TRANSPORT MODELING IN HETEROGENEOUS AQUIFERS .2. 3-DIMENSIONAL TRANSPORT MODEL AND STOCHASTIC NUMERICAL TRACER EXPERIMENTS

Statistical information on the coherent sedimentary structures of high ly heterogeneous gravel deposits (Jussel et al., this issue) is used t o investigate numerically the transport of conservative tracers. The d ata are the basis for a numerical generation of synthetic aquifer mode ls, whose statistical distributions of the sedimentary structures and their hydraulic conductivity and porosity correspond to the findings i n the investigated deposits. A three-dimensional finite element flow m odel and a corresponding random-walk transport model were developed fo r this purpose. Because of the large number of finite elements needed, the solution algorithm is optimized for applications on vector-type c omputers. In order to minimize the discretization errors a special int erpolation technique is applied to the determination of the local velo city vector. Ten stochastic, numerical transport experiments over a tr ansport distance of 100 m were carried out with synthetic gravel aquif er models. They allow the mean tracer velocity, the effective hydrauli c conductivity, and the dispersion parameters to be estimated. These e stimates are compared with estimates of these parameters from current theories for the flow and the tracer transport in random, correlated, anisotropic hydraulic conductivity fields.