Visitor Use and Impact Monitoring - ORVs

Visitor Use and Impact Monitoring Program

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River Values
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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: September 20, 2017

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Yosemite National Park, CA 95389

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