How to i send water and power to the Arcology?

it just happens as long as you have enough extra in the area

yep, you need to have an extra like 200 MW power and 160k/gal/hour water.

So you're saying as long as the region meets the power and water needs of the Arcology, it will automatically allocate those resources?

I am here because I had the same question. You don't have to do anything except make sure the power plants and water pumps have the box checked to sell to neighbors.

The main problem is that it takes a good amount of time to register at the arcology. Put it on fast speed and wait a few minutes.