Document Type

Technical Report

Publication Date



Several limnological studies have been conducted in Lake Mead during the past decade. The recent studies clearly show that most of Lake Mead is deficient in nutrients, especially phosphorus, and very low in productivity. The reservoir-wide average total phosphorus concentration for 1981 - 1982 was only 9 mg/m3. This is below levels found In most oligotrophic lakes and reservoirs. Algal biomass, as measured by chlorophyll-a, averaged only 1.5 mg/m3. That also places Lake Mead in the oligotrophic range. Transparency, as measured by a Secchi disc, averaged 9-5 m in Lake Mead during 1981-1982. That far exceeds levels found in most oligotrophic lakes and reservoirs. Lake Mead is oligotrophic based on every trophic state criteria used to classify lakes and reservoirs.

The phosphorus deficiency in Lake Mead began to develop in 1963 when Glen Canyon Dam was formed 286 miles upstream. As that reservoir slowly filled, it cut off the phosphorus supply in the Colorado River inflow to Lake Mead. Algal productivity in the upper basin of Lake Mead decreased considerably after 1963. Phosphorus concentrations and productivity in Virgin Basin have been extremely low since monitoring began in 1977. The Overton Arm, upstream of Fish Island, and Iceberg Canyon/Grand Wash are the only areas left in the upper basin where phosphorus levels are sufficient to sustain higher productivity... Artificial fertilization is the only way that nutrient levels can be restored in the upper basin of Lake Mead.


Chlorophyll; Colorado River (Colo.-Mexico); Effluent quality; Freshwater fishes; Lake Mead (Ariz.-Nev.); Las Vegas Bay (Nev.); Limnology; Phosphorus; Phytoplankton; Water reclamation; Water temperature; Zooplankton


Aquaculture and Fisheries | Desert Ecology | Environmental Chemistry | Environmental Health and Protection | Environmental Indicators and Impact Assessment | Environmental Monitoring | Fresh Water Studies | Natural Resource Economics | Natural Resources and Conservation | Sustainability | Terrestrial and Aquatic Ecology | Water Resource Management




From the Lake Mead Limnological Research Center, University of Nevada, Las Vegas.