Why Use Analytical Element Groundwater Models and What Are They Capable of

Groundwater flow models are created quickly using graphical user interfaces. The limited time available for most groundwater modeling projects lead to a minimum of critical testing as to whether the models are realistic. Analytic element models require less input than discrete numerical models; only physical features are entered. Current analytic element models deal with polygonal inhomogeneities, rather than a varying field of properties as discrete numerical codes can. Users of analytic element models gradually increase complexity of their model; this tendency is encouraged by the difficulty of getting a complex model to work in a single step. Analytic element models satisfy the governing equations exactly. As a result, errors in concept or data become clearly visible, which tends to make analytic element models less popular than one might expect, but this is a built-in safeguard to misuse. The property of the method that the governing equations are satisfied exactly is one reason for the significant effort required for continued development of the method. The mathematical derivation and publication of analytic elements capable of satisfying exactly the partial differential equations that govern transient flow, multi-aquifer leaky flow, and the combination of the two has become successful only recently, and has now reached the stage of development necessary to build analytic elements capable of large scale modeling of transient regional aquifer flow. It will take years before these new analytic elements will be available for use in groundwater modeling practice. This presentation has three parts. First we discuss how analytical models react in a very visible way to erroneous data. Second we give brief examples of where analytic models have advantages over numerical models. Third, we give an overview of recent developments by researchers in this area, and a view of the future of analytic element modeling of groundwater flow.