This data is from a grape crop at Lodi, California. The actual crop water use is low (0-2 mm/day), but the ET0 from the CIMIS model (LODIET0.DWU) is predicting that the crop should be using 10-12 mm/day.
The reason for the discrepancy, in this case, is that the soil became water repellent. The irrigation water was from snow-melt, was not retained. by the soil but poured through the profile. It was only by taking soil moisture measurements was the problem recognised.
CIMIS is a weather monitoring service in California that supplies crop water use predictions. It is considered to be one of the most reliable systems, with numerous weather stations located throughout California.