Display omitted
•More microplastics were found during neap than spring tide period.•Microplastic particles were larger during the neap than the spring tide period.•No variation in the abundance of ...microplastics on the semidiurnal scale.•Microplastics were more abundant in the vegetation zone than in the mudflat.•Variation in microplastics abundance was driven by local hydrology.
Microplastics are small, degrade slowly, and easily persist in the water column because they are close to neutrally buoyant. Understanding the distribution of microplastics is fundamental to evaluating the ecological risks that they cause and to identifying ways to control microplastics pollution. Most of the existing research on the distribution of microplastics in the coastal zone has focused on large spatial and temporal scales. To build on past work, we investigated variation in microplastics in a tidal flat of the Yangtze Estuary on small spatial (sediment depth, mudflat vs. vegetation zone) and temporal (fortnightly and semidiurnal) scales. Microplastics were more abundant in surface (0–2 cm) sediments during neap versus spring tide cycles, likely indicating increased deposition during periods with calm waters and increased suspension when water was more turbulent, but did not vary at greater depths in the sediment. Individual microplastics particles were also larger during neap versus spring tide periods. In contrast to the variation between spring and neap tide periods, we found no variation in the abundance of microplastics on the semidiurnal scale. Microplastics were also more abundant in the transect in the vegetation than at slightly lower elevations in the adjacent mudflat. Across all samples, the abundance of microplastics was negatively correlated with the strength of hydrological processes such as submergence time and flow velocity. Our results showed that sampling of microplastics in the intertidal environment needs to consider variation among spring and neap tide cycles, and also among different intertidal habitats that may differ only slightly in elevation. We encourage coupling sampling with direct measures of hydrological processes so that variation in microplastics abundance and size can be rigorously linked to hydrological processes.
The Yellow River source region is located in the transition region between permafrost and seasonally frozen ground on the northeastern Qinghai-Tibet Plateau. The region has experienced severe climate ...change, especially air temperature increases, in past decades. In this study, we employed a geomorphology-based eco-hydrological model (GBEHM) to assess the impacts of climate change on the frozen ground and eco-hydrological processes in the region. Based on a long-term simulation from 1981 to 2015, we found that the areal mean maximum thickness of seasonally frozen ground ranged from 1.1–1.8m and decreased by 1.2cm per year. Additionally, the ratio of the permafrost area to the total area decreased by 1.1% per year. These decreasing trends are faster than the average in China because the study area is on the sensitive margin of the Qinghai-Tibet Plateau. The annual runoff exhibited variations similar to those of the annual precipitation (R2=0.85), although the annual evapotranspiration (ET) exhibited an increasing trend (14.3mm/10a) similar to that of the annual mean air temperature (0.66°C/10a). The runoff coefficient (annual runoff divided by annual precipitation) displayed a decreasing trend because of the increasing ET, and the vegetation responses to climate warming and permafrost degradation were manifested as increases in the leaf area index (LAI) and ET at the start of the growing season. Furthermore, the results showed that changes to the frozen ground depth affected vegetation growth. Notably, a rapid decrease in the frozen ground depth (< −3.0cm/a) decreased the topsoil moisture and then decreased the LAI. This study showed that the eco-hydrological processes in the headwater area of the Yellow River have changed because of permafrost degradation, and these changes could further influence the water resources availability in the middle and lower reaches of the basin.
Display omitted
•A process-based distributed model for eco-hydrological simulation in cold regions•The spatio-temporal variations in frozen ground are analyzed during 1981–2015.•Recent warming and wetting trends increased river discharge and evaporation, but the runoff coefficient decreased.•The degradation of seasonally frozen ground could decrease soil moisture, which is a constraint on vegetation growth.
ABSTRACT
In this study, the ability of the seasonal autoregressive integrated moving average (SARIMA) and autoregressive integrated moving average (ARIMA) models was investigated for long‐term runoff ...forecasting in the United States. In the first stage, the amount of runoff is forecasted for 2011 in each US state using the data from 1901 to 2010 (mean of all stations in each state). The results show that the accuracy of the SARIMA model is better than that of the ARIMA model. The relative error of the SARIMA model for all states is <5%. In the second stage, the runoff is forecasted for 2001 to 2011 by using the average annual runoff data from 1901 to 2000. The SARIMA model with periodic term equal to 20, R2 = 0.91, and mean bias error (MBE) = 1.29 mm is the best model in this stage. According to the obtained results, a trend is observed between annual runoff data in the United States every 20 years or almost a quarter century.
Understanding the relationship between hydrological processes and environmental changes is important for improved water management. The Geba catchment in Ethiopia, forming the headwaters of ...Tekeze-Atbara basin, was known for its severe land degradation before the recent success in integrated watershed management. This study analyses the hydrological response attributed to land management change using an integrated approach composed of (i) simulating the hydrological response of Land Use/Cover (LULC) changes; (ii) assessing the alteration of streamflow using Alteration of Hydrological Indicators (IHA); and (iii) quantifying the contribution of individual LULC types to the hydrology using Partial Least Square Regression model (PLSR).
The results show that the expansion of agricultural and grazing land at the expense of natural vegetation has increased the surface runoff 77% and decreased dry season flow by 30% in the 1990s compared to 1970s. However, natural vegetation started to recover from the late 1990s and dry season flows increased by 16%, while surface runoff declined by 19%. More pronounced changes of the streamflow were noticed at sub-catchment level, mainly associated with the uneven spatial distribution of land degradation and rehabilitation. However, the rate of increase of low-flow halted in the 2010s, most probably due to an increase of water withdrawals for irrigation. Fluctuations in hydrological alteration parameters are in agreement with the observed LULC change. The PLSR analysis demonstrates that most LULC types showed a strong association with all hydrological components.
These findings demonstrate that changing water conditions are attributed to the observed LULC change dynamics. The combined analysis of rainfall-runoff modelling, alteration indicators and PLSR is able to assess the impact of environmental change on the hydrology of complex catchments. The IHA tool is robust to assess the magnitude of streamflow alterations obtained from the hydrological model while the PLSR method is useful to zoom into which LULC is responsible for this alteration.
Display omitted
•Tekeze-Atbara basin is known for its severe land degradation before the recent success in integrated watershed management.•Combining parsimonious hydrological modelling, alteration and PLSR analysis were used to understand hydrological response.•Expansion of agricultural resulted in an increased surface runoff and decreased dry season flow in the Geba catchment.•This study applied a promising approach to understand impact of environmental change on the hydrology.
The impact on the hydrologic cycle of permafrost degradation under the influence of climate change has caused an inestimable threat to sustainable regulation of the ecosystem. This study quantified ...the responses of main hydrological elements, including soil moisture, groundwater, runoff components and discharge to totally degraded permafrost in eastern High Asia by establishing cases with and without thermodynamics using a cold region model combining hydrological processes and thermodynamics. The results showed that the model successfully simulated discharge in cold region basins. Totally degraded permafrost decreased soil moisture in the vadose zone (SMV) and increased the absolute depth to ground water (ADGW). In the daily scale, total permafrost degradation decreased the direct flow in autumn, slightly increased direct flow in spring and decreased interflow in summer. Total permafrost degradation also increased daily baseflow all year round and by >50% in spring, decreased daily discharge during autumn and increased daily discharge during spring. In the annual scale, total permafrost degradation increased direct flow, baseflow, and discharge, and decreased interflow. The magnitudes of these changes were positively related to the ratios of permafrost to the subbasin area. The responses of daily runoff components and discharge to totally degraded permafrost were significantly larger than the annual value. The groundwater level, direct flow and baseflow were far more sensitive to permafrost degradation than SMV, interflow and discharge. The responses of annual individual hydrological elements were more obvious than the annual discharge. These quantified results can be extensively used in lumped hydrology simulations, water resource assessments and eco-system management for partial permafrost degradation.
Display omitted
•Responses of hydrologic elements to permafrost degradation are still un-quantified.•Two cases with and without thermodynamics using a fully coupled hydro-thermal model•Permafrost degradation decreases autumn and increases winter/spring discharge.•Smaller annual discharge increase in permafrost degradation than hydrologic elements
The hydrological and pollution processes are an important science problem for aquatic ecosystem. In this study, the samples of river water, reservoir water, shallow groundwater, deep groundwater, and ...precipitation in mining area are collected and analyzed. δD and δ18O are used to identify hydrological process. δ15N-NO3- and δ18O-NO3- are used to identify the sources and pollution process of NO3−. The results show that the various water bodies in Fenhe River Basin are slightly alkaline water. The ions in the water mainly come from rock weathering. The concentration of SO42- is high due to the impact of coal mining activity. Deep groundwater is significantly less affected by evaporation and human activity, which is recharged by archaic groundwater. There are recharge and discharge between reservoir water, river water, soil water, and shallow groundwater. NO3− is the main N species in the study area, and forty-six percent of NO3−-N concentrations exceed the drinking water standard of China (NO3−-N ≤ 10 mg/L content). Nitrification is the main forming process of NO3−. Denitrification is also found in river water of some river branches. The sources of NO3− are mainly controlled by land use type along the riverbank. NO3− of river water in the upper reaches are come from nitrogen in precipitation and soil organic N. River water in the lower reaches is polluted by a mixture of soil organic N and fertilizers.
Display omitted
•Identify main sources of dissolved chemical ions in water and their impact factors.•Reveal hydrological cycling processes via δD-H2O and δ18O-H2O.•Determine sources and transformations of nitrates by δ15N-NO3-, δ18O-NO3-, and hydrochemical methods.
Climate change and land use/cover change (LUCC) are two factors that produce major impacts on hydrological processes. Understanding and quantifying their respective influence is of great importance ...for water resources management and socioeconomic activities as well as policy and planning for sustainable development. In this study, the Soil and Water Assessment Tool (SWAT) was calibrated and validated in upper stream of the Heihe River in Northwest China. The reliability of the SWAT model was corroborated in terms of the Nash–Sutcliffe efficiency (NSE), the correlation coefficient (R), and the relative bias error (BIAS). The findings proposed a new method employing statistical separation procedures using a physically based modeling system for identifying the individual impacts of climate change and LUCC on hydrology processes, in particular on the aspects of runoff and evapotranspiration (ET).
The results confirmed that SWAT was a powerful and accurate model for diagnosis of a key challenge facing the Heihe River Basin. The model assessment metrics, NSE, R, and BIAS, in the data were 0.91%, 0.95%, and 1.14%, respectively, for the calibration period and 0.90%, 0.96%, and −0.15%, respectively, for the validation period. An assessment of climate change possibility showed that precipitation, runoff, and air temperature exhibited upward trends with a rate of 15.7 mm, 6.1 mm, and 0.38 °C per decade for the 1980 to 2010 period, respectively. Evaluation of LUCC showed that the changes in growth of vegetation, including forestland, grassland, and the shrub area have increased gradually while the barren area has decreased. The integrated effects of LUCC and climate change increased runoff and ET values by 3.2% and 6.6% of the total runoff and ET, respectively. Climate change outweighed the impact of LUCC, thus showing respective increases in runoff and ET of about 107.3% and 81.2% of the total changes. The LUCC influence appeared to be modest by comparison and showed about −7.3% and 18.8% changes relative to the totals, respectively. The increase in runoff caused by climate change factors is more than the offsetting decreases resulting from LUCC. The outcomes of this study show that the climate factors accounted for the notable effects more significantly than LUCC on hydrological processes in the upper stream of the Heihe River.
•We developed a numerical framework incorporating trees in an urban canopy model.•Shade trees have more prominent energy saving potential than urban lawns.•The trade-off between water-energy is a key ...for urban landscape management.•Urban vegetation can significantly alleviate outdoor thermal stress.
The use of urban vegetation in cities is a common landscape planning strategy to alleviate the heat island effect as well as to enhance building energy efficiency. The presence of trees in street canyons can effectively reduce environmental temperature via radiative shading. However, resolving shade trees in urban land surface models presents a major challenge in numerical models, especially in predicting the radiative heat exchange in canyons. In this paper, we develop a new numerical framework by incorporating shade trees into an advanced single-layer urban canopy model. This novel numerical framework is applied to Phoenix metropolitan area to investigate the cooling effect of different urban vegetation types and their potentials in saving building energy. It is found that the cooling effect by shading from trees is more significant than that by evapotranspiration from lawns, leading to a considerable saving of cooling load. In addition, analysis of human thermal comfort shows that urban vegetation plays a crucial role in creating a comfortable living environment, especially for cities located in arid or semi-arid region.
Accurate flood mapping is crucial for enhancing community resilience in the face of flooding. Among the several factors that affect the flood extent, the effect of fluvial dynamics is not clearly ...recognized so far. Fluvial dynamics play an important role in shaping the patterns and magnitudes of water flow and sediment transport in riverine environments, that consequently affect flood extent. By conducting a scoping review, this paper aims to show how the river's hydrological processes and channel morphology impact floods and flood mapping. To do that, previous studies dealing with flood modeling have been explored to provide a comprehensive understanding of the interactions between fluvial dynamics and flood mapping outcomes. The results showed that morphodynamic variations and sediment transport impact flooding differently depending on local morphological conditions. Some studies indicate that these processes can increase the likelihood of flooding, potentially posing greater risks to nearby areas. Conversely, other research suggests that these morphodynamic variations may help reduce flood occurrences, signaling a nuanced relationship between river morphology and flood dynamics. Additionally, it was found that while bed-load movements significantly influence the synchronization of peak water surface elevation and peak flow times, suspended sediment concentration has minimal impact on the timing and shape of the hydrograph. The results emphasize the crucial role of integrating fluvial hydro-morphodynamics into flood mapping to enhance flood management in riverine environments, contributing to both increased resilience and broader sustainable development goals.
Display omitted
•The influence of sediment dynamics and channel morphology on floods is reviewed.•Sediment impacts flooding differently depending on local morphological conditions.•The findings stress the need to include sediment dynamics in flood studies.
•We simulated hydrological and biogeochemical processes in a forested watershed.•We investigated impacts of climate change compounded with wildfire scenarios.•Streamflow, sediment, and organic carbon ...decreased due to climate change (CCH)•Streamflow, sediment, and organic carbon increased due to wildfire and CCH.•Intensified precipitation and high-severity burns may lower downstream water quality.
Increasing temperatures and irregular precipitation associated with climate change, along with increasing frequency and severity of wildfires, contribute to increased downstream transport of sediment and total organic carbon (TOC), with potential impacts on aquatic ecosystem structure and resilience, recreational use of water bodies, and downstream drinking water treatment. Our study aimed to investigate the effects of both climate change and wildfires on water budget, sediment, and organic carbon by simulating the response of sub-catchments and in-stream processes to changes in future climate and wildfire scenarios. To achieve this, we applied a physical process-based hydrologic model, where an in-stream Organic Carbon Simulation Module was embedded within the Soil and Water Assessment Tool (SWAT-OCSM), to the Elbow River watershed in Alberta, Canada. Post-wildfire conditions of both moderate and high burn severities were replicated in the model within two burn perimeters to assess in-stream organic carbon processes related to particulate organic carbon (POC) and dissolved organic carbon (DOC) as state variables under changing climate. Results of the climate change scenarios indicated lower streamflow relative to the baseline period (1995–2014), particularly between May–August, with 25.3–46.9% less water in the near future (2015–2034) compared to 9.9–31.8% less water in the distant future (2043–2062). Sediment concentrations generally decreased, whereas TOC concentrations increased, in both the near future and distant future scenarios reflecting uncertainty in climate effects on water quality. Wildfire simulations compounded with climate change significantly changed local hydrology, increasing surface runoff, sediment, and TOC transport by over 500% in some study sub-catchments. However, at the watershed outlet, sediment yields only increased up to 6.5% and TOC yields increased up to 13.1%. Burn severity invoked a stronger watershed response than burn area, and greater relative changes were observed for wildfires occurring with the worst-case climate change scenarios. This study provided a strong basis for analyzing watershed responses to potential future wildfires. However, recommendations are provided for further model developments to account for wildfire consequences and feedbacks with hydrological and biogeochemical processes.
PDF
