Abstract: A sensor arrangement for identifying various states of water on a surface of a structure, comprises a sensor element and a transmitter-receiver unit. The sensor element, adapted to be placed on the surface, has two ends and is made of an acoustically conductive material. The transmitter-receiver unit is connected between the two ends of the sensor element. The transmitter-receiver unit alternately transmits acoustic signals to each of the two ends and receives acoustic signals corresponding to the transmitted signals from each of the two ends for subsequent processing.