Micro hydro is a type of small-scale hydroelectric power system that takes advantage of naturally-flowing streams to produce up to around 50W-300kW of electricity.  The process itself is relatively simple. Water is diverted from a river into a penstock, which then transports the water to a turbine or waterwheel. After these mechanisms generate electricity, the water is delivered back into the river. 
Figure: A simple micro hydro system layout. 
There are many advantages associated with using micro hydro as an electricity source. The process produces no direct emissions, and there are little to no harmful environmental effects; the water is simply diverted and redirected back into the stream in a ‘run-of-river’ process.  Micro hydro power is also renewable and sustainable. No fuel is required, and the maintenance and upkeep costs are low.  Another advantage is its efficiency; micro hydro can operate using flows as low as five gallons per minute and an elevation difference as low as two feet. 
Although there seem to be many benefits, there are still some disadvantages to consider. The biggest disadvantage is that the technology is only limited to areas with water flow and an elevation difference.  This can cause issues with distribution if the power source is not located nearby. Another disadvantage is that although the environmental impact is small, there are still some factors that cannot be ignored. The systems must be built carefully so as not to disturb the local ecosystem of the river, and noise pollution can also upset nearby residents.  Still another disadvantage is that stream-size fluctuations during the summer months can cause drops in power output. 
Where applicable, micro hydro has many benefits with little downsides. It is an ideal power source for developing countries with remote areas away from the grid. Mountainous regions in Peru, Nepal, Sri Lanka, and the Philippines have already developed active micro hydro programs.  In a world where alternatives to carbon-intensive energy processes are on the rise, the potentials of micro hydro look more and more promising.