about 50 years.
Hydroelectricity has been available for public use for decades; hydroelectricity supplies around 20% of demand, and several countries have it as their main (in the case of Norway, almost only) source of power...
unlimited, as long as you have water and a dam
So long as there is enough water to run the turbines.
how long has deforestation been around
As long as guns have been around.
YES! Mexico. See related link.
As long as So Random has been around.
how long has the london eye been around for
Hydroelectricity is reliable because it's about 90% efficient and converts 90% of the available energy to electricity. There is a low failure rate and a quick start and shutdown. Another reason why hydroelectricity is reliable is because it is useful as long as there is water and there will always be water.
234 years fool
how long have boxing been around?
boner