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close this book A training manual in conducting a workshop in the design, construction, operation, maintenance and repair of hydrams
close this folder Session 18: Hydram system site selection (2-4 hours)
View the document Handout 18A: Hydram system site selection
View the document Handout 18B: Diagram system for site selection

Handout 18A: Hydram system site selection

Hydram system site selection

There are three main components to a hydram system that require site selection: 1) the take off from the stream, 2) the hydram itself, and 3) the storage facility.

The Take Off System: The water for a hydram is never taken directly from the stream. Sand and debris would enter the drive pipe and destroy the hydram. Therefore a settling area for the water must be included in the system. The characteristics to look for are a relatively flat area near the stream but out of the way of the rainy season's floods.

The Hydram: The first important factor here is to choose a site that will give sufficient head to run the pump. Basically, the higher the head, the greater the amount of water that can be pumped. As a general rule of thumb, the site should give at least 3m (10 ft) of head. Systems can be run with a smaller head, but the flow rate needs to be that much larger. If there are a number of places along the stream where sufficient head can be generated, then the spot where the distance from the water source to the hydram is the shortest will be the best. The drive pipe (from source to hydram) must be made of metal to withstand the pressure and pounding of the system. Metal pipe is usually more expensive than plastic pipe (which can be used for the delivery line). So even though the delivery line may be longer than at other potential sites, the costs for the total system may be less.

The hydram can be situated in any safe/stable area that will give the proper head and distance mix. An added consideration is convenient access to this site to do repairs and maintenance. It is advisable to build a box to enclose the hydram - to protect it from animals and vandals and to minimize erosion to the hydram's foundation. This usually means that cement needs to be carried and mixed nearby, and this may influence your selection of the site. One last concern is that the waste water from the hydram will need to find its way back to the stream. If in doing so, it transverses cultivated land and that could cause a problem, then this factor must be considered in the selection of the site.

The Storage Facility: The third major component of the system is the site to which the pump will deliver. The delivery point/storage facility should be at some convenient location that allows the water to gravity flow to where it is needed. The major determinants of the site for the storage facility are the delivery head the system can accommodate and the length of the delivery line. The delivery head must be within the range of the systems' capabilities, and the length of the delivery pipe must be within reasonable cost constraints. The distance from the storage facility to the point of use (see handout 18B, d3), should be kept to a minimum. But this distance, d3, is secondary to the needs of the hydram system.

The factors that influence the siting of these components are:

1) flood considerations,

2) available head,

3) distances/pipe length between components,

4) cost factors,

5) convenience of location,

6) social factors.

1) Flood Considerations: The seasonal variations of the stream must be taken into consideration - this is particularly true of flood conditions. Each component of the system must be placed outside the potential flood area.

2) The available head and that necessary for the system is the key factor in siting the system. There are three heads involved here: the drive head, the delivery head, and the supply head. The most important of these is the drive head, H. This ~ basically determines what the capabilities of the system are. The delivery head, h, is next in importance; it is however limited by the constraints placed on the system by the size of the drive head. The least important of the heads is the supply line head, h. Basically this head just needs to have a negative slope - that is, sufficient drop to let the water run down hill.

3) Distances or pipe lengths are the next major consideration in selecting a site for the system, Pipes are usually the most costly items of the system. There are three distances that must be taken into account: the length of the drive line, the length of the delivery line, and the length of the supply line. The most crucial of these is the drive line because this piping is usually the most expensive per foot and because the size of the pipe is influenced by the distance it must transverse. As a rule - the shorter the drive pipe line the better (considering that it delivers the necessary head). The length of the delivery line is next in order of importance. It is constrained by the capacity of the system and by costs. However plastic pipe can be used here. The supply line is constrained by cost factors only. It can be run as far as the terrain and the budget allows.

4) The cost of a system may be the final determinant as to whether or not it is implemented. Pipes and plumbing components are the main expense, with cement and possibly labor second. The hydram itself is a lowly third. If care is taken in the siting and the design of the system, the costs can be kept to their minimum.

5) Convenience of location of the hydram and the storage facility is another siting factor. Basically the components of the system should be sited in a location that allows for ease of construction, repairs and maintenance.

6) Lastly, the "best" site for the system may not be the one that the villagers want - it may be on the wrong persons land, or whatever. Remember that they are responsible for maintaining the system, and their concerns must be honored.

Presented below is a handy table to keep the components of the system and the siting factors in mind as the survey work is being done.