1. Location & Specifications of the River

Karkheh River originates from the middle and south-west zones of Zagros Mountain range, located on the west and north-west regions of the Country.
After crossing a distance of about 900(km.) from north to west, the River reaches Huralazim Lagoon, on the border of Iran and Iraq. Karkheh is the third largest river (considering water yield) in Iran, after Karun and Dez. The watershed of Karkheh consists of an area of 42000(km2) , located between 46º ,57´ to 49º ,10´ of east length and 31º, 48´ to 34º, 58´ of north width, which covers Hamedan, Kermanshah, Kurdestan, Ilam, Lorestan, and Khuzestan provinces.
The main headwaters constituting Karkheh River are Seymareh, Kashkan, Qarresu, Gamasyab, and Cherdavel Rivers. Probable floods and resulting damages are of characteristic of Karkheh River.

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2. Location & Specifications of the Karkheh Reservoir Dam & Hydroelectric Power Plant

In 1956, an American company named “Development and Resources Corporation” started studies on water and soil resources development of Karkheh River watershed, for the irrigation of north- west lands in Khuzestan plain.
Successively, some Iranian and international companies carried out studies concerning dam construction on this River, as bellow:
• Reconnaissance studies of irrigation development of Kurdestan and      Kermanshah provinces-from upstream watershed of Karkheh (upstream of    pay-e-pol)-were carried out in 1966 by Sir Alexander Gibs, a British    company.
• Ab-o Khak Company from Iran and an Italian company named Electro   Consult made complementary studies in 1969.
• The feasibility studies of Karkheh Reservoir Dam was performed by Iran    Development and Resources Consulting Engineers. In 1980, the    construction of a Reservoir dam (Karkheh zero) located in 54(km.)    upstream of Pay-e-pol was proposed by this company.
• After the Islamic Revolution, further studies were carried out by the Ministry   of Jehad-e Sazandegi .
• Final studies of phase one of Karkheh zero Reservoir Dam was given to   Mahab Ghods Consulting Engineers, in 1989.
  During years 1989-90, Mahab Ghods Consulting Engineers made   complementary design of Karkheh zero axis, and tried to locate axes more   suitable than Karkheh zero (which required 7.6(km.) length and a great   volume of 72.85(k.m3) embankment of the dam body). Simultaneously, they   studied other axes of A,B,C,D1, and D2, in.
  collaboration with a Chinese Company called CAITEC. Through preliminary   studies, axes A and C were selected to be compared with Karkheh zero   axis. After making geological studies and drilling exploratory boreholes,   primary designs for, both, axes A and C were made.
  Finally axis C, which is located in 21(km.) north-west of Andimeshk, and   12 (km) upstream of Naderi Bridge- because of enjoying the most suitable   geological conditions and existence of proper and sufficient borrow pits and   materials, and also having considered the fact that this axis maintains   desirable conditions for the execution of the Diversion System and   construction activities- was selected as the best choice.

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3. Objectives of the Project
• Storage and regulation of water for irrigation of 320,000(Hec.) of the lands    of downstream plains, which are placed on pay-e-pol (Avan, Arayez,    Dosaleq, and Baqeh), and Hamidi-yeh, Ghods, Dasht-e Azadegan, Dasht-e    Abbas, Fakkeh, and Eynkhosh Plains, which are located in the north- west    and the west of Khuzestan Province.
• Hydroelectric power generation amounting to 934(G.wh) per year.
• Prevention of destructive floods of the River, and resulting damages.
 

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4. Total Information of the Project

4-1. Topography
Karkheh River upstream of Pay- e- Pol hydrometric station, passes through the hills and mountainous lands, but downstream of the station flows in the vast and flat Plain of Khuzestan Province.
The selected location of Karkheh Reservoir Dam is situated in the most suitable downstream, along the River. Karkheh River has changed direction almost up to 90º on the upstream of the Dam axis, and the Dam Reservoir is mainly placed on the right bank of the axis. Due to the low slope of the River, the Dam Reservoir enjoys a considerable expansion and volume.
The slope of the left abutment at the location of the Dam axis, is steeply sharp, but the right abutment has a mild slope. There is a relatively large channel on the left bank, about 200 (m) upstream of the Dam axis, the current of which flows into the River. There is also a smaller channel, downstream of the Dam axis, on the left side of which, the Power- house Building is located. The width of the River bed, at the elevation of 115 m.a.s.l., is 120 (m). There are three terraces on the right bank, with different widths of 80-120(m) , 60(m) and 250-300(m), at the elevations of 125, 135, and 145 m.a.s.l, consecutively. The spillway course, on the right bank, leads to this channel, with an angle of about 60º. In addition to the above mentioned, there is another channel, upstream of the dam axis, on the right bank.
 

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4-2. Climatology
The watershed of Karkheh River is greatly vast, it enjoys, therefore, a variety of climates. Khuzestan plain and the southern parts of the watershed, are semiarid, with mild winters and hot & long summers. While, north parts and mountainous areas have cold winters and mild summers. The temperature across the watershed also varies from minimum -25º to maximum 50º Centigrade, throughout the year.
The average annual precipitation in Karkheh watershed is 300- 800(m.m), half of which, normally, falls during winter, and the majority of the rest falls in fall and spring.
The climate of Karkheh River watershed is of the Mediteranean Type.
The average annual precipitation at the Karkheh Reservoir Dam Site is 290.6(m.m.), and the maximum annual rain has been 588(m.m.), which belongs to 1975-76. The average annual temperature at the Dam Site is 24.6º, and the maximum & minimum temperatures have been recorded as 53.6º and 4.2ºC, consecutively.
The average annual evaporation from free water surface reaches 2079(m.m.), and the average annual relative moisture is 45.5%.
The number of freezing days at the Site are just 4.5 days during the year. The average wind velocity at Karkheh Site amounts to 2.5(m/s), and the maximum recorded velocity at the Site has been 41.2(m/s), with the direction mainly from the west. The average number of sunny hours amounts to 2762.7 hours per year.

 

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4-3. Hydrology
47 hydrometric stations have been installed along Karkheh River and its major branches.
The area of Karkheh River watershed, at Pay- e- Pol hydrometric station, is 41740(k.m2).
The area of the watershed which is located between this station and the dam axis is about 63(k.m2). Having considered the insignificant area of the watershed between the Dam Site and the above mentioned station, the calculations and statistical analysis resulting from the data released from this station, have been used in Karkheh Dam design process.
The average annual water yield of the River at Pay- e- Pol hydrometric station, is 5916(Mm3), and the average annual long term water yield at this station amounts to 188(m3/s).
The time distribution of the runoff is quite uneven throughout the year. More than 64% of the total annual runoff flows during four months of Feb.-May, and the maximum runoff occurs in April.

 

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4-4. Floods
According to the statistical records, the floods occur during the wet months of November to May. Large floods happen during March to April, among which April has the maximum floods.
Probable Maximum Floods
The probable maximum flood at Karkheh Dam Site is 23670(m3/s), which is estimated to be 8.1(B.m3), during a period of 12 days.
Probable Maximum Precipitation
The probable maximum precipitation for a 7- day- period is 280(m.m), excluding thawing.
 

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4-5. The Quality of Water
Since, the main purpose of constructing Karkheh Dam, is to supply water for irrigation, and having considered that the annual evaporation at Karkheh River watershed is 3500(m.m) - which is relatively high - and the annual precipitation amounts to 588(m.m) per year, therefore special attention has been paid to the issue of salinity, in the studies of water quality.
The Standard of FAO has been employed for the estimation of quality of water and the Schuler Diagram has been applied for the drinking water.
Tested samples with 29% TDS, and 38% Chlorine at Pay- e- Pol station, and also 55% TDS, and 57% Chlorine at Hamidi-yeh station, expresses a range of minimum to maximum risk for irrigation purposes, in the dry period of July- December. Samples which have been tested in the above mentioned stations, indicate that the amount of TDS and T.H. (total hardness) existed in the water, is not harmful for drinking. The harmful cases are mainly related to bacteria and other types of microbes. All the tested samples of the dry and wet periods with considering the above mentioned issues are acceptable for drinking.
 

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4-6. Sedimentation of the Reservoir
Karkheh River contains a great volume of sedimentation. Hec 6 Program, has been used for the calculations leading to the Karkheh Dam Reservoir sedimentation profile. In order to prepare this model, samples of real distribution of accumulated sediment in the Reservoir of the Dez Dam, were taken, calibrated, and then- based on which- a simulation was created, to estimate the sediment distribution, in the Karkheh Dam Reservoir.
The records of the past 43 years of daily water yield of Karkheh River, and 17 years of sedimentation of suspended materials, at the Pay- e- Pol station are available. According to the released data of the daily sedimentation of suspended materials, at this station, calculations were carried out for a period of 43 years. While grading of the suspended materials was prepared, in 1979.
In order to get to the normal water level of 220 m.a.s.l., the total sediment, which will be deposited, during a period of 50 years, is estimated to be 1730.5(M.ton).
 

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4-7. Water Resources Planing
The objectives of studies concerning water resources, are as bellow:
1- The potential exploitation of water resources to meet agricultural       requirements, power supply, and other beneficial uses.
2- Determination of the maximum normal water level of the Reservoir.
3- Determination of minimum water level of the Reservoir.
4- Determination of the agricultural development limit, to be covered by the      irrigation system.
5- Construction of the hydroelectric power plant.
6- Flood control.
    Total amount of agricultural lands, which could, potentially, be under     irrigation system, through Karkheh Dam, is estimated to be
A- 110,000(Hec.)of Upper Karkheh Projects [including:I) 55000(Hec.) of      the plains, located at Pay- e- pol plains, namely : Avan, Dosaleq, Arayez,      and Baqeh, II) 17,000(Hec.) of Dasht-e Abbas Plain, III) 38,000(Hec.)      of Fakkeh, Eyn- Khosh, and Musian plains].

B- 195,000(Hec.) of Lower Karkheh Projects [including: I) 60,000(Hec.) of      Dasht-e Azadegan Project, II) 40,000(Hec.) of South Karkheh Noor      Project, III) 30,000(Hec.) of South Karkheh and North Hoofel      Development Project, IV) 65,000(Hec.) of Shahid Chamran Project].
C- 35,000(Hec.) of other projects.
     The irrigation of the Pay- e- pol plains (including: Avan, Arayez, Dusaleq,       and Bagheh) will be performed through the Pay- e- pol Regulatory Dam,       located on 10(km.) downstream of Karkheh. And the irrigation of Dasht-      e Abbas, Fakkeh, and Eynkhosh will, directly, be done out of Karkheh       Dam Reservoir, through Dasht-e Abbas pressure tunnel. The irrigation of       Hamidi-yeh Ghods, Azadegan, and Karkheh Nour, will also be carried       out by the means of Hamidi-yeh Regulatory Dam.
 

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4-8. Geology
Karkheh Large Dam is located on the margin of the south- west of the folded sections of Zagros rang. The heights of this area are formed by conglomerate of Bakhtiari Formation, and fine sediment of Aghajari Formation. The main part of the Dam upstream (including the reservoir) is of Aghajari formation, constituted of alternate layers of sandstone and mudstone, upper part of which, is formed of microconglomerate. The upper part of this Formation constitutes Lahbari member, which is formed of alternate layers of sandstone and mudstone, creating a suitable condition for establishing confined aquifers.
The downstream of the reservoir up to the dam axis is constituted of Bakhtiari weak- cemented conglomerate. The Bakhtiari conglomerate is divided into two rock units of BK1 and BK2, which are separated from each other, by a mudstone layer. Unit BK1 forms the downstream of Bakhtiari Formation, which consists of sandstone lenses and mudstone layers. Unit BK2 forms the upstream of Bakhtiari Formation, which is formed of continuous conglomerate with sandstone and mudstone lenses.
The above mentioned area is located on the Arabic Platform. The Dam Site and the Reservoir are situated on the north part of Dalpari Graben. The layers slope is 7-12º on the far end of upstream of the Reservoir, and 3-4 degrees near the Dam Site. Since the layers slope is mild, and discontinuity is rarely existed, no land slide on the margin area of the Reservoir, is estimated.
Falling rock off the conglomerate slopes of the Reservoir is likely to happen, but the process of which is predicted to be slow and continuous, so it will not jeopardize the safety of the hydraulic structures.
 

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4-9. Seismology
Considering structural geo- seismic, Karkheh Dam Site is located on Zagros State, which is one of the most active areas of structural geo- seismic, in Iran. This state has experienced severe earthquakes, resulting in great casualties and financial losses.
The structural geo- seismic of the area around Karkheh Dam Site indicates the existence of potential faults. The Lahbari Fault contains the most potential seismic activities in this area, which may cause the strongest motion at Karkheh Dam Site.
In the seismic risk analysis of Karkheh Site, the analytic, probabilistic, and statistic methods have been applied. Because of special specifications of structural geo- seismic State of Zagros and the existence of rock founded faults- which do not outcrop on the surface of the ground- floating seismic model has, also been used. By using the above mentioned methods, the following parameters of different seismic levels, have been proposed:
 

In seismic studies and earthquake analysis of Karkheh Dam, statistical analysis has been performed, by exploiting suitable accelero- graphs, and a response spectrum of horizontal & vertical semi acceleration, for different seismic levels, have been recommended. For each seismic level, three accelero-graphs have been calibrated, and proposed to be used in dynamic analysis.
Seismic risk studies have been carried out by using probabilistic methods, based on which, horizontal acceleration of maximum design earthquake (MDE), and the design based earthquake (DBE), were proposed 382(cm/s2) (equal to 0.39 g), and 251(cm/s2) (equal to 0.25 g), consecutively, which have been applied in Dam and hydraulic structures.
In order to study the seismic activities of the Project area, during construction, impounding, and operation, seismograph and accelero-graph networks were designed, to be installed around Karkheh Dam Site.
Seismography network of Karkheh Dam includes , five seismograph stations. These stations have been designed symmetrically around Karkheh Site, in an area with the radius of 25(k.m.), to obtain the most geographical covering. A three- directional- station has been designed to be installed in the network center, adjacent to the Dam Site. There are other four stations of single- directional which, continuously, transmit data, telemetrically to the network control center, through a radio transmitter. The data released from these five stations, is analyzed in the network control center, so that access to various seismic parameters (including: center, depth of the center, magnitude, and the exact time of occurrence) of different earthquakes, which occurred in the past, will be rendered possible. Seismograph networks are usually installed, a few years before the construction of a dam, so that, the effect of reservoir impounding on induced earthquakes is specified.
The accelero-graph network of Karkheh Dam, which has been designed to measure the strong motion of the ground, contains six (three- directional - accelero - graphs), installed in different parts of the Dam body. One of which is installed in the left abutment, one in the right abutment, and three of them on different berms of the body (adjacent to the foundation, middle of the body, and the Dam crest), and the last one is considered as the free field, out of the Dam body. They are of digital type and capable of recording the acceleration of probable medium and large earthquakes in the region.

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4-10. Reservoir

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5.Cooperated Companies
The Cooperated Companies of Karkeh Dam and Power Plant
1-Diversion System : Sepa Sad Engineering Co.
2-Access Road L1 : Civil & Road Construction Iran Co.
3-Access Road L2: Sepa Sad Engineering Co.
4-Spillway Body : Sepa Sad Engineering Co.
5-Tunnels and Tail Race of Power Plant : Water Resurces Development      Jahad Co.
6-Power House and Power Plant Culvert Tail Race : Sab Building Co.
7-Dasht-e-Abbas Water flow Tunnel : Hara Co.
8-Switch yard 400 K/V : Nasb Niro Co.
9-Construction and Installing the equipments of pwer Plant : Farab Co ( With     Cooperation of companies : Azar Ab, Fardis, Kerman Tablo, Hepco,     Machine Sazi Arak, Iran Transfo, Elin & Harin ).
10- Construction and Installing the equipments of Bottom Outlet: Nier Pars       Co.
11- Construction and Installing the Waterway equipments of Power Plant:        Nier Pars Co.
12- Construction and Installing the equipments Dasht-e-Abbas Tunnel: Nier       Pars Co.
13-Construction and Installing the spillway gates: Sadid Co.
14-Installing the equipment of Substation 400 K/V: Nasb Niro Co.
     The reconnaissance and later on studies of Karkheh river,the studies of             phase I and II,site supervision and high supervision,carried out by Mahab       Ghods consulting engineers Co.
The generalities of design and computation,inspected by Client technical office  (Lamayer International Co)
The below companies have cooperated with Karkeh project :
    - Soil Mechanical Technical Laboratory of Ministry of Roads &       Transportation .
    - Khak Azma Co.
    - Khak & Sangh Co.
    - Pars Ghostareh Consulting Engineers Co.
    - Tasvir Saz Kavosh Co.
    - Sadr Sazeh Kosha Co.
    - Geophysics Institute of University of Tehran.
    - Kaitak The Geotechnical Consulting Co ( china ).
    - Tradod Rah Co.
    - Water Equipments Engineering Co.
    - Bardasht Co.
    - Kongereh Honar Iran Co.
 

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