ABSTRACT: Sinusoidal natural phenomena are frequent in nature, such as changes in daily and seasonal air temperature. Periodic temperature change is transmitted to the environment and the degree of transition is influenced by existing soil environment temperature parameters which can be calculated by amplitude dampening and phase shift of sinusoid signal. The least square method is the most appropriate for precise evaluation of sinusoid parameters because it enables exact data fitting, so we used this method on Sihoť Island where Slovak Bratislavan water resources are located. The Danube River has created harmonic boundary conditions, and so groundwater temperature measurements at adjacent observation wells can determine temperature diffusivity and heat transport velocity. The temperature diffusivity value was calculated at approximately 60 m2·day–1 and transport velocity at approximately 1 m·day–1. These results agree with Stauffer et al´s. (2014) findings at a similar locality on the Rhine River near Zürich in Switzerland.