Glen Canyon National Recreation AreaPagina 38 di 60
Glen Canyon's Springs, Fishes, Tinajas, Frogs and Streams: A 2022 Condition Assessment
Most studies of Glen Canyon National Recreation Area look at Lake Powell and the Colorado River. This Natural Resource Condition Assessment (NRCA) turned to the water resources that are often overlooked: springs and seeps, fishes, tinajas, amphibians and streamside vegetation along tributary rivers. An NRCA is a "status of knowledge" review that updates what is known about the condition of a limited number of important park resources and identifies critical data gaps, drivers and stressors. Where little was known about a resource, it was not dropped but became the subject of a data gap analysis.
Glen Canyon is on the Colorado Plateau in northern Arizona and southeastern Utah, about 439 km (273 mi) north of Phoenix. The park includes Lake Powell, 42 km (26 mi) of the Colorado River and several tributary river systems. It covers more than 0.5 million hectares (1.25 million acres), 51% of it proposed or potential wilderness.
The assessment also looks at drivers and stressors, the forces behind change in resource condition, which help a park set priorities for stewardship. The NPS has historically tried to keep natural resources in their historical, or "pristine," condition, but ecosystems evolve and adapt to large-scale changes, and park ecosystems will change too.
What it found
| Resource | Findings |
|---|---|
| Springs and seeps | They bring groundwater to the surface, and hanging gardens, a lush spring type that is a hotspot of biodiversity with rare plants, are so large and prominent that the park is named after them. Native plant communities were generally in good condition, and non-native plants were rare at most springs. About one-third of the springs checked for intactness were disturbed or degraded, often by livestock trampling or grazing. More data are needed on water quality |
| Fishes | Twenty-six species occur, but only eight are native. Four native fishes are federally listed (razorback sucker, humpback chub, bonytail chub, Colorado pikeminnow). Four others are in a conservation effort by four states (bluehead sucker, flannelmouth sucker, roundtail chub, speckled dace). None of the four rivers where those four occur has significant water quality impacts, though data on some contaminants are lacking. In the upper Escalante River all four were consistently present and stable; in the lower Escalante and San Juan rivers some were absent or severely reduced and non-native fishes dominated |
| Tinajas | The study mapped over 300 square miles of potential tinajas. Few studies exist. Drought and warming temperatures, which increase evaporation and shorten how long water persists, are the main stressors |
| Amphibians | The status of the group as a whole is unknown. Of 29 locations that used to hold northern leopard frogs, only four currently do and eight others may. The species is breeding in the known locations, and none of the frogs tested for chytridiomycosis has tested positive |
| Riparian zone | The study evaluated seven streams and rivers. No water quality impairments were found, and aquatic intactness was rated high or moderately high at 78% of watersheds. Streamside vegetation is in poor condition, mostly because of invasive species such as tamarisk, Russian olive and ravenna grass |
April and May flows on the Escalante River decreased from 1943 to 2020 at the stream gage, but all of the river within the park is downstream of it, and with many springs feeding the lower river it is not known whether flows decreased there too.
Tinajas and the creatures that need them
Tinajas, also called waterpockets and pools, are depressions eroded in sandstone bedrock that hold water from rain and snowmelt. Small ones dry out, while larger ones can hold water all year and support riparian plants. They are especially common in the Waterpocket Fold area. Amphibians, aquatic invertebrates and mammals use them. Indigenous communities relied on permanent pools when water was scarce elsewhere, and backcountry visitors still do.
Tinajas filled with rainwater in the red sandstone of Glen Canyon. NPS photo.
Springs, fish and frogs
NPS scientists collecting data at a spring in Glen Canyon. NPS photo.
Razorback sucker (Xyrauchen texanus). U.S. Fish and Wildlife Service/Sam Stukel.
Amphibians have a "double life," with a larval stage such as a tadpole and an adult stage such as a frog that can look and be very different. They are indicators of water quality and wetland health. The northern leopard frog was more prevalent before Lake Powell filled, and the frogs now live in fewer, more isolated locations.
Northern leopard frog, photographed at the Gavins Point National Fish Hatchery in Yankton, South Dakota. U.S. Fish and Wildlife Service/Sam Stukel.
Streams
Glen Canyon has over 3,000 miles of waterways with riparian habitat. Streamside plants shade streams, which keeps the water cooler for fish, and give habitat to many other animals and insects. The seven streams and rivers studied were the Dirty Devil, Escalante River, Halls Creek, Lake Canyon, Coyote Gulch, Harris Wash and the San Juan River.
Crews work to remove invasive Russian olive plants that have trapped sediment to form an unnatural levee. NPS photo.
From findings to action
An NRCA includes a discussion between managers and scientists to decide how the park can use the information. The takeaways:
- Several stressors act on each resource, which makes the resources hard to protect.
- Warming temperatures and more frequent and intense droughts affect the hydrology or habitat of every resource studied.
- Managers named more research, monitoring and inventories as their greatest need, for example on how rising temperatures will affect springs and seeps, tinajas and riparian areas.
- The findings help managers decide where to spend limited budgets on habitat or species restoration, fencing to keep out livestock and removal of exotic plants.
- Managers stressed partnerships such as the Escalante River Watershed Partnership, and many visitor education and use planning strategies.
Visitors can help too, because tinajas and hanging gardens are popular destinations and sources of water for backcountry users. The page asks them to protect water quality, fragile vegetation and wildlife habitat and to prevent fires in vulnerable places.
Sources
- National Park Service, "Condition of Glen Canyon's Tributary Rivers and Associated Resources: Natural Resource Assessment 2022" (https://www.nps.gov/articles/000/nrca_glca_2021.htm), summarizing Albright J and others, "Natural resource conditions at Glen Canyon National Recreation Area: Findings & management considerations for selected resources," Natural Resource Report NPS/SCPN/NRR-2022/2374; rewritten in hubnx's own words. The page's second illustration, which has no description, is left out. The page places the frog's photograph in "Yukton, South Dakota"; the spelling of the city is corrected here.