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"Drainage control"
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Aridity is expressed in river topography globally
It has long been suggested that climate shapes land surface topography through interactions between rainfall, runoff and erosion in drainage basins
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. The longitudinal profile of a river (elevation versus distance downstream) is a key morphological attribute that reflects the history of drainage basin evolution, so its form should be diagnostic of the regional expression of climate and its interaction with the land surface
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. However, both detecting climatic signatures in longitudinal profiles and deciphering the climatic mechanisms of their development have been challenging, owing to the lack of relevant global data and to the variable effects of tectonics, lithology, land surface properties and human activities
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. Here we present a global dataset of 333,502 river longitudinal profiles, and use it to explore differences in overall profile shape (concavity) across climate zones. We show that river profiles are systematically straighter with increasing aridity. Through simple numerical modelling, we demonstrate that these global patterns in longitudinal profile shape can be explained by hydrological controls that reflect rainfall–runoff regimes in different climate zones. The most important of these is the downstream rate of change in streamflow, independent of the area of the drainage basin. Our results illustrate that river topography expresses a signature of aridity, suggesting that climate is a first-order control on the evolution of the drainage basin.
A global dataset of river longitudinal profiles shows that river profiles become straighter with increasing aridity and numerical modelling suggests that this can be explained by rainfall–runoff regimes in different climate zones.
Journal Article
Apex structures enhance water drainage on leaves
The rapid removal of rain droplets at the leaf apex is critical for leaves to avoid damage under rainfall conditions, but the general water drainage principle remains unclear. We demonstrate that the apex structure enhances water drainage on the leaf by employing a curvature-controlled mechanism that is based on shaping a balance between reduced capillarity and enhanced gravity components. The leaf apex shape changes from round to triangle to acuminate, and the leaf surface changes from flat to bent, resulting in the increase of the water drainage rate, high-dripping frequencies, and the reduction of retention volumes. For wet tropical plants, such as Alocasia macrorrhiza, Gaussian curvature reconfiguration at the drip tip leads to the capillarity transition from resistance to actuation, further enhancing water drainage to the largest degree possible. The phenomenon is distinct from the widely researched liquid motion control mechanisms, and it offers a specific parametric approach that can be applied to achieve the desired fluidic behavior in a well-controlled way.
Journal Article
Drainage controls on the Donglingxing landslide (China) induced by rainfall and fluctuation in reservoir water levels
Rainfall, groundwater, and fluctuation in reservoir levels are considered among the main external factors affecting the stability of slopes. The impact of groundwater is particularly evident during the rainy season. In this paper, a case study on a geological investigation of the Donglingxing (DLX) landslide is presented to demonstrate a drainage control strategy. Due to the characteristics of the landslide and the limitations on the construction of stabilizing piles, a drainage tunnel system is herein used to reduce the risk of landslide. A comprehensive analysis is conducted on the monitoring data of rainfall, groundwater levels, reservoir water level, and drainage discharges from the tunnels. Based on field measurement data on groundwater level, water discharge, and deformation of the landslide before and after construction of the drainage tunnel, the effectiveness of the drainage tunnel system is evaluated. The results indicate that the drainage tunnel is effective in increasing the stability of landslide, and this work can serve as a reference case for other landslides.
Journal Article
Mineralogical characteristics of sediments and heavy metal mobilization along a river watershed affected by acid mine drainage
Trace-element concentrations in acid mine drainage (AMD) are primarily controlled by the mineralogy at the sediment-water interface. Results are presented for a combined geochemical and mineralogical survey of Dabaoshan Mine, South China. Developed sequential extraction experiments with the analysis of the main mineralogical phases by semi-quantitative XRD, differential X-ray diffraction (DXRD) and scanning electron microscopy (SEM) were conducted to identify the quantitative relationship between iron minerals and heavy metals. Results showed that schwertmannite, jarosite, goethite and ferrihydrite were the dominant Fe-oxyhydroxide minerals which were detected alternately in the surface sediment with the increasing pH from 2.50 to 6.93 along the Hengshi River. Decreasing contents of schwertmannite ranging from 35 wt % to 6.5 wt % were detected along the Hengshi River, which was corresponding to the decreasing metal contents. The easily reducible fractions exert higher affinity of metals while compared with reducible and relatively stable minerals. A qualitative analysis of heavy metals extracted from the sediments indicated that the retention ability varied: Pb > Mn > Zn > As ≈ Cu > Cr > Cd ≈ Ni. Results in this study are avail for understanding the fate and transport of heavy metals associated with iron minerals and establishing the remediation strategies of AMD systems.
Journal Article
On the theory of drainage area for regular and non-regular points
The drainage area is an important, non-local property of a landscape, which controls surface and subsurface hydrological fluxes. Its role in numerous ecohydrological and geomorphological applications has given rise to several numerical methods for its computation. However, its theoretical analysis has lagged behind. Only recently, an analytical definition for the specific catchment area was proposed (Gallant & Hutchinson. 2011 Water Resour. Res. 47, W05535. (doi:10.1029/2009WR008540)), with the derivation of a differential equation whose validity is limited to regular points of the watershed. Here, we show that such a differential equation can be derived from a continuity equation (Chen et al. 2014 Geomorphology 219, 68–86. (doi:10.1016/j.geomorph.2014.04.037)) and extend the theory to critical and singular points both by applying Gauss’s theorem and by means of a dynamical systems approach to define basins of attraction of local surface minima. Simple analytical examples as well as applications to more complex topographic surfaces are examined. The theoretical description of topographic features and properties, such as the drainage area, channel lines and watershed divides, can be broadly adopted to develop and test the numerical algorithms currently used in digital terrain analysis for the computation of the drainage area, as well as for the theoretical analysis of landscape evolution and stability.
Journal Article
Past ice-sheet behaviour: retreat scenarios and changing controls in the Ross Sea, Antarctica
Studying the history of ice-sheet behaviour in the Ross Sea, Antarctica's largest drainage basin can improve our understanding of patterns and controls on marine-based ice-sheet dynamics and provide constraints for numerical ice-sheet models. Newly collected high-resolution multibeam bathymetry data, combined with two decades of legacy multibeam and seismic data, are used to map glacial landforms and reconstruct palaeo ice-sheet drainage. During the Last Glacial Maximum, grounded ice reached the continental shelf edge in the eastern but not western Ross Sea. Recessional geomorphic features in the western Ross Sea indicate virtually continuous back-stepping of the ice-sheet grounding line. In the eastern Ross Sea, well-preserved linear features and a lack of small-scale recessional landforms signify rapid lift-off of grounded ice from the bed. Physiography exerted a first-order control on regional ice behaviour, while sea floor geology played an important subsidiary role. Previously published deglacial scenarios for Ross Sea are based on low-spatial-resolution marine data or terrestrial observations; however, this study uses high-resolution basin-wide geomorphology to constrain grounding-line retreat on the continental shelf. Our analysis of retreat patterns suggests that (1) retreat from the western Ross Sea was complex due to strong physiographic controls on ice-sheet drainage; (2) retreat was asynchronous across the Ross Sea and between troughs; (3) the eastern Ross Sea largely deglaciated prior to the western Ross Sea following the formation of a large grounding-line embayment over Whales Deep; and (4) our glacial geomorphic reconstruction converges with recent numerical models that call for significant and complex East Antarctic ice sheet and West Antarctic ice sheet contributions to the ice flow in the Ross Sea.
Journal Article
Prediction of Pressure Fluctuation of Double-Suction Centrifugal Pump in Different Cavitation Conditions based on EMD-GRU
The double-suction centrifugal pumps play a crucial role in various applications such as in irrigation-drainage projects, water diversion projects, and urban water supply and drainage projects. The pressure fluctuation is one of the crucial parameters for assessing the operational stability of pump. The pressure fluctuation exhibits distinct characteristics in various cavitation conditions. A pressure fluctuation prediction method based on Empirical Mode Decomposition (EMD) and Gated Recurrent Unit (GRU) is proposed in this paper. The model enables accurate forecasting of pressure fluctuation signals when pump operates at different cavitation conditions. The data were obtained from experimental measurements of a double-suction centrifugal pump. The original signal was decomposed into multiple sub-signals with varying energy levels using the EMD method. The neural network of GRU was employed for training and data prediction on individual sub-signals. The predicted results of each sub-signal were combined to form the final pressure fluctuation signals. The method based on EMD-GRU proves effective in predicting pressure fluctuation in three different cavitation conditions. The mean absolute error (MAE) in time-domain characteristics is below 6%, and the prediction error for the main frequency is below 1%. The prediction of low-frequency characteristics still requires improvement.
Journal Article
Drainage network characteristics of the Ghaghghar River Basin (GRB), Son Valley, India
The present study helps to understand the relation between the different morphometric parameters to delineate the drainage characteristics of the Ghaghghar River Basin (GRB), Son Valley, India. Shuttle Radar Topographic Mission (SRTM) data were used to prepare the Digital Elevation Model (DEM), Aspect, Drainage, and Slope maps by using ArcGIS 10 software. The Ghaghghar River is third-order stream that exhibits dendritic to sub-dendritic pattern. The trails drainage patterns are also observed in some areas of the basin which may be due to the effect of regional tectonics. The mean bifurcation ratio is 5.1 showing normal basin which is somehow controlled by structural disturbances. High bifurcation ratio (>10) determines that the region is subjected to strong structural control on the drainage. Drainage density (0.36) shows very coarse drainage texture also having positive correlation with stream frequency. The elongation ratio is 0.64 along with circulatory ratio (0.6) shows elongated nature of the basin. The low values of drainage density and stream frequency imply that surface run-off is not quickly removed from the basin, making it susceptible to flooding and gully have very little effect on the extent to which the surface has been lowered by agents of denudation.
Journal Article
Real-Time Operation of Pumping Systems for Urban Flood Mitigation: Single-Period vs. Multi-Period Optimization
To reduce flood risk in urban regions, it is important to optimize the performance of operational elements such as gates and pumps. This paper compares the performances of two approaches of multi-period and single-period simulation-optimization that are used to derive real-time control policies for operating urban drainage systems. The EPA storm water management model (SWMM), converting real-time rainfall data to surface runoff at network control points, i.e. pump stations, is linked to the particle swarm optimization (PSO) algorithm, evaluating the system operation performance measure (objective function) for different sets of control policies. A prototype network in a portion of the Seoul urban drainage system is used to investigate the efficiency of the proposed approaches. Results justify the high efficiency of multi-period optimization, leading to 32 and 29% average reductions in peak water level violations from a pre-defined permissible threshold at target points and the number of pump switches, respectively, in comparison with the online single-period optimization. The myopic policies derived by single-period optimization are not reliable, and in some cases, they even perform worse than ad-hoc policies applied by system operators based on their past experiences.
Journal Article