What I see appears to be a split in the pipe on the lower left corner of the photo. The simple answer to the question is to cut the split out, solder a new piece of pipe with couplers on each side. I would guess you did not winterize the system in the fall. I don't recognize the device in the center of the picture. Is that supposed to be a back flow preventer? You definitely need one if you are using your domestic water supply for lawn irrigation, but I've never seen one that looks like what is pictured.