

Drainage Basin =1266 km²

Spillway Design Entrance Flow =2314 m³/s

25-Years Frequency Flood Discharge =700.90 m³/s

50-Years Frequency Flood Discharge =777.80 m³/s

Suggested Energy Facility Project Flow (max) =43.60 m³/s

2. Climatological Data

Maximum Mean Temperature =43°C

Minimum Mean Temperature = -13°C

Dominant Wind Speed =28.5 km/h

3. Seismic Data

Garzan Dam and HEPP seismic data design earthquake parameters as follow:

  • Maximum Considered Earthquake (MCE)

  • Operating Basis Earthquake (OBE)

  • Maximum Design Earthquake (MDE)

Probability methods used for OBE and MDE. Deterministic methods used for MCE parameters

Maximum Horizontal Ground Acceleration (PGA) =0.295g

Earthquake Magnitude (Mw) =7.8

Maximum Horizontal Ground Acceleration (PGA) =0.176g

Earthquake Magnitude (Mw) =7.8

3. Dam Data

Dam’s general characteristics as follows:

Dam Body

Pre-data use for the dam design as follows and dam’s slope and crest elevation determined in dam project design phase.

Dam Type =Clay Core, Rock Fill

Crest Elevation =800.00 m

Maximum Elevation from Foundation =128 m

Crest Length =404.79 m

Crest Width =12 m

Upstream Slope =2.00 H:1V

Downstream Slope =1.90H:1V


Normal Water Elevation =788.30 m

Minimum Water Elevation =722.20 m

Maximum Water Elevation =798.80 m

Reservoir Area in Max. Water Elevation =4.60 km²

Reservoir Area in Min. Water Elevation =0.71 km²

Reservoir Volume in Max. Water Elevation =202.626 hm³

Suggested Useful Storage =191.73 m3

4. Tail Water Data

Tail Water Elevation =676.00 m

5. Derivation Data

Upstream Cofferdam Type =Rock fill inside dam body

Upstream Cofferdam Crest Elevation =723.69 m

Upstream Cofferdam Crest Width =7.00m

Front Upstream Cofferdam Type =Rock fill

Front Upstream Cofferdam Crest Elevation =693.00

Front Upstream Cofferdam Crest Width =5.00

Downstream Cofferdam Type =Masonry

Derivation Tunnel Type =Circular

Tunnel Length =697.05 m

Entrance Base Elevation =683.00 m

Exit Base Elevation =676.50 m

Tunnel Diameter =7.0 m

Entrance Cofferdam Gate =2@3.25 m x 7.00 m

Capacity (50-Years Frequency Flood Disc.) =700.00 m³/s

6. Power Tunnel Data

Power Tunnel Type =Circular

Tunnel Length =386.55 m

Entrance Base Elevation =741.17 m

Entrance Tunnel Axial Elevation =742.63 m

Tunnel Inner Diameter =4.00 m

Penstock Inner Diameter =3.20 m

Penstock Axial Elevation In Entrance Valve =672.60 m

Maximum Design Discharge For The Tunnel =43.60 m³/s

Maximum Design Velocity For The Tunnel =3.47 m/s

7. Spillway Data

Spillway Type =Free Flow Ogee and ski- jump

Crest Elevation =788.30 m

Spillway Discharge Channel Length =210.60 m

Spillway Approach Channel Base Elevation =785.30 m

Project Discharge Capacity for Max. W.E. =2,100 m³/s

Threshold Width =31.00 m

Ski-Jump Threshold Width =31.00 m

8. Bottom Outlet

Location =Diversion Tunnel Tapping

Safety Valve =1100 mm Diameter Butterfly Valve

Bottom outlet Entrance Grid =4 times 1m x 3m,1 times 3m x 3m

Capacity =12.39 m³/s

9. Power Plant Data

Maximum Facility Design Flow =43.60 m3/n

Maximum Head =122.80 m

Turbine Type and Count =Francis, 2

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