In non-perennial rivers, flow intermittency significantly influences dissolved organic carbon (DOC) dynamics. However, understanding how spatial and temporal flow intermittency patterns influence DOC dynamics at the basin scale is challenging. While several models have been employed to study DOC dynamics in perennial rivers, most cannot integrate and simulate flow intermittency. To address this limitation, in this study, the Soil and Water Assessment Tool (SWAT) was adapted into SWAT-IR, tailored to non-perennial river characteristics. Using the SWAT-IR model, DOC dynamics were simulated in a Mediterranean river basin from 2006 to 2020 (streamflow calibration performance of NSE = 0.51 and R2 0.54 and DOC simulation accuracy of R2 = 0.31 with n = 50). The results reveal accurate DOC simulation, showcasing diverse annual and seasonal patterns intricately linked to flow intermittency. Dry years exhibited heightened DOC concentrations and spatial heterogeneity. Moreover, increased frequency and duration of dry periods corresponded with decreased annual DOC load. Applying SWAT-IR in non-perennial river systems promises to enhance model capabilities and deepen our understanding of flow intermittency’s critical role in carbon dynamics, particularly for future climate change scenarios. Graphical Abstract This study presents a novel modeling framework to simulate dissolved organic carbon (DOC) dynamics in non-perennial rivers, where flow intermittency plays a key role. By modifying the widely used Soil and Water Assessment Tool (SWAT), we developed SWAT-IR, a model capable of capturing hydrological and biogeochemical processes during both flowing and non-flowing stages. Key innovations include the explicit simulation of bidirectional water and nutrient exchanges between the stream and the aquifer, and the representation of non-flowing periods through simplified mass transfer processes, where dissolved nutrients are routed to groundwater and particulate nutrients settle as sediment organic matter. Using this tool, it was possible to assess DOC patterns in the Mediterranean Algars basin from 2006 to 2020. The model successfully reproduced spatially and temporally heterogeneous DOC concentrations, highlighting how drier years intensify DOC accumulation and spatial heterogeneity while reducing annual DOC loads, as well as revealing marked seasonal patterns closely linked with seasonal flow intermittency. SWAT-IR represents a significant step in simulating carbon dynamics in non-perennial rivers, particularly for future applications under climate change scenarios and in currently perennial river systems that are expected to shift toward non-perennial regimes globally.

Simulating Dissolved Organic Carbon Dynamics in Non-perennial Rivers: A Novel SWAT-IR Modeling Approach

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发表日期：

2025年8月11日

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O. Llanos-Paez,
J. Qi,
S. Sabater,
V. Acuña

摘要

In non-perennial rivers, flow intermittency significantly influences dissolved organic carbon (DOC) dynamics. However, understanding how spatial and temporal flow intermittency patterns influence DOC dynamics at the basin scale is challenging. While several models have been employed to study DOC dynamics in perennial rivers, most cannot integrate and simulate flow intermittency. To address this limitation, in this study, the Soil and Water Assessment Tool (SWAT) was adapted into SWAT-IR, tailored to non-perennial river characteristics. Using the SWAT-IR model, DOC dynamics were simulated in a Mediterranean river basin from 2006 to 2020 (streamflow calibration performance of NSE = 0.51 and R² 0.54 and DOC simulation accuracy of R² = 0.31 with n = 50). The results reveal accurate DOC simulation, showcasing diverse annual and seasonal patterns intricately linked to flow intermittency. Dry years exhibited heightened DOC concentrations and spatial heterogeneity. Moreover, increased frequency and duration of dry periods corresponded with decreased annual DOC load. Applying SWAT-IR in non-perennial river systems promises to enhance model capabilities and deepen our understanding of flow intermittency’s critical role in carbon dynamics, particularly for future climate change scenarios.

Graphical Abstract

This study presents a novel modeling framework to simulate dissolved organic carbon (DOC) dynamics in non-perennial rivers, where flow intermittency plays a key role. By modifying the widely used Soil and Water Assessment Tool (SWAT), we developed SWAT-IR, a model capable of capturing hydrological and biogeochemical processes during both flowing and non-flowing stages. Key innovations include the explicit simulation of bidirectional water and nutrient exchanges between the stream and the aquifer, and the representation of non-flowing periods through simplified mass transfer processes, where dissolved nutrients are routed to groundwater and particulate nutrients settle as sediment organic matter. Using this tool, it was possible to assess DOC patterns in the Mediterranean Algars basin from 2006 to 2020. The model successfully reproduced spatially and temporally heterogeneous DOC concentrations, highlighting how drier years intensify DOC accumulation and spatial heterogeneity while reducing annual DOC loads, as well as revealing marked seasonal patterns closely linked with seasonal flow intermittency. SWAT-IR represents a significant step in simulating carbon dynamics in non-perennial rivers, particularly for future applications under climate change scenarios and in currently perennial river systems that are expected to shift toward non-perennial regimes globally.