Rainwater + Solar Power = DIY Rainbow Machine
Artist Michael Jones McKean has harnessed nature with his DIY rainbow machine, a mechanism that uses reclaimed rainwater and solar power to shoot man-made rainbows across the sky at whim. High powered jets and fountain nozzles shoot a heavy wall of rainwater into the air, creating a faux rainstorm. Sunshine does the rest.
From the artist's site:
Proposal for Certain Principles of Light and Shapes Between Forms
"A small prismatic rainbow, about 80 feet wide and 30 feet tall arching over my studio building in Richmond, Virginia, USA made using sunlight and water supplied by a series of pumps, hoses and nozzles. The rainbow used 80 gallons on water recaptured and continuously re-circulated by way of the buildings water/gutter system."