River Runners' Guide to Utah and Adjacent Areas
A comprehensive guidebook to whitewater rivers in Utah and neighboring regions, covering river access, rapids, flow considerations, trip logistics, and historical context for river runners.
Flow
— cfs
Season
Spring, summer
Duration
1–2 days (typical 1)
Permit
NPS permit required for all launches — apply through recreation.gov, lottery for...
Shuttle
Logistics
Advanced
Green River — UT
Split Mountain
Split Mountain is the Green River's most concentrated whitewater — 9 miles punching through a breached anticline, capped by the Class IV SOB Rapid and one of the most dramatic canyon exits in Dinosaur National Monument.
Split Mountain is the dramatic finale of the Dinosaur National Monument river system — a 9-mile gorge where the Green River cuts directly through an anticline rather than around it, creating a canyon of tilted and folded rock unlike anything else on the Colorado Plateau. Four major rapids, including the Class IV SOB, deliver concentrated whitewater in a short distance that makes this the most intense day-trip on the upper Green. Whether run as a standalone day trip or as the capstone of a Lodore–Whirlpool–Split Mountain expedition, it's a worthy finish.
8.3
miles
1
day typical
4
named rapids
Flows & Hydrology
The Jensen gauge reads conditions directly at the take-out; flows above 4,000 cfs raise the stakes at SOB Rapid significantly.
Reference Gauges
Green River at Jensen, UT
Primary operational gauge for planning Split Mountain Canyon floats. Located near Jensen, UT, below Dinosaur National Monument, this gauge integrates snowmelt from the Uinta Basin watershed and is the most direct reading for Split Mountain and lower Lodore trip planning.
USGS #09261000Current flow — Green River at Jensen, UT
USGS
—
Water temperature
Gage height
Reading the Water
Low water
Below 1,500 cfs — technical and punchy; SOB Rapid requires precise lines through exposed rocks.
Medium water
1,500–4,000 cfs — classic Split Mountain conditions; all four major rapids run powerfully and cleanly.
High water
Above 4,000 cfs — SOB Rapid becomes a serious Class IV commitment with large hydraulics; experienced whitewater teams only.
Hazards by season
- Spring
- cold water, high flows amplifying SOB Rapid, powerful hydraulics
- Summer
- low water, rock exposure in rapids, heat in confined canyon
7-Day Forecast
Seasonality
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Peak flows May–June from Rocky Mountain snowmelt; frequently run in April at lower flows.
- Spring
- cold water, high flows amplifying SOB Rapid, powerful hydraulics
- Summer
- low water, rock exposure in rapids, heat in confined canyon
Reading the Rock Record
Rock sequence of Split Mountain
↑ Rim
- Nugget Sandstone
- Park City Formation
- Weber Sandstone
- Morgan Formation
- Madison Limestone
- Uinta Mountain Group
↓ River level
Ecology
Life in the Corridor
Flora
- Biomes
- canyon riparian, desert shrubland
Fauna
- Notable species
- bighorn sheep, river otter, red-tailed hawk, mule deer
History
Split Mountain sits adjacent to the Dinosaur National Monument Quarry — one of the richest dinosaur fossil sites in North America. Powell's 1869 expedition exited Dinosaur through Split Mountain, completing the first recorded navigation of the upper Green River canyon system.
Layers of Human Presence
- Indigenous homelands
- Ute, Fremont
- Historical layers
- Powell 1869 expedition, Dinosaur quarry access route
Logistics
Permit required even for day trips; the short paved shuttle and nearby Jensen services make Split Mountain one of the most accessible Dinosaur permit runs.
Getting There and Getting Out
Put-in — Rainbow Park Boat Ramp
- Elevation
- 4970 ft
- Facilities
Take-out — Split Mountain Boat Ramp
- Elevation
- 4806 ft
Shuttle
Rainbow Park Boat Ramp to Split Mountain Boat Ramp
Google used a car, their times do not account for towing a trailer, driving on washboard, pitted pavement, and dirt that goes to grease in the rain — our adjusted times help align to the reality of running real river shuttles.
Permit
Dinosaur NM requires a day-use permit to float Split Mountain (owner, 2026-09-02). This listing binds a party LAUNCHING here — the Rainbow Park to Split Mountain daily. A multi-day party arriving from upstream on a Lodore or Yampa river permit (recreation.gov 250014) is already covered and does NOT need this permit as well; dayUseOnly is what tells the trip permit rollup to skip it on those routes. appliesTo: day_use (2026-09-02, replacing the transitional dayUseOnly boolean) — this listing binds a party LAUNCHING here. A multi-day party arriving from upstream on the Dinosaur Green And Yampa River Permits (recreation.gov 250014) is already covered; rec.gov's own 250014 listing states it covers Split Mountain Canyon.
- Required
- Yes
- Agency
- National Park Service — Dinosaur National Monument
Trip realities
- Gateway towns
- Vernal, UT, Jensen, UT
- Groover
- Required
- Managed by
- National Park Service — Dinosaur National Monument
Gear
Camp Kitchen
On a seven-day trip, you'll cook roughly 20 meals on a folding table in the sand. The constraint isn't ambition — it's ice management. Days one through three, you have real cooler capacity. Days four and five are the transition zone. Days six and seven are pantry cooking.
The best river cooks plan backward from the last night. If your final dinner is still good — not just edible, but genuinely good — the trip ends on a high.
Feeding a Crew for Seven Days
Ice management strategy
Two coolers, segregated by access frequency. A well-managed deep cooler will hold usable ice through day 6 in 100°F air temps.
Kitchen setup
Folding table, two-burner propane stove, cast iron skillet, Dutch oven, and a large pot. The Dutch oven is the single most versatile piece.
Reading the River
Books that shape the science, history, and stories behind this place.
The Exploration of the Colorado River
Powell's original account of the first scientific expedition through the Grand Canyon, documenting the geology, natural history, and challenges of navigating the unknown Colorado River.
