The aim of this thesis was to design, construct and test a horizontal ground water flow (velocity and direction) measurement probe prototype to support the efforts of the research project “GeoWSP” in (1) monitoring and optimizing the performance of the underground thermal energy storage (UTES) facility under development, and in (2) long-term monitoring of the groundwater flow conditions in the vicinity of the UTES to identify any induced alterations. Other possible applications include, for instance, flow measurement and modeling for groundwater resources management and protection. Firstly, a review of the mathematical and physical fundamentals of groundwater flow in a near wellbore region and state-of-the-art measurement techniques was performed. Based on the findings and the requirements set, a measurement concept was defined and the pertinent background information was described. The measurement system was designed and built to conduct measurements in a single wellbore on a thermal basis without introducing any foreign tracer substances into the groundwater, or significantly altering the local natural flow conditions. To test the measurement system, a full-scale test stand representing the groundwater flow in an unconsolidated permeable rock was constructed. Tests were then carried out under controlled conditions to determine the measurement range, accuracy, and repeatability at various flow rates in two screened observation wells measuring approximately 3 inch and 5 inch. Underlying assumptions and simplifications as well as a critical discussion of the limitations of the system are reported in the text.