> What do you think happens when hundreds of millions of gallons of water is separated from the salt?

Where do you think the water that forms the runoff comes from? Rain. Rain from where? Clouds. Clouds from where? The ocean is a significant source of rainwater.

Where do you think the water goes when the river takes it to the ocean? Well, goes back into the ocean.

How many gallons of water does the ocean have? Trillions? A few million will not measurably increase the salt content of the ocean. And, because it's a cycle, it already happens naturally.

So keep the cycle going. Guide the cycle to be more useful to us.