1) correlation calculation method. According to the data of water level and water quantity accumulated for many years, the relationship between water level and water quantity is obtained through regression analysis. Its advantages are intuitive, concise and convenient calculation, but this method needs a lot of water level and water quantity observation data.

2) Source function method and complex variable function method. They all assume that the confined aquifer is homogeneous, uniform in thickness, isotropic and infinitely extended, and there is no overflow recharge. The relationship between water level and water quantity is solved by using unsteady flow theory and complex variable function theory respectively. This method is calculated under the assumption that there is no overflow recharge, which is far from reality. According to the research results of the Eighth Five-Year Plan of the Ministry of Geology and Minerals, a quasi-three-dimensional multi-layer aquifer system of groundwater flow is established under the condition of considering the occurrence of overflow and the release of water from cohesive soil to replenish the aquifer. After practical application, the effect is good.

3) Numerical method. The water level model is tending to adopt three-dimensional flow model. Because of the complexity of the equation and considering the heterogeneity of each soil layer, finite difference method and finite element method are often used to calculate the change of water level. Among them, the MODFLOW mathematical model developed by the US Geological Survey (a mathematical model for simulating the three-dimensional movement of groundwater) has been constantly revised and improved, which makes it contain rich connotations and flexible modules.