One of the largest NRS reserves, the Boyd Deep Canyon Desert Research Center encompasses a major drainage system descending from the high peaks of the Santa Rosa Mountains down to Colorado Desert. Deep Canyon's tributaries begin in montane forests, flow across a rolling plateau covered with piñon-juniper woodland and chaparral, join at the head of a precipitous gorge, and plunge 1,180 feet into the canyon. From there, the mouth of the canyon opens out into a broad alluvial fan with sandy washes on the southern edge of the Coachella Valley. Except for a few permanent pools, the streambed in Deep Canyon’s lower reaches is dry. However, winter storms can trigger dramatic flooding. The vertebrate fauna is exceptionally rich, with forty-six reptile species, 228 birds, and forty-seven mammals. The reserve is part of the U.N. Mojave and Colorado Desert Biosphere Reserve. Desert research is also possible at two other NRS sites: the Burns Piñon Ridge Reserve and the Jack and Marilyn Sweeney Granite Mountains Desert Research Center.