OM-MADE: an open-source program to simulate multi-peaked skewed breakthrough curves observed in karstic systems

@inproceedings{CollonRM2019,
 abstract = { Tracer tests are commonly used in karstic environments to provide information on the existing hydraulic connections between two observations points. Beyond the proof of a connection, the shape analysis of the resulting breakthrough curves (BTCs) is, indeed, the direct expression of the specificities of the local flows. Thus, the presence of pools or immobile water zones generally produces asymmetric BTCs with long tails, while auxiliary conduits or even large pools have been reported to produce multi-peaked BTCs. To check the consistency of some configuration hypotheses, numerical tools can be used. As dispersion is most significant in the flow direction, one-dimensional models have been used to analyse and/or reproduce tracer tests. But existing codes are restricted to simulate one single flow zone coupled or not with storage zone, or to compute the results of a dual-advectivedispersive equation modelling of the system, without longitudinal configuration changes. To overcome these limitations and enlarge the possibilities of karstic configuration hypotheses, we developed an open-source python code, OM-MADE. OM-MADE stands for One-dimensional Model for Multiple Advection, Dispersion, and storage in Exchanging zones. It is based on the resolution of classical mass conservation equations. In OM-MADE, several configurations can be simulated: there is no technical restriction on the number of flow zones, which can be either mobile or storage zones, and can exchange within each other. All flow zones are divided along the direction of flow into homogeneous reaches. Solute lateral in flows or out flows are considered, as well as first-order decay process. The partial differential equations can be solved using two second order schemes, one based on an operator-split approach, the other on Crank-Nicholson pondered scheme. OM-MADE has been verified against analytical and existing numerical solutions. OM-MADE is available on Github for a free use by the community. We demonstrate the software capacities on a tracer test carried out in the karstic area of Furfooz (Belgium). In this field case, the conceptual interpretation of the dual-peaked positively skewed BTC supposes three exchanging zones, among which two are mobile ones, and one represents a storage zone. As only two observation points are available, the simplest approach considers two reaches. Alternative approaches, considering three and four reaches have also been considered and show the capacities of the code to help BTC interpretation. },
 author = { Collon, Pauline AND Tinet, Anne-Julie AND Dewaide, Lorraine AND Hallet, Vincent },
 booktitle = { 2019 Ring Meeting },
 publisher = { ASGA },
 title = { OM-MADE: an open-source program to simulate multi-peaked skewed breakthrough curves observed in karstic systems },
 year = { 2019 }
}