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.. Yampa, Colorado, it flows northward and then westerly fbrapproximately 320 km (200 mi), before joining the Green River in DNM. Flows begin to rise in mid to late April due to snow melt, increasing from daily averages of 100-500 cfs during August-March to daily averages in excess of 10,000 cfs in June. In the winter of 1980-81, precipitation and snow pack were much less than normal and 1981 spring runoff in the Yampa River was consequently reduced in both duration and magnitude. In contrast, the winter of 1982-83, was very wet and the 1983 runoff consisted of a large volume and high peak flow. The study area included the lower 160 km (100 mi), of the Yampa River but emphasis was placed On the -lower 80 km (50 mi), which lies within DNM. The river habitat in this location is composed of two main types which extend from River Kilometer (RK) 198 to 74 and from RK 7Z to RK 0 (confluence with the Green River) respectively. From RK 198 (RM 124), downstream to RK 74 (RM 46), the Yampa River meanders slowly through low gradient agricultural valleys. This flow pattern is briefly interrupted at two points: Juniper Mountain, RK 141.9 - 145.6 (RM 88 - 9'1.0) and Cross Mountain RK 89 - 94 (RM 55.6 - 58.8), where the river has steep-sided canyons with boulder/bedrock substrate. Near the lower end of Juniper Canyon is the only manmade impediment to flow within the study area, a low level irrigation div- ersion formed by bulldozing rubble into the river. The Yampa River enters DNM at RK 77 (RM 48), and at RK 72 (RM 45) it enters a steep-walled canyon with near-vertical walls which rise to 400 m (1370 ft) above river level. The upper canyon, from RK 72 (RM 45), to RK 32 (RM 20), is characterized by several long sections inter~ rupted by side canyon flood depos its conta i ni ng bou 1 der that genera 11 y result in riffles or rapids. At RK 32 (RM 20), the Yampa enters the Weber sandstone and the boulder/cobble substrate where it gradually picks up increasing amounts of sand. With the exception of Warm Springs Rapid at RK 5.6 (RM 4.1), this section of the lower Yampa River is relatively deep and slow-moving with many meanders. The Green River receives the Yampa at RK 552 (RM 345), within DNM and abruptly enters Whirlpool Canyon, a section with deep eddies and steep, boulder-strewn cliffs. The Green River leaves Whirlpool Canyon and meanders through cottonwood-lined sand/cobble shorelines in Island Park and Rainbow Park until entering Split Mountain Canyon at RK 523 (RM 327). During its passage through Split Mountain the Green River passes through several large boulder fields, which create four major rapids. The river exits Split Mountain Canyon and DNM at RK 510 (RM 319) and enters the agricultural valley of the Uintah Basin, where the river becomes very broad, shallow and flat. 3