Water Quality and Limnology

Long-term Limnological and Aquatic Resource Monitoring for Lakes Mead and Mohave Category 1:

 
Water Sampling
Water sampling at Lake Mead’s James Bay.


The roles of Lakes Mead and Mohave in meeting community and regional needs for drinking water, recreation, and wildlife habitat underscore the vital importance of maintaining exceptional water quality.

Lake Mead provides drinking water for more than 25 million people and first-rate water-based recreation for more than eight million people each year, including an average of 250,240 annual angler use days1 of recreational sport fishing. The lakes provide additional critical habitat for the federally listed endangered razorback sucker as well as key habitats along the Pacific flyway for shorebirds and other waterfowl. Lake Mead, with a surface area of 157,900 acres (at full pool) and a 29-million-acre-ft storage capacity, is the largest reservoir in North America. Lake Mohave with 26,500 acres of surface area provides re-regulation of Hoover Dam releases to insure consistent volume to meet downstream delivery.

Major indicators of water quality include clarity, pH, specific conductance, temperature, bromide, dissolved oxygen, total organic carbon (TOC), chlorophyll-a, and inorganic nutrients. Each of these and 29 other parameters are monitored at 53 sites across Lake Mead: 26 stations in Lake Mead's Boulder Basin are monitored on a weekly basis and an additional 27 sites (dependent on lake level) throughout Lake Mead are monitored on a monthly to quarterly basis. The Safe Drinking Water Act and other regulatory systems and laws set standards for water quality. The Southern Nevada Water Authority, U.S. Bureau of Reclamation, and water reclamation districts (i.e., Clark County, City of Las Vegas, and City of Henderson) conduct the monitoring activities. Automated U.S. Geological Survey stations also continuously monitor water quality, and additional measurements are taken at different intervals by researchers working on specific projects at other locations on the lakes. In Lake Mohave, there are five monitoring sites, which are monitored for constituents of water quality by the U.S. Bureau of Reclamation's Lower Colorado River Region as part of its quagga mussel veliger-monitoring program.

 
Lake Mead water quality map
Lake Mead water quality map

View Lake Mead Map

 
Lake Mohave water quality map
Lake Mohave water quality map

View Lake Mohave Map

 

Lake Mead's Boulder Basin

 
U.S. Bureau of Reclamation water sampling in Las Vegas Wash
U.S. Bureau of Reclamation water sampling in Las Vegas Wash

Photo by Larry Paulson

Boulder Basin, which receives urban inflows from the Las Vegas Wash and as the basin from which drinking water is drawn, is a focal point of interest for water quality. Downstream users of the Colorado River also have a great interest in the overall water quality released from Boulder Basin through Hoover Dam. For these reasons, Boulder Basin is the most extensively studied portion of Lake Mead.

 

Strategic fundamental objectives for this category:

• A healthy sportfishery

• Healthy populations of native fish

• Healthy populations of aquatic dependent wildlife

• Healthy shoreline dependent native vegetation

• Existing high quality setting for water-based recreation

• Regional and community needs for municipal and industrial uses, including domestic water supply and Colorado River System return flow credits

Management questions best answered by monitoring:

• What are the status and trends of physical and chemical water quality parameters (e.g., conductivity, dissolved oxygen, nutrients, temperature, transparency, pH, and water levels)? more

• What are the status and trends of biological water quality parameters (e.g., plankton and chlorophyll-a)? more

• What are the status and trends of contaminants in the water column [e.g., disinfection byproduct precursors, volatile organic compounds (VOCs), radionuclides, priority pollutants (EPA and State), and pathogens]?

Management questions best answered by research:

• What are the relationships between any changes in wastewater management, tributary inflows, and climate and impacts to water quality parameters, drinking water, fish, aquatic dependent wildlife, and recreation?

• How does water column stratification affect the position or distribution of tributary inflows?

• What are the mass transport and internal cycling budgets for contaminants and nutrients?

• What is the impact of changes in operations at Glen Canyon Dam and Hoover Dam on water quality?

 

References

1. (Nevada Department of Wildlife 2004 – 2008 data)

 

Last updated: March 30, 2016

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