Predicting the Aggregate Hydro-Biogeochemical Response of Mountainous Watersheds Across Scales and Subsystems
Dipankar Dwivedi* (DDwivedi@lbl.gov), Zexuan Xu, Lucien Stolze, Bhavna Arora, Sergi Molins, Carl Steefel, Eoin Brodie
Lawrence Berkeley National Laboratory, Berkeley, CA
Reactive Transport Models (RTMs) are crucial to improve scientists’ ability to predict the hydro-biogeochemical response of watersheds. However, these models must be able to accurately represent the complex multiscale, multiphysics processes that occur in watersheds. A scale-adaptive reactive transport modeling approach that involves using distinct codes was implemented to capture processes at the appropriate scale across watershed subsystems. In the subalpine and upper montane regions, the Copper Creek subcatchment was studied as a test case to understand how seasonal and interannual climate variability affects the observed relationship between the volume of water flow and solute concentrations (Xu et al. 2022). A Pumphouse lower montane (PLM) hillslope transect, established across a representative lower montane system, in turn, was used to disentangle the complex interplay between physical, geochemical, and biological processes controlling long-term chemical weathering of shale, with a focus on microbial aerobic respiration and changes in nitrogen stocks and fluxes resulting from snowpack variability (Stolze et al. 2022; Arora et al. in preparation). Hydro-biogeochemical exchange functions in the floodplain were also used to understand subsurface biogeochemical exports and their effects on river chemistry (Dwivedi et al. in preparation). The Lower Triangle region (LTR) of the East River is unique, as its hydrology is dominated by discharge from upstream subcatchments such as the Copper Creek, and comprises interacting hillslope and floodplain subsystems (Özgen-Xian et al. 2020, 2023). As such, this system was used to integrate understanding developed across subsystems. The complex reaction network from the PLM hillslope transect and floodplain subsystems was used to capture nitrogen dynamics in LTR. The resulting model is being used to quantify the uncertainties associated with meteorological forcings, evapotranspiration, and subsurface flow and how they affect the aggregate hydro-biogeochemical response of the East River watershed.
Arora, B., et al. “Changes in Plant Productivity and Nitrogen Fluxes in a Mountainous Watershed as Affected by Snowpack Decline in Recent Decades.” In preparation.
Dwivedi, D., et al. “Developing Insights into River Corridor and Watershed Hydro-Biogeochemistry Across Scales.” In preparation.
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Stolze, L., et al. 2023. “Aerobic Respiration Controls on Shale Weathering.” Geochimica et Cosmochimica Acta 340, 172–188. DOI:10.1016/j.gca.2022.11.002.
Xu, Z., et al. 2022. “Understanding the Hydrogeochemical Response of a Mountainous Watershed Using Integrated Surface–Subsurface Flow and Reactive Transport Modeling,” Water Resources Research 58(8), e2022WR032075. DOI:10.1029/2022WR032075.