The work presented here is aimed at investigating the effect of the terrain roughness on the behavior of aircraft wake vortices. The tests are conducted in the water tunnel with a smooth ground plane first. Then, streamwise ridges are added to the ground in order to simulate terrain roughness. In addition, a case is presented without the ground plane. This latter data, showing the behavior of the vortices in the absence of any ground, provides a basis for comparison as well as allowing calculation of the wake vortex strengths. The experimental data shows temporal and spatial behavior of the vortices. In the cases without a ground plane and with a smooth ground plane, the water tunnel measurements are consistent with information in the literature. With the information garnered from these tests, the authors are able to quantify the effect of ground roughness on wake vortex behavior.