Modeling Analysis of the Upper Limit Water Level Mechanism in the Upstream Reservoir of a Dam Embankment

The dam embankment (DE) is a highway structure used in the Loess Plateau to integrate the functions of a highway embankment and a dam. This paper studies the upper limit water level mechanism of the reservoir in the upstream of the DE to determine the criterion for setting upper culverts on the DE. A reservoir model is first established, and then the replenishment and loss of the reservoir water is simulated. The principle of water balance is employed to obtain water level formulas for the reservoir. Finally, an engineering example is used to verify the upper limit water level mechanism. The results show that the water level of the reservoir fluctuates near an ideal balance water level and an upper limit water level exists. Moreover, the upper limit water level has no relation to the water storage time, and is only related to the reservoir shape with big upper and small bottom, the small amount of water entering the reservoir each year, and the large water loss caused by evaporation and leakage. The upper culvert setting criterion is obtained through the upper limit water level mechanism, and it will provide important reference significance for the necessity of the DE culvert setting.

Inter-annual change of the drought limit water level of a reservoir based on system dynamics

Drought is one of the major natural disasters affecting the development of economies and society. Drought early warning is the primary step and most important non-engineering measure for drought relief. This paper took Yuqiao Reservoir in Tianjin as a case study and analysed inter-annual changes of the drought limit water level. First, the causality between variables in the water supply–demand system was analysed, and a structural diagram of water sources allocation was drawn. Coupled with the parameters and a structural diagram, a system dynamics (SD) model of the water supply volume was established. Secondly, simulation results were tested to ensure that the model was valid. The water supply volume from 2003 to 2020 was simulated by using the model. Finally, based on the inflow process and the water supply volume, the drought limit water level was calculated. The results showed the water supply volume of Yuqiao Reservoir has changed remarkably. The drought limit water levels in 2003–2012 and in 2016–2020 were 16.70 m and 16.30 m, respectively: a difference of 0.40 m. The regulation curve of guarantee for water supply during 2016–2020 is significantly lower than that of 2003–2012. This research is of great significance for drought resistance, disaster mitigation and reservoir management.