Nestled among the Little San Bernardino Mountains, the desert oasis at Big Morongo Canyon is one of the 10 largest cottonwood and willow riparian (stream) habitats in California.  The upstream end of the canyon lies in the Mojave Desert, while its downstream portion opens into the Colorado Desert.   The Preserve is managed by the Bureau of Land Management, including 147 acres that are managed under a cooperative agreement with San Bernardino County, to protect rare and endangered wildlife, enhance sensitive riparian zones, promote the growth and restoration of a wide variety of plants, and offer educational opportunities.  There are numerous trails to walk and hike, including a wheelchair-accessible boardwalk through the marsh and riparian habitats.  The Preserve begins about one-half mile southeast of the town of Morongo Valley in the Little San Bernardino Mountains and opens at the bottom of Big Morongo Canyon into the west end of the Coachella Valley northwest of Desert Hot Springs.  The Preserve is open daily throughout the year (7:30 am to sunset) but tiime to visit are fall, winter, and spring. All trails begin at the kiosk in the parking lot.