In practice, sites that are suitable for small-scale hydro schemes vary greatly.  They include mountainous locations where there are fast-flowing mountain streams and lowland areas with wide rivers. In some cases development would involve the refurbishment of a historic water power site.  In others it would require an entirely new construction. This section illustrates the four most common layouts for a mini-hydro scheme. 

A variation on the canal-and-penstock layout for medium and high-head schemes (Section 2.3) is to use only a penstock, and omit the use of a canal.  This would be applicable where the terrain would make canal construction difficult, or in an environmentally-sensitive location where the scheme needs to be hidden and a buried penstock is the only acceptable solution. 

For low head schemes, there are two typical layouts.  Where the project is a redevelopment of an old scheme, there will often be a canal still in existence drawing water to an old powerhouse or watermill.  It may make sense to re-use this canal, although in some cases this may have been sized for a lower flow than would be cost-effective for a new scheme.  In this case, a barrage development may be possible on the same site. 

With a barrage development, the turbine(s) are constructed as part of the weir or immediately adjacent to it, so that almost no approach canal or pipe-work is required.

A final option for the location of new mini-hydro turbines is on the exit flow from water-treatment plants or sewage works.  This application is growing in popularity with UK water companies.

Canal and Penstock:	Penstock:
Mill Leat:	Barrage: