22-27 September 2019
Trade Fairs and Congress Center (FYCMA)
Europe/Madrid timezone

Maximum-flux constraint for the MODFLOW DRAIN package to simulate dewatering wells

24 Sep 2019, 16:00
1h
Trade Fairs and Congress Center (FYCMA)

Trade Fairs and Congress Center (FYCMA)

Av. de José Ortega y Gasset, 201 29006 Malaga, Spain
Poster Topic 5 - Tools, methods and models to study groundwater Poster with refreshments

Speaker

Mr Cas Neyens (Vrije Universiteit Brussel)

Description

In dewatering design studies, wells are often implemented as head-dependent (Cauchy-type) boundary conditions in numerical models to obtain a discharge given a targeted drawdown in the excavation site. In the MODFLOW groundwater modelling code, this is often done through the use of the DRAIN package. This has the drawback, however, that initial abstraction rates can be higher than what can be supplied by the physical well. This results in simulated dewatering durations that are often too optimistic in addition to cumulative extracted volumes that are larger than those supplied by the well. A solution to this was found by adjusting the source code of the DRAIN package to allow the user to specify a maximum allowed discharge for the MODFLOW drains. If, during a time step, the simulated drain discharge is larger than the user-specified maximum discharge; the simulated value is limited to this maximum and the drain discharge reverts to a constant-flux (Neumann) type boundary condition independent of the hydraulic head in the cell. The effectiveness of the tool was demonstrated in a dewatering case-study in Belgium where simulated abstractions differed significantly between the adjusted DRAIN package and the traditional DRAIN package.

Primary authors

Mr Cas Neyens (Vrije Universiteit Brussel) Dr David Simpson (AGT) Prof. Marijke Huysmans (Vrije Universiteit Brussel)

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