BioRT-HBV 1.0: a Biogeochemical Reactive Transport Model at the Watershed Scale

Abstract

Reactive Transport Models (RTMs) are essential for understanding and predicting intertwined ecohydrological and biogeochemical processes on land and in rivers. While traditional RTMs have focused primarily on subsurface processes, recent RTMs integrate hydrological and biogeochemical interactions between land surface and subsurface. These emergent, watershed-scale RTMs are often spatially explicit and require large amount of data and extensive computational expertise. There is however a pressing need to create parsimonious models that require less data and are accessible to scientists with less computational background. Here we introduce BioRT-HBV 1.0 (hereafter BioRT), a watershed-scale, hydro-biogeochemical model that builds upon the widely used, bucket-type HBV model (Hydrologiska Bryåns Vattenavdelning), known for its simplicity and minimal data requirements. BioRT uses the conceptual structure and hydrology output of HBV to simulate processes including solute transport and biogeochemical reactions driven by reaction thermodynamics and kinetics. These reactions include, for example, chemical weathering, soil respiration, and nutrient transformation. This paper presents the model structure and governing equations, demonstrates its utility with examples simulating carbon and nitrogen processes in a headwater catchment. As shown in the examples, when constrained by data, BioRT can be used to illuminate the dynamics of biogeochemical reactions in the invisible, arduous-to-measure subsurface, and their connections to observed solute export in streams and rivers. We posit that such parsimonious models increase model accessibility to users without in-depth computational training. It also can serve as an educational tool that promote pollination of ideas across different fields and foster a more diverse, equal, and inclusive user community.

Illuminating the “Invisible”: Substantial Deep Respiration and Lateral Export of Dissolved Carbon From Beneath Soil

“…BioRT-HBV (Sadayappan et al, 2024) couples the widely used Hydrologiska Byråns Vattenbalansavdelninglight (HBV-light) hydrology model (Seibert, 1996;Seibert & Vis, 2012) with the BioRT reactive transport model (Zhi et al, 2019(Zhi et al, , 2022. HBV-light (standard version) represents entire watersheds with two groundwater zones (Seibert & Vis, 2012).…”

“…These hydrobiogeochemical insights from RTMs show promise of unraveling the interconnected processes that affect the timing, location, and magnitude of dissolved carbon production, export, and stream dynamics. Here we use a recently developed reactive transport model, BioRT-HBV (Sadayappan et al, 2024), which couples the widely used HBV-light hydrology model (Seibert & Vis, 2012) and the BioRT model for solute transport and biogeochemical reactions (Zhi et al, 2022).…”

Hydrology Outweighs Temperature in Driving Production and Export of Dissolved Carbon in a Snowy Mountain Catchment

“…BioRT-HBV inherits the reactions and setup of the BioRT module in BioRT-Flux-PIHM (Zhi et al, 2022) but uses hydrologic outputs (water storage and flow components) from HBV as input (Sadayappan et al, 2024a). It therefore follows the conceptual structure of HBV and simulates biogeochemical reactions and solute transport at the catchment scale.…”