In order to reduce stormwater runoff, source control through infiltration is increasingly practiced and recommended. However, the impact of its widespread implementation on the subsurface compartment remained poorly understood.
The objective of this work was to propose a physically based model of interactions between surface and subsurface compartments in the case of a shallow groundwater table.
The representation of these interactions was integrated into the distributed model of urban and peri-urban catchments, URBS.
A numerical experimental design was used to simulate a range of configurations combining different factors (climate, type of urbanization, soil types, presence of underground infrastructure, etc.) and to identify situations that could be unfavorable to infiltration.

Source-control infiltration practices are widely promoted by public authorities. However, the consequences of a systematization of these methods at the neighborhood or city scale remain poorly known, especially with regard to the underground compartment. In addition to the question of the possible pollution of groundwater by urban runoff, various studies demonstrate the risk of introducing an excessive recharge of aquifers or highlight the strong uncertainties regarding the proportion of infiltrated volumes that actually contributes to groundwater recharge and to base flows or that finally returns to the sewerage system by groundwater seepage into the pipes. However, the small number of studies and the site-specific nature of the applications limit the understanding of the mechanisms involved and of the influence of the natural and urban context. This thesis aims at specifying the potential effects of a systematization of stormwater source-control practices on the hydrological functioning of small urbanized watersheds and the factors governing these effects (characteristics of the climatic, hydrogeological and land use context and of the implemented infiltration strategy). It also aims to provide insights into the contributions and limitations of distributed hydrological models for the evaluation of infiltration strategies at the neighborhood or small watershed scale.

The response to these objectives is based on the use of the URBS model which allows continuous and distributed simulation of the hydrological functioning of urbanized areas. The underground compartment depiction has been enriched and consolidated to more finely simulate unsaturated and saturated flows and to model a wider variety of soils, aquifers and underground structures. The hydrological functioning of a set of hypothetical watersheds is modeled varying the characteristics of the climatic and hydrogeological context, the land use and the infiltration strategy. Results confirm the benefits of infiltration systems for runoff control and highlight their limitations in restoring the other components of the water balance, especially the evapotranspiration flow. As a consequence, infiltration devices increase groundwater recharge, which can lead to a rise in the water table, generating complex interactions between infiltrated volumes, water table, vegetation and underground structures, especially in the presence of a shallow water table and a low-transmissive aquifer. Besides the hydrogeological context, the climate (e.g. distribution of precipitation and evaporative demand) and the characteristics of the land use (e.g. density) and subsoil (e.g. type and distribution of subsurface structures) are determinant in the ability to recover a pre-development hydrological functioning. Results suggest that source-control infiltration strategies should be locally defined according to the specificities of the context and considered in combination with a control of imperviousness and/or other types of devices (e.g. green roofs). The simulation of the hydrological functioning of a partially urbanized watershed located in the Paris region highlights the relevance of such a tool to study the hydrological functioning of urbanized environments, but also its limitations for operational purposes. This application illustrates the high uncertainty linked to the lack of knowledge of the subsurface compartment composition and to identify ways to improve the model, especially regarding the description of transpiration.

Funding

100% French Ministry of Ecology and Sustainable Development (Training through research at ENTPE)

Pour plus d’information

• William Pophillat, 2022. Conséquences d’une systématisation des pratiques d’infiltration à la parcelle des pluies courantes à l’échelle de petits bassins versants – Apports de la modélisation intégrée, Ecole doctorale Terre, Univers, Environnement. Communauté Université Grenoble Alpes, soutenance le 13/04/2022, 375 pp. https://tel.archives-ouvertes.fr/tel-03770218, https://hal.science/tel-03770218v1
• Pophillat, W., Sage, J., Rodriguez, F., Braud, I., 2021. Dealing with shallow groundwater contexts for the modelling of urban hydrology – A simplified approach to represent interactions between surface hydrology, groundwater and underground structures in hydrological models, Environmental Modelling & Software, 144, 105144, https://doi.org/10.1016/j.envsoft.2021.105144.
• Pophillat, W., Sage, J., Rodriguez, F., Braud, I., 2022. Influence of interactions between stormwater infiltration systems, groundwater and underground structures on the hydrological functioning of urbanized areas in shallow groundwater environment, Urban Water Journal,19(8), 812-823, https://doi.org/10.1080/1573062X.2022.2090382.
• Sage, J., Pophillat, W., Rodriguez, F., Braud, I., 2024. Untangling the factors governing the catchment-scale impacts of on-site stormwater infiltration in shallow GW contexts – A systematic numerical analysis, in preparation

Cite the thesis

William Pophillat. Conséquences d’une systématisation des pratiques d’infiltration à la parcelle des pluies courantes à l’échelle de petits bassins versants urbains et péri-urbains – Apports de la modélisation intégrée. Hydrologie. Université Grenoble Alpes [2020-..], 2022. Français. ⟨NNT : 2022GRALU012⟩. ⟨tel-03770218⟩

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