Base Information

Topography

Bakhtiary Mountains in Zagros Chain Mountains are stretched from north-west to south-east and have several valleys. Height of its elevated peaks is more than 4000 masl and local altitude is between 1000 to 2000 masl. On land level alternations topographies, natural factors, geological creasing and land layers can be seen. Anticline peak is long; Valleys are generally low and V shaped and slopes are too steeped.
Zagros Mountains are still coming up. This issue causes the rapid erosion and formation of a rough region. Karun River is steeped and high speed of water is a common phenomenon. Regional water channels and some of main water channels in the region flow along with the land creasings. Undesirable features of water channels have affected river’s main system and Karun River main route passes among deep valleys.

Meteorology

The climate of Karun catchment area is hot with dry summers and moderate winters. Main part of rainfalls would occur in winter. Generally rainfalls of this region are resulted from three weather masses:

1- The Indian ocean seasonal weather mass that has great influence on Karun catchment area rainfall
2- Polar continental weather mass which generally causes the low humidity in Karun catchment area
3- Mediterranean nautical weather mass which causes periodical rainstorms in this area

Average Annual rainfall in Karun catchment area in Shalu Bridge is 620 mm; height of the snow-prone area is 2000 masl and the measurement of catchment snow-prone area is 16000 km2.

Hydrology

Discharge: According to 60-year statistics of water flow in Ahwaz, Shalu Bridge, Godarlandar and Gotvand, the annual average of discharge at the site of Karun 3 Project and Ahwaz is estimated to be 302 to 727 m3/s.
Return period of spillway design flood: Karun 3 dam spillways are designed for flood passing.
Return period of diversion system design flood: diversion system is constructed to bear floods with 10-year return period.
Probable maximum flood (PMF): probable maximum flood includes the maximum flood which may probably flow in the catchment area. In basic studies of Karun 3 Project, probable maximum flood is estimated from 22400 to 27000 m3, But in complementary studies with use of the latest statistics of Karun River discharge, this sum has reduced to 15000 m3 and due to the point that Karun 4 dam is located in upstream of Karun 3, the maximum entry to Karun 3 dam reservoir is about 14147 and the maximum outlet from the reservoir would be 13200 m3.

Flood

According to the latest studies in the field of PMP and PMF, Karun river system and the construction site of Gotvand Dam, the maximum discharge is estimated to be 15500 m3/s, flood volume is estimated about 4 billion m3 and according to these results, the PMF peak discharge of 15500 m3/s has been used as the basis of calculations related to Karun 3 flood evacuation system.

Water quality

Chemical quality of Karun River water sample at Shalu Bridge is as follows:

Composition	SAR	Na++ Meg/I	MG++ Meg/I	Ca++ Meg/I	SO4 Meg/I	CL Meg/I	Hco3 Meg/I	PH	Ec × 106 Min.hos 25°C	T.D.S Meg/I	O M3/s
Mean	1.4	2	1.3	2.4	0.9	2.2	2.8	7.9	576	353	289.2
Standard Dev.	0.6	1.1	0.5	0.5	0.6	1.2	0.4	0.2	187	119	100.8
Coeff. of var.	42.8	55	38.5	20.8	66.6	54.5	14.3	2.5	32	33	34.9
Min.	0.3	0.4	0.3	1	0.1	0.45	1	7	179	116	146.7
Max.	3.2	5.6	3.1	4.5	4.9	5.9	5	8.8	1220	780	524.5

Sedimentation

Sedimentation in Karun 3 dam reservoir is measured according to monthly flow statistics in Shalu Bridge, based on the daily measurement of suspended elements in water and samplings from river bed. With comparative studies of the mentioned issues, annual average of total sedimentation in dam reservoir is estimated to be 800-3000 tones/year. With this amount of sedimentation it takes minimum 200 years to fill the dead volume of reservoir. Certainly with construction of Karun 4 Reservoir Dam, the sum of sedimentation in this reservoir would be negligible.

Planning the water resources

Normal level is 845 m and minimum operation level for powerhouse would be 800 m.

Geology

Civil project of Karun 3 is located in rough areas of Zagros Chain Mountains. Sedimentary and thick stones of this region from north-east to south-west have caused formation of fold-like anticline and syncline. Geological combinations of dam site have formed the 20-30 km anticline of “Kifmalek” that is extended with one km width from north-west to south-east and consists of limestone with Chile and maronite core. These folds have passed through construction site and are extended toward south-east and Shalu Bridge. Generally geological structure of Project site consists of limestone, lime, maronite, chile stones and Asemary elements.

Seismicity

Studies in Khuzestan Province shows that all earthquakes of this region had been at the level of 6.8 on Richter scale. Also most of the occurred earthquakes in this province are not resulted from superficial cracks but from lower layers creasing; therefore considering all consequences, the velocity of 0.2-0.3 g is considered for designing.

Dam reservoir

Item	Quantity	Item	Quantity
Reservoir total volume	3 billion m3	Water minimum level	800
Reservoir beneficial volume	1720 million m3	Water maximum level	851.5
Water normal level	845	Sedimentation level

Geological combination of dam construction site is in 20 to 30 km distance of “Kifmalek” anticline which is extended from north-west to south-east with 1 km width and consists of limestone in Asemary elements with core of Chile and maronite stones. These creasings have passed from the construction site and are extended toward south-east and Shalu Bridge. Generally geology conditions of the project site include limestone, lime and maronite stones and Chile and Asemary elements.