Maintaining Intake Structures

Cleaning the intake structure should be a monthly part of the maintenance program due to the level of debris that can collect in the intake.

Turn off the valve leaving the intake structure to avoid any sediment entering the system while the intake is being cleaned. The intake filter should be removed and cleaned with a plastic brush to remove any silt. The cleanout on the intake should be opened and drained. Remove any excess debris.

Building Intake Structures

Time Required~5 days depending on design

Materials List

Qty	Item	Notes
	sack of cement	Dependent on final design
	20’ length of 3/8” rebar	Dependent on final design
	16ga wire	For tying rebar. Dependent on design. Sold by the pound
	5-gallon buckets of sand	For concrete mix 1:2:4. Dependent on design.
	5-gallon buckets of gravel	For concrete mix 1:2:4. Dependent on design
2	shovels	For mixing concrete
1	hacksaw	For cutting rebar, PVC
1	hammer	For staking form
2	metal trowel	For concrete work
2	5-gallon bucket	For measuring, storing water for concrete mix
1	3' of 2” or 3” tube	Dependent on final design. Will be cast into intake structure
	wood boards	For formwork.  Dependent on final design

Construction
Construction will vary source to source.  The photos shown below are for a spring with an impermeable clay layer.  Consult A Handbook of Gravity Flow Water Systems for design ideas and construction techniques for other types of catchment.

	This photo series shows the construction of a spring. The spring was excavated down to the impermeable clay layer. All the sand and debris is removed in the area where a catchment wall is poured. Create a dam to divert water away from the spring during construction. If clay is accessible, a thick wall of clay will divert the water.
	After clearing debris when the form will be placed, measure and cut formwork.
	This photo shows the complete form with the 2” pipe running through the form. The tube will be cast into the concrete. The concrete is also reinforced with 3/8” rebar.
	Screens can be placed at the intake to reduce amount of debris entering the intake box.
	A PVC tube with a series of slits cut into the tube makes a cheap filter. This will reduce particulate entering the system to the size of a hacksaw slit.

Here is a photo from a stream catchment intake structure.  The higher wall is to reduce sediment entering the system.

Designing Intake Structures

Why is it Needed
The intake structure is it all begins. This is the water source for the community. You can have multiple sources feeding into the same aqueduct system. Typically, the intake structure is built into a small spring or creek, but could also represent a dam for a larger stream or river. Since this is the water the community will be drinking, make sure that the watershed (200+ meters in all directions from the intake point) is free of contamination (livestock, other villages, etc.).

Design
The design varies from source to source. For a spring, look at either a dam or intake box. For a stream, a modified dam structure can be used. Design ideas are located in the gravity-flow handbook. Consult with an engineer or someone who has experience designing and building intake structures prior to construction.

Make sure that the source is free of contamination.

Conduct a census of the community.  Figure out a good growth rate multiplier to find the population at the end of the life of the aqueduct.  Usually a system is designed for thirty years.  What is the expected population thirty years from now?  Use WHO’s 30 gallons/day/person, which is generous, to calculate the total water usage of the future community. 

Measure the flow of the intake structure during the dry season to find the minimum daily amount of water coming from that source.  If the flow does not produce enough to meet the future demand of the community, another source will be needed in addition or in place of the original source.