Visitor Use and Impact Monitoring - ORVs

Learn and Explore

River Values

Rivers designated as Wild and Scenic are characterized by their free-flowing condition, water quality, and Outstandingly Remarkable Values (ORVs). These characteristics are referred to collectively as "river values."

 
Dana Fork water intake
Dana Fork water intake

Free-flowing Condition

A river must be free-flowing to be eligible for inclusion in the National Wild and Scenic Rivers System. A free-flowing river moves in its natural condition without impoundment, diversion, straightening, riprapping (using rock to stabilize streambanks), or other modification of the waterway. The management goal to protect and enhance a river’s free-flowing condition is supported by reducing the amount of human-constructed modifications within the bed and banks of the Merced and Tuolumne Rivers through restoration, redesign, and other appropriate methods. Free-flowing condition of the Tuolumne is protected through monitoring water diversion. Any construction that could potentially cause an impact within the bed or on the banks of either river must undergo analysis.

 
Person taking a water sample from above Nevada Fall in June 2017
Water sampling above Nevada Fall, June 2017

Water Quality

One of the goals of the Wild and Scenic Rivers Act (WSRA) is to protect the water quality of the designated rivers. The Visitor Use and Impact Monitoring Program (VUIMP) supports an ongoing monitoring program to protect the water quality in the Merced and Tuolumne river systems. The water of the Merced and Tuolumne rivers is far above EPA quality standards, so the current water quality of each river is measured against its long-term average water quality in order to record any trends. The plans identify potential risks to water quality due to runoff from parking areas, stables, fueling areas, dump stations, etc. Locations on each river above and below problem sites are sampled monthly during the summer months and assayed for total dissolved nitrogen (TDN), nitrate+nitrite (NO2+NO3), total phosphorus (TP), total dissolved phosphorus (TDP), E. coli, and total petroleum hydrocarbons (TPH). Standards are set for average annual concentrations for each location based on their condition when the plans were developed. Triggers for condition standards involve statistically significant increases in concentration of any monitored factor above that standard.

 

Outstandingly Remarkable Values (ORVs)

For rivers protected by the WSRA, the rare, unique, or exemplary resources that are river-related or river dependent are highlighted as Outstandingly Remarkable Values (ORVs) that should be protected or enhanced. ORVs are categorized as: Biological, Geological/Hydrological, Cultural, Scenic, and Recreational. Protecting this diverse set of ORVs supports a holistic protection of the river itself.

The Merced River Plan (MRP) and Tuolumne River Plan (TRP) identify 30 specific ORVs (20 in the MRP and 10 in the TRP).

 

Merced River

Outstandingly Remarkable Values for the Merced River and Associated Indicators

River Value

Segment(s)

Indicator(s) to be Monitored through Time

Biological ORVs

1. Numerous small meadows and riparian habitat with high biological integrity.

Segments 1 and 5 – Merced River Above Nevada Fall and South Fork Merced River Above Wawona

  1. Meadow bare soil

  2. Meadow fragmentation resulting from proliferation of informal trails

  3. Streambank stability

2. The meadows and riparian communities of Yosemite Valley comprise one of the largest mid-elevation meadow-riparian complexes in the Sierra Nevada.

Segments 2A and 2B – Yosemite Valley

  1. Meadow fragmentation resulting from proliferation of informal trails

  2. Status of riparian habitat

  3. Riparian bird abundance

3. Sierra sweet bay (Myrica hartwegii) is a rare plant found on river banks of the South Fork Merced River.

Segments 7 and 8 – Wawona and South Fork Merced River below Wawona

Population decline

Geologic/Hydrologic ORVs

4. The upper Merced River canyon is a textbook example of a glacially-carved canyon.

Segment 1 – Merced River Above Nevada Fall

None; the ORV is impervious to human disturbance

5. The “Giant Staircase,” which includes Vernal and Nevada Falls, is one of the finest examples in the western United States of stair-step river morphology.

Segments 2A and 2B – Yosemite Valley

None; the ORV is impervious to human disturbance

6. The Merced River from Happy Isles to the west end of Yosemite Valley provides an outstanding example of a rare, mid-elevation alluvial river.

Segments 2A and 2B – Yosemite Valley

The California Rapid Assessment Method (CRAM)

7. The boulder bar in El Portal was created by changing river gradients, glacial history, and powerful floods. These elements have resulted in accumulation of extraordinarily large boulders, which are rare in such deposits.

Segment 4 – El Portal

None; the ORV is impervious to human disturbance

Cultural ORVs

8. Yosemite Valley American Indian ethnographic resources include a linked landscape of specifically mapped traditional-use plant populations as well as the ongoing traditional cultural practices that reflect the intricate continuing relationship between indigenous peoples of the Yosemite region and the Merced River in Yosemite Valley.

Segments 2A and 2B – Yosemite Valley

  1. Meadow fragmentation due to the proliferation of informal trails

  2. Status of riparian habitat

  3. California black oak- number of adults and ratio of saplings to adults

9. The Yosemite Valley Archeological District is an unusually rich and linked landscape that contains dense concentrations of resources that represent thousands of years of human settlement.

Segments 2A and 2B – Yosemite Valley

Condition of Yosemite Valley Archeological District

10. The Yosemite Valley Historic District represents a linked landscape of river-related or river-dependent, rare, unique or exemplary contributing resources that bear witness to the historical significance of the river system.

Segments 2A and 2B – Yosemite Valley

FMSS Condition Assessments

11. The El Portal Archeological District contains dense concentrations of resources that represent thousands of years of occupation and evidence of continuous, far-reaching traffic and trade. This segment includes some of the oldest deposits in the region and the archeological remains of the Johnny Wilson Ranch, a regionally rare historic-era American Indian Homestead.

Segment 4 – El Portal

Condition of El Portal Archeological District

12. This segment includes regionally rare archeological features representing indigenous settlement and use along the South Fork Merced River at archeological sites with rock ring features.


Segment 5 – South Fork Merced River Above Wawona

Condition of archeological sites

13. The Wawona Archeological District encompasses numerous clusters of resources spanning thousands of years of occupation, including evidence of continuous far-reaching traffic and trade. Segment 7 includes the remains of the U.S. Army Cavalry Camp A.E. Wood documenting the unique Yosemite legacy of the African American Buffalo Soldiers and the strategic placement of their camp near the Merced River.

Segments 5, 6, 7, and 8 – South Fork Merced River Above Wawona, Wawona Impoundment, Wawona, South Fork Merced River Below Wawona

Condition of Wawona Archeological District

14. The Wawona Historic Resources ORV includes one of the few covered bridges in the region and the National Historic Landmark Wawona Hotel complex, which is one of the largest existing Victorian hotel complex in a national park and one of the few remaining in the United States with this high level of integrity.

Segments 5, 6, 7, and 8 – South Fork Merced River Above Wawona, Wawona Impoundment, Wawona, South Fork Merced River Below Wawona

Condition Assessment

Scenic ORVs

15. Visitors to this Wilderness segment experience exemplary views of serene montane lakes, pristine meadows, slickrock cascades, and High Sierra peaks.

Segment 1 – Merced River Above Nevada Fall

No indicator is proposed, as Wilderness designation precludes development

16. Visitors to Yosemite Valley experience views of some of the world’s most iconic scenery, with the river and meadows forming a placid foreground to towering cliffs and waterfalls.

Segments 2A and 2B – Yosemite Valley

Application of the Visual Resource Management System

17. The Merced River drops 2,000 feet over 14 miles, a continuous cascade under exemplary Sierra granite outcrops and domes.

Segment 3 – The Merced Gorge

Application of the Visual Resource Management System

18. The South Fork Merced River passes through a vast area of exemplary and wild scenic beauty.

Segments 5 and 8 – South Fork Merced River Above and Below Wawona

No indicator is proposed, as management as wilderness precludes development.

Recreational ORVs

19. Visitors to federally designated Wilderness in the corridor engage in a variety of river-related activities in an iconic High Sierra landscape, where opportunities for primitive and unconfined recreation, self-reliance, or solitude shape the experience.

Segment 1 – Merced River Above Nevada Fall

Wilderness Encounters

20. Visitors to Yosemite Valley enjoy a wide variety of river-related recreational activities in the Valley’s extraordinary setting along the Merced River.

Segments 2A and 2B – Yosemite Valley

Visitor Densities at Valley attractions, beaches or trails

 

Tuolumne River

Outstandingly Remarkable Values for the Tuolumne River and Associated Indicators

River Value

Segment(s)

Indicator(s) to be Monitored through Time

Biological Values

Subalpine meadow and riparian complex

Wild segments: Lyell Fork, Upper Dana Fork
Scenic segments: Lower Dana Fork, Tuolumne Meadows

Meadow fragmentation due to proliferation of informal trails

Physical streambank stability rating

Meadow bare soil

Low-elevation riparian and meadow habitat

Wild segment: Poopenaut Valley

NA (No indicator is defined because management of the valued habitat is constrained by the Raker Act and its location downstream of the Hetch Hetchy Reservoir.)

Geologic Value

Stairstep river morphology

Wild segment: Grand Canyon of the Tuolumne

NA (No indicator is defined because the condition of this value is governed by large-scale influences beyond human control.)

Cultural Values

Prehistoric archeological Landscape

All segments

Aggregate condition of prehistoric archeological sites

Parsons Memorial Lodge

Scenic Segment: Tuolumne Meadows

Condition of Parsons Memorial Lodge

Scenic Values

Scenery through Lyell Canyon

Wild segment: Lyell Fork

Visual resource management classification

Scenery through Dana and Tuolumne Meadows

Scenic segments: Tuolumne Meadows and Lower Dana Fork

Visual resource management classification

Scenery through Grand Canyon of the Tuolumne

Wild segment: Grand Canyon of the Tuolumne

Visual resource management classification

Recreational Values

Rare and easy access to the river through Tuolumne and Dana Meadows

Scenic segments: Tuolumne Meadows and Lower Dana Fork

NA (No indicator for a management standard is needed because parking supply is the means by which the plan’s user capacity will be enforced.)

Wilderness experience along the river

Wild segments: Lyell Fork, Upper Dana Fork, Grand Canyon of the Tuolumne, and Poopenaut Valley

Number of encounters with other hiking parties per hour

NA = not applicable

Last updated: August 2, 2021

Contact the Park

Phone:

209/372-0200

Contact Us

Stay Connected