CoCoRaHS: Volunteer Observers Taking Reference Evapotranspiration Measurements During 2012

During 2010-11 the Colorado Climate Center tested a low-cost instrument that was developed several years ago in Colorado that approximates the water use by grass and alfalfa. The instrument, known as an ETgage, was tested alongside a standard Class A Pan and also a complete weather station established for computing reference evapotranspiration (ETo) from the standardized ASCE equations.

As a result of favorable test results, the Community Collaborative Rain, Hail and Snow network (CoCoRaHS) has begun to incorporate reference ET measurements. With support from the National Science Foundation and NOAA, CoCoRaHS began a pilot project in several states in 2011 to place ETgages at selected locations. Extensive training materials for the public were developed during this time. CoCoRaHS opened ETo observing to members of it's 15,000 volunteer rain gauge community in May of 2012. In order to participate, volunteers needed to be highly motived and have an 'ideal' location … open exposures with surrounding vegetation that is representative for their area. More than 200 applications were received and over eighty stations in thirty states have begun collecting ETo data.

Our presentation will look at this growing network of reference ET measurements. Examples of time series and spatial patterns of ETo from volunteer stations will be shown. Finally, future plans will be suggested as we aim to help provide practical and affordable water balance data for the nation