Hydrological Processes最新文献

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.

Solar radiation is often the largest energy input for river heat budgets. However, river temperatures are commonly interpreted using paired air and stream temperatures. These methods can be helpful in differentiating watershed characteristics of rivers on a network- to regional-scale, but it is difficult to draw reach-scaled conclusions about what is influencing high river temperatures. This study determines whether river reaches were more or less sensitive to solar radiation along the Big Hole River in southwestern Montana and discusses the effects of solar radiation on diel temperatures of river inflows (groundwater discharge, tributaries, and canal returns). Areas of groundwater discharge along the river banks were identified with a handheld thermal infrared camera along a 23-km reach during Summer 2023 and 2024 based on characteristic cooler temperatures. Logged temperatures of the groundwater discharge sites, tributaries, and canals were compared to each other, river temperatures, air temperatures, and solar radiation. Delays in diel fluctuations of upstream and downstream river temperatures were used to develop hysteresis curves to identify river reaches that respond more quickly to daily solar radiation. River reach temperatures that demonstrated a clockwise hysteresis curve on a downstream river temperature versus upstream river temperature plot were tightly associated with measurements of solar radiation. Groundwater discharge temperatures were generally cooler than the river; however, their diel fluctuations increased as stage lowered. At some sites, groundwater discharge flowed overland as runoff and warmed from solar radiation before discharging to the river. Tributaries and canals were either cooler or warmer than the river throughout the day; however, the maximum they could increase the river temperature was 0.1°C. Identifying river reaches sensitive to solar radiation can help focus locations for preservation and/or enhancement of identified groundwater discharges to create thermal refuges for cold-water species.

Groundwater is a major source of stream baseflow during the summer and can supply additional water to plant transpiration, which may be particularly important in Mediterranean environments where the growing season is decoupled from wet season precipitation. However, little is known about how forest management may affect groundwater level. We used a paired watershed design in a northern California coast redwood forest to study how intrinsic and extrinsic factors as well as harvesting affect groundwater level and the connectivity between soils, groundwater, and streams. Geomorphic variables such as soil depth, well depth (or depth to the confining layer), and slope were influential factors in our random forest model on groundwater level, and basal area was of moderate importance. However, harvesting did not have a significant effect on either wet or dry season groundwater level, which may be due to the large drought that occurred post-harvest. In this coast redwood forest, it appears that factors that affect vertical infiltration and lateral flow of rainfall, such as slope, soil depth, and well depth, may be more important than vegetative characteristics like stand density.