Hydrological Processes最新文献

Multiple successive tracer tests are often conducted to obtain reliable breakthrough curve results under regional groundwater flow, especially when the accuracy is crucial. In such cases, the period of rest between the end of the first divergent tracer test and the initiation of the second divergent tracer test allows the tracer from the first test to travel along with the background regional flow, thereby influencing the distribution of residual tracer concentration. This residual tracer could potentially interfere with breakthrough curve results from the tracer injection in the second tracer test. Additionally, the conventional analytical solution used for the divergent tracer test considers only radial flow; regional flow and consecutive tracer tests are ignored. Consequently, interpreting the behaviour of the tracer in consecutive divergent tracer tests under regional flow conditions is challenging using conventional measures because of background regional concentration. This study proposes a new semi-analytical solution, considering the effects of divergent radial and regional flows in consecutive tracer tests, addressing a critical gap in the conventional analytical solutions that, despite their practical necessity, have not been previously developed. The proposed semi-analytical solution was subjected to parameter studies under various scenarios. In our case studies, the conventional analytical solution based on a single tracer test can be safely used for parameter estimation only in cases where the injected mass for the subsequent tracer test is approximately six-fold that of the first tracer test or if the drift time is longer than 10 days.

The geographical uniqueness of the Qinghai–Tibet Plateau (QTP) determines its significance as ‘Asia's Water Tower’. It is expected that climate change in this area will cause extreme weather occurrences, stress water resources and increase the vulnerability of ecosystems in the future. However, the precise quantitative impact of climate change on the QTP remains uncertain. In this study, using coupled model intercomparison project (CMIP) phase 6 multi-model data and a distributed time-variant gain hydrological model (DTVGM), we examined the spatiotemporal attributes of climate and hydrology across the QTP under various socioeconomic progress trajectories and greenhouse gas emission scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5). Over the next 80 years, an overall warming trend was observed on the QTP, accompanied by a decrease in annual total water resources. The drier the arid regions, the wetter are the humid regions on the future QTP. Runoff will decrease by 74.92% in the region, and evaporation will increase by 84.93% from 2020 to 2099. In SSP5-8.5, the precipitation change rate was −6.22 mm/10a, and the runoff change rate was −8.84 mm/10a. After a year of abrupt precipitation change (2052–2064), the decrease in runoff became significantly faster. The total runoff was approximately 58.00% of the surface runoff. Unlike the runoff trend, evaporation displayed a fluctuating upward pattern, with an average change rate of 2.78 mm/10a. Spatially, the variations in dry–wet conditions became more evident, showing a substantial decrease in runoff and a noteworthy increase in evaporation on the northeastern plateau. In the southeastern region of the Yarlung Tsangpo River Basin, the precipitation and runoff increase rates were notably higher than those in other regions. Moreover, there was a significant surge in runoff in areas adjacent to the glaciers. In conclusion, this study offers valuable insights into decision-making concerning future developmental trajectories in the region.

Urban winter runoff management was mainly regulated by temperature variations and the snow-removing measures, but the underlying mechanism of the temperature-hydraulic conductivity (T-K) relation was seldom studied for urban environments and far from clearly understood. It is imperative to consider the T-K relation for snowmelt runoff calculation especially when the compound effects with the snow-removing measures and low impact development (LID) need to be considered. This work investigated the temperature regulation on urban infiltration and snowmelt runoff by a proposed modelling framework. A series of hydrologic model experiments revealed a crucial link between the hydraulic conductivity and snowmelt runoff emphasising the role of temperature in the partitioning between percolation and runoff. The inclusion of a T-K relation in the SWMM model resulted in a 26.0%–37.1% decrease in infiltration and a 12.7%–25.8% increase in runoff. The effects of the T-K relation were found to become more significant when the anthropogenic interventions such as snow-clearing measures and LID were applied. After the T-K mechanism was modelled, the infiltration and the runoff caused by the snow-clearing measures were reduced by 33.7%–48.2% and raised by 19.7%–35.6%, respectively, and LID would further reduce infiltration by 46.2%–65.2% and increase runoff by 71.0%–105.2%. This study serves as one of the first a few attempts to improve the understanding of the freeze–thaw cycles of land surface in urban environments.

Runoff generation and concentration are essential processes of the hydrological cycle. Understanding runoff generation mechanisms is crucial for improving the accuracy of hydrological forecasting and regional water resource assessment. This research aims to explore runoff generation mechanisms of farmlands in the North China Plain through analysing the impact of farmland vegetation on runoff generation in typical slopes. Seven experimental scenarios were designed based on various land uses under an artificial rainfall intensity of 60 mm/h, using two soil tanks with slopes of 2° and 4°, respectively. The regional climates, cropping structures and management practices were considered for the scenario design. The experiments were conducted at the experimental plot of artificial rainfall runoff on the Linmingguan campus of Hebei University of Engineering, located in Hebei Province, China, from October 2019 to June 2021. The results indicated that the surface runoff rate varied significantly, while the interflow rate remained relatively stable. The surface runoff accounted for 64%–89.36% of the total runoff volume, and the proportion increased with the increase of slope gradient. The start time of surface runoff (T_Rs) was delayed by 7.5 min, and runoff volume (V_Rs) decreased by 42%–50% as winter wheat grew from seedling to maturity. In contrast, the start time of interflow (T_Ri) occurred 3.5 min earlier, and runoff volume (V_Ri) increased by 54%–55%. T_Rs advanced, and both V_Rs and peak flow increased with the slope increasing under the same vegetation type; however, the results of interflow showed the opposite trend. The runoff volume increased and start time of runoff advanced in the bare land, probably benefiting from the impact of the crop rotation system on soil characteristics in North China. The findings of this research provide an insight into understanding runoff mechanisms in North China, reducing the uncertainty between model parameters and watershed characteristics and offering beneficial references for research and practice in related fields.

Climate change significantly impacts natural hydrological systems worldwide, affecting water availability and sedimentation dynamics. The upper Indus Basin is one of the most crucial basins in South Asia, which is undergoing severe climatic variations, resulting in extreme flooding. This study examines the impact of climate change on the hydrological cycle, water availability, and sedimentation dynamics in the Shyok River basin in the Karakoram region. The study focuses on investigating the increasing outflows on a seasonal basis, as found in the previous studies, by utilising daily river discharge data between 2003 and 2014 at Yugo hydrographic station operated by WAPDA with geographic information systems (GIS), SWAT+ (Soil and Water Assessment Tool), remote sensing, and statistical techniques. To analyse climatic variables, using only available ground weather stations inside the basin, we have utilised the ERA 5 reanalysis dataset to evaluate seasonal precipitation and temperature trends. The significance of ERA5-derived climatic variables has been assessed using the Mann-Kendall test, Sen's slope analysis and the Coefficient of Determination R² from 2000 to 2020 on a monthly basis. Analysis of seasonal discharge data using SWAT+ reveals a decline in water flow from July to October and a general upward trend during the last 20 years, such as a significant decrease in streamflow in the simulated trend, which was 293 m³/s in 2005 and dropped to 158 m³/s in 2017. In contrast, the maximum actual vs. simulated discharge decreased by 10 m³/s in 2010 and 2019, respectively. The temperature has increased by approximately 1.5°C. Seasonal precipitation analysis reveals an increasing trend in winter, while other seasons have shown fluctuating trends. Where the precipitation trends were found to be non-significant, with p > 0.05. An analysis of sediment load and discharge of the model output suggests active erosion in the channel at a rate of approximately 40 megatons/ha. The study highlights the impacts of climate change on water availability and sedimentation dynamics in the Shyok River basin in the Karakoram region. It attempts to contribute to the existing literature on the evaluation of climate-induced changes in river channel morphology. The study also highlights the necessity of continuous climatic and hydrographic data at the basin scale.