Building hollow highways with structural supports in between to allow water to be transported along it. Wouldn't such an apparatus be easier and also would allow a more specific reach to our population? It can be actively powered in certain cases and passive in others and we could possibly pressurize such in a certain manner to make it easy to pass water by.

In addition, why not invest that money into better railway lines so we can have a streamlined water transport system via that? Or even water pipeline where we can control the pressure?

300 Billion is enough for us to build enough photo-voltaic farms to do the feat as well by electric rail. And these electric railways can serve a dual use.

In addition, that is enough to also fund really high quality food research that uses less water to farm or even no water if we go onto creating substances like Soylent.

Such different alternatives could also be much more manageable to do and also would be less catastrophe-prone if a small failure occurs.

You can start to have immediate results from many of these alternatives.

Its a shame, really how we are going into such impractical plans instead of testing out small, manageable ones.