One of the most remarkable features of both the Ocotillo Golf Course and the Ocotillo Community Association is the lake system. This lake system, which is comprised of 167 acres of interconnected lakes and water features, exclusively uses reclaimed and reprocessed City of Chandler wastewater, better known as effluent.
The developer of the Ocotillo lakes takes great pride in that both the golf course and the Community Association, through a series of dedicated pumps and mainlines, use the reclaimed water from these lakes for irrigation of the lush grass, plants and trees that Ocotillo residents and golfers from all over the world have enjoyed since Ocotillo's inception in 1986. Consequently, Arizona's precious groundwater is being preserved.
The Ocotillo lakes are balanced biologically, through the use of specific breeds of fish, such as tilapia, grass carp (White Amur), small mouth bass, catfish, bluegills, and goldfish. These fish are self-sustaining and require little to no outside assistance. The only fish that require regular stocking is the grass carp. Due to their rapid reproductive rate, the State requires that this type of fish be genetically altered so as not to overwhelm the lake and canal systems with their capacity for over breeding. All other fish thrive on the grass and plant materials that are found in any freshwater lake. Tilapia, normally an aggressive breeder, tend to die off in colder weather, usually when the ambient lake temperature drops below 70 degrees Fahrenheit. This typically occurs from mid-December through February. These fish keep the lakes free of debris and are an excellent food source for all manner of aquatic fowl, from the small black coot to the large blue heron. In addition, Ocotillo also enjoys ducks, geese, sandpipers, tern and an occasional pelican.
The Ocotillo Community Association continually monitors the lakes, common areas, and more than 17 miles of shoreline as well as maintains the sophisticated pumping system which is used to supply effluent to the common areas and the individual residences at Ocotillo. The Ocotillo Community Association contracts the maintenance of the lake system, to Aquatic Consulting, Inc. The golf course is privately owned and maintained. The golf course is a proud member of the PGA sanctioned Audubon Society of New York. For additional information on The Ocotillo Golf Resort visit their website at www.ocotillogolf.com
The
Ocotillo Lake System
by Frederick A. Amalfi, Ph.D., Aquatic Consulting &
Testing, Inc.
Q. What causes the green appearance of our lakes?
A. The presence of suspended or dissolved materials in the water causes a change in color. The green color is a result of microscopic plants called algae. Algae contain the green pigment chlorophyll, which absorbs and converts sunlight into energy. The algae may be single cells, filaments (chains of cells), or colonies (groups of cells). The algae cells are typically in the range of 5 to 200 microns (that is 2/10,000th to 8/1000th of an inch). When the chains continue to grow, they can form mats which of- ten float to the surface of the water.
Q. Where does the algae come from?
A. Most algae are carried into the lakes by wind blown soil. Birds and ducks can also transfer algae from one lake to another.
Q. What makes the algae grow?
A. Algae are plants. Like all plants, they require sunlight, carbon dioxide, and nutrients.
Q. It is obvious where the sunlight comes from, but where does carbon dioxide come from?
A. When animals breathe (respire), they take in oxygen and expel carbon dioxide. Fish and other aquatic animals also respire and discharge carbon dioxide into the water where it can be taken up by the algae cells.
Q. Where do the nutrients come from?
A. Nutrients can enter a lake from wind blown soil, storm water runoff, and the source water. It can also be recycled from the sediment at the bottom of the lake. At Ocotillo, most of the nutrients come from the reclaimed wastewater that is used to fill the lakes. Treated wastewater is usually very high in nitrogen and phosphorus, the major plant nutrients. This causes algae to flourish during the summer. During the winter, when plant growth is slowed by cold temperatures and reduced periods of sunlight, algae growth is often reduced and improved water clarity is observed.
Q. Is there any way we can reduce the nutrient levels in the reclaimed water?
A. Yes, but the treatment plant was not designed to remove nutrients, and it is extremely expensive to convert the equipment. Facilities and operations to remove only a portion of the nutrients would cost hundreds of thousands of dollars per year. Removing nutrients to a level that would inhibit algae growth could cost millions per year.
Q. Why would they design a wastewater treatment plant without nutrient removal capability?
A. First, it costs too much. Second, the nitrogen and phosphorus is beneficial when the lake water is used to irrigate common areas and golf courses. The water reduces the fertilizer requirements for the lawns, trees, and shrubs and saves money.
Q. Is there any way the lake water can be treated to reduce the amount of algae?
A.
Yes, there are a number of algae control techniques. The applicability of each
technique depends on the water chemistry, biology, and physical attributes of
the lake to be treated. Not every method is successful in every lake system.
Several techniques are listed below. Some of these, like aeration/circulation a
chemical treatment will be discussed in detail in future articles.|
ALGAE
MANAGEMENT
►Chemical treatment with algaecides
Kills algae cells and temporarily reduces the density of algae in
the lake.
►Fertilizer
restriction for areas near the lake
Reduces nitrogen and phosphorus quantities in storm water runoff that flows into
the lakes.
►Addition of alum
Combines with phosphorus and removes it from the water column
(usually only effective in lakes
much deeper than those at Ocotillo).
►Addition
of lime
Combines with suspended particulates and algae and causes them to sink to the
bottom of lakes
(usually only effective in lakes much deeper than those at
Ocotillo and with different water
chemistry).
►Addition of liquid dyes
Reduces light penetration into the water and slows algae growth.
Reduces light penetration into the water and slows algae growth.
►Artificial aeration/circulation
Stops recycling of nutrients from the lake sediments.
►Stocking with algae-eating fish
Installing aquascapes, biofilters, or nutripods - absorb nutrients by permanent
or removable
vegetation and thus make fewer nutrients available to algae.
►Adding coagulants
Physically combines with the algae and cause it to sink to the lake bottom.
►Bio-manipulation
Enhancing natural predators of algae such as small crustaceans.
Q. Are any of these techniques being used at Ocotillo?
A. Yes. Fertilizer restrictions, artificial circulation/aeration, stocking with algae-eating fish, and aquascapes are all algae control techniques currently used at Ocotillo. Bio-manipulation using zooplankton, although not introduced or enhanced artificially, is used to assist in reducing algae cells in the water column. Management is collecting chemical and biological data to better understand how these lakes work and to determine the actual levels of nutrients and algae in the lakes. This information will be used to identify additional or improved algae control strategies that are applicable specifically to these lakes and which have a good chance of being successful.
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