Entire bands of the earths surface receive the same amount of sunlight per square metre for similar amounts of average time per day.

Only some of these regions are left with only dry desert sand.

There might be more to this than simple hours per day of sunlight, topography for one factor.

Come to think of it, energy stored in the dam is the result from the Sun evaporating water from other areas, and then convection currents, aka wind, blowing the clouds over the continent and condensing.

So, it's all energy from a nuclear explosion.