40 CIVIL WORKS GUIDELINES FOR MICRO-HYDROPOWER IN NEPAL
Photo 4.2 A raised masonary channel supplying a mill (Mustang).
masonry in mud mortar canals). A stone masonry in cement
mortar canal should be used at locations where the soil type is
porous (leading to losses of unacceptable amounts of flow)
and/or seepage is likely to trigger landslides. For micro-hydro
sites located 3-4 days walk from the roadhead, the need for a
long cement mortar canal can make a micro-hydro scheme
uneconomic due to the high cost of cement.
An example of a stone masonry in cement mortar headrace
canal can be seen below in Photograph 4.3.
Photo 4.3 Stone masanory in cement
mortar headrace canal of the 50kw
Galkot MHP, Galkot, Baglung, Nepal.
Photo 4.4 Reinforced concrete cover slabs provide protection from
falling debris (Bolivia).
4.2.4 CONCRETE CANALS
Most micro-hydro schemes do not have headrace canals
constructed of concrete since they are very expensive. There is
virtually no seepage through such canals. Sometimes,re-
inforced concrete canals are used for short crossings.
Generally, HDPE headrace pipes are more economic than
concrete canals.
4.2.5 OTHER TYPES OF CANAL
In certain areas there may also be other types of canal than
those mentioned above. For example, an irrigation canal in
Ecuador constructed of used oil drums cut into two semi-
circular halves can be seen in Photograph 4.5. Such a canal
may be useful for short and difficult sections or for aqueducts
where used drums are easily available and economical.
Another example is the use of timber canal as can be seen in
Photograph 4.6. This requires the use of hardwood and skilled
labour. Similar to oil drums, timber canals can be possible for
short crossings and aqueducts or where timber is abundant
and inexpensive.
Examples of other types of canal are presented in Boxes 4.1 to 4.5.