Condition of Glen Canyon's Tributary Rivers and Associated Resources: Natural Resource Assessment 2022

America’s National Parks protect abundant and diverse natural resources. The excitement of seeing wildlife, the opportunity to touch a glacier, and the serenity of standing in the woods draw millions of visitors into our parks every year. Natural resources exist as parts of complex ecosystems that interact with each other and respond to both natural and man-made drivers and pressures. Translating these broad concepts of resource condition and trend down to the level of specific, measurable, and management-useful resource condition indicators is an ongoing challenge. The effort remains necessary because ecological resources can’t be effectively managed without reliable condition-status information.
Natural Resource Condition Assessment (NRCA) projects (such as this study) are designed to provide an efficient, yet defensible, “status of knowledge” review and update on current natural resource conditions, and identify critical data gaps and drivers and stressors for a limited number of important park ecological resources.

Ecosystem drivers and stressors: What is causing change in resource conditions?

An important part of the NRCA is identifying the primary threats and stressors affecting the condition of the selected natural resources. Understanding what forces are driving changes in conditions can help a park prioritize stewardship activities. Historically, the NPS has sought to maintain natural resources in the historical or “pristine” condition, but ecosystems evolve and adapt to large-scale changes, and park ecosystems will change as well.
Illustration of drivers as wind blowing the resources as leaves.

Focusing in on a set of natural resources in Glen Canyon

GLCA PCS 2021 Illustration
Glen Canyon National Recreation Area (GLCA) is situated in the Colorado Plateau region of northern Arizona and southeastern Utah, approximately 439 km (273 mi) north of Phoenix, Arizona. The park includes Lake Powell, 42 km (26 mi) of the Colorado River, and several tributary river systems, and encompasses more than 0.5 million ha (1.25 million ac), 51% of which is identified as proposed or potential wilderness. The interplay between the porous geologic layers, arid desert, and river-fed water environments support a unique and diverse assemblage of vegetation and wildlife that are highly dependent on the water cycles and sources of the Colorado Plateau.

Studies of natural resources in Glen Canyon often focus on Lake Powell and the Colorado River. For this NRCA, often overlooked resources associated with tributary rivers and smaller water sources were selected as focal resources. Focal resources found to have little existing information were not excluded; instead, they were the focus of a data gap analysis rather than a pure condition assessment.

Springs and Seeps

Springs and seeps connect groundwater to the surface, providing an important source of water to plants and animals throughout the desert. One particular type of spring, called a hanging garden, is a hotspot of biodiversity and home to rare plants. In fact, these lush hanging garden alcoves are so large and prominent at Glen Canyon that the park was named after them.
Scientist perch on a red sandstone outcrop sampling water from the spring-fed pond below.
NPS scientists collecting data at a spring in Glen Canyon.

NPS Photo

Our assessment mapped springs throughout Glen Canyon. We found that native plant communities were generally in good condition and non-native plants were rare at most springs. Non-native plants, drought, and flooding were the main threats found at a subset of springs where intactness was evaluated. About one-third of these springs were disturbed or degraded, and this was often related to livestock trampling or grazing. Water quality is an important indicator of pollutants and disturbances at springs, but more information is needed to truly understand the water quality of springs at Glen Canyon.


Nearly one-half of all known fish species across the globe live in fresh water. This means they live in rivers, wetlands, and lakes, including those in Glen Canyon. Twenty-six fish species occur in Glen Canyon NRA, but only eight of them are native.
Learn more about fishes in Glen Canyon
Razorback sucker (Xyrauchen texanus).

US Fish and Wildlife Service/Sam Stukel

Of the eight native species, four are federally listed under the Endangered Species Act (razorback sucker, humpback chub, bonytail chub, and Colorado pikeminnow), and four are part of a conservation/protection effort by four states, including Arizona and Utah (bluehead sucker, flannelmouth sucker, roundtail chub, and speckled dace).

This second group of four native species has been less studied than other fishes in the region and was one area of focus in our assessment. We found that none of the four rivers where the fishes occur have significant impacts to water quality, although information is lacking for some types of contaminants. We also found that in the upper Escalante River, all four fish species were consistently present and their populations appeared stable. However, in the lower Escalante and San Juan rivers, some of the fish species were absent or severely reduced and dominated by non-native species.


Tinajas (also called waterpockets and pools) are depressions eroded in the sandstone bedrock that hold water from precipitation and snowmelt. While smaller tinajas tend to dry out, larger tinajas can retain water year-round and support riparian plants.
Eroded circles in red sandstone filled with water.
Tinajas filled with rainwater in the red sandstone of Glen Canyon.

NPS Photo

Tinajas are important sources of water for amphibians, aquatic invertebrates, and mammals. Historically, Indigenous communities relied on permanent pools when water was scarce elsewhere, and tinajas continue to serve as an important source of water for backcountry users today.

Tinajas are common throughout Glen Canyon NRA, and they are especially prevalent in the Waterpocket Fold area of the park. This study mapped over 300 square miles of potential tinajas in Glen Canyon. We know tinajas are important, but there have been few studies on this resource. Drought and warming temperatures are the primary stressors for tinajas, increasing evaporation and decreasing how long water persists in pools.

Amphibians: featuring the Northern Leopard Frog

Amphibians, including frogs, toads, and salamanders, primarily reproduce and develop in aquatic habitats, although some spend much of their time (as adults) in drier environments.
Northern leopard frog, green with black spots swimming
Northern leopard frog (photo taken at the Gavins Point National Fish Hatchery in Yukton, South Dakota).

US Fish and Wildlife Service/Sam Stukel

This group of vertebrates is fascinating because of their “double lives”—they have a larval stage (such as a tadpole) and an adult stage (such as a frog), and these two stages can look and be very different from one another. In Glen Canyon NRA and elsewhere, amphibians are an important part of aquatic ecosystems and are indicators of water quality and wetland health. Some species (such as the northern leopard frog), are of particular conservation interest due to declining numbers.

At Glen Canyon NRA, the current status of amphibians as a group is unknown due to a lack of information. More, however, is known about northern leopard frogs. This species was more prevalent before Lake Powell filled, but now these frogs live in fewer locations that are more isolated from one another. Of 29 locations that used to contain northern leopard frogs, only four currently do and eight others may (but this is not known for sure). Good news, however, is that the species is breeding in the known locations, and of frogs that have been tested for a serious amphibian disease (chytridiomycosis), none have tested positive.

Riparian Zone

Glen Canyon has over 3,000 miles of waterways that provide riparian habitat along rivers and streams. Riparian plants shade streams and keep water temperatures cooler for fish and provide habitat for a multitude of other wildlife and insect species. This study evaluated water availability, stream health, and vegetation for seven streams and rivers in Glen Canyon: the Dirty Devil, Escalante River, Halls Creek, Lake Canyon, Coyote Gulch, Harris Wash, and the San Juan River.

russian olive shrubs grow along a stream bank
Crews work to remove invasive Russian olive plants that have trapped sediment to form an unnatural levee.

NPS Photo

April and May stream flows on the Escalante River decreased from 1943 to 2020. But all of the river within Glen Canyon is downstream of the stream gage, and we don’t know if stream flows have decreased there as well, since there are numerous springs that feed the lower Escalante River. There were no impairments to water quality in the seven streams, and aquatic intactness was rated as high or moderately high at 78% of watersheds on these streams. The condition of vegetation along streams is poor, mostly due to invasive exotic species. The NPS and partners work hard to remove exotic plants, but the proliferation of tamarisk, Russian olive, ravenna grass, and other species present an ongoing management challenge.

Using what we learned to take action

Knowing the condition of these resources and what information is missing is only the first step. We also need to link our findings to actions park managers can take to better protect the resources in their park. A critical part of any NRCA project is a manager-scientist discussion to identify how the park can use this information to prioritize stewardship actions, guide future monitoring activities, and select important next steps. Here are some things that we learned.

  • Multiple stressors affect each resource and drive changes that make it challenging for the park to protect them.
  • Warming temperatures and increasing frequency and intensity of droughts affect the hydrology or the habitat of all of the resources evaluated in this study.
  • Park managers identified their greatest need as acquiring additional information through research, monitoring, and inventories. One example of this is the need to better understand how increasing temperatures will affect the hydrology of springs and seeps, tinajas, and riparian areas.
  • Our findings help land managers make the most informed decisions about where to spend their limited budgets on treatments like restoration of habitat or species, fencing to exclude livestock, or exotic plant removal.
  • Park managers acknowledged the importance of partnerships, such as the Escalante River Watershed Partnership, for addressing larger-scale resource issues and stressors.
  • Park managers identified many visitor education and visitor use planning strategies to effectively protect resources.

You too can be part of the solution!

Visitors to Glen Canyon play an important part in protecting natural resources. Tinajas and hanging gardens, for example, are popular destinations and serve as an important source of water for backcountry visitors. Understand what you can do to maintain water quality, protect fragile vegetation and wildlife habitat, and prevent fires in vulnerable locations. Learn more about how you can protect each of these resources in our articles about spring and seeps, fishes, tinajas, amphibians, and riparian zones at Glen Canyon.

Information in this article was summarized from: Albright J and Others. 2022. Natural resource conditions at Glen Canyon National Recreation Area: Findings & management considerations for selected resources. Natural Resource Report. NPS/SCPN/NRR—2022/2374. National Park Service. Fort Collins, Colorado.

Part of a series of articles titled NRCA 2022: Condition of Glen Canyon's Tributary Rivers and Associated Resources.

Glen Canyon National Recreation Area

Last updated: July 14, 2022