Tailings ponds evaporation: in situ vs theoretical calculations

Large man-made bodies of water at mining sites such as tailings ponds are designed for water to evaporate. Exposure to the greatest tool for evaporation – the sun – means water level changes require water balance tracking due to precipitation and evaporation. 

The conventional monitoring method using evaporation pans takes a good deal of work and has drawbacks. For instance, metal sides of the pan are much warmer than the sides of an earthen dam. Being in situ presents a host of issues, spanning possible interference from curious wildlife to freezing temperatures. The pans also require hands-on maintenance.

There is another way. Just three pieces of meteorological data (solar radiation, relative humidity, and temperature) processed mathematically can provide a theoretical evaporation that is every bit as useful and certainly a lot simpler to obtain. This method is based on Valiantzas’ work published in 2006, which tested the performance of a newly derived simplified Penman evaporation equation to estimate potential evaporation from open-water bodies.

Crunching data and automating reporting are places where Air Sciences excels. We have created a web-accessible data display (hosted by our partners, eagle.io) for clients to view (and download as a .CSV file) the past 60 days of National Oceanic and Atmospheric Administration (NOAA) meteorological data at select stations. Daily and monthly averages of meteorological data and calculated theoretical evaporation rates (using the simplified Penman equation 33 developed in the Valiantzas’ paper) are served up for the user. 


Examples of how data are presented on the Air Sciences dashboard for the Denver area.


Visit the links below to explore the dashboard for sites in Colorado, Nevada, and Washington:

Further reading:

Valiantzas, J. D. 2006. “Simplified Versions for the Penman Evaporation Equation Using Routine Weather Data.” Journal of Hydrology, no. 331: 690–702. https://doi.org/10.1016/j.jhydrol.2006.06.012.

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