Cal Poly Evaporation Study Demonstrates Water Savings

A study conducted at the Cal Poly National Pool Industry Research Center (NPIRC) found that considerable water savings could be realized if outdoor swimming pools were covered by market-available covers.

Use of pool covers could reduce 95 percent of evaporation from California pools, saving more than 55,000 acre-feet of water per year — enough to supply a city of approximately 500,000, said principal investigator Misgana Muleta, an associate professor in Cal Poly’s Civil & Environmental Engineering Department.

The study was sponsored by the National Plasterers Council (NPC), the California Pool and Spa Association, the Association of Pool and Spa Professionals, and the Independent Pool and Spa Service Association. 

“Given the severity of drought in California, this potential water saving is substantial,” said Alan Smith, chair of NPC’s Research Committee. 

The study involved taking daily water-level measurements and weekly water-chemistry readings for eight pools at the NPIRC for 90 days, starting in July. Climate data included air temperature, wind speed and rainfall collected at a Cal Poly weather station. 

Several companies and associations donated funds, supplies and equipment needed to conduct the 90-day protocol.  

The study can be downloaded at along with a full description of the protocol, objectives, timeline, and donors.

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Photo: Civil Engineering Professor Misgana Muleta (right) and graduate student research assistant Ernesto Jimenez.


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