On the determination of pixel-based groundwater withdrawals using SWEO water accounting procedures. Part 1: methodology

Abstract

Figure provides a schematic representation of the flows, fluxes, and states within the SWEO framework. It gives an overview of the parameters defined by the SWEO model and provides a visual interpretation of the overall framework discussed in this paper. Groundwater is a critical resource for human and ecosystem needs, yet its availability is increasingly stressed by over-abstractions as well as climate change. Monitoring remains challenging due to limited data of well abstractions, regular piezometric readings, and complex subsurface processes. This study presents Scalable Water balance from Earth Observations (SWEO), a novel water accounting framework that estimates groundwater recharge and withdrawals without requiring detailed hydrogeological information, complex groundwater flow models, hydraulic heads, or metered abstractions. The framework is mainly driven by satellite-based remote sensing data of rainfall surplus/deficit and storage changes into spatially distributed key groundwater balance terms by sequentially applying long- and short-term water balances at local and basin scales. River discharge measurements are used to internally calibrate percolation and baseflow. The framework is transparent, scalable, and applicable to large basins with groundwater irrigation. SWEO can be implemented in the cloud, and processing 25 years can be completed within a few days. The groundwater resource information generated by SWEO is currently not available to groundwater policymakers for preparing longer term policies to make aquifer abstractions more sustainable. An accompanying article describes the validation of this new analytical framework for surface water and groundwater accounting.