Water is bulky and heavy and we use it in vast amounts. You get some idea of how expensive it is to move water by looking at the price of bottled water on supermarket shelves. Most of the price of the water is in the transport.
The cheapest way to move water is to let nature do it. Even if a river is dammed and water stored behind it, it is best to let the water flow in a controlled way back into the river and pump the water out near to where it is wanted.
The alternative is to bring it by canal called an aqueduct.
