Hydrological Processes最新文献

River infiltration is important to groundwater recharge. The vertical infiltration volume of rivers is an important index for studying the mutual recharge of surface water and groundwater. In this study, the factors influencing the vertical infiltration of heterogeneous sediments were identified, and a vertical infiltration model of heterogeneous sediments was constructed via mathematical functions and machine learning. This study also applied a calculation method to the calculation of tributaries in the upper reaches of the Wenyu River. The effective grain size d₁₀ and the inhomogeneity coefficient C_u are the main controlling factors of the infiltration coefficient, and a genetic algorithm was introduced to fit a functional formula for the vertical infiltration volume based on the main controlling factors. It was found that the gradient boosting decision tree (GDBT) vertical infiltration model with the Lad function as the loss function was more effective than the back propagation neural network (BP) vertical infiltration model created with the Adam optimiser and ReLU activation function. The results of this study provide technical support for the quantitative calculation of natural sediment infiltration coefficients and principal support for the formulation of relevant standards for river ecological safety and management, which are of great theoretical significance and far-reaching application value.

Recent studies have suggested that cryogenic vacuum distillation (CVD) may cause the deuterium depletion of plant stem water. To assess the prevalence of this phenomenon, the stem rehydration experiments using four different water sources were conducted. The results showed that deuterium in the CVD extracts from 12 plant species was significantly depleted compared to the reference water. In addition, the CVD system also caused δ¹⁸O bias of plant water. Z-score analysis indicated that all isotopic values of plant samples extracted by CVD were questionable or unacceptable due to δ²H bias. The significant relationship between stem relative water content (SRWC) and δ²H bias was found across various water sources for plants. However, correcting the δ²H bias cannot be achieved using a fixed bias value and measurement of only SRWC considering the source water effect. The δ¹⁸O bias from CVD can be corrected by measuring RWC. Future studies should account for multiple factors when correcting the δ²H bias in plant xylem water extraction using CVD.

Drought is a multifaceted hazard, influenced directly or indirectly by factors such as precipitation, evapo-transpiration, soil moisture content and groundwater levels. Drought dynamics is fundamentally linked to hydrological processes, as droughts directly impact water availability, soil moisture and overall hydrological balance. Given the global climate change and consequent increasing frequency of extreme events, assessing the vulnerability to drought stress in underprivileged areas has become highly relevant. In this context, drought characterization has become crucial for understanding the complex patterns of droughts and its impacts on agriculture, ecosystems and communities, thereby contributing to food security, environmental sustainability and disaster preparedness. The major goal of this study was to evaluate the onset, duration, frequency and extent of agricultural drought using satellite-based datasets. The hyper-temporal Système Pour l'Observation de la Terre (SPOT) VEGETATION (VGT) Normalized Difference Vegetation Index (NDVI) data were used in this study to quantify the drought related stress on vegetation cover. The spatial extent of drought and its pattern were estimated using the long-term Vegetation Condition Index (VCI) derived from hyper-temporal SPOT-VGT NDVI datasets. Notably, strong agreement was found between the estimations of onset and duration, particularly during severe drought years such as 2002 and 2008. The study reveals that more over 95% of the total area encountered severe crop stress before the second week of July in 1999, 2002 and 2008, which are identified as severe drought years in the region. The frequency maps effectively captured the occurrence of drought events over a sixteen-year span, highlighting distinct drought episodes in the study area and underscoring the significant prevalence of drought stress across a considerable area. The high r² (0.61) value indicates a significant level of shared variability between VCI and yield of major crops, demonstrating their consistent alignment in capturing vegetation health and crop yield anomalies. The comprehensive delineation of drought patterns in the Bundelkhand region revealed by this study is potential for future preparedness efforts, enabling strategic planning and facilitating the implementation of sustainable policy interventions.

Urban flooding is an increasing threat to cities and resident well-being. The Federal Emergency Management Agency (FEMA) typically reports losses attributed to flooding which result from a stream overtopping its banks, discounting impacts of higher frequency, lower impact flooding that occurs when precipitation intensity exceeds the capacity of a drainage system. Despite its importance, the drivers of street flooding can often be difficult to identify, given street flooding data scarcity and the multitude of storm, built environment, and social factors involved. To address this knowledge gap, this study uses 922 street flooding reports to the city in Denver, Colorado, USA from 2000 to 2019 in coordination with rain gauge network data and Census tract information to improve understanding of spatiotemporal drivers of urban flooding. An initial threshold analysis using rainfall intensity to predict street flooding had performance close to random chance, which led us to investigate other drivers. A logistic regression describing the probability of a storm leading to a flood report showed the strongest predictors of urban flooding were, in descending order, maximum 5-min rainfall intensity, population density, storm depth, storm duration, median tract income, and stormwater pipe density. The logistic regression also showed that rainfall intensity and population density are nearly as important in determining the likelihood of a flood report incidence. In addition, topographic wetness index values at locations of flooding reports were higher than randomly selected points. A linear regression predicting the number of reports per area identified percent impervious as the single most important predictor. Our methodologies can be used to better inform urban flood awareness, response, and mitigation and are applicable to any city with flood reports and spatial precipitation data.

Quantitatively distinguishing between climate change and anthropogenic activities is crucial for flood management in the middle-lower reaches of the Yangtze River (MLRYR). However, the quantitative contribution of climate change and anthropogenic activities to flood occurrences in the region over long time scales (spanning more than one climatic state) and across extensive spatial areas remains unclear. This study aims to address such issue by analysing runoff data from 12 hydrological stations in the MLRYR from 1961 to 2020. By combining the Peak Over Threshold (POT) method with the detection of flood event initiation and termination days, we analysed changes in mean annual flood duration days (MAFD) across two distinct periods: 1961–1987 (Phase I) and 2001–2020 (Phase II). Our results demonstrate a significant positive correlation between precipitation and flood in the MLRYR throughout the study period, though this correlation is weaker in Phase II compared to Phase I. By applying the double mass curve method, we quantified the contributions of climate change and anthropogenic activities to changes in MAFD in the MLRYR, comparing the period of rapid urbanisation since the 21st century to Phase I, when urbanisation was at its initial stage. The results indicate that anthropogenic activities have significantly suppressed average annual flood occurrences in Phase II, with contribution rates ranging from 118% to 199%. Conversely, changes in precipitation have positively influenced flood occurrences in Phase II, with contribution rates ranging from 18% to 99%. The extensive construction of hydraulic engineering has played a crucial role in regulating the runoff of the main and tributary rivers in the MLRYR, thereby weakening the precipitation–flood relations since the 21st century. This study suggests that the continued construction of hydraulic engineering in the MLRYR may remain a crucial measure for mitigating the increased flood risks associated with global warming and accelerated urbanisation in the future.

The Huangshui River is a major tributary of the upper Yellow River. Understanding the hydrogeochemical processes involved in the formation of brackish groundwater in the Huangshui River Basin is essential for the rational development and utilisation of water resources, as well as for the protection of water resources and aquatic ecosystems. The chemical composition of brackish groundwater can reveal the hydrogeochemical processes it has undergone, while isotopic tracing can indicate the sources and processes of groundwater formation. This study employs hydrochemical and isotopic analyses to elucidate the contribution of groundwater–rock interactions to the formation of brackish groundwater in the Huangshui River Basin. The groundwater is classified as HCO₃–Ca·Mg type freshwater and SO₄·Cl–Ca·Mg type brackish water. Based on ion ratio coefficients and ⁸⁷Sr/⁸⁶Sr ratios, mineral dissolution, evaporation concentration and cation exchange are the dominant processes in the hydrochemical formation of brackish groundwater in the basin. The primary minerals undergoing dissolution in the basin include evaporites, carbonates and silicates. Discrimination using a hydrochemical component end-member mixing model identifies evaporites (73.6%) and carbonates (4.5%) as the main dissolved components in the brackish groundwater segment, while evaporites (67.5%) and carbonates (16.25%) are predominant in the partial dissolution of minerals in the freshwater segment. This suggests that the dissolution of evaporites plays a significant role in shaping the hydrogeochemistry of the Huangshui River Basin.