Natural History of Juniper Canyon, Oregon

Gwen Leslie

Whitman College, Walla Walla WA 99362


Juniper Canyon is a unique nine-mile long tributary canyon to the Columbia River at Wallula Gap in northeastern Oregon. Located on U.S. Highway 730 just south of the Washington/Oregon state line, Juniper Canyon is part of the McNary Wildlife Refuge. The creek incised Juniper Canyon into Miocene Columbia River basalts. During the Pleistocene, outburst floods from glacial Lake Missoula partially filled the canyon with giant eddy bars of gravel and left scattered erratic boulders more than 200 m above the level of the Columbia River. After the floods, the creek recut Juniper Canyon through the gravel bars. Loess blankets the uplands, and sand dunes have migrated here from the Umatilla Basin. With less than 25 cm of mean annual precipitation, the ecology here is greatly affected by aspect. The wetter north-facing slope has juniper trees, a number of native shrubs, and a fragile cryptobiotic crust, while the sunnier and drier south-facing side is mostly devoid of vegetation except for native and exotic grasses. The canyon floor contains wetlands created by McNary Dam on the Columbia River and by beavers. Environmental issues such as exotic species management, grazing, wildfire management, and dam construction are significant here.