Environmental enthusiasts are expected in the thousands this weekend at Reid Park for a double dose of eco-friendly activities.

The park will host two festivals that have partnered up on Sunday - the 19th annual Tucson Earth Day Festival and Parade and the Water Festival, which is now in its fourth year.

The all-day events, running in conjunction from 8 a.m.-2 p.m., are chock-full of speakers, exhibits and demonstrations.

Among the happenings:

• An alternate-fuel vehicle show, featuring different modes of transportation running on ethanol, propane, waste vegetable oil, electricity and compressed natural gas.

• A solar electric competition with models of homes and cars designed by local middle school students.

• Speakers from both the political and scientific end of environmental conservation, including Rep. Raúl Grijalva and Lincoln Perino, a partner at Ethos Rainwater Harvesting.

• Performances from arts groups such as the Zuzi Youth and Apprentice Dance Company and Mariachi Nueva Melodía.

The day kicks off with an Aveda Institute 3-mile Walk for Water at 8 a.m.

Other activities don't start until 9 a.m.

The Earth Day Festival parade, with the theme "Green Planet, Green Future," begins at 10.

Water Festival activities will be held at the DeMeester Outdoor Performance Center, with Earth Day fest happenings taking place in the northwest quadrant of the park.

Admission is free. Visit tucsonearthday.org or waterfestivaltucson.org for more information.

Gerald M. Gay