查看更多>>摘要：This study explores the hydraulic relationship between marine tides and groundwater levels in Medvjeđa špilja Cave on Lošinj Island, northern Adriatic, Croatia. Using water level loggers in the cave pool and adjacent sea, we recorded a peak tidal lag of 20-30 min and nearly identical amplitudes, confirming a strong hydraulic connection driven by the cave's proximity to the sea and high hydraulic conductivity. To complement this, geochemical parameters such as dissolved oxygen and pH were measured to assess the mixing of seawater and freshwater within the cave system and its response to tidal forces. Seasonal monitoring revealed notable tidal amplitude variations, with the largest observed in autumn, indicating the importance of this period for future studies. Tidal variations influenced the mixing of oxygenated seawater into the cave system, as reflected in dissolved oxygen levels, while stable pH values highlighted the buffering capacity of the system. These findings suggest that Medvjeđa špilja Cave holds significant potential for reconstructing historical sea levels using phreatic overgrowths on speleothems (POS). As the first study of its kind in the Adriatic, this research provides a methodological framework for analysing tidal dynamics in coastal karst systems. It emphasises the importance of high-resolution monitoring for understanding coastal aquifers and the potential of such studies to inform sea-level reconstructions in changing environmental conditions.
J. Renée BrooksHenry M. JohnsonKeira JohnsonSteven P. Cline...
1-16页
查看更多>>摘要：Snowpacks are an important water source for mountainous rivers, worldwide. The timing and volume of streamflow in systems reliant on snowmelt can be affected by changes in snow accumulation and melt time. In the Cascade Range (western USA), seasonal snowpacks are predicted to decrease by over 50% within the next century. During the last decade, Cascade Range snowpacks have varied between 17% and 150% of the median 1981-2023 peak snowpack values. To understand how snowpack variation could affect Willamette River streamflow, we monitored water stable isotopes over 13 years from two sites on the mainstem and 60 streams draining small catchments across the Willamette River Basin. Small catchment water stable isotope values integrated and dampened variation in precipitation isotopes and varied with elevation, providing a marker for determining the mean elevation from which streamflow in the Willamette River was derived. During winter, while snow accumulates in the mountains, most streamflow in the Willamette River originates from rainfall at lower elevations. During summer low-flow conditions, most streamflow in the river was derived from winter snow that accumulated at elevations above 1200 m, which represents < 12% of the Willamette River Basin area. Peak snow water equivalent from the previous winter was positively correlated with the proportion of Willamette River streamflow derived from > 1200 m during the summer low-flow period, but both high elevation (> 1200 m) precipitation and temperature trends explained nearly as much variance as snow water equivalent. However, after accounting for climate trends, the estimated amount of high-elevation streamflow in the Willamette River during summer low-flow has decreased over the past 13 years. Improved understanding of the origin of, and trends in, summer streamflow in the Willamette River will aid in reconciling human demands with biological instream requirements during periods of low snowpack.
查看更多>>摘要：River water quality degradation poses significant challenges for catchment nutrient management. Effective catchment-scale nutrient management requires a clear understanding of how different contaminants are transported along different flowpaths. Here we investigated nutrient transport pathways and their relative contributions for two prevalent contaminants (total phosphorus: TP; and nitrate-nitrite nitrogen: NNN) at 58 river water quality sites across New Zealand, by applying the Bayesian, chemistry-assisted hydrograph separation approach, in which river flow is partitioned into three components: near-surface event flow (fast flow), seasonal shallow groundwater discharge (medium flow) and long-term groundwater discharge (slow flow). After excluding 15 sites that were impacted by dam/lake outflows or model convergence, results from 43 sites revealed that on an annual basis, medium flow contributes over 50% of annual streamflow at 19 sites and fast flow contribution exceeds 50% at 9 sites. Regarding TP load, TP is primarily transported via fast flow (26 sites), followed by medium flow (14 sites). Concerning NNN loads, most NNN originates from medium flow (25 sites). Correlation analysis with upstream catchment characteristics indicated that annual flow is most highly correlated with precipitation and potential evapotranspiration, followed by geomorphologic factors (e.g., slope) and livestock density, whereas TP loads are most strongly correlated with the number of days with high rainfall, catchment elevation and dairy cow density, and NNN loads are most correlated with annual temperature, geomorphology and geology factors (e.g., slope), as well as land cover (e.g., pastoral) and livestock density which serve as sources of NNN. These findings provide valuable insights for both surface and subsurface transport pathways in New Zealand. The approach offers a practical framework for similar assessments in other regions, to mitigate water quality degradation.
查看更多>>摘要：Wind-driven sediment resuspension is a common phenomenon and impacts water quality and ecological balance in shallow lake systems. Aquatic vegetation (AV) alters the local hydrodynamics and thus influences the sediment resuspension processes, with its morphology as one of the most important factors. To understand the effect of AV on wave and sediment motion, field experiments were conducted for a year across a complete plant growth cycle in Dongping Lake, China. The vegetation morphology, water velocity, suspended sediment concentration, and wind direction/velocity were monitored within a patch of submerged flexible vegetation (i.e., Potamogeton crispus). Results showed that the existence of AV not only dampened the significant wave height (Hs) within the patch, but also attenuated the in-canopy wave orbital velocity (Uw_horiz) compared with the water surface, which indicated a dual reduction for near-bed wave velocity compared with bare-bed conditions. Variations of wave height and velocity reduction were related to vegetation morphological parameters. With vegetation experiencing its flourishing to senescent stages, the decrease of plant roughness density (i.e., from 3.89 to 1.81) weakened the wave velocity attenuation (i.e., from 12.7% to 5.4%). In the present study, the near-bed wave velocity in the centre of the vegetation patch was reduced by 40%-55%, even for the cases with vegetation in the senescent stage. The reduced near-bed wave velocity increased the critical velocity for sediment incipient motion from 3.0 cm/s for bare-bed conditions to 5.0 cm/s in vegetated cases. Besides, relationships between near-bed sediment concentration and hydrodynamics demonstrated wave dominance in resuspension initiation, transitioning to combined wave-current control during sustained suspension events. This study highlighted the effect of vegetation morphology induced by phenological evolution on wave-sediment motion, and its results have great significance for water pollution control and ecological restoration in shallow lakes.
查看更多>>摘要：In Pleistocene glacial regions, glacial till aquitards typically exhibit a significant regional-scale decrease in hydraulic parameters, such as specific storage (Ss) and hydraulic conductivity (K), with depth due to increased sediment compaction, reduced porosity, and lower pore connectivity. Pumping rates also decrease over time due to equipment wear and hydraulic friction. This study developed a novel analytical model for variable groundwater discharge in a leaky aquifer system, incorporating the often-overlooked vertical heterogeneity of aquitards. The model integrates two exponential decay mechanisms: one for the aquitard Ss and K with depth, and one for the pumping rates over time. Special cases addressing only depth-decaying Ss, depth-decaying K, or constant rates were also derived. New analytical solutions investigate how the decay exponents of aquitard Ss and K, variable pumping rates, and aquitard thickness influence drawdown and groundwater budgets. Results reveal that variable pumping rates cause local maxima and minima in aquifer drawdown, especially with higher decay of Ss and K. While aquitard thickness and pumping rates affect depletion and leakage, changes in the physical properties of aquitards, such as the decay of Ss and K, are more critical in determining the actual patterns of depletion and leakage fractions. Larger Ss decay or smaller K decay enhance early peak depletions caused by time-decaying pumping rates. These results highlight the importance of prioritising depth-dependent parameters in groundwater management, particularly in regions with significant vertical heterogeneity, like glacial deposits. The study offers valuable insights for hydrological assessments and optimising groundwater resource management in similar settings.
查看更多>>摘要：Groundwater is a key strategic water resource in times of drought, yet climate and land use change are increasing threats; this means that quantitative understanding of groundwater dynamics in lowland catchments is becoming more urgent. Here, we used a spatially distributed numerical groundwater model to simulate seasonal and long-term changes in the spatio-temporal patterns of water storage dynamics and groundwater-surface water interactions in the 66 km2 lowland Demnitzer Millcreek catchment (DMC) in NE Germany. DMC experienced a long period of drought following the hot, dry summer of 2018, with groundwater stores becoming depleted and stream flows increasingly intermittent. The architecture and parameterisation of the model domain were based on groundwater observations, hydrogeological mapping and geophysical surveys. Weekly simulations using a single model layer with a 50 × 50 m grid of 15 m depth were able to broadly reproduce observed shallow groundwater dynamics in glacial and post-glacial deposits across the catchment. We showed that most groundwater flow is shallow and focused around topographic convergence zones fringing the channel network in more permeable glaciofluvial deposits. Most stream flow is generated by shallow groundwater in the catchment headwaters, which is relatively young (i.e., ~5 years old). With potential evapotranspiration rates exceeding precipitation, the groundwater balance is very sensitive to hydroclimate at DMC. The past two decades have been dominated by negative anomalies in annual rainfall, causing a general lowering of water tables and persistent storage deficits. Spatio-temporal patterns of recharge are also strongly influenced by vegetation cover, with coniferous forests, in particular, having high evapotranspiration losses that inhibit groundwater recharge. This underlines the importance of developing integrated land and water management strategies in NE Germany where climate change is expected to further reduce rainfall, increase temperatures and decrease groundwater recharge. For an evidence base to guide policy, we need to develop more robust ways to interface groundwater models with ecohydrological models to better characterise the impacts of land use on rechange in groundwater-dominated lowland catchments.
查看更多>>摘要：This research paper investigates the interplay between urban vegetation, surface energy fluxes, and hydrological processes in mitigating heat and adapting to global warming. Through climate model simulation, this study explored how vegetation coverage (measured by leaf area index, LAI) and the impervious surface fraction (fimp) influence hydrological dynamics, urban heat island (UHI), and energy fluxes across various climate zones within Asian cities for the period of 2000 to 2014. Kuala Lumpur and Singapore (tropical rainforest) showed significant increasing UHI trends of 0.319℃ and 0.271℃/month, respectively. Bangkok and Ho Chi Minh (tropical savanna) showed a negative correlation between LAI and temperature (UHI) of -0.31 (-0.57), indicating the cooling effects of vegetation through evapotranspiration. In tropical rainforest climates, a strong positive correlation between LAI and latent heat flux highlights the critical role of water availability in modulating hydrological cycles and vegetation dynamics. Humid continental/subtropical climates showed a positive correlation between LAI and sensible heat flux, highlighting the influence of sensible heat exchange on vegetation growth. A positive correlation was demonstrated between energy fluxes and fimp across all climate zones, indicating that urbanisation intensifies hydrological disruptions, exacerbating the UHI effect. This study emphasises the importance of integrating hydrological insights into urban vegetation strategies for effective heat mitigation and climate adaptation.
查看更多>>摘要：Streamflow forecasting using interpretable machine learning methods (MLs) for exploring runoff processes has received a lot of attention. However, exploring multi-step ahead daily streamflow forecasting considering antecedent streamflow as an input for various interpretable MLs is very limited. Thus, three interpretable MLs for daily streamflow forecasting in the Huaihe River basin of China during 2002-2020, including eXtreme Gradient Boosting (XGBoost), long short-term memory neural network (LSTM) and convolutional neural network (CNN) with SHapley Additive exPlanations (SHAP) method, were implemented to study the role of potential controlling factors, including antecedent streamflow, soil moisture and vegetation growth, in runoff processes at lead times of 0-6 days. The forecasting performances decreased with lead times. Specifically, the LSTM model performed best at lead times of 0-3 days, followed by CNN and XGBoost. CNN was superior to LSTM and XGBoost models when the lead time was greater than 3 days. The optimal forecasting performances were 0.71-0.97, 311.45-674.27 m3/s, 0.84-0.97 and 0.75- 0.97 according to Nash-Sutclife efficiency, root-mean- square error, correlation coefficient and Kling-Gupta efficiency, respectively. The interpretable results varied across different MLs and at different lead times. The antecedent streamflow consistently dominated the runoff processes, particularly in the LSTM and XGBoost models. However, the significant role of soil moisture at the depth of 28-100 cm and leaf area index for low vegetation gradually emerged with increased lead times for CNN models, even outranking the importance of antecedent streamflow. Furthermore, the interpretability demonstrated by the optimal machine learning models was validated through the infiltration model and uncertainty analysis. Overall, interpretable machine learning has great potential to enhance our understanding of basin-scale runoff processes.
Raul MendozaWillem van VerseveldChris SeijgerAlbrecht Weerts...
1-16页
查看更多>>摘要：An appropriate soil configuration is essential in hydrological models given the role of subsurface processes in the hydrological functioning of a catchment. Hydrological models are typically set up with shallow soil depths as restricted by measurements and soil datasets that are often unavailable in greater depths. While this may be sufficient for some catchments, in some areas the water table is located deeper and thus the shallow groundwater and its link with the rest of the hydrological processes may not be captured well by the model. An important soil parameter, that is known to vary with soil depth, is the saturated hydraulic conductivity (Ksat). In this study, we assessed different vertical profiles of Ksat which exceed the typical soil measurement depths. The Ksat profiles were implemented in wflow.jl for the distributed hydrological model wflow_sbm and tested for the Vecht catchment. Results demonstrated that increasing the soil thickness and implementing any of the Ksat profiles assessed improved the discharge and mean groundwater depth predictive capabilities, albeit altering the groundwater dynamics. A sensitivity analysis revealed the respective influence of four model parameters on the groundwater dynamics which can be used as basis to optimise the model performance further.
Linus S. SchauerJames W. JawitzMatthew J. CohenAndreas Musolff...
1-14页
查看更多>>摘要：The deterioration of stream water quality threatens ecosystems and human water security worldwide. Effective risk assessment and mitigation requires spatial and temporal data from water quality monitoring networks (WQMNs). However, it remains challenging to quantify how well current WQMNs capture the spatiotemporal variability of stream water quality, making their evaluation and optimisation an important task for water management. Here, we investigate the spatial and temporal variability of concentrations of three constituents, representing different input pathways: anthropogenic (NO~(3-)), geogenic (Ca~(2+)) and biogenic (total organic carbon, TOC) at 1215 stations in three major river basins in Germany. We present a typology to classify each constituent on the basis of magnitude, range and dominance of spatial versus temporal variability. We found that mean measures of spatial variability dominated over those for temporal variability for NO~(3-) and Ca~(2+), while for TOC they were approximately equal. The observed spatiotemporal patterns were robustly explained by a combination of local landscape composition and network-scale landscape heterogeneity, as well as the degree of spatial auto-correlation of water quality. Our analysis suggests that river network position systematically influences the inference of spatial variability more than temporal variability. By employing a space-time variance framework, this study provides a step towards optimising WQMNs to create water quality data sets that are balanced in time and space, ultimately improving the efficiency of resource allocation and maximising the value of the information obtained.
NETL
NSTL
Wiley