Simulation of unsteady flow in open channels has always been of great interest to the hydraulic engineers. In the present study, the objective is to model and assess the shock phenomenon within a steep channel connecting two reservoirs. The dynamic nature of water level in the downstream reservoir creates a chain of events in the channel corridor which is the main focus of the current article. After a critical review of conventional textbooks on two-reservoir problems, the water level in the downstream reservoir is assumed to be changing as opposed to be stationary. Here, the main problem is to investigate the impact of state variables selection on possibility of capturing the dynamics of shock wave using conservation form of the Saint–Venant equations. The second component of flux vector is of momentum nature for a combination of Q and the pressure field variables (i.e., A , h , and Z ) while it is of energy nature when u is combined with the pressure field variables. The governing equations in both groups are solved via finite volume and various flavors of finite difference codes written in MATLAB environment and the results are compared and contrasted with a program so-called FLDWAV. Numerical results confirm the fact that the state variables have to be chosen with great care in reference to the process under consideration. In conclusion, hydraulic engineers have to be warned upon wise implementation of numerical schemes when it comes to interaction among such terms as conservation, non-conservation form of Saint–Venant equations along with the state variables considered. The animation of chain of events emerged from computer programming can be used as an effective tool for educational purposes as the chain of events cannot be reproduced in the laboratory.

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两水库问题：重新审视

水力工程师对明渠非定常流动的模拟一直很感兴趣。在本研究中，目标是对连接两个水库的陡峭通道内的冲击现象进行建模和评估。下游水库水位的动态特性在航道走廊中产生了一系列事件，这是本文的主要焦点。在对关于双水库问题的传统教科书进行严格审查后，假设下游水库中的水位在变化而不是静止。在这里，主要问题是研究状态变量选择对​​使用圣维南方程的守恒形式捕获冲击波动力学的可能性的影响。通量矢量的第二个分量对于 Q 和压力场变量（即 A 、 h 和 Z ）的组合具有动量性质，而当 u 与压力场变量组合时具有能量性质。两组中的控制方程均通过有限体积和在 MATLAB 环境中编写的各种有限差分代码求解，并将结果与​​所谓的 FLDWAV 程序进行比较和对比。数值结果证实了这样一个事实，即必须根据所考虑的过程非常谨慎地选择状态变量。总之，当涉及到圣维南方程的守恒、非守恒形式以及所考虑的状态变量等项之间的相互作用时，必须警告液压工程师明智地实施数值方案。