Submitted as: model description paper
08 Nov 2022
Submitted as: model description paper | 08 Nov 2022
Status: this preprint is currently under review for the journal GMD.

HiWaQ v1.0: A flexible catchment water quality assessment tool with compatibility for multiple hydrological model structures

Xiaoqiang Yang1,2, Doerthe Tetzlaff2,3,4, Chris Soulsby4,2, and Dietrich Borchardt1 Xiaoqiang Yang et al.
  • 1Department of Aquatic Ecosystem Analysis and Management, Helmholtz Centre for Environmental Research – UFZ, Magdeburg, 39114, Germany
  • 2Department of Ecohydrology and Biogeochemistry, Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, 12587, Germany
  • 3Department of Geography, Humboldt University of Berlin, Berlin, 10117, Germany
  • 4Northern Rivers Institute, School of Geosciences, University of Aberdeen, Aberdeen, AB24 3UF, UK

Abstract. Mitigating diffuse-source nutrient pollution has created an urgent need to advance understanding of catchment hydrological and nutrient dynamics, and develop robust integrated hydrological and water quality models to support decision making. However, the current availability of integrated catchment-scale water quantity and quality assessment tools is very limited compared to that of hydrological models, and the common developing strategy of extending existing hydrological platforms might be restricted by specific hydrological structures and associated data requirements. Here we introduce a new flexible catchment water quality assessment tool – HiWaQ that aims to be compatible with multiple, often contrasting hydrological model structures and that comprehensively considers spatio-temporally varying water quality impacts of anthropogenic activities. The flexibility of HiWaQ is realised through: (1) a unified configuration interface for catchment characteristics and the coupled hydrological structure; and (2) a generalised structure of storage-flux interactions for all bucket-type storages. We also present the detailed N module development (HiWaQ-N) for nitrate simulation and its coupling tests with two contrasting fully distributed hydrological models (the process-based ecohydrological EcH2O-iso model and the multi-scale conceptual mHM model). The two couplings were tested and cross-compared in the mixed forest-agricultural Silberhütte catchment (99 km2), central Germany, using the continuous daily discharge and Nitrate-N observations over 2012–2018. Results demonstrated that: (1) HiWaQ-N could well reproduce the observed discharge and stream Nitrate-N patterns and provided reliable spatio-temporal estimates of catchment N balance and networked in-stream N retention; (2) the two couplings were generally consistent with each other, while they showed subtle, but insightful differences in N transport (e.g., responses to small summer rainfall events) and transformations (e.g., the soil denitrification process), which could be attributed largely to different hydrological structures. Despite promising potential for further exploiting the coupled catchment modelling (e.g., combining in-depth uncertainty analysis), HiWaQ has the unique value of making better use of advanced hydrological modelling that embeds thoughtful modelling workflows and localised perceptual knowledge, thus better leveraging these advancements in the integrated catchment water quantity-quality assessments. We encourage interested researchers and modellers to contribute to further open-source development, which is oriented to be scientifically insightful and practically useful for catchment management.

Xiaoqiang Yang et al.

Status: open (until 03 Jan 2023)

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Xiaoqiang Yang et al.

Xiaoqiang Yang et al.


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Short summary
We develop the catchment water quality assessment platform HiWaQ v1.0, which is compatible with multiple hydrological model structures. The nitrogen module (HiWaQ-N) and its coupling tests with two contrasting grid-based hydrological models demonstrate the robustness of the platform in estimating catchment N dynamics. With the unique design of the coupling flexibility, HiWaQ can leverage advancements in hydrological modelling and advance integrated catchment water quantity-quality assessments.