I didn't read the article, and I know it's more about math than an actual plan, but as a tangent I wanted to say that there's a cost to preventing rain from reaching the earth - even if we eventually returned the water there and didn't pollute or reduce the water. I think by altering this age-old cycle, we would lose some of the impact on the soil, and plants, the way it rolls downwards into increasing rivers.

We've caused a lot of damage with pavement and structures. The benefit of the power generated would have to be weighed against this cost.