The Next Generation of Evaporation Pans Agreement R17AC00074 Modification 004 and 005

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The agreement is improving our understanding of evaporative losses from reservoirs, which are not well understood due to climate conditions, size and shape of the reservoir, and reservoir operations. The scope change is to better characterize the water budget of the Elephant Butte Reservoir and Zuni Salt Lake located in Catron County, New Mexico. Project activities will include deployment of a Collison Floating Evaporation Pan (CFEP) to compare evaporation losses using a new evaporation rate monitoring technique for measuring open-water evaporation rates. Project activities will support the accurate tracking of open-water evaporative losses, one of the largest consumptives uses of water in the Southwestern United States, and provide information needed by Zuni Pueblo for more reliable water management and decision-making, especially in times of prolonged drought and climatological uncertainty. The CFEP’s evaporation measurements will be compared with various standard methods (including the Class A Pan) which have been shown to have the potential to underestimate evaporation during previous studies. The evaporation data will also be used to calibrate the hydrologic model that is being developed by the U.S. Geological Survey in support of the water rights settlement. This project is in alignment with other Reclamation-funded deployments of the CFEP at Lake Powell, Elephant Butte and Caballo Reservoirs, and additional research that is planned involving the CFEP.

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