The ETgage is a simple evaporation device that simulates crop reference ET. It is a modified atmometer where the ceramic evaporating cup is covered with a green canvas/wafer to simulate crop albedo and vapor diffusion resistance. This instrument has been used since 1984 in a variety of field studies and for operational irrigation scheduling and water management.

The Colorado Climate Center has been using the ETgage now for several years. Comparisons with weather-data based reference ET estimations and from Class A pan evaporation data show fairly high correlations on a daily basis and better relationships when accumulated over consecutive days. Based on these findings and the growing popularity of this instrument within the irrigated agricultural community, the Community

Collaborative Rain, Hail and Snow Network (CoCoRaHS), www.cocorahs.org, began a pilot project in 2011. ETgages have been installed alongside CoCoRaHS rain gauges at several stations in Colorado and in other states. Results will be presented including new water balance reports and graphics that will be available through CoCoRaHS. The ETgage is a simple hands-on measurement that demonstrates the water balance in action. It is proving to be an ideal complementary measurement to enhance both the educational capabilities and the data resources provided by CoCoRaHS.