I really need help with Paradise Falls. How do I get the land irrigated…

"Irrigation" doesn't actually have anything to do with water. All it does is take the textured terrain that you can't walk or build on, and changes it to regular land (that you can walk or build on). Just to clarify again, irrigation doesn't have anything to do with water in the game, just terrain change. Its good for clearing building space, or in obvious cases, for clearing a walking path to secret treasures and stuff.