We demonstrate a 24 GHz hydrology radar system. The continuous‐wave Doppler radar is capable of noncontact and wide‐range surface‐flow velocity detection in various scenarios. The radar receives the reflected echo signal through a directional narrow‐beam antenna. After amplification and demodulation by the proposed low‐noise amplifier and the subharmonic down‐conversion mixer, respectively, the Doppler frequency‐shift is analyzed by the digital signal processing (DSP) module for estimation of the water flow velocity. Moreover, for water level detection, a phase‐locked loop with micro control unit (MCU)‐controlled division ratio is included in the RF module for generating a stable and tunable (or frequency modulation) 24‐GHz‐band transmitting signal with low phase noise. To verify the radar system, outdoor field tests have been conducted. The measured results are consistent with the theoretical values, and the results of both the float method and the commercial handheld (Stalker Pro II) surface velocity radar. In the condition of water ripple lower than 3 cm, the radar functions well for flow speed range of 0.3 ~ 34.6 m/s. Overall, the hydrology radar is suitable for surface‐flow velocity detection (especially in bad weather) and water resource management (such as water‐level detection).