Site selection of an Intake Works | Characteristics of intake – Irrigation

Introduction of Intake

After the source of water is decided, the arrangements have to make for drawing the water from the source and distribute it after necessary purification.

Intakes are masonry or concrete structure which essentially consists of openings, grating or strainer through which raw water from surface sources enters and is carried to the slump well by means of conduits.

The main function of intake works is to collect the water from the source and discharge this water so collected, by means of pumps or directly to the treatment plant.

An intake structure is constructed at the entrance of conduit and thereby helping in protecting the conduit from being damaged or clogged. Intake consists of

  • A conduit with protective works
  • Screen at open ends
  • Gates and values to regulate flow

Site selection of an intake

While selecting the site for the intake, the following points should be kept in mind. They are as follows

1. The site should be so selected that there is availability of  sufficient quality and good quality of water even in worst condition i.e. in all seasons.

2. Heavy water currents shouldn’t strike the intake directly. 

3. There should be sufficient a cope for future.

4. The site should be such that at the site, the velocity of flow in the source is gentle.

5. The site should be easily accessible as for as possible and should be free from the effect of flood.

6. The site should be near to the treatment plant so that there is minimum cost for conveying the water. 

7. Site should be so located that good foundation conditions are available and the possibility of scouring is least. 

8. The river or stream intake should be located on the straight reach of the river or stream (gentle Slope) (e. no meandering).
9. Should built in or never gullies or at unstable ground or on  the top of swampy ground. 

10. The site should never be located in the vicinity of the point of sewage disposal. Should locate on the upstream side of town. 

11. Shouldn’t be located in navigation channels due to pollution.

Characteristics of intake

There are various types of intakes for drawing the water from the source, but in our syllabus there are only the following types of intakes that we have to know their characteristic and construction.
1. Spring Intake

2. Reservoir Intake

3. River Intake

1.Reservoir Intake

A reservoir intake consists of a circular well, with its floor sufficiently below the MWL. of the reservoir. The intake conduit at different levels to let the clear water into the well as level of water in the reservoir fluctuates.

The intake conduits are provided with values which may be either closed or open, can be controlled by the control room, Exposed intakes are most suitable for collection of large quantities of water as there are less chances of clogging of intakes. Their operation and inspection is easier than submerged.

2.River intake

220 River intake is always providing on the n/s side of the point of sewage disposal of the city or town so that water entering into it is free from contamination.

It consists of a circular masonry. R.C. C. or concrete block well having 3-6 in diameter. It is located in the river in such place that even during the minimum water level water remains available in sufficient quantity, Penstock pipes with screen covers are provided at different levels a stage is penstock to install pump to pump out water for treatment.

Sometimes a weir is also constructed across the flow of river in order to raise the water level if the level of water falls below the lower penstock pipe.

3.Spring intake:

A spring occurs when an underground aquifer penetrate the ground surface by means of gravity or hydro-static pressure. The quality of water from spring is usually better than underground and surface sources.

Fewer structures are required for spring intakes making their initial as well as operational costs lesser than the other types of production components. However, continuity of such a spring should be confirmed before deciding other design parameters. 

Features of spring intakes:

1. Screened in flow piping: It is derivable to provide the screen (wire mesh) to eliminate suspended particles which protects the pipe being wear & tear.

2. Sedimentation chamber: -To sediment the suspended particles into the small chamber sedimentation chamber is provided into the intake. 

3. Service pipe: – In proper spring intake there should contact inlet pipe, outlet pipe, overflow pipe and wash outs. All of these pipes are regulated by values. 

4. Air vents It serves to allow air to escape from the pipeline without bulling out through the intake and interfering with the flow. They are usually located d/s from thegate value of outlet pipe 

5. Roofing Should provide with R. C. C. or G. C. I. roofing.

6. Protective measures: To protect the collected water in the intake from being contamination, it is necessary to adopt some measures as for as possible for this, fencing, reforestation, planting of grass, constructing drainage ditch around the source are necessary.

I hope this article on “Characteristics of intake” remains helpful for you.

Happy Learning – Civil Concept

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