Accurate and suitable turbine discharge measurement is crucial for the efficiency, safety, and economic operation of hydropower plants, directly impacting power generation efficiency, equipment lifespan, and reservoir discharge. This paper introduces a comparative study of two flow measurement methods applied in the Francis turbine: ultrasonic flowmeters installed at the spiral case inlet and differential pressure flow measurement that measures data from pressure measuring points at selected cross-sections within the spiral case. Inside the spiral case, flow characteristics are mathematically modeled, considering a uniformly distributed velocity across spiral case height and tangential-radial velocity component analysis, providing the base of a valid pressure-flow relationship. The model is comprised of real-time data comparison between ultrasonic flowmeter and differential-pressure data from the Karot Hydropower Plant, Pakistan. The results show that when differential pressure is used along with the derived equation the measured discharge is close to ultrasonic measurements with an acceptable error of ± 2%. This concluded that despite the simplicity and low cost of differential-pressure methods it can be a reliable alternative to ultrasonic flowmeters. The insights provide a practical and theoretical basis for optimized flow monitoring, which is the main concern for the installation of large-scale hydropower plants in situations where the implementation of ultrasonic systems is challenged by structural feasibility and economic limitations.