## 1 Introduction  
Energy dissipation facilities (EDFs) are structures designed to dissipate the energy of flowing water, commonly used in open channels at hydropower stations to reduce flood damage [1; 2]. Energy dissipation downstream of large-scale dams is a critical concern, particularly in high dam projects or mega-projects. In addition to traditional primary methods of flood discharge and energy dissipation, such as ski-jump energy dissipators, underflow energy dissipators, and tunnel energy dissipators, several innovative energy dissipation techniques have been proposed. These include stepped and cascade spill-ways [3; 4], slit-type energy dissipators [5], pendulum sills downstream of sluice gates [6], trapezoidal labyrinth weirs [7], and flaring gate pier schemes for chambers [8]. These novel approaches aim to achieve efficient energy dissipation under various flood discharge conditions. Evaluating the effectiveness of reconstructed EDFs is crucial to ensuring adequate protection [9]. Hydraulic model tests (HMTs) provide a more realistic assessment of EDF effectiveness by simulating water flow through a scaled-down hydraulic system, achieving geometric similarity with the prototype using dimensionless parameters, and maintaining constant fluid properties [10; 11; 12]. HMTs can analyze water flow behavior under various flow conditions, such as velocity distribution, flow resistance, and sediment transport [13]. However, HMTs have limitations in replicating the real characteristics of water flow and structural response imposed by dynamic water pressure at the prototype scale, such as the effects of turbulence, air entrainment, sediment transport, and various influencing factors, including forces, materials, cavitation, and geology [14; 15; 16; 17; 18]. For instance, turbulence and air entrainment can significantly affect flow characteristics, and sediment transport can affect hydraulic response. Structural response can be influenced by various factors, such as material properties, boundary conditions, and flow conditions. Replicating these effects in a laboratory environment can be challenging due to the limited size of the model and difficulty controlling flow conditions. Another way to validate and improve the results obtained from HMTs is to conduct a corresponding hydraulic prototype observation (HPO), which involves measuring and analyzing the real water flow characteristics and structural response imposed by dynamic water pressure at the prototype scale [19; 20; 21]. Observing the hydraulic prototype can provide more accurate and reliable project design and operation data than the model test alone. [PERSON] et al., discovered through a prototype study that significant scale effects are present in the physical investigation of hydraulic aerated flow, particularly with regard to bubble density, size, and frequency [22]. Several studies have highlighted the importance of HPO in hydraulic structure design and operation. For instance, [PERSON] et al., conducted a HPO to investigate the performance of a hydraulic turbine under different operating conditions, finding it provided more accurate and reliable data than the model test alone. Similarly, [PERSON] et al., conducted a HPO to validate the results obtained from a HMT and found that it provided valuable insights into the real water flow characteristics that were not captured by the HMT [10; 12]. However, few researchers have investigated the hydraulic properties of an open channel under different discharge releases through direct observation and measurement of the real properties of discharge flow. Overall, studying HPO tests on reconstructed EDFs is crucial for ensuring the safe and efficient operation of open channels at hydropower stations and for advancing our understanding of the complex hydraulic phenomena involved in energy dissipation.