Algae in Lake Mead
|In 2001, a unique combination of hydrologic
factors caused the large algae bloom at Lake Mead (photo left). The
photo at right depicts the lake with its normal water color.
Algae is common in most bodies of both fresh and
salt water. The widespread bloom of the green algae species (Pyramichlamys)
seen in bays and coves at Lake Mead in 2001 was a highly unusual event
caused by a unique combination of hydrologic factors.
This particular species of green algae is most likely
to bloom when a sequence of warm and cold temperature changes occurs over
a short period of time and when there is phosphorus and nitrogen available
on the lake's surface.
Although it reduces the
clarity of the water, green algae poses no threat to Southern Nevada's
water quality. The algae bloom occurs only near the surface of the lake,
approximately 100 feet higher than the intake pipes that draw drinking
water. Additionally, this species of algae is not toxic and could be removed
from the water during the treatment process. Algae growing in Boulder
Basin or any other body of water is a normal event, and is in fact beneficial
to aquatic life. Additionally, the algae is not considered a recreational
Sources of phosphorus in the lake include wildlife, treated
wastewater and urban runoff. While the valley's wastewater treatment agencies
are voluntarily reducing the amount of phosphorus reaching the Las Vegas
Wash, residents can further reduce the amount of phosphorus available
for algal growth by correcting lawn care practices.
The combination of over fertilizing and subsequently overwatering
lawns results in concentrated phosphorus flows entering the lake through
urban runoff. The SNWA recommends residents apply the proper amount of
fertilizer as indicated on the package and follow the SNWA's lawn watering