There are various types of dams used for storage of water, here we will learn the major types of dam with diagram.
A dam is a barrier built into a river or natural stream that creates a reservoir for water or facilitates the diversion of river water.
Water accumulates behind this barrier forming a pool of water, while the side on which the water collects is called the upstream side and the other side of the barrier is called the downstream side.
The lake of water that collects on the top of the dam is called a reservoir.
The dam is a very large structure, typically, about half a kilometer in length is constructed around the river to store water for many purposes such as irrigation, industrial supplies, hydropower, recreation, etc.
Site selection for dams:
The following points should be considered while selecting the site for the various types of dams as follows:
- A good foundation should be available.
- It should be located in a narrow valley.
- It should have enough space for the spillway.
- They have an impermeable bed and sides to minimize erosion.
- It should serve the purpose of irrigation, drinking, etc.
- Materials should be easily available on a nearby site.
- It should have less submerged area i.e. not more than 10%.
- The site should be such that the length of the dam should be minimal as it directly affects the cost.
- It should be easily accessible throughout the year.
Types of dams used in Hydro power:
Classification of dams based on the purpose:
Following the various types of dams classified based on purpose as follows:
These dams are used to store water during the rainy season and further, they can be used for various purposes like water supply, hydroelectric generation, and irrigation in the other season.
Cofferdam is a temporary structure built in a river or lake, so that the area below is completely water-free to take the construction work to a reasonably dry state.
They are temporarily built for projects such as bridge piers and abutments, dams or locks, etc.
These debris dams are being constructed to avoid the flow of sand, gravel, effluent debris along rain water in the river.
In this way the water becomes relatively clean after the debris passes over the dam.
This diversion dam is of relatively low height specially constructed to convert the river water into a closed canal or drain.
These detention dams are being constructed in case of excessive flood and these such dams control the floods.
Classification of dams based on hydraulic action:
Following are the various types of dams classified based on hydraulic action as follows:
A dam in which surplus water is allowed to flow through the crest of the spillway is called overflow dam.
7.Non Overflow Dam:
A dam in which no water flow allowed to flow through the crest is called non overflow dam.
These dams can be made from any material like concrete, earth, wood, rock filler, masonry etc.
Classification of dams based on Structural action:
Following the various types of dams classified based on the structural action as follows:
The gravity dam is a concrete structure made of masonry or concrete, while they are built on its own weight across the river.
They are heavy and massive wall-like structures with full load downstream.
As the entire load is transmitted over a small area of the foundation, dams are built where the rocks are capable and stable.
These arch dams are constructed from concrete or masonry dams which are curved or convex within the plan, while this shape helps decompose the major part of the water load.
Arc dam has been constructed across narrow deep rivers however in recent times considered to have only a few valleys.
Buttress dam are to assist that exerts pressure from one roof or wall to a different supporting structure.
The buttress dam is a gravity dam reinforced by structural support, they might be considered even when the foundation rocks are slightly weak.
These are non-rigid structures constructed on extensive valleys with various foundations.
They are trapezoidal in shape manufactured from identical kinds of material such as earth filler or rockfill or a combination of a number of materials.
The primary benefit of those dams is that it may be constructed on a weak foundation, the impervious core is positioned in the middle of the embankment body.
The material used for such a dam is rock fill and earth fill, while the earthen dam and rockfill dam fall below the types of an embankment dam.
Most frequently a large part of a dam might be either an embankment or a gravity dam responsible for producing electrical energy.
Classification of dam based on Material:
Following the various types of dams classified based on materials used for their construction as follows:
Concrete dams are gravity dams that are usually constructed in large blocks divided by joints to make construction more convenient and reduce thermal stress.
The joints are grooved after the dam cools, the transverse joints are perpendicular to the dam’s axis, while the material used for such a dam is concrete.
Concrete dams are principally classified into two types:
A) Concrete Gravity Dam:
A concrete gravity dam is an inflexible dam by which exterior pressure such as water pressure, wave strain, silt pressure, the uplift pressure is the weight of the dam itself.
All major and critical gravity dams are inbuilt concrete, they might be straight or curved within the plan.
B) Concrete Buttress Dam:
This concrete buttress dam consists of a number of piers or buttresses which are broken in a number of spans dividing the space.
Panels are constructed within the form of horizontal arches or flat slabs to retain water between the buttresses.
A dam whose main load bearing structural elements are made of wood are mainly coniferous varieties such as pine and fir.
Timber dams are built for small heads (2–4 m or, rarely 4–8 m) and usually have sluices.
Merits of timber dams:
- There is a great speed in construction.
- These dams are suitable for any types of foundation.
- It has a low initial cost.
- These dams are more suitable in places where only temporary dams are to be constructed.
Demerits of Timber Dam:
- The life of such a dam is short.
- This requires high maintenance costs.
- There is great seepage loss through the body of such a dam.
- These dams are suitable only for small elevations.
A steel dam is a type of dam made of steel instead of common earthquake, concrete or wood building material.
Merits of steel dams:
- These dams are cheaper as compared to rigid dams.
- The construction speed is high.
- These dams are not affected by frost action.
- The stresses in steel dams are more firm.
- It has great flexibility to resist uneven settlements without excessive leakage.
Demerits of steel dams:
- Steel dam requires continuous maintenance compared to concrete.
- They are lightweight therefore do not absorb shock from the vibrations of the circulating water.
- The life of a steel dam is shorter than concrete dams.
- It is difficult to anchor the foundation.
The dams which are constructed from clay material like clay sand, silt, and clay are called earthen dams, they are trapezoidal in shape and relatively small in height, and broad at the base.
These dams are built where foundations or underlying materials or rocks are vulnerable to support a masonry dam or where suitable competent rocks are at greater depths.
Merits of Earthen Dam:
- Use of locally available materials.
- Design and construction is relatively simple and easy.
- Such types of dams have high resistance to settlements and movement under the ground.
- The equipment and plant required are simple and small.
Demerits of earth dams:
- Non-availability of material at or near the dam site.
- Higher maintenance costs than a good concrete dam.
- Earthen dams are unsuitable for spillways.
Also read: River Training Works, Surge Tank & Open Channel Flow
17.Rock fill dam:
Rockfill dam is a type of embankment called earth-rock dam, while it is a water-holding barrier.
It is composed of three major parts: fill with a loose rock by dumping or roller compaction, an impermeable membrane made of masonry, concrete, asphalt concrete, steel sheet piles, wood or other materials and a transition layer.
Merits of earth and rockfill dams:
- Rockfill dams can be constructed over any available foundation.
- These dams are generally economical compared to other types.
- They can be constructed more rapidly and with unskilled labor.
- These camps can be constructed from locally available materials.
- The height of these dams can be increased without much difficulty in the future.
Demerits of earth and rockfill dams:
- These dams can be damaged by floods.
- They can fail suddenly without any prior warning.
- It needs heavy maintenance costs.
- This requires constant supervision.
- These dams cannot be used as overflow dams, so separate spillways have to be provided.
- Not suitable in places where heavy recession is more common.
Also read: Types of Curves, Types of Roads & Types of Pavement
Before constructing the dam, the site selection and preliminary investigation is a vital factor whereas designing the dam and the selection of the types of dams is also depending on the soil condition at the dam site.