INTEGRATED SURFACE-SUBSURFACE HYDROSYSTEM MODELING ACROSS SCALES: THE NEED FOR 3D SUBSURFACE DATA

Providing a scientific basis for water management policy, and assessing the physical characteristics underlying hydrologic risk, typically involves watershed-scale assessments that encompass a few hundred km² at a minimum. However, water resources for agriculture or resource development often require an understanding of river basin scale processes, which can cover areas up to or greater than 100,000 km². Given the recent increase in losses attributed to large-scale extreme climate related events, and the concern that the frequency of these events will progressively increase in response to climate change, there is growing demand for large-scale hydrologic risk assessments. Because of complex nonlinear interactions between climate, surface water, groundwater and soil moisture, robust physically-based 3D integrated hydrologic models provide a holistic means of performing water-related risk assessment for these types of applications. In this presentation, I will discuss the results from a series of studies covering a range of scales whereby fully-integrated surface/subsurface water models have been developed using the HydroGeoSphere platform, including its capability to perform real-time 3D forecasting of the entire hydrosphere as driven by an ensemble of weather forecasts and guided by data assimilation using wireless field instruments. Within the platform, hydrologic responses within sub-basins are nested seamlessly within full-basin scale models in order to capture additional details at an increased resolution. High-resolution modelling that covers large regions has been made feasible in recent years largely because of advancements in numerical solution methodologies including the parallelization of the non-linear solver, automated model nesting to capture local-scale details within a larger-scale model and access to high-performance computational resources. However, it is emphasized that such models also require a significant, harmonized level of land cover, soil and geologic data to parameterize them and to ensure their skill to meet stakeholder demands.