Tank model is a scientific and practical hydrological model, which has been widely used in the world. It is mainly used for hydrological forecast, hydrological and water resources calculation, runoff data interpolation and hydrological test inspection.
A watershed is regarded as a water tank, and the rainfall process is transformed into the runoff process of the outlet section through regulation and storage. There is a complicated physical process in the process. We can ignore this physical process and use manual adjustment of outlet hole size and height parameters to simulate the process similar to the actual flow process, which is the parameter calibration of water tank model.
According to the basin characteristics, the water tank model can be designed as: single water tank model, series water tank model, parallel water tank model, series and parallel mixed water tank model, overflow water tank model, regulating storage water tank model and sub box water tank model. According to the basin characteristics, there are flood model, humid area model, arid and semi-arid model, snow melting model and glacier model.
If linear approximation is made for each tank of the water tank model, the half-life of the first tank is 1-3 d; the second tank is about 7 d; the third tank is 2-3 months; and the fourth tank is about 6 months. From the top to the bottom, the outflow of the four water tanks is close to the surface runoff, soil flow, quasi base flow and base flow respectively, which conforms to the physical process of runoff generation and confluence in a watershed. It shows that the water tank model is a scientific and practical rainfall runoff model.
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