Temporal estimation of hydrodynamic parameter variability in stormwater constructed wetlands – The hysteresis effect during multi-rainfall events
Résumé
Constructed wetland (CW) systems are increasingly implemented as rustic water treatment facilities, the efficiency of which varies with time due to possible malfunctions such as clogging related to excessive loads of suspended solids or inadequate CW sizing. A numerical flow modeling can be used to evaluate filtering performance and to improve the design of CWs. Such a modeling usually involves the so-called van Genuchten-Mualem (vGM) soil hydrodynamic parameters which are notoriously difficult to measure. The meticulous attention brought to the sensitivity of the model to the vGM parameters reveals a predominant influence of the shape parameters and the saturated conductivity of the filter on the piezometric heads, during feeding and drainage. We then discuss a simple, robust and low-cost inverse modeling approach, deterministic and stochastic, for the identification of the soil hydrodynamic properties from piezometric heads measured during successive storm events. The temporal variability of hydrodynamic parameters is assessed and analyzed with regards to modeling efficiency. Principal component analysis shows that the estimated hydrodynamic parameters from the feeding and drainage sub-periods are significantly different.
Loading...