A microwave resonator water-cut sensor system comprising: a helical T-resonator comprising: a feed line comprising a conductive material extending in a circumferential direction about an external surface of a cylindrical pipe; and a helical open shunt stub comprising a conductive material extending from the feed line in a spiral pattern along the external surface of the cylindrical pipe, the helical open shunt stub being conductively coupled to the feed line; a helical ground conductor comprising: a ground ring comprising a conductive material extending in a circumferential direction about the external surface of the cylindrical pipe, the feed line overlapping at least a portion of the ground ring; and a helical ground plane comprising a conductive material extending from the ground ring in a spiral pattern along the external surface of the cylindrical pipe, the helical ground plane being located opposite the helical open shunt stub, and the helical ground plane being conductively coupled to the ground ring; and a separator disposed between the overlapping portions of the feed line and the ground ring, the separator being configured to electrically isolate the feed line from the ground ring to electrically isolate the helical T-resonator from the helical ground conductor, wherein the helical T-resonator comprises: an input terminal located at a first end of the feed line, wherein the input terminal is configured to receive source signals from an external circuit; and an output terminal located at a second end of the feed line, wherein the output terminal is configured to provide for sensing, by an external circuit, of response signals corresponding to the source signals, and wherein a resonant frequency of the resonator water-cut sensor is determined based on the source signals and the response signals, and a water-cut of fluid in the cylindrical pipe is determined based on the resonant frequency of the microwave resonator water-cut sensor. a helical T-resonator comprising: a feed line comprising a conductive material extending in a circumferential direction about an external surface of a cylindrical pipe; and a helical open shunt stub comprising a conductive material extending from the feed line in a spiral pattern along the external surface of the cylindrical pipe, the helical open shunt stub being conductively coupled to the feed line; a feed line comprising a conductive material extending in a circumferential direction about an external surface of a cylindrical pipe; and a helical open shunt stub comprising a conductive material extending from the feed line in a spiral pattern along the external surface of the cylindrical pipe, the helical open shunt stub being conductively coupled to the feed line; a helical ground conductor comprising: a ground ring comprising a conductive material extending in a circumferential direction about the external surface of the cylindrical pipe, the feed line overlapping at least a portion of the ground ring; and a helical ground plane comprising a conductive material extending from the ground ring in a spiral pattern along the external surface of the cylindrical pipe, the helical ground plane being located opposite the helical open shunt stub, and the helical ground plane being conductively coupled to the ground ring; and a ground ring comprising a conductive material extending in a circumferential direction about the external surface of the cylindrical pipe, the feed line overlapping at least a portion of the ground ring; and a helical ground plane comprising a conductive material extending from the ground ring in a spiral pattern along the external surface of the cylindrical pipe, the helical ground plane being located opposite the helical open shunt stub, and the helical ground plane being conductively coupled to the ground ring; and a separator disposed between the overlapping portions of the feed line and the ground ring, the separator being configured to electrically isolate the feed line from the ground ring to electrically isolate the helical T-resonator from the helical ground conductor, wherein the helical T-resonator comprises: an input terminal located at a first end of the feed line, wherein the input terminal is configured to receive source signals from an external circuit; and an output terminal located at a second end of the feed line, wherein the output terminal is configured to provide for sensing, by an external circuit, of response signals corresponding to the source signals, and wherein a resonant frequency of the resonator water-cut sensor is determined based on the source signals and the response signals, and a water-cut of fluid in the cylindrical pipe is determined based on the resonant frequency of the microwave resonator water-cut sensor. an input terminal located at a first end of the feed line, wherein the input terminal is configured to receive source signals from an external circuit; and an output terminal located at a second end of the feed line, wherein the output terminal is configured to provide for sensing, by an external circuit, of response signals corresponding to the source signals, and wherein a resonant frequency of the resonator water-cut sensor is determined based on the source signals and the response signals, and a water-cut of fluid in the cylindrical pipe is determined based on the resonant frequency of the microwave resonator water-cut sensor.