Development of a gridded reference evapotranspiration dataset for the Great Lakes region Journal of Hydrology: Regional Studies

Study region: Great Lakes region of North America Study focus: Reference Evapotranspiration (ETo) is a key variable in water use management and irrigation of agricultural crops. This study describes the development of a gridded historical ETo dataset for the period 1983-2012 derived from North American Data Assimilation System Phase 2 (NLDAS-2) forcing fields for the Great Lakes region of North America. The gridded dataset is intended to fill a gap in the resource toolbox available to growers in this region of rapidly expanding irrigation. As a prerequisite for development of the ETo dataset, a correction procedure is applied to the NLDAS-2 downward solar radiation to account for overall bias and a tendency to underestimate the range of solar radiation on hourly and daily timescales. New hydrological insights: Analyses of spatial and temporal variability reveal that the lakes play an important role in modulating seasonal and geographical variability in evaporative demand. An example application of the gridded historical ETo dataset to irrigation management is provided. A 30-year climatology of crop irrigation for field maize is developed from the ETo dataset and is applied in a hypothetical irrigation-scheduling scenario. Overall, the study illustrates the utility of the NLDAS-2 ETo dataset in describing spatial and temporal patterns of evaporative demand across the Great Lakes region, and as a source of reference climatological information for irrigation management. Grant no. NA10OAR4310213 Grant no. NA15OAR4310148