Improving the water budget in the urban surface scheme TEB for a better evaluation of green infrastructures for adaptation purposes

9th International Conference on Urban Climate, TOULOUSE, FRANCE, 20-/07/2015 - 24/07/2015Urban population grew fast these last decades and is expected to still increase during the future decades. Urban areas, due to artificial materials, impacts both urban climate and hydrology: urban heat island, more frequent floods, longer droughts... Furthemore, these modifications related to urbanization can go together with those due to climate change. City planning evaluation in both hydrological and climate terms becomes crucial. Numerical models are useful tools for such evaluations. Nevertheless, even if numerous models dedicated to urban areas are used, very few models are able to simulate both detailed energy and water budgets. Most of them are specialized in one topic and simulate roughly the other one. Introduction of vegetation in cities is supposed to be one of the solutions to limit urbanization impacts as urban heat island and/or floods, by increasing water infiltration and favoring evapotranspiration. Thus, such green infrastructures impact both energy and water budgets. Our objective is then to develop a model dedicated to urban areas and able to simulate both energy and water realistic budgets. This model is based on the Town Energy Budget scheme that has known different evolutions these last years: introduction of vegetation inside the canyon, simulation of the greenroofs. Its water budget has been improved by introducing soil and groundwater under buildings and roads and the sewer network (combined or stormwater) that transfers the surface runoff and the drained groundwater to the outlet. The groundwater balance under the different surface types (building, road and garden) is performed and can impacts the evapotranspiration flux from the garden surfaces. This paper will present these last model evolutions related to the water budget as well as their evaluation. The hydro-climate evaluation of greening scenarios of a large part of the City of Nantes (France) using different green infrastructures (as greenroofs, trees, varying vegetation rates) will be discussed