In the framework of an experimental study on the influence of in- and outflow sequences on flow patterns and suspended sediment behavior in reservoirs, flow fields and inflowing jet were sampled by Ultrasonic Velocity Profilers (UVP). The laboratory set-up consisted of two interconnected rectangular basins between which water was moved back and forth. A parametric study was performed on the magnitude and the frequency of in- and outflow cycles. Jet centerline velocities during inflow sequences were measured by UVP transducers with sampling frequencies of 0.5 and 1.0 MHz. Results were compared to jet behavior given in literature and used to calibrate a numerical model. Then, the main basin was equipped with seventeen 2 MHz UVP transducers to measure horizontal 2D velocity fields at several levels inside the test volume. Such, flow patterns during in- and outflow sequences were monitored, allowing the detection of three-dimensional flow behavior and the estimation of the mean kinetic energy in the test volume.