HUMAN-POWERED WATER-LIFTERS
The choice of water lifters available is large and varied, making the selection of an appropriate device difficult. In America and Europe during the 19th century the design of mass-produced hand pumps evolved by trial and error rather than through scientific research and development. There are now a large number of adequate, rather than optimum, designs conceived by local manufacturers, and it is hard to know which pump is the best for each application. This brief presents an overview of the types of human-powered water-lifters available, the applications appropriate to them and their comparative advantages.
Water-lifters can be broken down into the following categories:
• Groundwater (open-well, shallow-well and deep-well pumps)
• Surface Water (shadouf, dhone, chain and washer and Archimedean screw)
Groundwater
When rain falls, it seeps into the ground and collects in an underground reservoir known as groundwater. The upper limit of this reservoir, the "water-table", may vary in depth, from just below the surface (like in a spring or oasis) to well over 100 metres. The only way to get at this water is to dig down.
Open-well
The simplest and cheapest method of lifting groundwater remains the rope and bucket in a wide, shallow well. These can operate to a depth of 100 metres, although they rarely exceed 45 metres, and can last for a very long time without maintenance. It is worth considering this design before proceeding with more complicated methods.
It may not be possible to construct an open-well if the water table is too deep or if the foundations are very hard (such as rock) or very soft (such as fine running sands). These restrictions also depend on the method of construction.
If the groundwater can only be accessed through a bore, then a groundwater pump must be used. Groundwater pumps can be split into two categories, shallow-well and deep-well.