Two major impoundments at Lake Mead National Recreation Area have been providing  recreation, hydroelectric power and  water for millions of residents of the desert Southwest for decades. A recent study offers a report card on the health of the park's all-important aquatic resources, and although the news is generally promising, there are some caveats.

According to a park spokesperson the study found that "Lake Mead National Recreation Area's water quality is good, the sport fish populations are sufficient, and the lakes provide important habitat for an increasing number of birds."

The park actually includes two separate impoundments on the Colorado River'”Lake Mead and Lake Mohave'”and together they attract about 8 million visitors a year. That's a lot of boaters, fishermen, swimmers and campers, and there's no question all that water in the midst of a very arid landscape is a major recreational resource.

The lakes also provide important aquatic habitat for a wide variety of wildlife, including endangered species. For example, Lake Mead contains one of the few populations of the razorback sucker in the Colorado River Basin and the only known population of a regional endemic species, the relict leopard frog (R. [L.] onca).

 Two Big Lakes with Major Impacts on the West

That said, the park's waters play a much bigger role in life in the West than a place for fun in the sun. A summary of the report notes, "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."

There's clearly plenty at stake for economic and environmental interests when it comes to both the quality and quantity of the water at Lake Mead NRA, so a number of groups should be interested in the findings of the recent study.

Good News on Several Fronts

"While the Lake Mead ecosystem is generally healthy and robust, the minor problems documented in the report are all being addressed by the appropriate agencies, and are showing substantial improvement since the mid 1990's," said U.S. Geological Survey hydrologist, Michael Rosen, the lead scientist for the report.

"This is thanks to proactive enhancements to wastewater treatment facilities for the Las Vegas Metropolitan area, the installation of wetlands in Las Vegas Wash, and the treatment of legacy pollutants from industrial areas near Las Vegas Wash," Rosen continued.

As illustrated by the last statement, the report offers a bit of interesting terminology, and some good news, when it comes to problems posed by both old ("legacy") and new ("emerging") sources of pollution from upstream development.

"Legacy contaminants are declining due to regulations and mitigation efforts in Las Vegas Wash. Emerging contaminants, including endocrine-disrupting compounds, are present in low concentrations. While emerging contaminants, such as pharmaceuticals, personal care products, or plasticizers have been documented to cause a number of health effects to individual fish, they are not seen at concentrations currently known to pose a threat to human health. In comparison to other reservoirs studied by the U.S. Environmental Protection Agency, Lake Mead is well within the highest or 'good' category for recreation and aquatic health."

Other Highlights from the Report

Other key findings in the report included the following:

"Basic water-quality parameters are within good ranges of Nevada and Arizona standards and EPA lake criteria." (In this case, "good" is just fine. That's the highest of three categories assigned by the EPA for these criteria.) "Potential problems with nutrient balance, algae, and dissolved oxygen can occur at times and in some areas of Lake Mead. The Lake Mead-wide scope of monitoring provides a solid baseline to characterize water quality now and in the future."

Scientist holding Razorback sucker fish caught and to be released during survey of populations in Lake Mead. NPS photo.

"Lake Mead and Lake Mohave continue to provide habitat conditions that support a rich diversity of species within the water, along shorelines, and in adjacent drainage areas, including organisms that are both native and non-native to the Colorado River drainage."

"Sport fish populations appear stable and have reached a balance with reservoir operations over the past 20 years and are sufficient to support important recreational fishing opportunities. Native fish populations within Lake Mohave are declining, but the small native fish populations in Lake Mead are stable without any artificial replenishment."

"Lake Mead and Lake Mohave provide important migration and wintering habitat for birds. Trends include increasing numbers of wintering bald eagles and nesting peregrine falcons. Lake Mead water level fluctuations have produced a variety of shorebird habitats, but songbird habitats are limited. Although some contaminants have been documented in birds and eggs in Las Vegas Wash, mitigation efforts are making a positive change."

Two Lingering Issues

There were, however, a couple of cautionary findings as well, and they involve two key issues with no easy solutions: quagga mussels and long-term drought.

"Invasive quagga mussels have become the dominant lake-bottom organism and are a significant threat to the ecosystems of Lake Mead and Lake Mohave because they have potential '¨to alter water quality and food-web dynamics. "

"Climate models developed for the Colorado River watershed indicate a high probability for longer periods of reduced snowpack and therefore water availability for the Lake Mead in the future. Federal, state and local agencies, and individuals and organizations interested the future of the water supply and demand imbalance are working together to examine strategies to mitigate future conditions."

The report was prepared cooperatively by the U.S. Geological Survey, National Park Service, U.S. Fish and Wildlife Service, Bureau of Reclamation, Nevada Department of Wildlife, Southern Nevada Water Authority, BIO-WEST, University of Nevada, Reno, and University of Nevada, Las Vegas. It you'd like to see a copy of the full report, USGS Circular 1381, "A synthesis of aquatic science for management of Lakes Mead and Mohave," it's available online at this link.