Hydrological Processes最新文献

While research on the hydrologic impact of different types of stormwater control measures (SCMs) is extensive, little research exists linking urbanization, widespread implementation of SCMs and channel stability in headwater streams. This study evaluated whether the unified stormwater sizing criteria (USSC) regulations in the state of Maryland, USA, which require the use of both end-of-pipe and distributed, small-scale SCMs, protect channel stability. To achieve this goal, a coupled hierarchical modelling approach utilizing the Storm Water Management Model (SWMM) and the Hydrologic Engineering Center River Analysis System 6.3 (HEC-RAS) was developed to predict changes in streamflow and sediment transport dynamics in a first-order gravel-bed, riffle-pool channel. Storm event discretization revealed that 88% of observed storm events during the 16 years (2004–2020) had durations less than 18 h and that the greatest peak flows resulted from storm events with durations less than 24 h. HEC-RAS simulation results also showed that both channel degradation and aggradation, as high as 1.2 m, will likely occur due to regulations which require the use of 24 h duration design storms with a target stormwater detention time rather than bed material sediment transport limits. Overall, this study provides valuable insights into the complex interactions between SCM practises, flow regimes and sediment transport dynamics in heavily urbanized watersheds. It is recommended that SCMs be designed using a continuous simulation model with at least 10 years of continuous rainfall data. Furthermore, to protect channel stability, the SCM design goal should focus on maintaining pre-development sediment transport regimes across a range of flows.

Snow cover ablation within the Ohio River Basin (ORB) plays an important role in regional hydroclimatology, while also representing a potential hazard during large and rapid events. Rain-on-snow ablation is a particular challenge, where runoff rates are typically enhanced due to the dual inputs of snowmelt and liquid precipitation. Here, we present a 40-year climatology of snow ablation events frequency, intensity, and timing for the ORB using a 4-km gridded snow-water-equivalent dataset, focusing on the relative proportion of events caused by rain-on-snow and changes over time. Spatial patterns of snow ablation frequency and intensity mirror that of seasonal snowfall totals, with higher (lower) values in the northern and eastern (southern) portions of the basin. Rain-on-snow events represent approximately 40% of all ablation events within the basin and result in approximately 24%–25% more snow-water-equivalent loss than non-rain-on-snow events, plus an additional 3–12 mm of liquid precipitation per event on average. Peak frequency of ablation and rain-on-snow events occurs in late winter and early spring, similar to that of the surrounding region. Over time, the frequency of ablation and rain-on-snow events has decreased in the northern and eastern portions of the basin, in some cases by as much as 30%. Trends in event magnitudes were more isolated but decreased across portions of central IN, northern KY, eastern OH and northern WV. Additionally, the magnitude of precipitation during rain-on-snow events has increased across the region, extending from northern KY into western PA by over 100% in many cases. Broadly, we find tendencies towards fewer events with less snow loss but more liquid precipitation that suggest complicated impacts to the hydroclimatology warranting further investigation.

Investigating the relationship between tree growth within a year and environmental factors is crucial for understanding how climate change affects seasonal tree growth patterns. In this study, high-resolution point dendrometers were used to monitor the stem radial changes of Oak trees (Quercus acutissma) over two years (2020 and 2021) in the eastern subtropical monsoon region of China. We find that the main growth period of Oak trees spans from March to September, and air temperature significantly affects the growth onset of Oak trees but with no clear impact on their growth cessation. The observations show that precipitation substantially affects daily stem radial increment (SRI), but the frequency of precipitation days plays a more crucial role in enhancing seasonal growth than the total precipitation amount. In the growing season, the stem radius of the Oak trees shows obvious diurnal cycles with shrinkage during the day and expansion at night, reflecting a delicate balance between canopy water loss and soil water absorption. The diurnal variations of the stem radius during the cold period (January and December) show an opposite pattern to that of the growing season, due to the sap's freezing under the condition of low air temperature at night as well as no or weak transpiration in the daytime. Because the temporal dynamics and intensity of tree activities significantly affect the timing and mechanisms of carbon assimilation in terrestrial ecosystems, our results are helpful to evaluate the carbon sequestration capacity of subtropical forests under the global climate change.

The ‘hydrological connectivity inside the soil’ refers to both the spatial pattern inside the soil (structural component) and the physical–chemical process at a molecular level (functional component). Fast field cycling (FFC) nuclear magnetic resonance (NMR) relaxometry allows for measuring structural and functional connectivity by two suitable indexes named structural connectivity index (SCI) and functional connectivity index (FCI). In this study, FFC NMR relaxometry was applied to soils sampled in a very degraded environment (i.e., a badland area) to detect the capability of the measurement technique to distinguish the hydrological connectivity of these samples having different conditions (layer explored by roots, sparsely-vegetated and bare soil). The relaxograms measured by the FFC NMR, using Proton Larmor frequencies in the range 0.01–10 MHz, were integrated and the resulting S-shaped curves were analysed to obtain the connectivity indexes. Results showed that the ‘Sparsely vegetated’ sample is characterized by more small-sized pores than the ‘Rooted’ one. The comparison between the ‘Sparsely vegetated’ and ‘Bare’ conditions pointed out that the presence of vegetation reduces the measured relaxation times and, as a consequence, the corresponding pore sizes and modifies the structural connectivity. The analysis also revealed that the three samples are characterized by similar values of SCI, which are independent of the proton Larmor frequency, while the FCI values of the ‘Bare’ soil are the lowest. Conversely, samples from soil with vegetation (‘Rooted’ and ‘Sparsely vegetated’) present comparable functional connectivity. Finally, the analysis of the frequency distribution of the ratio of each connectivity index and its mean value (SCI/m(SCI) and FCI/m(FCI)) allowed to establish its normal distribution. For the investigated samples, this result established that FCI and SCI can be represented by their mean value.

Permeable pavements, which not only increase rainwater infiltration and purify surface runoff water but also absorb noise and promote evaporative cooling, are an effective measure for alleviating urban flooding and the heat island effect. Moreover, permeable pavements have significant implications for the urban hydrological cycle and for human development that promotes ecosystem health. This paper reviews the development history of permeable pavements, evaluates the technical aspects and benefits thereof in the context of green city construction, and analyzes existing issues in the development of permeable pavements. This paper mainly discusses the current classifications of permeable pavements, the indicators used to evaluate permeable pavements, and construction techniques with a focus on two aspects: improving strength and removing blockages for planning, and three aspects: enhancing permeability, recycling resources, and preventing pollution for ecohydrological effects. Further, this paper discusses the benefits of permeable pavements and the commonly used methods for evaluating benefits. The main problems in the development and construction of permeable pavements include the limitations of permeable pavements, difficulty in evaluating their benefits, and restrictions on their applications. The following recommendations are proposed: improve the evaluation mechanism for permeable pavements, establish appropriate guidance for construction, scientifically and quantitatively analyse the feasibility of permeable pavement construction, evaluate the rationality of permeable pavement construction in various regions, and encourage the construction of permeable pavements in suitable areas. The importance of developing standards and technical specifications is also emphasized.

As climate change intensifies, understanding the dynamics of lake evaporation is imperative, especially in semi-arid regions where water resources are already scarce. This study examines the regulatory role of lake depth on evaporation rates, focusing on a terminal lake in a semi-arid region: Dali Lake in China. Using the Complementary Relationship Lake Evaporation model, we simulated the heat and temperature lag time of Dali Lake, an 8 m deep lake, due to its heat storage capacity. This approach was validated through moderate-resolution imaging spectroradiometer (MODIS)-based surface temperatures of Dali Lake and adjacent Ganggenor Lake. Dali Lake, by storing heat during the warmer months, maintains lower surface temperatures compared with the shallower Ganggenor Lake. Under the same climatic conditions, Dali Lake has an annual evaporation of 980 mm, which is 45 mm less than that of Ganggenor Lake, which has an annual evaporation of 1024 mm. To further study the impact of lake depth, we simulated the heat storage and evaporation of Dali Lake during the Holocene, when the lake reached up to 34 m average depth, representative of the maximum depth reached by Dali Lake. During the Holocene, under constant climate conditions, the annual evaporation would be 44 mm/year less than the average evaporation from 1984 to 2016. Average annual evaporation decreased with increasing depth, showing a significant reduction during warmer months, while the release of heat during the ice-cover period did not result in additional evaporation. Our results highlight the important relationship between lake depth and evaporation under climate change, emphasizing the necessity for depth-specific water management strategies in semi-arid regions.

Notwithstanding the recognized influence of Biological Soil Crusts (BSCs) on surface roughness and its implication for hydrological processes, limited information is currently available on the effect of BSCs on overland flow resistance. The objective of this paper was to investigate the applicability of a theoretically deduced flow resistance equation, based on a power-velocity profile, using the experimental data set by Jafarpoor et al. (2022) and Sadeghi et al. (2023) for bare soil, which is a control condition, and three inoculated soils (cyanobacteria, bacteria, cyanobacteria+bacteria). In particular, the available data set was used to calibrate the relationship between the velocity profile parameter Γ and the flow Froude number. The developed analysis allowed for stating that (a) the Darcy-Weisbach friction factor can be accurately estimated using the proposed theoretical approach, and (b) the available measurements do not allow for detecting a trend with the soil treatment.

Separating existing historical precipitation data into solid and liquid precipitation remains a challenge in the study of climate change, extreme precipitation, and hydrological modelling. Based on historical daily air temperature and precipitation data, as well as visual observations of precipitation phase (weather phenomena records) in China mainland, this study proposed a snow-day direct definition method (SDDM) to determine the threshold air temperature (TAT) of rainfall and snowfall, and analysed the spatial pattern and its influential factors. The main findings include: (1) the TAT based on the SDDM varied from −1.2 to 6.3°C, with a mean value of 2.8°C for the entire study region; (2) TAT was generally higher and more variable in the low-latitude areas, and the Qinghai-Tibet Plateau was characterized by an abnormally high average TAT of 5.2°C, almost twice as large as that of the eastern monsoon region; (3) TAT exhibited a significant positive correlation with altitude and negative correlation with precipitation and relative humidity. The results presented in this paper have potential application for studies of large-scale snowfall climatology and climate change, weather forecasting techniques, and hydrological model parameterization in areas with complex and diverse geographical and climatic conditions.