Hydroelectricity uses the energy from moving water to create electricity. Using natural sources of water like rivers, dams and rainfall, hydro power seems to be a feasible option for renewable energy. I found a page that discusses the gravitational power of rainfall in Britain per year. Taking the total amount of rainfall (584 mm per year), times the density of water (1000 kg/m^3), the altitude above sea level (100 m), and the strength of gravity (10 m/s^2), we would get about 0.02 W/m^2 of power per unit at best. This number represents the amount of power per unit land area that the rainfall landed.

(584 mm / year * 1000 kg/m^3 * 10 m/s^2 * 100 m = 0.02 W/m^2)

When we multiply the amount of power per land unit by the area per person, in this region of Britain (0.02 W/m^2 * 2700m^2 / 60 million people) we would be left with about 1 kWh per day per person, at max rainfall. Right away we can see that this is nowhere near the amount of energy needed to sustain even one person for a day.

A major roadblock for hydroelectric power is that it never uses water’s full potential energy due to high rates of evaporation as well as scarcity of hydro power/electric plants. It is clear that hydroelectric power itself cannot power our everyday lives, though perhaps through further experimentation and research we may see an increase in hydroelectricity usage worldwide.