Intake type for hilly area of Nepal

Type of intake and the reason

In the rural hilly area of Nepal a spring intake (spring box) is generally used, or, where there is no spring, a simple stream/side intake. The spring intake is recommended because:

• springs usually come from deep underground, so their water is clean and bacteriologically safe and needs little or no treatment;
• the spring is usually at a high level, so water flows to the village by gravity, with no pumps;
• construction is simple, uses local stone, sand and labour, and its cost and maintenance are low (suitable for community management);
• the yield is dependable through the year, and the intake keeps the water protected.

Description of a spring intake

A spring intake (spring box or spring capture) is a small chamber built at the spring eye to collect all the flow from the spring, protect it from pollution, and send it to the pipeline by gravity.

Parts of a spring intake

• Collection chamber (spring box) of stone masonry or concrete, with a pre-cast cover and manhole.
• Gravel filter / perforated pipes at the back wall to collect water uniformly from the spring eye.
• Outlet pipe with a gate valve (and a strainer) to the pipeline.
• Overflow pipe to take excess water; washout (drain) pipe with a valve for cleaning; vent pipe with a screen.
• Protection works: clay/impervious cap over the spring, a diversion drain (catch drain) uphill to divert surface water, a fence, and a vegetation or plantation cover.

Plan

   Diversion drain (uphill)
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  |    fence                    |
  |   +---------------------+   |
  |   | gravel filter ::::  |   |
  |   |  (spring eye)       |-->| overflow
  |   | collection chamber  |   |
  |   |  [manhole]   outlet |==>| pipe to tank
  |   +----------+----------+   |
  |         washout pipe        |
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Section / elevation

        Vent      Manhole cover
         |   ____|_____
  ground |  |          |  clay cap (0.5 m)
  =======+--+          +=============
         |  |  air     |
 Spring->|::| water lvl|--> overflow
 gravel  |::|~~~~~~~~~~|
 filter  |::|          |==> outlet+valve
         |__|__________|
              washout pipe