Spatiotemporal analysis and quantification of groundwater withdrawals in the Po basin: methodology and data homogenization within the “MidAS-PO” project

Developing groundwater numerical models at basin scale is essential for sustainable water resource management but also challenging. Data collection is in fact often critical, as information is rather fragmented, inconsistent, or incomplete due to the different administrative and geological character of different sub-areas within the basin. As part of the project Modello idrogeologico delle Acque Sotterranee del distretto idrografico del fiume Po (MidAS-PO), coordinated by Autorità di Bacino Distrettuale del Fiume Po, which aims at developing a groundwater numerical model of the Po Plain, a methodology to quantify and spatialize all the groundwater withdrawals was adopted. Data provided by Environmental Agencies, Regional authorities and Water Suppliers have been gathered, resulting heterogeneous and incomplete for modelling purposes. A gap filling procedure was thus developed to homogenize and integrate incomplete data: a) missing coordinates (14% of wells) were assigned by randomly spatializing these wells within their municipality based on well type (e.g., industrial, irrigation) and land use; b) missing screen positions (81% of wells) were inferred as elevations from the closest well of the same type or as model layers if the exploited aquifer was known; c) missing well elevations (21% of wells) were determined by extracting the corresponding DTM value; d) missing flow rates (73% conceded + 13% unknown), were respectively filled using the conceded data modulated with a type-specific coefficient derived from the ratio of the conceded to the measured, when both of them are available, and with the average calculated by use type. The gap filling procedure was pivotal to create the first homogenized dataset of groundwater withdrawals for the entire Po plain, including 158000 wells divided into 14 typologies. These results evidence how homogenizing data collection among different institutions could aid the realization of basin-scale groundwater models.