Near Buckeye, Arizona, five evapotranspirometers were installed in the fall of 1962. Water losses were measured from these tanks, two of which were planted to salt cedar and the other three kept bare. Rates of water loss from vegetated tanks plotted against time show a diurnal wave wih a maximum loss in the early afternoon of hot summer days. The losses from bare tanks so plotted show two maximums. The rate drops sharply during the middle of the day. Harmonic analysis reveals that the second harmonics of both curves are nearly identical in amplitude and phase angle. Later in the season the second harmonic of the vegetated tanks disappears. Certain unexplained anomalies remain in the analyzed data. (Key words: Evapotranspiration; soil moisture; lysimeters.)