M. A. Chaudhry, S. Kiemle, A. Pohlmeier, R. Helmig, J. A. Huisman
Saline water evaporation from porous media is a key phenomenon in the terrestrial environment and is linked to problems such as soil salinization and weathering of building materials. Recent modeling studies suggest the development of local instabilities due to density differences during evaporation in case of saturated porous media with high permeability. To experimentally investigate this and improve our understanding of near surface solute accumulation, we performed evaporation experiments on two types of porous media (F36 and W3) with intrinsic permeabilities that differed by two orders of magnitude. Using magnetic resonance imaging (23Na-MRI), we monitored the development of solute accumulation and subsequent redistribution during evaporation under wicking conditions. The F36 sample showed an initial enrichment at the surface, but soon after a downwards moving plume developed that redistributed NaCl into the column. Average depth profiles of Na concentrations obtained from 3D imaging showed that the surface concentration reached only 2.5 mol L−1, well below the solubility limit. In contrast, the W3 sample with lower permeability showed enrichment in a shallow near-surface zone reaching a concentration of over 6 mol L−1. No fingering occurred although the mean evaporation rate was similar to that of F36 sand. Comparison of experimental results with numerical simulations using DuMux for both samples showed qualitative agreement between measured and modeled solute concentrations. This study experimentally confirms the importance of density-driven redistribution of solutes in case of evaporating saturated porous media, carrying implications for predicting evaporation rates and the time to start of salt crust formation.
{"title":"Non-Invasive Imaging of Solute Redistribution Below Evaporating Surfaces Using 23Na-MRI","authors":"M. A. Chaudhry, S. Kiemle, A. Pohlmeier, R. Helmig, J. A. Huisman","doi":"10.1029/2025wr041207","DOIUrl":"https://doi.org/10.1029/2025wr041207","url":null,"abstract":"Saline water evaporation from porous media is a key phenomenon in the terrestrial environment and is linked to problems such as soil salinization and weathering of building materials. Recent modeling studies suggest the development of local instabilities due to density differences during evaporation in case of saturated porous media with high permeability. To experimentally investigate this and improve our understanding of near surface solute accumulation, we performed evaporation experiments on two types of porous media (F36 and W3) with intrinsic permeabilities that differed by two orders of magnitude. Using magnetic resonance imaging (<sup>23</sup>Na-MRI), we monitored the development of solute accumulation and subsequent redistribution during evaporation under wicking conditions. The F36 sample showed an initial enrichment at the surface, but soon after a downwards moving plume developed that redistributed NaCl into the column. Average depth profiles of Na concentrations obtained from 3D imaging showed that the surface concentration reached only 2.5 mol L<sup>−1</sup>, well below the solubility limit. In contrast, the W3 sample with lower permeability showed enrichment in a shallow near-surface zone reaching a concentration of over 6 mol L<sup>−1</sup>. No fingering occurred although the mean evaporation rate was similar to that of F36 sand. Comparison of experimental results with numerical simulations using DuMu<sup>x</sup> for both samples showed qualitative agreement between measured and modeled solute concentrations. This study experimentally confirms the importance of density-driven redistribution of solutes in case of evaporating saturated porous media, carrying implications for predicting evaporation rates and the time to start of salt crust formation.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":"18 1","pages":""},"PeriodicalIF":5.4,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The prediction of river planimetric evolution and related interactions with anthropic activities and public safety is one of the most critical aspects in the planning of a sustainable land-use. Since the beginning of the past century, a large number of theoretical and experimental studies have focused on the investigation of river meandering dynamics, coming to sometimes contrasting conclusions in the forecast of the associated bend sequence pattern. Drawing inspiration from the phenomenological equivalence between fluid-dynamic and morpho-dynamic dispersion within the river floodplain, the present contribution proposes an explicit analytical solution in terms of scale-dependent and equilibrium sinuosity. Such analytical solution, which reveals the strong dependence of river equilibrium planform on valley bank-full velocity distribution, is successfully validated on the basis of a field data set provided via a restoration pilot project by Basilicata Region Environment and Energy Department (Italy), and further discussed by related lagrangian simulations. Moreover, the governing equation from which the equilibrium solution originates is shown to be compatible with the interpretation of near-equilibrium dynamics highlighted by stochastic numerical experiments documented in the literature.
{"title":"A Cascade-Like Energy Dissipation Mechanism Behind the Gradual Achievement of River Equilibrium Sinuosity","authors":"M. Pannone","doi":"10.1029/2025wr041123","DOIUrl":"https://doi.org/10.1029/2025wr041123","url":null,"abstract":"The prediction of river planimetric evolution and related interactions with anthropic activities and public safety is one of the most critical aspects in the planning of a sustainable land-use. Since the beginning of the past century, a large number of theoretical and experimental studies have focused on the investigation of river meandering dynamics, coming to sometimes contrasting conclusions in the forecast of the associated bend sequence pattern. Drawing inspiration from the phenomenological equivalence between fluid-dynamic and morpho-dynamic dispersion within the river floodplain, the present contribution proposes an explicit analytical solution in terms of scale-dependent and equilibrium sinuosity. Such analytical solution, which reveals the strong dependence of river equilibrium planform on valley bank-full velocity distribution, is successfully validated on the basis of a field data set provided via a restoration pilot project by Basilicata Region Environment and Energy Department (Italy), and further discussed by related lagrangian simulations. Moreover, the governing equation from which the equilibrium solution originates is shown to be compatible with the interpretation of near-equilibrium dynamics highlighted by stochastic numerical experiments documented in the literature.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":"49 1","pages":""},"PeriodicalIF":5.4,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yubo Jia, Xiaoling Su, Vijay P. Singh, Bingnan Zhao, Te Zhang, Jiangdong Chu, Haijiang Wu
Accurate runoff forecasting helps mitigate flooding and drought risks and ensure water security under changing conditions. Compared to deterministic prediction models, interval prediction can more effectively quantify uncertainty, enhancing practical applicability. However, the Mixture Density Network (MDN) model—a state-of-the-art probabilistic modeling approach in hydrology—is susceptible to bias from distributional misspecification, and its prediction intervals are often overly wide, reducing practical utility. We therefore innovatively incorporated the Weighted Conformal Inference (WCI) strategy, which accounts for distributional shifts in runoff sequences, and integrated it with MDN to develop the WCI-MDN model for runoff interval prediction. To validate the effectiveness of the WCI strategy, we constructed six models in total: MDNs and WCI-MDNs under three distributions—Gaussian Mixture (GMM), Laplace Mixture (LMM), and Countable Mixtures of Asymmetric Laplacians (CMAL)—and evaluated their accuracy and robustness using data from 222 basins in the CAMELS-AUS data set. Results indicated that among the three MDN models, the LMM distribution achieved the best interval prediction performance, followed by the CMAL and GMM distributions. After introducing the WCI strategy, the coverage width-based criterion (CWC) for GMM, LMM, and CMAL distributions decreased by approximately 61.1%, 48.7%, and 54.3%, respectively, across all basins, demonstrating that the WCI-MDNs achieved higher prediction reliability. Furthermore, compared to the MDNs, the standard deviation of the CWC for the WCI-MDNs was reduced by 66.7%–81.8%, indicating higher robustness. Thus, the study improved the existing MDNs, providing a promising new approach for runoff interval prediction.
{"title":"A Novel Hybrid Predictive Model Based on Mixture Density Networks With Weighted Conformal Inference Strategy for Runoff Interval Prediction Across Australia","authors":"Yubo Jia, Xiaoling Su, Vijay P. Singh, Bingnan Zhao, Te Zhang, Jiangdong Chu, Haijiang Wu","doi":"10.1029/2024wr039807","DOIUrl":"https://doi.org/10.1029/2024wr039807","url":null,"abstract":"Accurate runoff forecasting helps mitigate flooding and drought risks and ensure water security under changing conditions. Compared to deterministic prediction models, interval prediction can more effectively quantify uncertainty, enhancing practical applicability. However, the Mixture Density Network (MDN) model—a state-of-the-art probabilistic modeling approach in hydrology—is susceptible to bias from distributional misspecification, and its prediction intervals are often overly wide, reducing practical utility. We therefore innovatively incorporated the Weighted Conformal Inference (WCI) strategy, which accounts for distributional shifts in runoff sequences, and integrated it with MDN to develop the WCI-MDN model for runoff interval prediction. To validate the effectiveness of the WCI strategy, we constructed six models in total: MDNs and WCI-MDNs under three distributions—Gaussian Mixture (GMM), Laplace Mixture (LMM), and Countable Mixtures of Asymmetric Laplacians (CMAL)—and evaluated their accuracy and robustness using data from 222 basins in the CAMELS-AUS data set. Results indicated that among the three MDN models, the LMM distribution achieved the best interval prediction performance, followed by the CMAL and GMM distributions. After introducing the WCI strategy, the coverage width-based criterion (CWC) for GMM, LMM, and CMAL distributions decreased by approximately 61.1%, 48.7%, and 54.3%, respectively, across all basins, demonstrating that the WCI-MDNs achieved higher prediction reliability. Furthermore, compared to the MDNs, the standard deviation of the CWC for the WCI-MDNs was reduced by 66.7%–81.8%, indicating higher robustness. Thus, the study improved the existing MDNs, providing a promising new approach for runoff interval prediction.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":"24 1","pages":""},"PeriodicalIF":5.4,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145968874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aquifer storage and recovery (ASR) is increasingly used worldwide to maintain, enhance and secure freshwater availability. However, its implementation presents challenges due to the potential risk of virus contamination from injected water sources such as stormwater runoff and treated wastewater, as well as premature breakthrough of native groundwater caused by density-dependent flow. This study incorporates the virus transport and removal processes into a 2D-axisymmetric numerical model of coupled density-dependent groundwater flow and salt transport, accounting for physical heterogeneity with varying connectivity features, correlation lengths and layer structures. Geochemical heterogeneity is modeled using Colloid Filtration Theory (CFT), linking attachment rate coefficients to permeability distribution. The results reveal that density-dependent flow enhances virus removal, particularly during the storage phase, by distorting virus plume and increasing virus attachment. Neglecting density effects leads to an underestimation of virus removal, which in turn overestimates the required post-treatment intensity, especially under stricter potable standards. Aquifer heterogeneity exerts a coupled and dual control on density-driven virus removal, enhancing it through high-permeability connectivity during storage but reducing it through preferential flow and limited attachment during recovery. This study underscores the potential of native brackish-to-saline groundwater conditions to enhance virus attenuation in ASR systems. The findings contribute to existing guidelines for site selection and ASR system design, along with considerations for pre-/post-treatment and/or desalination facilities, by emphasizing the importance of density-dependent flow, aquifer heterogeneity, and project-specific objectives of ASR.
{"title":"Impact of Density-Dependent Flow and Aquifer Heterogeneity on Virus Transport and Removal During Aquifer Storage and Recovery","authors":"Hongkai Li, Zhilin Guo, Kewei Chen, Rixin Wu, Xuchen Zhai, Zhenzhong Zeng, Chunmiao Zheng","doi":"10.1029/2025wr040755","DOIUrl":"https://doi.org/10.1029/2025wr040755","url":null,"abstract":"Aquifer storage and recovery (ASR) is increasingly used worldwide to maintain, enhance and secure freshwater availability. However, its implementation presents challenges due to the potential risk of virus contamination from injected water sources such as stormwater runoff and treated wastewater, as well as premature breakthrough of native groundwater caused by density-dependent flow. This study incorporates the virus transport and removal processes into a 2D-axisymmetric numerical model of coupled density-dependent groundwater flow and salt transport, accounting for physical heterogeneity with varying connectivity features, correlation lengths and layer structures. Geochemical heterogeneity is modeled using Colloid Filtration Theory (CFT), linking attachment rate coefficients to permeability distribution. The results reveal that density-dependent flow enhances virus removal, particularly during the storage phase, by distorting virus plume and increasing virus attachment. Neglecting density effects leads to an underestimation of virus removal, which in turn overestimates the required post-treatment intensity, especially under stricter potable standards. Aquifer heterogeneity exerts a coupled and dual control on density-driven virus removal, enhancing it through high-permeability connectivity during storage but reducing it through preferential flow and limited attachment during recovery. This study underscores the potential of native brackish-to-saline groundwater conditions to enhance virus attenuation in ASR systems. The findings contribute to existing guidelines for site selection and ASR system design, along with considerations for pre-/post-treatment and/or desalination facilities, by emphasizing the importance of density-dependent flow, aquifer heterogeneity, and project-specific objectives of ASR.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":"94 1","pages":""},"PeriodicalIF":5.4,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145956220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Understanding how snowmelt is partitioned into different hydrologic flowpaths/storages—and how this partitioning varies over time—is essential for predicting water availability and quality under climate variability. In this study, we examine the time-variance of snowmelt partitioning patterns (SPP) in response to interannual variations in antecedent (Fall) rainfall before snowmelt seasons, across two snow-dominated catchments in Canada and Sweden with contrasting geologic and topographic features. Using integrated subsurface–surface flow and transport modeling, combined with observational data, we simulate the partitioning of snowmelt into shallow flowpath, deep flowpath, evapotranspiration, and long-term storage. To generalize our findings beyond the two case studies, we design a suite of virtual experiments that systematically vary catchment slope and the extent of the hydraulic conductivity's vertical and lateral heterogeneity. Results show that lateral heterogeneity in conductivity mediates the sensitivity of snowmelt partitioning to interannual variations in antecedent rainfall. While laterally homogeneous catchments display minimal sensitivity of snowmelt partitioning pattern to wet or dry Fall rainfall conditions, catchments with heterogeneous lateral structure store a significantly larger portion of snowmelt and reduce snow-sourced shallow flow contributions in years with high pre-snow rainfall than years with low pre-snow rainfall. In contrast, while slope and vertical conductivity architecture govern SPP, they play a limited role in mediating SPP's temporal sensitivity to antecedent rainfall variability. These findings reveal that subsurface structure—including the extent of lateral subsurface heterogeneity—modulates the influence of climate variability on snowmelt partitioning and catchment hydrologic function. This has implications for predicting streamflow responses, groundwater recharge, and solute transport under changing climate regimes, and highlights the importance of representing time-variable hydrologic behavior in hydrologic models.
{"title":"Time Variance in Snowmelt Partitioning: A Mechanistic Modeling Approach to Explore the Role of Catchment Structure and Pre-Snow Rainfall","authors":"Mahbod Taherian, Ali A. Ameli","doi":"10.1029/2025wr040679","DOIUrl":"https://doi.org/10.1029/2025wr040679","url":null,"abstract":"Understanding how snowmelt is partitioned into different hydrologic flowpaths/storages—and how this partitioning varies over time—is essential for predicting water availability and quality under climate variability. In this study, we examine the time-variance of snowmelt partitioning patterns (SPP) in response to interannual variations in antecedent (Fall) rainfall before snowmelt seasons, across two snow-dominated catchments in Canada and Sweden with contrasting geologic and topographic features. Using integrated subsurface–surface flow and transport modeling, combined with observational data, we simulate the partitioning of snowmelt into shallow flowpath, deep flowpath, evapotranspiration, and long-term storage. To generalize our findings beyond the two case studies, we design a suite of virtual experiments that systematically vary catchment slope and the extent of the hydraulic conductivity's vertical and lateral heterogeneity. Results show that lateral heterogeneity in conductivity mediates the sensitivity of snowmelt partitioning to interannual variations in antecedent rainfall. While laterally homogeneous catchments display minimal sensitivity of snowmelt partitioning pattern to wet or dry Fall rainfall conditions, catchments with heterogeneous lateral structure store a significantly larger portion of snowmelt and reduce snow-sourced shallow flow contributions in years with high pre-snow rainfall than years with low pre-snow rainfall. In contrast, while slope and vertical conductivity architecture govern SPP, they play a limited role in mediating SPP's temporal sensitivity to antecedent rainfall variability. These findings reveal that subsurface structure—including the extent of lateral subsurface heterogeneity—modulates the influence of climate variability on snowmelt partitioning and catchment hydrologic function. This has implications for predicting streamflow responses, groundwater recharge, and solute transport under changing climate regimes, and highlights the importance of representing time-variable hydrologic behavior in hydrologic models.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":"47 1","pages":""},"PeriodicalIF":5.4,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145938232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qiang An, Liu Liu, Lixin Wang, Arie Staal, Yongming Cheng, Jing Liu, Guanhua Huang
Water security in China is challenged by pronounced spatial and temporal heterogeneity in water resources, driven by distinct moisture sources: advected (externally transported) and recycled (locally generated) moisture. However, the quantitative impacts of different moisture sources on hydrological variability remain unexplored. This study quantified their contributions to precipitation (P) and water availability (WA) across China and its nine major river basins from 2000 to 2022 using atmospheric moisture tracking. We propose a novel decomposition framework to partition the variability of total P and WA into independent contributions from each moisture source and their synergistic interactions. We find that synergistic effects between the two sources amplify national-scale spatial disparities but mitigate intra-basin heterogeneity in five of the nine major basins. At the national scale, advected moisture peaks earlier in the year than recycled moisture. However, a distinct north-south contrast emerges: southern regions depend more on advected moisture, while northern regions depend primarily on recycled moisture. Unsynchronized peaks between advected and recycled moisture in southern basins buffer seasonal extremes, whereas synchronized peaks in northern basins intensify intra-annual variability. These findings underscore the need for region-specific water management: climate-informed strategies for advected moisture-dependent regions and land-atmosphere feedback-aware approaches for recycled moisture-reliant areas. This study provides a framework for addressing hydrological imbalances under changing climate and land-use patterns.
{"title":"Spatiotemporal Contributions of Advected and Recycled Moisture to Water Resource Variability in China","authors":"Qiang An, Liu Liu, Lixin Wang, Arie Staal, Yongming Cheng, Jing Liu, Guanhua Huang","doi":"10.1029/2025wr041192","DOIUrl":"https://doi.org/10.1029/2025wr041192","url":null,"abstract":"Water security in China is challenged by pronounced spatial and temporal heterogeneity in water resources, driven by distinct moisture sources: advected (externally transported) and recycled (locally generated) moisture. However, the quantitative impacts of different moisture sources on hydrological variability remain unexplored. This study quantified their contributions to precipitation (P) and water availability (WA) across China and its nine major river basins from 2000 to 2022 using atmospheric moisture tracking. We propose a novel decomposition framework to partition the variability of total P and WA into independent contributions from each moisture source and their synergistic interactions. We find that synergistic effects between the two sources amplify national-scale spatial disparities but mitigate intra-basin heterogeneity in five of the nine major basins. At the national scale, advected moisture peaks earlier in the year than recycled moisture. However, a distinct north-south contrast emerges: southern regions depend more on advected moisture, while northern regions depend primarily on recycled moisture. Unsynchronized peaks between advected and recycled moisture in southern basins buffer seasonal extremes, whereas synchronized peaks in northern basins intensify intra-annual variability. These findings underscore the need for region-specific water management: climate-informed strategies for advected moisture-dependent regions and land-atmosphere feedback-aware approaches for recycled moisture-reliant areas. This study provides a framework for addressing hydrological imbalances under changing climate and land-use patterns.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":"84 1","pages":""},"PeriodicalIF":5.4,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145938233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
There is a global abundance of non-perennial rivers and streams, of which are predicted to increase due to environmental change and anthropogenic influences. However, most modeled representations of streamflow have been constructed with perennial systems in mind, leaving a gap in our understanding and representation of non-perennial systems. To adapt to future challenges, there is a need to determine what modeled representations of low- and no-flow in non-perennial rivers and streams do well and where uncertainties may lie in the internal representations of hydrologic processes. Here we compare four publicly available process-based hydrologic models: Variable Infiltration Capacity, Precipitation Runoff Modeling System, and National Water Model versions 2.1 and 3.0, in their ability to represent non-perennial streamflow regimes across 156 streamgages that experience non-perennial streamflow behavior in the Pacific Northwest. Our results show that process-based models are largely unable to capture non-perennial streamflow behavior, and that simulation skill decreases as a function of increasing aridity of a streamgage location. Most simulations underestimate the number of no- and low-flow days a streamgage experiences and overestimates the magnitude of low-flows. The ability to accurately model non-perennial systems is paramount to draw inferences about the connections between hydrologic characteristics of low- and no-flow and the potential ecological, biogeochemical, and societal implications of these important systems. Our findings suggest that improving our predictive understanding of non-perennial streamflow of rivers and streams within the Pacific Northwest will fill critical gaps and better target the timing and location of future research, management, and conservation efforts as well as improve the usability of these models for a wider audience of practitioners across fields.
{"title":"Process-Based Hydrologic Model Representations of Non-Perennial Streamflow in the Pacific Northwest, USA","authors":"Adam N. Price, Kendra E. Kaiser","doi":"10.1029/2025wr040626","DOIUrl":"https://doi.org/10.1029/2025wr040626","url":null,"abstract":"There is a global abundance of non-perennial rivers and streams, of which are predicted to increase due to environmental change and anthropogenic influences. However, most modeled representations of streamflow have been constructed with perennial systems in mind, leaving a gap in our understanding and representation of non-perennial systems. To adapt to future challenges, there is a need to determine what modeled representations of low- and no-flow in non-perennial rivers and streams do well and where uncertainties may lie in the internal representations of hydrologic processes. Here we compare four publicly available process-based hydrologic models: Variable Infiltration Capacity, Precipitation Runoff Modeling System, and National Water Model versions 2.1 and 3.0, in their ability to represent non-perennial streamflow regimes across 156 streamgages that experience non-perennial streamflow behavior in the Pacific Northwest. Our results show that process-based models are largely unable to capture non-perennial streamflow behavior, and that simulation skill decreases as a function of increasing aridity of a streamgage location. Most simulations underestimate the number of no- and low-flow days a streamgage experiences and overestimates the magnitude of low-flows. The ability to accurately model non-perennial systems is paramount to draw inferences about the connections between hydrologic characteristics of low- and no-flow and the potential ecological, biogeochemical, and societal implications of these important systems. Our findings suggest that improving our predictive understanding of non-perennial streamflow of rivers and streams within the Pacific Northwest will fill critical gaps and better target the timing and location of future research, management, and conservation efforts as well as improve the usability of these models for a wider audience of practitioners across fields.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":"30 1","pages":""},"PeriodicalIF":5.4,"publicationDate":"2026-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145903631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ludwig Strötz, Matti Leppäranta, Kaarina Weckström, Maija Heikkilä, Jan Weckström
The Arctic is the fastest-warming region globally. Lake ice is a sentinel indicator of Arctic change, with wide impacts on hydrological regimes, biodiversity, and ecosystem services. While small lakes are ubiquitous across northern boreal and tundra zones, ice observations remain biased toward large lakes with distinct freezing and melting dynamics. We present high-resolution, field camera-based ice phenology records of 10 small lakes (2–20 ha) in northwest Finnish Lapland spanning low (LE, ∼300 m) and high (HE, 770–1,010 m) elevations over two consecutive seasons. Ice-on timing was uniform across elevations, occurring at cumulative degree-day sums of −10°C·d on shallow LE lakes, and −30°C·d on deeper HE lakes. Thawing from groundwater upwelling was observed across many LE lakes. While the recorded melting process at LE occurred over several days during late May, at HE it extended over weeks into late June to early July, due to long-lasting continuous snow cover, cold meltwater inflow, and increased sublimation. Our thermodynamic lake ice model accurately predicted total ice thickness (R = 0.99, RMSE ≤ 5.8 cm), reaching ∼80 cm at LE and ∼100 cm at HE, but the snow-ice fraction was underpredicted. Freezing and melting were strongly modulated by snow, highlighting the impact of future precipitation changes on ice thickness, quality, and ice-off timing. The rapid and spatially uniform freezing suggests a direct response of small lake phenology to Arctic warming—unlike large lakes, where the summer heat storage, depth, and turbulent mixing are important modulators.
{"title":"Ice Phenology and Thickness in Small Arctic Lakes: Field Observations and Mechanistic Controls","authors":"Ludwig Strötz, Matti Leppäranta, Kaarina Weckström, Maija Heikkilä, Jan Weckström","doi":"10.1029/2025wr041332","DOIUrl":"https://doi.org/10.1029/2025wr041332","url":null,"abstract":"The Arctic is the fastest-warming region globally. Lake ice is a sentinel indicator of Arctic change, with wide impacts on hydrological regimes, biodiversity, and ecosystem services. While small lakes are ubiquitous across northern boreal and tundra zones, ice observations remain biased toward large lakes with distinct freezing and melting dynamics. We present high-resolution, field camera-based ice phenology records of 10 small lakes (2–20 ha) in northwest Finnish Lapland spanning low (LE, ∼300 m) and high (HE, 770–1,010 m) elevations over two consecutive seasons. Ice-on timing was uniform across elevations, occurring at cumulative degree-day sums of −10°C·d on shallow LE lakes, and −30°C·d on deeper HE lakes. Thawing from groundwater upwelling was observed across many LE lakes. While the recorded melting process at LE occurred over several days during late May, at HE it extended over weeks into late June to early July, due to long-lasting continuous snow cover, cold meltwater inflow, and increased sublimation. Our thermodynamic lake ice model accurately predicted total ice thickness (<i>R</i> = 0.99, RMSE ≤ 5.8 cm), reaching ∼80 cm at LE and ∼100 cm at HE, but the snow-ice fraction was underpredicted. Freezing and melting were strongly modulated by snow, highlighting the impact of future precipitation changes on ice thickness, quality, and ice-off timing. The rapid and spatially uniform freezing suggests a direct response of small lake phenology to Arctic warming—unlike large lakes, where the summer heat storage, depth, and turbulent mixing are important modulators.","PeriodicalId":23799,"journal":{"name":"Water Resources Research","volume":"40 1","pages":""},"PeriodicalIF":5.4,"publicationDate":"2026-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145897764","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. L. P. Warburton, J. Del Vecchio, C. R. Meyer, M. C. Palucis
On some frozen hillslopes, subsurface water above permafrost is routed through regularly spaced, linear features known as water tracks, which are active sources of greenhouse gas release. We test whether water tracks form through thermal channelization, where heat from viscous dissipation in flowpaths deepens the thaw, creating a preferred flow path that attracts more water. We derive equations for suprapermafrost Darcy flow—that occurring in unfrozen ground (the active layer) above perennially frozen soil. Using linear stability analysis, we calculate growth rates and obtain wavelength selection for this system, which we compare to observed water track spacing from the Low Arctic. Our model predictions are sensitive to flow speed, but the predicted cross-slope water track patterns are consistent with observed water track spacing under high flow conditions in the Low Arctic. Our analysis implies that signatures of a warming, wetter climate may be found in reduced inter-track spacing and increasing water track extent.
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