Impact of urban growth and high residential irrigation on streamflow and groundwater levels in a peri-urban semi-arid catchment

International audience; The impact of urbanization on groundwater is by no means simple to understand, as it depends on a variety of factors such as climate, hydrogeology, water management practices and infrastructure. In semi-arid landscapes, the urbanization processes can involve high water consumptions and irrigation increase, which acts as a new groundwater recharge. We assessedes the hydrological impacts of urbanization and irrigation rates in an Andean peri-urban catchment located in Chile, in a semi-arid climate. For this purpose, we built and validated a coupled surface-groundwater model that allowed verifying a strong stream-aquifer interaction in areas with shallow groundwater, higher than some sewers and portions of the stream. Moreover, we also identified a significant local recharge associated with inefficient urban irrigation. From the evaluation of different future scenarios, we determined that increasing irrigation efficiency will decrease the current groundwater levels, while the median (Q50%) and low flow (Q95%) discharges will reduce from 408 l/s and 43 l/s to 389 l/s and 22 l/s respectively. Overall, our results show the relevance of integrating the modelling of surface and subsurface water resources at different spatial and temporal scales when assessing the effect of urban development and the suitability of urban water practices.