Geology topics

Kent Turner

Publications and source records attributed to Kent Turner.

8 recordsLinked to original sources

USGS2013

An overview of the Southern Nevada Agency Partnership science and research synthesis

Maintaining and restoring the diverse ecosystems and resources that occur in southern Nevada in the face of rapid socio-economic and ecological change presents numerous challenged to Federal land managers. Rapid population growth since the 1980s, the land uses associated with that growth, and the interactions of those uses with the generally dry and highly variable climate result in numerous stresses to ecosystems, species, and cultural resource. In addition, climate models predict that the rate of temperature increase and, thus, changes in ecological processes, will be highest for ecosystems like the Mojave Desert. The Southern Nevada Agency Partnership (SNAP; http:www.SNAP.gov) was established in 1999 to address common issues pertaining to public lands in southern Nevada. Partners include the Bureau of Land Management, National Park Service, U.S. Fish and Wildlife Service, and USDA Forest Service and they work with each other, the local community, and other partners. SNAP agencies manage more than seven million acres of public lands in southern Nevada (95% of the land area). Federal land includes two national recreation areas, two national conservation area, four national wildlife refuges, 18 congressionally designated wilderness areas, five wilderness study areas, and 22 areas of critical environmental concern. The partnership's activities are mainly centered in Southern Nevada's Clark County (fig. 1.1), but lands managed by SNAP partner agencies also include portions of Lake Mead National Recreation Area in Mohave County, Arizona, U.S. Fish and Wildlife Service, and USDA Forest Service-managed lands in Lincoln and Nye Counties, Nevada, and all lands and activities managed by the Southern Nevada District Office of the Bureau of Land Management. These lands encompass nine distinct ecosystem types (fig. 1.2), support multiple species of management concern an 17 listed species, and are rich in cultural and historic resource. This introductory executive summary discusses the Science and Research Strategy developed by the SNAP agencies, the Science and Research Report, and need for science-based management in southern Nevada.

Nevada↗

USGS2012

Introduction and summary of findings

Lakes Mead and Mohave, which are the centerpieces of Lake Mead National Recreation Area (LMNRA), provide many significant benefits that have made the modern development of the Southwestern United States possible. Lake Mead is the largest reservoir by volume in the nation and it supplies critical storage of water supplies for more than 25 million people in three Western States (California, Arizona, and Nevada). Storage within Lake Mead supplies drinking water and the hydropower to provide electricity for major cities including Las Vegas, Phoenix, Los Angeles, Tucson, and San Diego, and irrigation of more than 2.5 million acres of croplands (National Park Service, 2010). Lake Mead is arguably the most important reservoir in the nation because of its size and the services it delivers to the Western United States (Holdren and Turner, 2010).

Arizona, Nevada↗

USGS2012

A synthesis of aquatic science for management of Lakes Mead and Mohave

Lakes Mead and Mohave, which are the centerpieces of Lake Mead National Recreation Area, provide many significant benefits that have made the modern development of the Southwestern United States possible. Lake Mead is the largest reservoir by volume in the nation and it supplies critical storage of water supplies for more than 25 million people in three Western States (California, Arizona, and Nevada). Storage within Lake Mead supplies drinking water and the hydropower to provide electricity for major cities including Las Vegas, Phoenix, Los Angeles, Tucson, and San Diego, and irrigation of more than 2.5 million acres of croplands. Lake Mead is arguably the most important reservoir in the nation because of its size and the services it delivers to the Western United States. This Circular includes seven chapters. Chapter 1 provides a short summary of the overall findings and management implications for Lakes Mead and Mohave that can be used to guide the reader through the rest of the Circular. Chapter 2 introduces the environmental setting and characteristics of Lakes Mead and Mohave and provides a brief management context of the lakes within the Colorado River system as well as overviews of the geological bedrock and sediment accumulations of the lakes. Chapter 3 contains summaries of the operational and hydrologic characteristics of Lakes Mead and Mohave. Chapter 4 provides information on water quality, including discussion on the monitoring of contaminants and sediments within the reservoirs. Chapter 5 describes aquatic biota and wildlife, including food-web dynamics, plankton, invertebrates, fish, aquatic birds, and aquatic vegetation. Chapter 6 outlines threats and stressors to the health of Lake Mead aquatic ecosystems that include a range of environmental contaminants, invasive species, and climate change. Chapter 7 provides a more detailed summary of overall findings that are presented in Chapter 1; and it contains a more detailed discussion on associated management implications, additional research, and monitoring needs.

Arizona, Nevada↗

USGS2012

Environmental setting of Lake Mead National Recreation Area: Chapter 2 in A synthesis of aquatic science for management of Lakes Mead and Mohave

Lakes Mead and Mohave provide opportunities for millions of regional, national, and international visitors to enjoy a wide array of water-based recreation in a spectacular desert setting. The national significance of the site’s recreational opportunities and scientific values led to its designation as the nation’s first National Recreation Area in 1964. The stark contrast of the deep blue lakes with spacious open water basins against a backdrop of mountain and canyon scenery creates a diversity of landscapes inviting recreation from the active to the contemplative (Maxon, 2009). The quality of the setting as a backdrop for the recreational experience has resulted in designation of approximately 200,000 acres of lands surrounding the lakes as wilderness (National Park Service, 2005).

Circular↗

USGS2012

Hydrology and management of Lakes Mead and Mohave within the Colorado River Basin: Chapter 3 in A synthesis of aquatic science for management of Lakes Mead and Mohave

The Colorado River Basin covers parts of seven States: Colorado, Wyoming, Utah, New Mexico, Nevada, Arizona, and California; at 1,450 mi (2,333.5 km) in length, the Colorado River is the seventh longest river in the United States (fig. 3-1). The Bureau of Reclamation has the responsibility for management of this system, in coordination with the seven basin States, within a complex framework of law, regulations, compact, treaty, and policies often referred to collectively as the “Law of the River.” Lake Mead is a critical component of the overall Colorado River management, providing the capacity to store almost 2 years of the average runoff of the river.

Circular↗

USGS2012

Threats and stressors to the health of the ecosystems of Lakes Mead and Mohave: Chapter 6 in A synthesis of aquatic science for management of Lakes Mead and Mohave

Ecosystem impacts from visitor activities or natural environmental change are important concerns in all units of the National Park system. Possible impacts to aquatic ecosystems at Lake Mead National Recreation Area (LMNRA) are of particular concern because of the designation of Lakes Mead and Mohave as critical habitat for the federally listed endangered razorback sucker (Xyrauchen texanus), the significance of the sport fishery, and the regional importance of its habitats to more than 90 documented species of waterbirds. Potential threats to shoreline habitats are of concern not only for their ecosystem values but also for maintaining the recreational setting. Many areas adjacent to the shorelines of Lakes Mead and Mohave are designated wilderness areas. For purposes of this document, stressors are any chemical, biological, or physical agent that has a detrimental effect on aquatic ecosystems at the organism, population, or community level. Human-made stressors at Lakes Mead and Mohave include direct effects of recreation on the lakes, like boating and fishing, as well as indirect effects of activities away from the lakes, such as growing population and increasing urbanization. Common natural environmental stressors include extended changes in climate (precipitation or temperature), or the erosion, transport, and loading of chemical constituents in rocks and sediments to aquatic environments. Human activity also can exacerbate natural stressors in a variety of ways.

Circular↗

USGS2012

Management implications of the science: Chapter 7 in A synthesis of aquatic science for management of Lakes Mead and Mohave

Lake Mead, particularly its Boulder Basin, is one of the most intensively monitored reservoirs in the United States. With its importance to societal needs and ecosystem benefits, interest in water quality and water resources of Lake Mead will remain high. A number of agencies have authorities and management interests in Lake Mead and maintain individual agency monitoring programs. These programs were enhanced on an interagency basis from 2004 to 2012 to facilitate intensive monitoring in all major basins of the lake. Recognition that increasing stressors and influences in individual basins can affect water quality throughout Lake Mead and gave rise to an even stronger effort towards the development of holistic and effective interagency approaches. In 2010, agency monitoring programs were used to develop a management plan for water-dependent resources at Lake Mead National Recreation Area (LMNRA). The Long-Term Limnological and Aquatic Resource Monitoring and Research Plan for Lakes Mead and Mohave (the Plan; National Park Service, 2010) documented key management questions to be addressed through monitoring and research, and identified interagency strategic objectives for water quality and water-dependent resources. Moreover, the Plan provides a framework for summarizing water quality and water resource information in five resource categories: water quality and limnology; fish and aquatic biota; sediments; birds; and riparian vegetation. The Plan also addresses three stressors to lake resources: contaminants, invasive species, and climate change. For each of these topics, the current (2012) state of knowledge is summarized for LMNRA (table 7-1), including key scientific questions and findings, management implications, and information needs. A more detailed discussion for each topic follows.

Circular↗

USGS2010

Early invasion population structure of quagga mussel and associated benthic invertebrate community composition on soft sediment in a large reservoir

In 2007 an invasive dreissenid mussel species, Dreissena bugensis (quagga mussel), was discovered in Lake Mead reservoir (AZ–NV). Within 2 years, adult populations have spread throughout the lake and are not only colonizing hard substrates, but also establishing in soft sediments at depths ranging from 1 to >100 m. Dreissena bugensis size class and population density distribution differs between basins; cluster analysis revealed 5 adult cohorts within Boulder Basin and Overton Arm but low densities and low cohort survival in the Las Vegas Basin. Regression analysis suggests depth and temperature are not primary controllers of D. bugensis density in Lake Mead, indicating other factors such as sediment type, food availability or other resource competition may be important. Monthly veliger tows showed at least 2 major spawning events per year, with continuous presence of veligers in the water column. Adult mussels have been found in spawn or post-spawn condition in soft sediments in shallow to deep waters (>80 m) indicating the potential for reproduction at multiple depths. Comparisons to a 1986 benthic survey suggest there have been shifts in nondreissenid macroinvertebrate composition; however, it is unclear if this is due to D. bugensis presence. Current distribution of nondreissenid macroinvertebrates is heterogeneous in all 3 basins, and their biodiversity decreased when D. bugensis density was 2500/m 2 or greater.

Nevada;Arizona↗