Hydrological Processes最新文献

Chloride is a natural ion and widely used tracer in hydrological and ecological studies. Tree canopies possess a natural filtration capacity that enables them to effectively capture aerosols, leading to potentially higher rates of ion deposition beneath the canopies compared to open areas. Therefore, understanding the spatial and temporal variability of chloride deposition in throughfall is crucial, particularly in coastal areas where chloride deposition exhibits significant variation. This study aims to estimate chloride throughfall deposition and analyze its distribution among different vegetation types on a small island, while concurrently comparing deposition rates in vegetated sites and open areas. The monitoring network consisted of 17 throughfall collectors positioned beneath the primary vegetation types. The findings demonstrate that vegetation plays a substantial role in enhancing chloride deposition by effectively intercepting marine aerosols, resulting in total deposition values among throughfall sites ranging from 8% to 3742% higher than nearby open sites over a ~ 2-year period. Norfolk pines, white oak, and hardwood forest exhibit significantly elevated chloride deposition in throughfall compared to a shrub stand (Hawaiian holly) and a mixed palm forest. Notably, isolated Norfolk pine sites exhibit exceptionally high chloride deposition. Key factors contributing to the spatial variation of chloride deposition in throughfall include vegetation type, leaf area index (LAI), and exposure to wind and marine aerosols. Additionally, temporal analysis using multiple regression reveals the considerable influence of rainfall depth and wind gust speed on the temporal distribution of chloride deposition in throughfall. The relatively high chloride deposition recorded on Norfolk Island highlights the significant role of vegetation in shaping total chloride deposition in small islands or coastal environments with extensive canopy cover. These findings add to the limited global evidence that neglecting vegetation effects in hydrological studies can underestimate chloride inputs, with implications for chloride mass balance and related methods.

The MESH hydrological model, driven by a 10 km meteorological reanalysis, was deployed to simulate the Saskatchewan River Basin (SRB), a 406 000 km² cold-region basin in Western Canada with diverse climate zones and extensive human regulation. The model was validated using multi-source observation and enabled detailed assessment of the basin's water balance components, runoff generation processes and irrigation impacts on hydrology. The model achieved Kling-Gupta Efficiency values of 0.35–0.85 across 23 streamflow stations (2005–2016), indicating reliable capture of observed flow regimes and reservoir regulation effects. Simulated evapotranspiration correlated strongly with satellite estimates (GLEAM, r = 0.98), and the model realistically reproduced seasonal snowpack dynamics and GRACE-derived water storage variations, with minor underestimation of peak snow water equivalent. Glacier diagnostics revealed that total runoff from glacier-covered areas contributes ~2.9% of SRB's mean annual runoff, of which 0.75% is glacier ice melt. Glacier ice melt runoff contributions varied by sub-basin, with the highest proportions from high-elevation regions: 1.96% to the North Saskatchewan near Edmonton, 1.14% to the Bow near its mouth, 0.66% to the Oldman and 0.32% to the Red Deer. A negative glacier mass balance trend strongest in southern sub-basins, signals declining ice reserves and the long-term vulnerability of glacier-fed water supplies. Diagnosis of runoff processes revealed significant variability in runoff generation, particularly in mountain headwaters and identified snowmelt as the dominant contributor, involved in 84.2% of runoff generation, broken down as snowmelt 43.4%, rain-on-snowmelt 10.2% and mixed events 30.6% of the SRB's annual runoff. Rainfall events contributed 15.8% and events with rainfall involved totalled 56.6% of annual runoff. This highlights the complexity of runoff generation processes in the SRB and the substantial role of snowmelt in sustaining the basin's hydrology. The impact of irrigation on evapotranspiration and streamflow was significant, with irrigation increasing mean annual evapotranspiration by 26.4% and reducing streamflow in key locations by up to 11%. Overall, this study provides a comprehensive and validated understanding of the SRB's hydrology and water resources, emphasising the influence of interactions between natural processes and human interventions. The insights from this research can inform water management strategies, particularly those aimed at adapting to future environmental changes. The findings underscore the importance of MESH as a robust tool for coupled hydrological and water resources modelling in managed, diverse, cold-regions basins.

As high latitudes warm, there is limited knowledge of how rapidly changing species composition and density, combined with shifting precipitation and thawing permafrost, will affect critical zone water fluxes across the subarctic. Here, we use stable isotopes of hydrogen and oxygen to assess the role of soil moisture, precipitation dynamics and plant species on the timing, magnitude and sources of plant water uptake at three sites along an elevational gradient in a subarctic, alpine catchment in southern Yukon, Canada. The sites ranged from a low-elevation boreal forest to higher elevation shrub taiga with variable shrub cover. We sampled soil and xylem water approximately every 3 weeks from pre-leaf out to post-senescence over two hydrologically distinct years. We answer the questions: (1) What are the seasonal and interannual changes in the isotopic composition of soil and xylem water across this range of subarctic vegetation covers?, (2) How does the seasonal origin of xylem water vary in wet and dry conditions? and (3) Do different shrub species at the same location rely on different sources of water? Results showed that while δ²H and δ¹⁸O of volume weighted precipitation became more negative with elevation, the opposite was true of xylem water. Despite less snowfall at lower elevations, plant water uptake was more reflective of snow water at the forest than at the high elevation shrub sites. Near-surface bulk soil water had lower line-conditioned excess at the forest than at the shrub sites throughout the season and with depth, highlighting increased contributions from soil evaporation at the forest. Differences in annual precipitation and climate had a strong influence on stable isotopes of hydrogen and oxygen in the soil. These results demonstrate that vegetation type and elevation strongly mediate plant water sourcing and evaporative partitioning in subarctic catchments, underscoring the need to account for species-specific and landscape-scale variability when predicting blue/green water fluxes in a changing climate.

To decipher the effects of space–time dynamics of precipitation on the resulting streamflow hydrographs, we herein analyse the controls of timing and shape of the 85 863 hourly streamflow events observed in 180 small German catchments. Using rainfall radar observations, spatially distributed snowmelt, soil moisture data and landscape properties we derive a comprehensive set of potential dynamic controls that apart from standard catchment- and event-averaged precipitation and wetness (i.e., lumped) characteristics represent: the space–time structure and the location of precipitation events within catchments; interaction of precipitation with surface (land use) and subsurface (soil) properties; and interaction of precipitation with antecedent wetness conditions. Interpretable machine learning based on random forest and accumulated local effects shows that among considered spatially and temporally differentiated controls, particularly the characteristics describing the location of precipitation events relative to catchment outlet and stream network, as well as the interaction of precipitation with the dynamic soil moisture and static soil characteristics have a strong effect on the timing of hydrographs. Instead, spatial and temporal structure (i.e., its uniformity or variability in space and time) affects their shapes. We also find that lumped precipitation and wetness characteristics are less relevant for large streamflow events (i.e., magnitudes larger than the 95th percentile). Instead, the space–time interaction of precipitation events with antecedent soil moisture is crucial for accurately predicting the timing and shape of large events. Their importance highlights the need to account for these aspects to improve the accuracy of flood simulations.

Water is an essential resource to preserve, yet it faces numerous pressures, including nitrate pollution from nitrogen inputs in agriculture. Models serve as valuable tools for analysing nitrate transfer and regulation processes within watersheds, helping to identify pollution sources. The coupling of the Soil and Water Assessment Tool (SWAT) with the drainage network biogeochemical model RIVE provides a comprehensive modelling approach called SWAT-RIVE, which was previously tested on a section of the Garonne River (France). This study evaluates the ability of SWAT-RIVE to represent hydrological and biogeochemical dynamics in the Vienne catchment (France). The objective of this paper is to evaluate and simulate hydro-biogeochemical dynamics from 1993 to 2017, focusing on nitrate transfer and regulation at the watershed scale, including wetlands and epilithic biofilm interfaces. As the nitrogen cycle is interconnected with other elements, such as organic carbon, phosphorus and silica, influencing processes like denitrification and plant or algal growth, the SWAT-RIVE representation of these elements was also assessed. Daily water and nitrate dynamics were well simulated at the catchment scale, with average NSE values of 0.45 and 0.15, R² values of 0.52 and 0.62 and KGE values of 0.65 and 0.39, respectively. Some other variables were accurately simulated at the outlet, particularly dissolved oxygen (NSE = 0.96, R² = 0.96, KGE = 0.89), dissolved silica (NSE = 0.85, R² = 0.93, KGE = 0.72) and dissolved organic carbon (NSE = 0.52, R² = 0.82, KGE = 0.50), confirming the possibility of using SWAT-RIVE outputs to evaluate nitrate dynamics at the catchment scale. Despite several limitations, the coupling of SWAT and RIVE leads to a more precise quantification of biogeochemical processes on hillslopes and in the watercourse, making it possible to consider the use of SWAT-RIVE in other watersheds.

Seawater flooding on sandy beaches can mobilise sediments, elevate water tables, and salinize fresh groundwater, driving complex fluid, solute, and heat fluxes that are challenging to monitor. While past studies have assessed vertical saltwater intrusion, they seldom consider the thermal dynamics of beach sediments or how temperature signals can yield insights into other coastal dynamics. This study examines the influence of seawater flooding and erosion/accretion on beach sediment temperature dynamics to identify distinct thermal signatures for future quantitative applications of heat as a tracer of coastal zone dynamics. Over 1 year of multi-depth beach sediment temperature, groundwater level, and electrical conductivity data collected on Sable Island, Canada, reveal the influence of meteorologic, oceanic, hydrogeologic, and morphologic drivers on beach thermal regimes. Meteorological forcing expectedly exerts a dominant diurnal and seasonal control on shallow sediment temperatures in clear conditions. During seawater flooding, shallow sediment temperatures rapidly change to equilibrate with local sea surface temperatures as seawater infiltration drives ‘thermal plug flow’ due to advection-dominated heat transport. Winter floods warm beach sediments while spring floods cool beach sediments, revealing seasonally distinct thermal disturbances due to flooding. Beach morphodynamics influence the propagation of sediment temperature dynamics because erosion (accretion) increases (decreases) the amplitude ratios between sediment temperatures at the surface and a fixed subsurface elevation. Thermal consonance timing (TCT) and an analytical solution to the one-dimensional heat diffusion equation yield time series of morphologic evolution that match manual measurements. Complex temperature signals from moisture, salinity, and thermal dynamics limit the applicability of established heat tracing approaches for quantifying vertical porewater fluxes in beaches; however, distinct thermal signatures help qualitatively trace seawater flooding and erosion/accretion. Results lay the foundation for future quantitative algorithms that use heat to infer concurrent beach morphodynamics and groundwater fluxes and their influence on biogeochemical processes and coastal ecosystem functioning.

Tracer-enabled hydrological models are increasingly used to investigate water pathways by integrating hydrometric and stable isotope data. While quantifying the sensitivity of model outputs to global parameters is a common practice, structural sensitivity to empirical evaporative fractionation models is rarely explored, despite its critical influence on isotopic signatures, especially in evapotranspiration-dominated basins. In this study, we build upon the process-based distributed model EcH₂O-iso to quantify both types of isotopic sensitivities—conceptual, from changing the Craig and Gordon formulation used to quantify soil evaporative fractionation, widely applied in tracer-enabled hydrology, and parametric, from varying classical non-isotopic hydrodynamics parameters—in a tropical savanna basin in northern Benin with mixed land cover (fallow and forest). Looking at five locations and hydrological compartments, covering both local and basin scales, our results show that both types of sensitivities are of similar magnitude and significance, leading to changes in δ¹⁸O outputs by several per mil. We further show that the choice of conceptual fractionation framework influences parametric sensitivities, especially locally, while at basin scales, sensitivities decrease as mixing may dominate over fractionation processes. Additionally, we highlight how vegetation-dependent root uptake further modulates the impact of modelling choices on tracer sensitivity. The differentiated relationships between inputs (parametric and conceptual) and outputs (isotopic time series) not only demonstrate the leverage of isotopic information to identify model configurations but also benchmark how evaporation fractionation formulations may alter the propagation of this information for estimating parameters controlling water storage and fluxes.

Dynamic water storage is the water that remains for enough time in watersheds to influence streamflow generation, chemically weather rock and drive the release of solutes, breakdown organic carbon (C) through microbial activity, and sustain vegetation between periods of precipitation. The amount and connectivity of dynamic water stores control critical zone processes, including evapotranspiration, vegetation productivity and mortality, streamflow, weathering and solute transport. Here, we present recent advances and identify frontiers in the study of dynamic water storage in the critical zone, focusing on observational techniques for quantifying dynamic storage, advances in conceptual and numerical models that capture dynamic storage, and emerging hypotheses that drive dynamic storage evolution. We specifically identify and focus on four primary dynamic water storages: snow, plant-accessible water, groundwater, and surface water. While we use semi-arid mountain environments as an exemplar of dynamic storage controls on critical zone processes, this work offers implications for a broad range of geoclimatic settings.