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Journal of Hydrology
Elsevier
Journal of Hydrology

Elsevier

0022-1694

Journal of Hydrology/Journal Journal of HydrologySCIISTPEIAHCI
正式出版
收录年代

    Uranium isotopes in a subtropical mountainous river of Taiwan: Insight into physical and chemical weathering processes

    Wang, Ruo-MeiYou, Chen-FengChung, Chuan-HsiungHuang, Kuo-Fang...
    13页
    查看更多>>摘要:The correlation between physical and chemical weathering in mountainous rivers is debatable. A reliable geochemical tracer for physical erosion and chemical weathering is necessary to obtain crucial information on the relationship between weathering processes and environmental changes on the Earth's surface. Small mountainous rivers (SMRs) of Taiwan are characterized by extremely high physical and chemical weathering, and therefore, they provide the foremost natural laboratory for studying weathering processes in tectonically active high-standing islands. In this study, water samples collected from the Kaoping River, the largest river catchment in southern Taiwan, were analyzed for elemental concentrations, as well as for U and Li isotopes, to understand the weathering processes and to evaluate the use of the U-234/U-238 activity ratio, hereafter (U-234/U-238), as a probe for weathering. The average (U-234/U-238) of the Kaoping River is significantly higher than that of other rivers worldwide, and variations in (234U/238U) reflect the degree of physical and chemical weathering. The weathering environment corresponds to the weathering-limited regime, and the mountain area is a natural example of the kinetic-limited control on chemical weathering by intense physical erosion. High physical erosion predominates in the mountainous region, which increases (U-234/U-238), relatively reduces U concentrations, and inhibits chemical weathering. The decreased (U-234/U-238) and increased Na/Li and delta Li-7 downstream clearly indicate enhanced chemical weathering in the alluvial plain. Our results demonstrate that dissolved (U-234/U-238) in the SMRs of Taiwan can reflect the relative contributions of physical and chemical weathering within the river catchment. The coupling between chemical weathering and physical erosion can be observed downstream and the relationship becomes less pertinent in the mountain area due to changes in weathering kinetics. A positive correlation between (U-234/U-238) and uplift rate in the Kaoping River suggests that the riverine (U-234/U-238) is mainly controlled by uplift-induced physical erosion, which may be influenced by landslide activities in the rapidly eroding mountainous river of Taiwan.

    Development and evaluation of hybrid deep learning long short-term memory network model for pan evaporation estimation trained with satellite and ground-based data

    Jayasinghe, W. J. M. Lakmini PrarthanaDeo, Ravinesh C.Ghahramani, AfshinGhimire, Sujan...
    19页
    查看更多>>摘要:Evaporation, as a core process within the global hydrological cycle, requires reliable methods to monitor its variation, for decision-making in agriculture, irrigation systems and dam operations, also in other areas of hydrology and water resource management. Accurate monitoring of pan evaporation (E-p) is one the most popular approaches to understand the evaporative process. This work aims to construct a hybrid Long Short-Term Memory (LSTM) predictive model that is coupled with Neighbourhood Component Analysis for feature selection to predict E-P in drought-prone regions in Queensland, Australia (Amberley, Gatton, Oakey, & Townsville). Utilizing the daily-scale dataset [31 August 2002 to 22 September 2020], the performance of the proposed deep learning (DL) hybrid model, denoted as NCA-LSTM, is compared with competitive benchmark models, i.e., standalone LSTM, other types of DL, single hidden layer neuronal architecture and decision tree-based method. The testing results reveal the lowest Relative Root Mean Square Error ( <= 20%), Absolute Percentage Bias ( <= 14.5%) and the highest Kling-Gupta Efficiency ( >= 87%) attained by the NCA-LSTM hybrid model (relative to benchmark models) tested for Amberley, Gatton, and Oakey sites. In respect to the predictive efficiency, the proposed NCA-LSTM hybrid model, improved with feature selection, outperforms all benchmark models, indicating its future utility in the prediction of daily E-p. In practical sense, the predictive model developed for E-p estimation provides an accurate estimation of evaporative water loss in hydrological cycle and therefore, can be implemented in areas of irrigation management, planning of irrigation-based agriculture, and mitigation of financial losses to agricultural and related sectors where, regular monitoring and forecasting of water resources are a vital part of sustainable livelihood and business.

    Approximate application of the method of images in fields with two boundaries intersected at angles between 180 degrees and 90 degrees

    Nikoletos, I. A.Katsifarakis, K. L.
    11页
    查看更多>>摘要:In this paper, we introduce approximate analytical solutions for groundwater flows in semi-infinite fields confined by two rectilinear boundaries (both constant head or both impermeable), which are intersected at an angle between 90 degrees and 180 degrees. The solutions are based on the method of images. Their main special feature is that both boundary conditions are observed, at the expense of the continuity of the velocity field along a particular straight line. First, we discuss the range of application of each solution and the validity of the results, using physical arguments. Then we compare our results with numerical ones, obtained by Modflow, namely an established numerical tool. Discrepancies are generally small. The main attractive feature of the proposed approximate analytical procedures compared to numerical ones is that the computational load is much smaller at all stages: a) Introduction of fictitious boundaries to contain the flow field is reduced to definition of the radius of influence of the wells, b) No grid construction is required and c) Calculation of the hydraulic head is conducted separately at any point of the flow field. Moreover, accuracy of the results is good, compared to that of numerical methods, which depends on the dimensions of the respective grid.

    The decline in the groundwater table depth over the past four decades in China simulated by the Noah-MP land model

    Li, MingxingWu, PeiliMa, ZhuguoLv, Meixia...
    15页
    查看更多>>摘要:Faced with intensified climate change and ever-increasing water demand, the groundwater table depth is vital to sustaining terrestrial environments in a country such as China; however, on a regional scale, insufficient research has been conducted on its variability thus far. Using a land model forced with reanalysis climate data, this paper investigates groundwater table depth changes across China for the 1979-2018 period. The results show a significant overall reduction in the groundwater table depth in China during the past 40 years without explicit consideration of direct human influence. There is an approximately 0.2 m decrease on average, but it is approximately 0.5 m in southern China and 0.8 m to the north of 35 degrees N despite a 1.2 m rise in part of this region due to an increasingly wet climate and a topographic water convergence. The findings provide a first-order pattern of historical groundwater table responses to climate change, highlighting inherent links among subsurface-surface-atmosphere water cycles and worsened terrestrial water availability in China. A model evaluation compared with in situ observations has demonstrated the model's ability to realistically portray terrestrial water and energy balances on regional scales, as well as the enhancement of their seasonality with incorporated lateral groundwater flow processes. This ability gives us reasonable confidence in the simulated trends and spatial variability. Nonetheless, the mean groundwater table still shows large biases relative to observations, and the problems of human influence, two-way interactions between groundwater and surface water, and local topographical complexity have yet to be properly addressed in the present study and deserve further research.

    Downscaling of soil moisture products using deep learning: Comparison and analysis on Tibetan Plateau

    Zhao, HongfeiLi, JieYuan, QiangqiangLin, Liupeng...
    20页
    查看更多>>摘要:Soil moisture (SM) is a very important physical parameter in land surface processes. The low-resolution microwave products are extremely useful for large-scale studies, but are limited in their ability to resolve landscapelevel variability. In this study, to overcome this limitation, we adopted three different deep learning based downscaling methods and performed a comparative analysis. Firstly, a downscaling method based on a deep belief network (DBN) model with a fully connected structure was employed to fit the complex nonlinear relationship between soil moisture and the auxiliary surface parameters. Then, to improve this simple point-to-point relationship, a neighborhood constraint based improved DBN model was developed to consider the effect of local spatial correlation among the surface factors on soil moisture. Finally, to maintain the integrity of the spatial structure in the process of model construction, a residual network (ResNet) model consisting of several residual dense blocks (RDBs) was introduced to use convolutions to obtain more complete and powerful spatial feature maps. The Tibetan Plateau was selected as the study area because of its importance to the global water cycle. The four soil moisture monitoring networks in the research area were used to verify the effectiveness of the proposed methods in the downscaling of soil moisture products, and four quantitative indicators were used to evaluate the effectiveness of the methods. From the verified results, it is shown that the three deep learning methods can maintain a higher correlation and better reduce the bias, on the whole, and the ResNet model, in particular, shows a higher stability. From the perspective of the spatial patterns and details, when compared to backpropagation neural network (BPNN) and random forest (RF) models, the three deep learning methods can provide more feasible spatial patterns and details, as well as reducing the uncertainty in the central regions of the Tibetan Plateau. The ResNet model shows a superior ability to enhance the texture details with lower uncertainty, due to the fact that it can meet the requirements of fitting the soil moisture to complex surfaces. Furthermore, the results of the ResNet model can also effectively capture the temporal changes of the microwave soil moisture product well.

    Investigation on the unsteady-state two-phase fluid transport in the nano-pore system of natural tight porous media

    Qiao, JunchengZeng, JianhuiJiang, ShuYang, Guangqing...
    18页
    查看更多>>摘要:Fluid transport across the natural tight micro-nanometer porous media governs numerous subsurface geological and industrial activities. The unsteady-state two-phase fluid flow at the very initial stage of non-wetting phase fluid intrusion, governing the hydrocarbon accumulation and CO2 geological sequestration process, remains uncertain. A modified unsteady-state pressurization gas displacement experiment incorporating systematic pore structure description combining mercury porosimetry, nuclear magnetic resonance, and X-ray computed tomography is conducted on the tight sandstone cores to investigate the fluid flow behaviors and to uncover their pore-scale controls. The results indicate that the unsteady-state gas-water flow deviates from Darcy's law, in which the threshold for the onset of continuous non-wetting phase fluid intrusion (ISTP) can be observed and degree of water movement and gas intrusion strongly depend on the injection pressure. Analyses under circular pore assumption, water layer distribution model based on DLVO theory, effective flow assumption, and overall pore connectivity evaluation suggest that the water movement and gas accessibility increases are dominated by the water displacement in the free water layer zone when injection pressure < ISTP, while the criticality of continuous gas intrusion is determined by the water movement in the inner layer of weakly bound water zone located in the narrow parts of the connected pathways, especially that in the pores < 40 nm, but its increment mainly occurs in the out layer of the weakly bound water zone when injection pressure > ISTP. Distinctions in the distributions and proportions of free and bound water layers in the different connected pore systems lead to the significant variations in the ISTP, water mobility, and gas accessibility of tight sandstone. The primary reasons for the differences in the static fluid mobility and flow behaviors lay in the differed structural attributes of connected pore systems. The narrowing, heterogeneity increase, and actual flow length increment of the connected pathways will raise the resistance for continuous non-wetting phase flow and lead to losses in water mobility, accessibility of non-wetting phase fluid, and flow velocity in the unsteady-state two-phase fluid flow. The high sensitivity of the dynamic fluid flow and gas accessibility to tortuosity of the connected pore system suggests the unsteady-state two-phase fluid flow behaviors are under the coupled control of pore size, complexity, and heterogeneity.

    Transport of perfluorooctanoic acid in unsaturated porous media mediated by SDBS

    Lyu, XueyanLi, ZhengyuWang, DengjunZhang, Qi...
    10页
    查看更多>>摘要:Per- and polyfluoroalkyl substances (PFAS) contamination is ubiquitous and likely co-exist with hydrocarbon surfactants in the subsurface environment. The transport of PFAS in unsaturated porous media (quartz sand-packed columns) with an anionic hydrocarbon surfactant was investigated using perfluorooctanoic acid (PFOA) and sodium dodecyl benzene sulfonate (SDBS) as representative PFAS and hydrocarbon surfactant at 1.5 and 30 mM NaCl, respectively. Our results show that SDBS inhibited the retardation of PFOA during transport. The degree of the inhibited retardation was more significant at higher concentration of SDBS (C-SDBS) for a given concentration of PFOA (C-PFOA) and higher ionic strength. In contrast, PFOA only marginally affected the transport of SDBS under all tested conditions. This is mainly due to the greater surface activity of SDBS with respect to PFOA, favoring the competitive preferential adsorption of SDBS at the air-water interface and then the transport of PFOA in the unsaturated sand. This assumption is further supported by the greater air-water adsorption coefficient (K-ai) and surface excess (Gamma) for SDBS than those for PFOA, as well as the surface tension isotherms that fairly weighted toward to SDBS in the binary PFOA-SDBS system. Our findings indicate the critical role of anionic hydrocarbon surfactant in retarding PFOA transport in unsaturated zone. This should be considered when assessing the transport potential and environmental risk, and developing remedial strategies of PFAS in the subsurface environment.

    A remote sensing data fusion method for continuous daily evapotranspiration mapping at kilometric scale in Sahelian areas

    Chazarin, Jean-PhilippeDelogu, EmilieIssoufou, Hassane Bil-AssanouMainassara, Ibrahim...
    19页
    查看更多>>摘要:Thermal infrared (TIR) remote sensing-based ET estimates are very appealing for a wide range of scientific applications in hydrology. However, they are prone to infrequency due to satellite revisit interval and cloud cover. Temporal interpolation techniques or multi-resolution and multi-frequency data fusion approach have thus recently been studied to provide continuous ET estimates. It has been already shown that the interest of temporal interpolation techniques is limited to short return interval that is troublesome in Sahelian regions where mesoscale convective systems linked to the West African Monsoon (WAM) renders unusable most of TIR images during the rainy season. Here we developed a data fusion approach to provide remote sensing-based continuous daily ET estimates at kilometric resolution in Sahelian areas. The proposed algorithm fill gaps in MODIS-based ET estimates from EVASPA S-SEBI Sahel (E3S) using the Global Land Evaporation: the Amsterdam Methodology (GLEAM) product and/or ET estimates from a simple parametric model for typical Sahelian ecosystems as a normalized basis. The fusion algorithm is evaluated at the pixel scale against eddy-covariance measurements and simulations of a locally calibrated and validated land surface model (LSM) on a millet crop and a fallow of shrubby savannah in the southwest of the Republic of Niger. Consistency of the fusion approach is also evaluated at mesoscale by comparing it with a set of 20 regional LSMs. Globally both level of comparison highlight the very good agreement of ET estimates based on the fusion approach with both in situ measurements and LSMs simulations. We also show the benefit of such a fusion approach compared to linear temporal interpolation techniques of the ratio between ET and either incoming solar radiation or reference evapotranspiration. The main benefits are observed during the first months of the rainy season in the depiction of the surface response to rainfall events and consecutive drying up of the surface soil layer. We suggest that such a fusion approach could be later used in disaggregation chain to enhance field scaled ET estimates by the combination of coarse, moderate and high resolution remote sensing-based ET estimates.

    Advancing environmental flows approaches to streamflow depletion management

    Lapides, Dana A.Maitland, Bryan M.Zipper, Samuel C.Latzka, Alexander W....
    21页
    查看更多>>摘要:Groundwater use can reduce streamflow by reducing groundwater flows into streams and/or increasing losses from the stream into the aquifer ('streamflow depletion'). Streamflow depletion can impact aquatic ecosystems through changes in the availability and temperature of surface water. Regions with a combination of groundwater withdrawals and groundwater-dependent resources therefore require management strategies that respond to the needs of both humans and aquatic ecosystems. Here, we review and evaluate opportunities and challenges for applying an environmental flows approach to streamflow depletion management based on functional flows and the Ecological Limits of Hydrological Alteration (ELOHA) frameworks. We highlight the need for explicit recognition of temperature in streamflow depletion science, especially given the realities of climate change. Using a demonstrative analysis on Wisconsin streams, we show that both the magnitude and variability of streamflow and stream temperatures are likely to be impacted by groundwater withdrawal, with particular impacts on low flows during the baseflow period. Then, we evaluate potential challenges to integrating existing groundwater withdrawal management and environmental flows approaches and provide a pathway to address inherent tensions between these two frameworks. In particular, we find that uncertainty associated with the first two ELOHA steps (setting a baseline and classifying streams) can lead to substantially different estimates of ecological impacts in streamflow depletion contexts. Navigating these tensions requires stakeholder engagement throughout the process of setting acceptable management thresholds to move towards practical, management focused integration of environmental flows and streamflow depletion science.

    High dissolved organic carbon deposition is buffered by surface soil in a headwater catchment of a subtropical plantation

    Song, XianweiLyu, SidanWang, JingSun, Kun...
    10页
    查看更多>>摘要:High atmospheric dry and wet deposition of dissolved organic carbon (DOC) may contribute to net ecosystem carbon balance (NECB), but the input and output fluxes of DOC and their transport processes in a catchment remain unclear. Here, to elucidate the importance of DOC in NECB from the view of Earth's critical zone, we measured the water fluxes of inputs (precipitation, throughfall, and stemflow) and outputs (soil leachate, surface flow, interflow, streamflow and groundwater) and their DOC concentrations in a subtropical plantation headwater catchment. Our results showed that dry DOC deposition from plant-derived dust and exudates (22,317 kg C km-2 yr- 1) was about 4.5 times higher than the wet DOC deposition from precipitation (4966 kg C km-2 yr- 1), and accounted for 3.88 and 0.86% of the net ecosystem C productivity (NEP) (5.75x105 kg C km-2 yr- 1), respectively. In comparison, DOC fluxes in stream and groundwater were 5912 and 3905 kg C km-2 yr- 1, indicating that soil-buffered DOC flux was 17,466 kg C km-2 yr- 1 and accounted for 3.04% of NEP. A positive correlation between DOC and pH and total dissolved solids in soil leachate indicated that the biophysical and chemical absorption bridged the interaction between soil minerals and organic carbon. Our results underline the importance of including plant-derived DOC deposition in carbon sink estimations in subtropical plantation headwater catchments.