Natural resource conditions at Glen Canyon National Recreation Area: Findings & management considerations for selected resources

Abstract

Glen Canyon National Recreation Area (GLCA) encompasses more than 0.5 million ha (1.25 million ac) and extends over 322 km (200 mi) from its northern boundary in southern Utah to its southern boundary in northern Arizona. It is one of the most rugged, remote, and floristically diverse national parks on the Southern Colorado Plateau (Thomas et. al 2005) and has more than 4,900 km (3,045 mi) of waterways flowing through its eight Hydrologic Unit Code (HUC 8) watersheds. GLCA’s larger perennial rivers include the Colorado, Escalante, Dirty Devil, San Juan, and Paria, with smaller perennial and intermittent streams flowing into each of these rivers. After the creation of the Glen Canyon Dam, Lake Powell formed, covering 13% of the park’s total land area when full and the national recreation area attracts over 4 million visitors annually, and in 2019 GLCA ranked 19th highest in recreational visits out of all national parks. The National Park Service Natural Resource Condition Assessment Program selected GLCA to pilot its new NRCA project series. NRCA projects evaluate the best available science to provide park managers with reliable, actionable information pertaining to natural resource conditions in their park. For the park-selected focal study resources, this includes consideration of drivers and stressors known or suspected of influencing resource conditions; assessment of current conditions and trends for indicators of condition; and potential near-term and future activities or actions managers can consider, improving their knowledge and management of natural resources in parks. For focal resources that lack adequate data to assess current conditions, a gap analysis is provided (in lieu of a condition assessment) to highlight the present status of knowledge of the resource and to suggest useful indicators, data, and studies for further consideration and investigation. Park managers are encouraged to identify information needs and pose questions during the NRCA scoping process, with the understanding that information will be provided to help address those needs and answer those questions when possible. For a comprehensive list of GLCA managers’ questions and needs, please refer to Appendix A, Table A-1. The focus of GLCA’s NRCA study was the water-dependent resources—tinajas, springs & seeps, including water quality, riparian zone, amphibians, including the northern leopard frog (Lithobates pipiens), and small, native fishes—that are found off the mainstem Colorado River. Managers were interested in these particular environments and the natural resources that depend on them because they are less studied, and the habitats are “biodiversity hotspots” due to the intersection of complex desert and freshwater ecosystems in a region limited by water. The following summaries highlight the key findings of GLCA’s focal resource drivers and stressors (Chapter 2), states (Chapter 3), and manager responses (Chapter 4).