Assessment of the ParFlow–CLM CONUS 1.0 integrated hydrologic model: evaluation of hyper-resolution water balance components across the contiguous United States

Mary M F O'Neill,Laura E Condon,Reed M Maxwell,Danielle T Tijerina

doi:10.5194/gmd-14-7223-2021

Abstract

Abstract. Recent advancements in computational efficiency and Earth system modeling have awarded hydrologists with increasingly high-resolution models of terrestrial hydrology, which are paramount to understanding and predicting complex fluxes of moisture and energy. Continental-scale hydrologic simulations are, in particular, of interest to the hydrologic community for numerous societal, scientific, and operational benefits. The coupled hydrology–land surface model ParFlow–CLM configured over the continental United States (PFCONUS) has been employed in previous literature to study scale-dependent connections between water table depth, topography, recharge, and evapotranspiration, as well as to explore impacts of anthropogenic aquifer depletion to the water and energy balance. These studies have allowed for an unprecedented process-based understanding of the continental water cycle at high resolution. Here, we provide the most comprehensive evaluation of PFCONUS version 1.0 (PFCONUSv1) performance to date by comparing numerous modeled water balance components with thousands of in situ observations and several remote sensing products and using a range of statistical performance metrics for evaluation. PFCONUSv1 comparisons with these datasets are a promising indicator of model fidelity and ability to reproduce the continental-scale water balance at high resolution. Areas for improvement are identified, such as a positive streamflow bias at gauges in the eastern Great Plains, a shallow water table bias over many areas of the model domain, and low bias in seasonal total water storage amplitude, especially for the Ohio, Missouri, and Arkansas River basins. We discuss several potential sources for model bias and suggest that minimizing error in topographic processing and meteorological forcing would considerably improve model performance. Results here provide a benchmark and guidance for further PFCONUS model development, and they highlight the importance of concurrently evaluating all hydrologic components and fluxes to provide a multivariate, holistic validation of the complete modeled water balance.

Highlights

Modeling the terrestrial water cycle at the global scale and at high resolution has recently been referred to as a “grand challenge in hydrology” (Bierkens et al, 2015; Wood et al, 2011), an undertaking that has excited the hydrologic community and encouraged the development of largescale modeling efforts, workshops, and working groups
We focus on performance of the CONUS version 1.0 model, a ParFlow– Common Land Model (CLM) integrated groundwater–surface water simulation configured across the continental United States (Maxwell et al, 2015)
We present the detailed evaluation of a transient, coupled hydrologic–land surface simulation at the continental scale and at hyper-resolution using a diverse set of monitoring networks and state-of-the-art remote sensing products

Summary

Introduction

Modeling the terrestrial water cycle at the global scale and at high resolution has recently been referred to as a “grand challenge in hydrology” (Bierkens et al, 2015; Wood et al, 2011), an undertaking that has excited the hydrologic community and encouraged the development of largescale modeling efforts, workshops, and working groups. These “everywhere and locally relevant” hydrologic models (Bierkens et al, 2015) differ from land surface models (LSMs) and general circulation models (GCMs) by providing spatially ubiquitous and hyper-resolution, physically based hydrologic simulations.

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Results

Conclusion