A diversion dam is a

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use ...

that diverts all or a portion of the flow of a

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of w ...

from its natural course. Diversion dams do not generally impound water in a

reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including contro ...

; instead, the water is diverted into an artificial water course or

canal Canals or artificial waterways are waterways or engineered channels built for drainage management (e.g. flood control and irrigation) or for conveyancing water transport vehicles (e.g. water taxi). They carry free, calm surface flo ...

, which may be used for

irrigation Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been devel ...

or return to the river after passing through hydroelectric generators, flow into a different river or be itself dammed forming an onground or

groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...

reservoir or a storm drain. An early diversion dam is the Ancient Egyptian Sadd el-Kafara Dam at Wadi Al-Garawi, which was located about twenty five kilometres south of

Cairo Cairo ( ; ar, القاهرة, al-Qāhirah, ) is the Capital city, capital of Egypt and its largest city, home to 10 million people. It is also part of the List of urban agglomerations in Africa, largest urban agglomeration in Africa, List of ...

. Built around 2600 BC for flood control, the structure was 102 metres long at its base and 87 metres wide. It was destroyed by a flood while it was still under construction.Günther Garbrecht: "Wasserspeicher (Talsperren) in der Antike", ''Antike Welt'', 2nd special edition: ''Antiker Wasserbau'' (1986), pp.51-64 (52f.)

Classification

Diversion dams are one of three classifications of dams which include: storage dams, detention dams, and diversion dams. Storage dams are used to store water for extended lengths of time. The stored water then can be used for

livestock Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to animal ...

, municipal water supply, recreation, and

hydroelectric power Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined an ...

generation. Detention dams are built to catch surface runoff to prevent floods and trap sediment by regulating the flow rate of the runoff into channels downstream. Diversion dams are used to raise the water level in order to redirect the water to the designated location. The diverted water can be used for supplying irrigation systems or

reservoirs A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including control ...

Purpose

Diversion dams are installed to raise the water level of a body of water to allow the water to be redirected. The redirected water can be used to supply irrigation systems, reservoirs, or hydroelectric power generation facilities. The water diverted by the diversion dam to the reservoirs can be used for industrial applications or for municipal water supply.

Construction

The design a diversion dam will fall into one of four basic types: embankment style dams, buttress style dams, arch style dams, and gravity style dams.

Embankment style diversion dam

Embankment style diversion dams are constructed to counteract the force of the water pushing on the dam by building a dam with enough weight to withstand the force. Embankment dams are commonly made from materials in the surrounding area where the dam is being built. The materials generally include: sand, gravel, and rocks. The combination of these building materials with either clay or an impervious membrane gives the embankment dam its integrity. As a result, the combination of its simple construction and locally available building materials the cost of building an embankment dam is lower than the other types of dams.

Buttress style diversion dam

Buttress style diversion dams are designed using angle supports on the downstream side of the dam. The supports are fixed to the wall of the dam in order to help counteract the force of the water on the dam. Buttress style dams are built across wide valleys that do not have a solid bedrock foundation. Bedrock is solid rock that makes up the upper part of the earth’s crust. Bedrock can be made from sedimentary, igneous, and metaphoric rock origins. Buttress dams require extensive steel framework and labor. As a result, buttress style dams are expensive to construct and are seldom built today.

Arch style diversion dam

Arch style diversion dams are designed using an arch shape with the top of the arch facing upstream. The arch shape provides extra strength to counteract the force of the water. Arch style dams are generally constructed in narrow canyons. Arch style dams are commonly made from concrete. To ensure the dam’s integrity, a solid contact between the bedrock foundation and the dam’s concrete base is required. The dome style dam is a type of arch dam. The dome style dam curves in both the horizontal plane and vertical plane. The arch style dam only curves in the horizontal.

Gravity style diversion dam

Gravity style diversion dams are built to counteract the force of the water pushing on the dam by building a dam with enough weight to withstand the force. Gravity dams are commonly constructed using masonry or cement. The foundations of the gravity dams are generally constructed on top of a solid bedrock foundation. However, gravity dams can be built over unconsolidated ground as long as proper measures are put in place to stop the flow of water under the dam. If water were to get under the dam, the dam could fail.

References

{{reflist Dams by type