查看更多>>摘要：Empirical approaches such as the Height Above Nearest Drainage method in conjunction with Synthetic Rating Curves (HAND-SRC) have emerged as particularly appealing alternatives to the traditional flood mapping techniques due to their lower complexity and fewer data requirements. However, SRCs use Digital Elevation Model (DEM) derived reach averaged hydraulic properties and assume one dimensional steady state flow condition with normal depth. These implicit model assumptions may introduce errors in flood stage and extent estimates using the HAND-SRC approach. This study investigates the reliability of SRC across continental United States (CONUS) by comparing them to the United States Geological Survey's (USGS) gauge rating curves. Results from this comparison show that the implicit model assumptions used in the SRC-HAND approach add significant error in the SRC derivation. The accuracy of the SRC is found to be related to the stream characteristics, including the bathymetry area, slope of the main channel two-year flow and drainage area. Results also show that SRCs in coastal areas, characterized by low slopes and large drainage areas, have higher error and tend to overpredict the stage height in comparison to the USGS rating curves; whereas they tend to underpredict stage height in the mountainous regions. The SRCs are most reliable for the midwestern plains of Ohio, Mid Atlantic, Tennessee and Upper Mississippi regions, and least reliable (higher error) for the Rocky Mountains. Further, the study finds that Deep Neural Network models can be effectively used to judge the performance of SRC for ungauged river reaches.
查看更多>>摘要：Satellite images, which are effectively used to monitor changes in water areas, water management and planning, and to determine the measures to be taken against possible natural disasters, provide data with high temporal and spatial resolution. This study represents the monitoring of temporal surface water dynamics and estimating the volume fluctuations by combining the in-situ data with remotely sensed area data for Kemer Dam, containing the Arapapis,ti Canyon (Turkey). Also, it demonstrates the production of the underwater topography in the water reservoir areas of absent or difficult to obtain bottom topography by integrating the in-situ water level and the PlanetScope Remote Sensing data in GIS environment. The temporal changes of dynamic volume of the reservoir above the lowest water level were estimated by the Hypsometric Relationship equation, Pyramidal Frustum Model and TIN-based Calculation method and their accuracy were evaluated using in-situ data. The simplicity and ease of application of the Pyramidal Frustum method, as well as its relatively low RMSE and Standard Error Rate of the Regression (SER) values, compared to other methods in this study, increase its usability in such studies. PlanetScope Imagery will make an important contribution to hydrological studies by producing daily images in high-resolution. Mission characteristics of satellite images (e.g. spatial, temporal and spectral resolution and, geometric accuracy), data sparseness, concurrency in parameters, chosen volume calculation method and linearity of hypsometry are important components that affect the performance of the Volume Fluctuation Monitoring studies using satellite images.
查看更多>>摘要：Interaction between capillary and viscous forces significantly affects the flow instability in immiscible displacement, which is usually investigated by visualization of flow patterns in 2d porous micromodels or in 3d system equipped with X-ray CT. However, in most practical applications, visualization of flow in porous media is not possible and the pressure signal is often as one of the important sources of information. Core flooding experiments were implemented in this study to investigate the interplay of capillary and viscous effects by analysis of differential pressure. Water and crude oil were employed as defending fluid, and different states of CO2 were injected as invading fluid. The inlet was set as the constant injection flow rate while the outlet as the constant pressure. In viscous-dominated displacement, differential pressure evidently depends on the injection rate and the pressure decline curve is fitted by a power function. The exponent of the function is found to be significantly larger at the crossover between capillary-dominated and viscous-dominated regions. In capillary-dominated displacement, the pressure profile is characterized by a pressure jump at the beginning and intermittent fluctuations during the displacement. Further analysis by wavelet decomposition indicates a transition point existing in standard deviation of pressure fluctuations when the displacement is transformed from capillary-dominated to viscous-dominated. The experimental results are finally verified by a macroscopic capillary number, which characterizes the interaction between capillary and viscous forces at a critical value of Nmacroca similar to 1, agreeing well with the Log Nca-Log M phase diagram.
NSTL
Elsevier