Assess Evaporation Performance of SolarBee Pond Circulator
The proposed project addresses one of the problems associated with the use of evaporation ponds in irrigation drainage and desalination projects; i.e., how to reduce the size and environmental impacts of the pond system. The need for a cost-effective solution to this problem is particularly acute as it applies to inland desalination projects, where evaporation ponds are becoming the only available option for concentrate disposal. Disposal to underground aquifers via deep well injection and/or to surface waters is now banned in some areas of the Western United States and prohibitively expensive in other areas.
Need and Benefit
The proposed investigation will test and evaluate the capability of the SolarBee Model SB5000-EV Pond Circulator, manufactured by Pump Systems, Inc., to enhance evaporation from the surface of brine ponds containing irrigation return flow at salinity levels ranging up to 45,000 milligrams per liter (mg/L) total dissolved solids (TDS). The SolarBee Model SB5000-EV is a floating, solar-powered water circulation machine that draws water from the lower depths of the pond to the surface and spreads it gently across the top of the pond in a near-laminar flow manner. The unit provides a direct flow of approximately 500 gallons per minute (gpm) and a total flow of about 3,000 gpm, while operating off a 1/8-horsepower pump. In addition to enhanced evaporation, this high rate of flow and flow mixing action accelerates the biological process to help minimize problems associated with algae blooms, low dissolved oxygen, and excessive shoreline vegetation.
The proposed tests will be conducted at Reclamation's evaporation test facility located next to the Salton Sea at the Old Navy Test Base in Imperial County, California. The test program will make use of the two 5-acre ponds at the site, each lined with 40-mil HDPE geomembrane. These two ponds are separated by a central dike and a valved-off culvert at one end of the dike which can be used for hydraulic control between the two ponds. The necessary utilities (plumbing and electrical grid connections, etc.) are also already in place at the Test Base.
The tests will be conducted using two SolarBee circulators, with one of the units installed in Pond 1 and the other installed in Pond 2. The test program will consist of three 30-day tests, during which time circulator operation will alternate between the two units with each unit operated continously 24-hours a day for 15 days at a time. The units will operate off the electric grid at night and during periods of low insolation.
Weather data will be collected continuously throughout the test period using a 150-ft meterological tower located onsite and a small, portable 10-ft tower, each of which will be equipped to measure ambient temperature (dry bulb and dew point), relative humidity, and wind speed and direction. The 150-foot tower has a complete set of instrumentation mounted at each of three elevations-at 10, 50, and 150 feet. The evaporation rates will be measured using two evaporation pans-one filled with fresh water and the other with water from the test ponds. The data will be collected every minute and averaged over a 15-minute period before being recorded on a data logger from which it can be downloaded onto a laptop computer.
Another potential benefit of this project is that, by learning more about the SolarBee and the way it works to enhance evaporation, it may be possible to use the test data to "reverse engineer" the process to develop practical and cost effective techniques that can be used to suppress surface evaporation and reduce water losses from our lakes and reservoirs.
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