# Check 18 - Multi-layer pumping test comparison with MLU

##### Checks multi-level flow, partially-penetrating multi-level well, transient flow, spatially-variable area sinks (SVAS)

This is a model of a pumping test in a thick, stratified aquifer in northern California. It has been modified slightly (no unconfined layer at top, initial heads are everywhere = 0) so that a direct comparison could be made between Anaqsim and MLU, which is an analytic multi-level model that uses Laplace transforms and analytic elements (LT-AEM) to get exact distributions of vertical leakage and storage fluxes, without finite time steps. This contrasts Anaqsim, which approximates the leakage and storage distributions using SVAS, and uses finite difference time steps. Anaqsim’s SVAS approach adds many important capabilities such as unconfined and fresh/salt interface domains and a wide range of line boundary conditions not available with the LT-AEM approach in MLU .

The models have 9 layers that are all confined and isotropic in the plane of the layering, as shown at below. The vertical hydraulic conductivity of each layer equals 1/5th the horizontal conductivity. The pumping well spans three of the 9 levels including the very transmissive 5th layer. Three shallow observation wells shown in the section were monitored in addition to the pumping well. The Anaqsim model uses a large number of time steps to minimize differences due to finite difference time stepping.

The model-simulated drawdowns in both the pumping well and in the three observation wells are essentially identical as the following plots show. Anaqsim simulation results are the lines and MLU simulation results are dots.