Let's look at the numbers
Let's look at the numbers. The Lake Powell catchment basin covers an area 280,000 square kilometres in size, or 280,000 million square meters. Ten centimetres of rainfall on this area would add up to 28,000 million cubic meters of water. This volume would be nearly equal to the entire volume of Lake Powell. Half of that, 5 centimetres, or roughly 2 inches, of extra rain, would restore Lake Powell to its full state, not considering evaporation. With an equivalent of 160 feet of water being located as vapor in the atmosphere, it shouldn't be hard to squeeze a few inches out of the huge volume of water that exists in the atmosphere, by technological means.
