Abstract: The water temperature of rivers, lakes, reservoirs, and other inland water bodies plays a crucial role in the growth of aquatic organisms and the surrounding ecological environment. The development of a water temperature observation system serves as the basis for theoretical research and engineering applications. Current surface water temperature measurement in inland waters mainly relies on manual visual observation using thermometers or automatic observation with hydrological station instruments. However, these methods have limitations such as equipment operation and maintenance difficulties, as well as discontinuous monitoring data when applied in high-frequency or non-fixed hydrological observations. To improve the stability and reliability of water temperature measurement and reduce the adverse effect of water level fluctuation on automatic observation, this paper presents the design and implementation of a novel infrared water temperature observation system. A comprehensive series of comparison tests and numerical corrections were conducted to validate the performance of the proposed method. The results of prototype observation demonstrate that over 85% of the relative errors of the corrected infrared water temperature are below 5%, and more than 80% of the absolute temperature differences are less than 1 ℃. In conclusion, the infrared water temperature measurement system demonstrates stable performance and high reliability. It proves to be an effective method for observing the surface water temperature of inland water bodies.

Key words: surface water temperature measurements, infrared radiation, comparative test, accuracy evaluation, inland water