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Groundwater Pumping. Session 4 Water Distribution. Protection of Water Source . A water point obviously attracts a great deal of human contact. This is a potential source of contamination and should be protected against:

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groundwater pumping

Groundwater Pumping

Session 4

Water Distribution

slide2

Protection of Water Source

  • A water point obviously attracts a great deal of human contact. This is a potential source of contamination and should be protected against:
  • The well should be in an elevated place, so that during the rainy season the water will run away from it, rather than into it
  • It should be at least 30 meters away from a latrine
  • It should be at least 30 meters away from a cattle kraal

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slide3

Protection of Water Source

  • The construction of a platform (or slab) at the wellhead is an important contribution to the general hygiene in a community.
  • The slab should be made from good quality concrete of
  • All surfaces must slope towards the drainage channel
  • The slab should be well reinforced with steel wire, to prevent cracking
  • Where possible, the drain can lead to a vegetable garden.

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slide4

Curing of Concrete work (Platform and Drainage channel)

  • A curing time of at least one week is needed.
  • During the curing period, the platform has to be watered regularly, so that the concrete never gets dry.
  • Direct sunlight must be avoided by covering the slab with wet hessian cloths, foliage, wet soil or sand.
  • Cover the well platform and drainage channel with thorn bush, for protection from being destroyed by people or passing animals.

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Fencing the Water Source

  • In some cases, it may be necessary to have a gateway to keep out smaller animals such as pigs and goats.
  • The fencing should be made of suitable local materials like wood or stones.
  • Problems of replacement and repair can be avoided altogether, by using a living hedge as a fence.
  • Whatever type of fencing is used, it is important that access by the well users is guaranteed.

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Soak pit

Construct a soak pit if no natural drain is available.

Excavate a hole and fill it with stones, broken bricks, gravel and sand.

To prevent sand from being washed away, fix a mud pot (with holes in the bottom) at the end of the drainage channel, so that the spill water can drain slowly

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Disinfecting the Well

  • As soon as the curing time is over and the platform is ready for installation of a handpump, the well needs to be disinfected with chlorine.
  • It is recommended to use between 150 to 200 grams of bleaching powder per m³ stored in the well casing.
  • Check amount of water collected in the well casing and calculate how many grams of bleaching powder are required.
  • Mix the required amount of bleaching powder thoroughly in 15 litres of water (in a bucket) and pour it into the well.

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water distribution

Water distribution

When water is pumped to a higher elevation the pumping effort is the total head plus the friction head loss in the pipeline. The friction head loss for a given flow rate can be calculated for any chosen pipe diameter. Smaller pipes create higher losses than bigger pipes because the water speed is greater. The pump has to be chosen that is able to produce the required flow and pressure.

Water demands varies across the year Peak hour demand = average hourly demand x hourly peak factor (k2).

water reservoirs

Water Reservoirs

A reservoir balances supply rate from the water source with the fluctuating water demand in the distribution area. The storage volume should be large enough to accommodate the cumulative difference between water supply and demand.

A storage volume of 20 to 40% of the peak day water demand should generally be adequate

The reservoir should be situated as close as possible to the distribution area. It should be situated at a higher elevation than the distribution area.

  • Reservoirs are of reinforced concrete; masonry; steel; plastic
distribution system

Distribution System

Two types of distribution systems are used; the branched or the looped systems.

For small-capacity a branched system can be used. It is laid out like a tree, in which the “trunk” is the Main Pipeline and the “branches” are the Service Pipes.

Looped system are based on a grid of interconnected delivery pipes. The Main Pipeline is feeding Branch Pipelines, which are connected in a loop, so that all Service Pipes are fed from two sides. This system is more complicated to design and more costly, but provides stable water pressure, and small sections of the system can be isolated for repairs.

public stand post

Public Stand post

Public stand posts are the best option for water distribution at minimum cost to a large number of people who cannot afford the much higher costs of house or yard connections.

Each stand post should be situated at a point within the community area to limit the walking distance to 200 m

The discharge is about 14 to 18 litres/minute at each outlet. A single tap stand should preferably be used by not more than 40 to 70 people (approx. 10 families); a multiple tap stand may provide a reasonable service for up to 250 to 300 persons