查看更多>>摘要：Streamflow is an important hydrological factor in water resources management. The Fluvial Acoustic Tomography (FAT) as a cutting-edge river monitoring technology measures the flow velocity using the travel time of the acoustic signals. The velocity is then multiplied by the river cross-section to obtain accurate and continuous streamflow data. Similar to all acoustic instruments, the FAT output velocity contaminated by spike data. Standard deviation (STD) as a simple method of spike removing, was used in previous FAT studies. The disadvantages of the STD method are that it not only does not replace the identified spikes with the appropriate values and therefore results in measurement discontinuity, but it also requires engineering judgment that may increase the measurement error. In this study, two despiking methods, i.e., Phase-Space Thresholding (PST) and threedimensional Rousseeuw Phase-Space thresholding (3D-RPS) are applied to detect/modify outliers of a 6-day FAT velocity signals. The results showed that the 3D-RPS method has the best performance with a Nash Sutcliffe efficiency coefficient (NSC) of 0.731 compared to 0.572 and 0.44 NSC values of STD and PST methods, respectively. The FAT-based streamflow data were also compared with the reference streamflow obtained from the Rating-Curve method. The results reveal that the streamflow measurement accuracy improves significantly, where the relative errors decrease from & PLUSMN; 40% for the STD method to & PLUSMN; 15% for the 3D-RPS approach. As a result, the 3D-RPS approach appears to be an effective method for improving the accuracy of the FAT-acquired streamflow data.
查看更多>>摘要：The popularity of subsurface distributed storage-based kerbside stormwater infiltration systems is increasing because they can be integrated within the strict spatial constraints of existing infrastructure. Distributed systems operate based on the concept of spreading a limited amount of storage throughout the catchment area to achieve runoff management objectives. Storage can also limit the performance of urban stormwater systems. This study investigated the role of storage capacity, especially the volumetric capacity and the emptying time, in the performance of kerbside leaky well systems in a residential catchment area with a native clay soil environment. A detailed, process-based deterministic hydrological model was used to analyze hydrologic storage via a continuous simulation approach. The model was calibrated against catchment outflows measured with stormwater infiltration devices. Individual kerbside infiltration systems were also calibrated to monitor the behavior of on site kerbside infiltration systems. By using approach of continuous simulations during designed scenarios, this study considered the prestorm storage availability in the hydrological analysis. The results demonstrated that hydrologic storage greatly influences the performance of kerbside leaky well systems during higher-intensity storms. In addition, the results show that distributing a stormwater storage volume equal to thirty-five 1-kL rainwater tanks across the catchment area as a kerbside infiltration system could notably reduce the runoff flow rates and volumes. The results further highlight that the addition of more homes within the connected area could diminish the stormwater reduction benefits achieved through the installation of a distributed kerbside infiltration system.
Wang, RuichengWang, HongmeiXi, ZhiqinTuovinen, Olli H....
11页
查看更多>>摘要：Microbiomes play fundamental roles in ecological function of peatlands. Despite the confirmed role of hydrology in the modulation of microbial communities in peatlands, its impact on microbial functional groups involved in methane cycle has remained poorly defined particularly at subtropical peatlands. To this end, prokaryotic communities and methane related functional groups from two peat profiles were investigated in the Dajiuhu Peatland, a subtropical peatland in central China; via high throughput sequencing of the 16S rRNA genes, quantitative PCR, and clone library construction for functional genes for methanogens (mcrA) and methanotrophs (pmoA). Results showed that depth to water table (DWT), indicator for water table variation, significantly impacted the vertical distribution of prokaryotic communities, especially Acidobacteria and Bathyarchaeota, and methane functional groups. FenC, RC I and RRC I dominated methanogens in middle and bottom samples of the profiles, whereas Methylocystis dominated methanotrophic communities in surface and middle samples. Quantitatively methanogens decreased with increasing DWT, whereas reverse pattern was seen for methanotrophs. Aerobic or anaerobic OTUs clustered into different modules in the co-occurrence network, indicating a strongly oxygen-dependent niche preference. Collectively, our observations demonstrated important ecological regulation of DWT on prokaryotes and CH4 related microbiomes in subtropical peatlands, which expanding our understanding of microbial responses and CH4 cycles in the context of environmental changes globally.
查看更多>>摘要：Coupled water and heat transfer models are widely used to analyze soil water content and temperature dynamics, evaluate agricultural management systems, and support crop growth modelling. In relatively dry soils, vapor transfer, rather than liquid water flux, becomes the main pathway for water redistribution. However, in some modularized soil simulators, e.g., 2DSOIL (Timlin et al., 1996), vapor transfer is not included, which may induce errors in soil water and heat modelling. Directly embedding vapor transfer into existing water and heat transfer modules may violate the modularized architecture of those simulators. Therefore, the objectives of this study are to design a vapor transfer model, evaluate its performance, and implement it as a separate module in a coupled soil water and heat simulator, e.g., 2DSOIL. The efficacy of the vapor transfer model is evaluated by comparing the simulated soil water content and temperature before and after including the new vapor transfer model, and the soil water content and temperature simulated with the standard Philip and de Vries (1957) model. By implementing vapor transfer as a separate module in 2DSOIL, modifications to existing water and heat transfer modules can be minimized and the modularized model architecture can be maintained. Numerical examples of 2DSOIL with the new vapor transfer model are presented to illustrate the effects of vapor flux on soil water and temperature redistributions. In conclusion, the new vapor transfer model provides an effective and easy-to-use method to account for the effects of vapor transfer on coupled soil water and heat simulations.
查看更多>>摘要：A generic framework is proposed to evaluate the relative discharge error made when ignoring stage-discharge hysteresis due to transient flow over large gauging station networks. The diagnosis is conducted using the Jones equation, a simple hydraulic concept relating discharge to stage and its time-gradient. The input data used for the method are the flow resistance coefficients, the temporal stage gradients, and the bed slopes. The hysteresis effect is quantified for each gauging station and mapped using the relative discharge error. The method was applied to 2618 gauging stations of France's national hydrometry network using data extracted from the national hydrological archive and from Digital Terrain Models. The diagnostic results highly depend on slope estimates used as inputs. Substantial hysteresis effects were found at stations with low bed slope combined with a fast flood regime. The application to France shows the difficulty of drawing a firm conclusion about stations prone to hysteresis due to the slope data uncertainty. This issue is not specific to France; slope estimates over a network of hydrometric stations are difficult to obtain in many countries. The use of local bed slope estimates is recommended to approach the slopes of the reaches controlling the station stage-discharge relation.
查看更多>>摘要：A major step in designing a subsurface drainage system is calculation of drainpipe spacing. Nearly, all unsteadystate drainpipe-spacing equations use ratio of hydraulic conductivity (K-s) to drainable porosity (f) in the form of kappa = K-s/f. This work developed a novel inverse model based on Bees Algorithm to estimate the kappa. We examined the efficiency of the developed inverse model to appraise the. using the existing data sets at laboratory and field scales. For each data set, we compared the performance of the developed inverse model with those of a dimensionless curve generated by the authors (generalized dimensionless curve), Skaggs's (1976) dimensionless curve being proportional to the data set (Skaggs's dimensionless curve), a drainpipe discharge method, and a direct method. The results showed that the best statistical indicator values were achieved for each data set when the drainage equations utilized the. deduced from the developed inverse model. All the studied techniques performed the worst for Skaggs et al.'s (1973) data at 57.5 hrs. after drainage start. For this data set, the studied techniques were, respectively, ranked as the developed inverse model, Skaggs's dimensionless curve, the generalized dimensionless curve, and the direct method. Even in this worst case, the global performance index was improved almost 93% when the drainage equation utilized the. appraised by the developed inverse model, instead of that appraised by Skaggs's dimensionless curve. The overall performance comparison of the three inverse techniques evaluated in this study revealed that the root mean square error and coefficient of determination related to the developed inverse model are the best ones, followed by those related to Skaggs's dimensionless curve, and the developed inverse model, respectively. In summary, the results revealed that, compared to the other studied techniques, the developed inverse model is the most efficient technique to estimate the., which is promising for practical purposes at the laboratory and field scales.
查看更多>>摘要：Streamflow variability is affected by both climate change and direct human impacts within the catchment. Quantification of the role of these two factors have significant implications for water resources. In recent years, Budyko-based analytical methods have been widely used for such quantification due to their simplicity and efficacy. This paper presents a comparison of such methods to attribute changes in streamflow in four Model Parameter Estimation Experiment (MOPEX) catchments in the contiguous United States. Further, a new, improved Two-stage Decomposition method to separate the role of climate and catchment changes on streamflow is proposed, considering the uncertainty in the catchment parameter that further leads to a range of evaporative index values within a catchment. We find that climate and catchment effects are sensitive to the choice of Budyko equation, disaggregation algorithm and approximation technique. Further, the catchment parameter can be expressed probabilistically, to account for the uncertainty because of limited hydrometeorological records. The proposed approach employs a bootstrap analysis to obtain the stochastic range of the catchment parameter, considering different choices of Budyko equations. We argue that rather than relying on a single Budyko-based approach for separation of climate and catchment effects on streamflow, the proposed method offers a more robust way by considering the entire range of uncertainty of the catchment parameter.
查看更多>>摘要：The partition of flood routing uncertainties from multiple sources provides a foundation for managing flood risks. This paper develops a partition approach for the one-dimensional river flood routing uncertainty due to boundary conditions (upstream inflow hydrograph and downstream stage hydrograph) and riverbed roughness. A theoretical derivation based on the Monte Carlo method is presented using a one-dimensional hydrodynamic model. The developed approach is successfully applied to a real-world case of the Xunjiang River in China. The results indicate the following: (1) each uncertainty source leads to unique effects on flood routing, and the uncertainty contribution ratio varies significantly with both time and space, providing evidences for identifying the dominant uncertainty sources; (2) the uncertainty of the simulated discharge is most influenced by the boundary conditions whereas the simulated water stage is most influenced by the riverbed roughness; and (3) the highly coupled uncertainty propagation is hardly affected by the flood pattern, as well as the probability distribution of uncertainty source, but it is significantly affected by the river morphology. The developed approach can effectively partition the uncertainty effects of the boundary conditions and riverbed roughness without explicating their interactions. And the uncertainty partition of flood routing is useful for risky decision making in flood management.
Li, JiayunWu, ChuanhaoXia, Chuan-AnYeh, Pat J-F...
14页
查看更多>>摘要：Flash drought (FD) is an extreme event causing severe impacts on ecosystems and agriculture due to its fast velocity of evolution and high frequency. Here, we develop a voxel-based three-dimensional FD (V3DFD) method to track the spatio-temporal dynamics of FD based on the soil moisture (SM) decline method proposed by Yuan et al. (2019). The key idea of V3DFD is that FD is identified in terms of the connectivity of drought voxels (i.e., cubes with width, length and height representing latitude, longitude and time, respectively) in 3D space instead of directly forming the drought events by merging drought clusters. The V3DFD is systematically evaluated and compared with the commonly used 3D severity-area-duration (SAD) method in four provinces in China: Guangdong (GD), Guangxi (GX), Guizhou (GZ), and Yunnan (YN). Results show that V3DFD can better reflect the dynamic development and recovery of FD events compared with SAD. Regional analyses indicate that FD occurs more frequent with a larger intensity and longer duration in GD and GX than YN and GZ. The onset (terminal) of FD in YN occurs mostly in April-May (April-June). The onset of FD in GX and GD is scattered at the intra-annual scale, but the terminal occurs mostly in November. In addition, the first FD event in a year is mostly located during April-May in YN and GZ, while the last FD event of a year occurs mostly during October-November in GX and GD.
查看更多>>摘要：Due to the heterogeneity and nonlinear process in the unsaturated soil zone, it is challenging to represent the analytical mechanism and actual in-situ water content in the soil layer. With this in mind, this study provides a novel approach to discern the water content in the shallow Quaternary gravel layer at various depths using temporal sunlight and air temperature observation. It demonstrates significant components in spectral density to evaluate the crucial importance concerning the time-dependent soil water content, sunlight quantum, and air temperature. It shows that the soil water content at 10 cm depth can distinguish the fluctuated manner of light quantum at the time lag of about 6.6 and 5.1 h for diurnal and semidiurnal processes, respectively. The time progress of soil water contents at 30 cm depth is less relevant to 10 cm depth, but the phase at 60 and 120 cm depth is nearly in phase. Due to heterogeneity in the shallow layer, the temporal changes of soil water content below 10 cm depth have varying coherence degrees. Thus, using spectral analysis, practically estimating the coherence and time lag between light quantum, air temperature, and soil water content becomes feasible and achievable.
NSTL
Elsevier