•LSPIV with stereo-vision can measure river surface topography and velocity simultaneously.•3D surface reconstruction is essential for accurate image orthorectification in LSPIV analysis.•Stereo ...Imaging LSPIV can be a reliable yet low-cost solution for autonomous mountain river gauging.
Large-Scale Particle Image Velocimetry (LSPIV) has been successfully applied for stream flow and flood measurements. In most LSPIV studies, the water surface has been approximated as a two-dimensional planar surface. Errors may arise due to this approximation for flows in steep channels and with complex riverbed topography, especially for small mountain rivers. In this study, a Stereo Imaging based LSPIV system (SI-LSPIV) is developed to reconstruct the three-dimensional topography and water surface distribution, in addition to surface velocity measurements. The SI-LSPIV system consists of two synchronized Raspberry Pi camera modules that can capture stereo images autonomously. Uncalibrated rectification and point cloud methods are implemented for surface reconstruction. Detailed three-dimensional surface topography as well as water level distribution can be obtained, which facilitates image ortho-rectification and wetted-area delineation for LSPIV calculation. Over the past years, an unattended SI-LSPIV system has been deployed in Longxi River, Sichuan, China. One major flow event was captured and the results were presented to demonstrate that LSPIV analysis aided with three-dimensional water surface distribution can improve velocity measurement and stream discharge estimation for torrential mountain river flows.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Since 1999, large‐scale ecosystem restoration has been implemented in the Loess Plateau, effectively increasing regional vegetation coverage. Vegetation restoration has significantly elevated the ...saturated hydraulic conductivity (Ks) of the near‐surface soil layers and increased the vertical heterogeneity of the Ks profile. Many studies have examined the change of runoff due to revegetation, yet the impacts of Ks profile on the soil moisture distribution and runoff generation processes were less explored. In this study, numerical simulations were conducted to investigate how changes in the Ks profile caused by vegetation restoration influenced the hydrological responses at event scale. The numerical simulation results show that the increase of surface Ks caused by vegetation restoration can effectively reduce runoff at event scale. Moreover, the enhancement of vertical heterogeneity of Ks profiles can significantly change the vertical profile of soil water content, prompting more water to percolate into the deep soil layer. When rainfall exceeds a threshold, the accumulation of soil water above the relatively less permeable layer can cause short‐term saturation in shallow soil layers, resulting in a transient perched water table. As a result, after the vegetation restoration in the Loess Plateau, though Horton overland flow is still the main runoff generation mechanism, there is a possibility of the emergence of Dunne overland flow under the high vegetation coverage (e.g., NDVI larger than 0.5). This emergence of new runoff generation mechanism, saturation excess runoff, in the Loess Plateau due to the vegetation restoration could provide scientific guidance for water and sediment movement, soil and water conservation practices, and desertification control in the Loess Plateau.
Vertical heterogeneity of saturated hydraulic conductivity (Ks) amplified by revegetation could lead to significant runoff reduction. Significant revegetation can enhance the infiltration, altering rainfall partitioning at event scale. Higher NDVI, corresponding to larger surface Ks, leads to a shift in runoff generation mechanism, from HOF to shallow DOF in the Loess Plateau.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
•A novel mechanism of shallow landslide was found.•Accumulation of infiltrated water on the soil interface was key in the mechanism.•Failure types and features were largely influenced by rainfall ...characteristics.
Rainfall-induced shallow landslide is a common geological hazard around the world that can pose serious threat to both lives and property. Previous studies suggested that rainfall induced shallow landslides always occurred either above the bottom of a downward wetting front in infiltration, or below a rising water table. This paper proposed a different mechanism of shallow landslides in a modelling approach. The comprehensive physics-based Integrated Hydrology Model (InHM) and the infinite slope stability model were employed on a virtual slope to simulate the hydrologic response and estimate the slope stability. Different failure mechanisms with various characteristics were investigated under diverse rainfall scenarios (i.e., various combinations of rainfall depths, durations and temporal patterns). The results showed a novel mechanism of shallow landslides: a significant vertical change in saturated hydrologic conductivity causes the accumulation of infiltrated water, and subsequently leading to an increase pore pressures and landslides in unsaturated soil layer. More importantly, this kind of landslide would bring larger landslide volume even with smaller total rainfall depths. This study expanded our understanding about landslides and had important application in alleviating the loss of lives and property.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Rainfall characteristics are key factors influencing infiltration and runoff generation in catchment hydrology, particularly for arid and semiarid catchments. Although the effect of storm movement on ...rainfall‐runoff processes has been evaluated and emphasized since the 1960s, the effect on the infiltration process has barely been considered. In this study, a physically based distributed hydrological model (InHM) was applied to a typical semi‐arid catchment (Shejiagou, 4.26 km2) located in the Loess Plateau, China, to investigate the effect of storm movement on infiltration, runoff and soil erosion at the catchment scale. Simulations of 84 scenarios of storm movement were conducted, including storms moving across the catchment in both the upstream and downstream directions along the main channel, while in each direction considering four storm moving speeds, three rainfall depths and two storm ranges. The simulation results showed that, on both the hillslopes facing downstream (facing south) and in the main channel, the duration of the overland flow process under the upstream‐moving storms was longer than that under the downstream‐moving storms. Thus, the duration and volume of infiltration under upstream‐moving storms were larger in these areas. For the Shejiagou catchment, as there are more hillslopes facing downstream, more infiltration occurred under the upstream‐moving storms than the downstream‐moving storms. Therefore, downstream‐moving storms generated up to 69% larger total runoff and up to 351% more soil loss in the catchment than upstream‐moving storms. The difference in infiltration between the storms moving upstream and downstream decreased as the storm moving speed increased. The relative difference in total runoff and sediment yield between the storms moving upstream and downstream decreased with increasing rainfall depth and storm speed. The results of this study revealed that the infiltration differences under moving storms largely influenced the total runoff and sediment yield at the catchment scale, which is of importance in runoff prediction and flood management. The infiltration differences may be a potential factor leading to different groundwater, vegetation cover and ecology conditions for the different sides of the hillslopes.
Catchment hydrological modelling indicated that the infiltration volume of the upstream‐moving storms (Iu) was larger than that of the downstream‐moving storms (Id), because both on the hillslopes facing downstream (facing south) and in the main channel the overland flow under the upstream‐moving storms lasted longer than that under the downstream‐moving storms, especially in recession time. As there are more hillslopes facing downstream in the catchment, more infiltration occurred under the upstream‐moving storms than that under the downstream‐moving ones (Figure b). Generally, the downstream‐moving storms generated up to 69% larger runoff and up to 351% more soil erosion than the upstream‐moving storms.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Check dams are an effective and widespread measure for soil and water conservation around the world (e.g., in the Chinese Loess Plateau). However, the quantitative impact of a heavy silted check dam ...with small remaining storage capacity and large deposition area on river flow and sediment transport during floods remained unclear. In this study, to investigate this impact, a physics‐based distributed hydrological model (the Integrated Hydrology Model, InHM) was employed to simulate runoff and sediment processes during floods in a small catchment with a check dam in the Loess Plateau, considering different heavy rainfalls and check‐dam remaining storages. The model was calibrated and validated against the observed hydrographs and sedigraphs in two flood events and obtained satisfactory modelling performance (the Nash–Sutcliffe efficiencies > 0.70). The scenario modelling results showed that a heavy silted check dam still remarkably reduced and delayed the peaks of river flow and sediment rate, due to the attenuated surface flow movement and sediment transport on the deposition area. The largest flow peak occurred around the 85% silting stage of the check dam rather than the fully silting stage (100%). Even in the fully silted stage, sediment deposition continually occurred on the deposition area with a maximum deposition of 11,700 t sediment in a heavy‐rainfall scenario and more sediment deposited on the tail‐end regions of the deposition area than other regions after a flood. Moreover, in heavy silted stage backwater on the tail‐end areas and gullies largely attenuated local erosion and promoted sediment deposition, indirectly reducing the total sediment yield of the catchment during flood. These results indicated that numerous ageing check dams built in the Loess Plateau and worldwide are still useful to attenuate flood risk and soil erosion, and sound maintenance and management of the check‐dam will be beneficial to flood and soil erosion control.
A heavy silted check‐dam can still reduce and delay flood peak. During rainfall‐runoff events much sediment deposited in the deposition area of the check dam, especially in the tail‐end regions, due to the slow surface flow movement and sediment transport there. These findings indicated that a heavy silted check‐dam was still capable to attenuate surface flow and sediment transportation, and sound maintenance and management of the check‐dam will be beneficial to flood and soil erosion control.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Eutrophication of rivers and receiving waters has become a major environmental issue worldwide, which may further intensify due to projected climate changes and expansion of urbanization or ...agricultural development to meet the needs of increased human population. However, our understanding of climatic and land use change impacts on riverine nutrient retention and export to receiving waters is limited due to lack of empirical measurements and uncertainties about the nature of future climate changes. The aim of this paper is to analyze the response of nitrate transport and transformation in river systems to potential changes in climate and land use management, individually, and in combination. A coupled hydrological and biogeochemical model is implemented in a hypothetical river basin, with realistic inputs and parameters, for the simulation of nitrate dynamics in river networks. Results indicate that for the same annual rainfall, increased within‐year rainfall variability propagates to increased streamflow variability and a significant reduction in nitrate retention. Analysis of the effects of the spatial distribution of nitrate inputs around the river network showed that for the same total nitrate input from land, nitrate retention increased considerably through locating land use types with high nitrate input away from the river outlet. Simulation results also indicated that even without a reduction in total nitrogen input from land, optimized land use distribution around the river network can compensate the enhanced nitrogen input that may arise from increased rainfall variability. These findings offer viable strategies for catchment management to mitigate increased water quality degradation caused by expected future climate changes.
Key Points
The increase in rainfall variability could lead to significant reduction in the overall nitrate removal by increasing streamflow variability
Spatial heterogeneity in lateral input could have impact on overall nitrate removal when they are scaled with distance to outlet
Better land use management is capable to compensate the increasing risk of eutrophication caused by climate change induced rainfall change
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
► An upgraded reliability ensemble averaging method is used for climate projections. ► An inverse distance weighting method with MODWEC is proposed under data scarcity. ► Uncertainty is considered by ...using different emission scenarios and time stages. ► Simulated changes indicate likely more floods in summer and droughts in autumn.
The hydrological cycle has been substantially influenced by climate change and human activities. It is therefore of utmost importance to analyze the impact of climate change on hydrology, particularly on a regional scale, in order to understand potential future changes of water resources and water-related disaster, and provide support for regional water management. However, during the evaluation of climate change impact on hydrology or water resources, large uncertainty exists. In this paper, the Soil Water Assessment Tool (SWAT) model is used to investigate the potential impact of climate change on hydrology of the upper reaches of Qiantang River Basin, East China, for the future period 2011–2100. The uncertainty is considered by employing upgraded reliability ensemble averaged GCM climate projections under three emission scenarios A1B, A2 and B1 for three different stages of the future period. These projections are downscaled and used in the hydrological model. Impact of climate change on precipitation, potential evapotranspiraton and river runoff is then investigated. The model calibration and validation outcomes show reasonable performance of the SWAT model. The final results suggest that annual river runoff will likely decrease almost under all emission scenarios and time stages of the future period. Particularly, at Jinhua Station, substantial decrease of annual river runoff can be noticed, indicating less water resource possibly available for the region in future. Simulated monthly patterns show that the largest decrease will likely occur in winter while increases will occur in summer, implying possible more water-related disasters in this region. However, it is also noticed that the change signs/amount could be different under different emission scenarios and time stages, indicating large uncertainty involved in the impact analysis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
► Upstream moving rainfalls generate hydrographs with earlier rise, lower peak. ► Surface sealing changes infiltration pattern and affects runoff generation. ► Runoff and erosion rate peaks appear at ...the same time for rainfall moving downstream. ► Soil moisture increases rapidly and then decreases for rainfall moving downstream. ► Soil cracks are likely to occur for rainfall moving downstream or position fixed.
The impact of rainfall characteristics on runoff generation and soil erosion are not fully understood despite their importance. In this study, a series of laboratory experiments, systematically considering different rainfall intensities, durations, moving directions, rainfall positions, and no-rainfall intervals, were conducted to investigate the impacts of rainfall characteristics on runoff generation and soil erosion. Significant differences, including hydrograph, sediment graph, soil water content, and infiltration depth (depth of wetting front), were observed. The following conclusions are drawn for the studied rainfall characteristics and soil from this study: (1) when compared with moving upstream rainfall scenarios (MURSs), moving downstream rainfall scenarios (MDRSs) can generally be characterized by hydrographs with a later rise and higher runoff peak for most of the rainfall events; (2) surface sealing changes the infiltration pattern so that MURS generally produce more total runoff than MDRS, and for some rainfall events MDRS generate lower runoff peak than MURS, which is different from what has been widely reported; (3) with the increase in the runoff peak, the erosion peak increases first and then decreases, indicating a switch from transport-limited erosion to detachment-limited erosion; (4) the increase ratio of underground water content for MURS is lower than MDRS; (5) rainfall duration is an important factor in soil crack occurrence. Not only does this study expand the understanding of hydrologic response and erosion, it also provides an important database for the hydrology community.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
This article enhances the physics‐informed neural networks (PINNs) method to effectively model the hydrodynamics of real‐world river networks with irregular cross‐sections. First, we pre‐process ...hydraulic parameters to optimize training speed without compromising accuracy, achieving a 91.67% acceleration compared with traditional methods. To address the vanishing gradient problem, layer normalization is also incorporated into the architecture. We also introduce novel physical constraints—water level range and junction node equations—to ensure effective training convergence and enrich the model with additional physical insights. Two practical case studies using HEC‐RAS benchmarks demonstrate that our improved PINN method can predict river network hydrodynamics with less data and is less sensitive to time step size, allowing for longer computational time steps. Incorporating physical knowledge, our enhanced PINN methodology emerges as an efficient and promising avenue for modelling the complexities of hydrodynamic processes in natural river networks.
This study optimizes physics‐informed neural networks (PINNs) for hydrodynamic modelling in real river systems, achieving a 91.67% increase in training speed with pre‐training integration and mitigating vanishing gradients using layer normalization. Incorporating unique constraints on water levels and junctions, it enriches physical understanding and training efficacy. Tested against HEC‐RAS benchmarks, our method predicts river hydrodynamics with less data and greater time step flexibility, establishing our enhanced PINNs as an efficient solution for complex river network modelling.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Check dams are one of the most common strategies for controlling sediment transport in erosion prone areas, along with soil and water conservation measures. However, existing mathematical models that ...simulate sediment production and delivery are often unable to simulate how the storage capacity of check dams varies with time. To explicitly account for this process—and to support the design of check dam systems—we developed a modelling framework consisting of two components, namely (1) the spatially distributed Soil Erosion and Sediment Delivery Model (WaTEM/SEDEM), and (2) a network-based model of check dam storage dynamics. The two models are run sequentially, with the second model receiving the initial sediment input to check dams from WaTEM/SEDEM. The framework is first applied to Shejiagou catchment, a 4.26 km2 area located in the Loess Plateau, China, where we study the effect of the existing check dam system on sediment dynamics. Results show that the deployment of check dams altered significantly the sediment delivery ratio of the catchment. Furthermore, the network-based model reveals a large variability in the life expectancy of check dams and abrupt changes in their filling rates. The application of the framework to six alternative check dam deployment scenarios is then used to illustrate its usefulness for planning purposes, and to derive some insights on the effect of key decision variables, such as the number, size, and site location of check dams. Simulation results suggest that better performance—in terms of life expectancy and sediment delivery ratio—could have been achieved with an alternative deployment strategy.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
