Inverse model as tool for pumping test interpretation

In the numerical model for the simulation of pumping tests, the groundwater reservoir is first schematized or conceptualized in a number of pervious and semi-pervious layers. These hydrogeological units are further discretized in a number of layers in the numerical model. Each layer of the numerical model is assumed homogeneous and is characterized by a single value for the horizontal conductivity and one for the specific elastic storage. The hydraulic resistance between the layers can be deduced from the thicknesses and the vertical conductivities of these layers. Knowing the discharge rate, one can calculate the drawdown at any distance from the pumped well, at any level and at any time after the start of the pump. The problem solved by the numerical model is called by Sun Ne-Zheng (1994) a forward problem.