Microhydro generally refers to hydroelectric power systems up to a rating of around 300kW. 

These may be small pelton wheel systems or run-of-river turbine systems.  Energy is extracted from both the potential energy (related to the height or head) of water and the kinetic energy (related to the flow rate of the water). 

Microhydro may be suitable if you have a river running through your property, and in particular if you have existing weir infrastructure, such as at a mill.  The civil engineering costs of microhydro schemes may be significant and the economics are generally much more attractive if the microhydro turbine can be integrated into an existing weir. If you think that there might be the potential for microhydro on your site, then you should engage with a specialist to assess further.