Water Level Difference Research Articles

Investigating the mysteries of groundwater in the Badain Jaran Desert, China

The Badain Jaran Desert (BJD) in China is a desert with impressive sand dunes and a groundwater situation that has attracted numerous researchers. This paper gives an overview of the mysteries of groundwater in the BJD that are exhibited as five key problems identified in previous studies. These problems relate to the origin of the groundwater, the hydrological connection between the BJD and the Heihe River Basin (HRB), the infiltration recharge, the lake–groundwater interactions, and the features of stable isotope analyses. The existing controversial analyses and hypotheses have caused debate and have hindered effective water resources management in the region. In recent years, these problems have been partly addressed by additional surveys. It has been revealed that the Quaternary sandy sediments and Neogene-Cretaceous sandstones form a thick aquifer system in the BJD. Groundwater flow at the regional scale is dominated by a significant difference in water levels between the surrounding mountains and lowlands at the western and northern edges. Discharge of groundwater from the BJD to the downstream HRB occurs according to the regional flow. Seasonal fluctuations of the water level in lakes are less than 0.5 m due to the quasi-steady groundwater discharge. The magnitude of infiltration recharge is still highly uncertain because significant limitations existed in previous studies. The evaporation effect may be the key to interpreting the anomalous negative deuterium-excess in the BJD groundwater. Further investigations are expected to reveal the hydrogeological conditions in more detail.

Height system connection between island and mainland using a hydrodynamic model: a case study connecting the Dutch Wadden islands to the Amsterdam ordnance datum (NAP)

We present an efficient and flexible alternative method to connect islands and offshore tide gauges with the height system on land. The method uses a regional, high-resolution hydrodynamic model that provides total water levels. From the model, we obtain the differences in mean water level (MWL) between tide gauges at the mainland and at the islands or offshore platforms. Adding them to the MWL relative to the national height system at the mainland’s tide gauges realizes a connection of the island and offshore platforms with the height system on the mainland. Numerical results are presented for the connection of the Dutch Wadden islands with the national height system (Normaal Amsterdams Peil, NAP). Several choices of the period over which the MWLs are computed are tested and validated. The best results were obtained when we computed the MWL only over the summer months of our 19-year simulation period. Based on this strategy, the percentage of connections for which the absolute differences between the observation- and model-derived MWL differences are le 1 cm is about 34% (46 out of 135 possible leveling connections). In this case, for each Wadden island we can find several connections that allow the transfer of NAP with (sub-)centimeter accuracy.

Multi-Domain 2.5D Method for Multiple Water Level Hydrodynamics

The mean water surface (interface) under the air cushion of a surface effect ship (SES) or an air cushion supported platform (ACSP) is generally lower than the outside water surface due to the overpressure of the air cushion. To precisely analyze the hydrodynamics under the air cushion, multiple water levels should be considered in numerical models. However, when using free surface Green’s functions as numerical methods, the water level difference cannot be taken into account, because free surface Green’s functions normally require users to set in the whole water domain a unique datum water surface that completely separates the air domain and the water domain. To overcome this difficulty, a multi-domain approach is incorporated into a 2.5D method that is based on a time domain free surface Green’s function with viscous dissipation effects in this paper. In the novel multi-domain 2.5D method, the water domain is partitioned into inner and outer domains, and the interface is located in the inner domain while the outside water surface is placed in the outer domain. In each domain there exists only one unique water level, while water levels in different domains are allowed to be different. Benefited from this characteristic, the multi-domain 2.5D method is able to precisely consider the water level difference and its influence on hydrodynamics. The newly proposed multi-domain 2.5D method is employed to predict the hydrodynamics of an SES, and it is confirmed that the multi-domain 2.5D method can give better numerical results than the single-domain one for the given case.

Automatic feedback control algorithm for canal for a quick upstream water supply interruption in the case of an emergency

For the sudden upstream water interruption in the canal of an emergency, the existing research method guiding gate control is mainly feed-forward compensation algorithm, under which algorithm the interruption of water diversions is the upstream first and then the downstream. In order to achieve a more flexible water demand for different water diversions purpose, this study used PI water level difference feedback control algorithm to control the gate under this condition. The research results showed that the PI water level difference feedback control algorithm can make the change trend of water level of multi-pool close and reduce the rate of water level decline, and thus prolong the continuous delivery time of pools with offtake delivery demand under sudden upstream water interruption. Moreover, the PI water level difference method has good robustness and can be applied to more complex combinations of inflow and delivery changes. This study provides another way of thinking for the regulation of the gate in the case of sudden upstream water interruption.

Remote Sensing of Hydrological Changes in Tian-e-Zhou Oxbow Lake, an Ungauged Area of the Yangtze River Basin

The hydrological pattern changes have a great influence on the wetland environment. However, some important wetland areas often lack historical observations due to economic and physical conditions. The Tian-e-Zhou oxbow lake wetland is an important habitat for two endangered species and also has very little historical hydrological data. Remote sensing images can be used to explore the historical water area fluctuation of lakes. In addition, remote sensing can also be used to obtain historical water levels based on the water boundary elevation integrated with a topographic data (WBET) method or the level-surface area relationship curve (LRC) method. In order to minimize the uncertainty of the derived results, both methods were introduced in the extraction of the water level of Tian-e-Zhou during 1992–2015. The results reveal that the hydrological regime of the oxbow lake has experienced a significant change after the Shatanzi Levee construction in 1998. With the impact of the levee, the mean annual water surface area of the lake was reduced by 5.8 km2 during the flood season, but, during the non-flood season, it was increased by 1.35 km2. For the same period, the water level of the lake during the flood season also showed a 1.47 m (WBET method) or 3.21 m (LRC method) decrease. The mean annual water level increased by 1.12 m (WBET method) or 0.75 m (LRC method). Both results had a good accuracy with RMSE (root-mean-square errors) of less than 0.4 m. Furthermore, the water level differences between the Yangtze River channel and the oxbow lake increased by at least 0.5 m. It is found that the hydrological pattern of the oxbow lake changed significantly after the levee construction, which could bring some disadvantages to the habitats of the two endangered species.

Simulation of hydropower turbine performance in duct for system utilizing tidal jet generator

The marine hydropower system proposed in this study creates a tidal jet generator from a seawater exchange type breakwater, with empty space similar to a basin to store ocean water. Due to the water level difference between the inner and outer sides of the breakwater, strong and uni-directional jets are generated. The energy from the jets is captured by turbines in the breakwater ducts. In this study, the proposed system is first introduced. The design process for a new turbine and its preliminary performance in openwater conditions, estimated using Computational fluid dynamics (CFD), are presented. Experiments with the turbine in a Circulating water channel (CWC) at Pusan National University were also carried out. The results from the simulations and experiments with the same conditions were compared to verify the CFD accuracy. The turbine performance in a duct is estimated; the target power can be generated using the newly developed turbine.

Turbine model used for energy conversion in river water streams

The water flow potential in rivers represents significant resources for aquiring cheap energy production. Depending on the three essential parameters of water flow rate, stream velocity and level difference, optimal constructive solutions are usually adopted for choosing the turbine type to be used in order to obtain energy in a hydroelectric power plant. A three-dimensional turbine model has been developed describing the real rotor model which has the possibility of being directly mounted on the water course in order to take over a part from the water energy and to obtain rotational motion at the rotor axis. A water flow analysis is performed in the fluid area built around the rotor model and the results obtained are presented as values for the water flow rate, velocity and water pressure registered within the fluid area.

Critical distance between copper mining roadway and a vertical water-blocked body

It is vital to determine the critical distance between a mining roadway and a natural vertical water-blocked body (VWBB) where a substantial water level difference and seepage gradient have developed between the two sides of the VWBB. A VWBB critical distance was defined and then determined using a 3D numerical simulation method based on the strength reduction method. The primary value of the VWBB critical distance was determined in consideration of the potential equivalent plastic strain zone induced by the roadways. In consideration of the other influencing factors, the VWBB critical distance was suggested as 105.00 m.

Morphodynamic modeling of a large inside sandbar and its dextral morphology in a convergent estuary: Qiantang Estuary, China

AbstractWe investigate the evolution of a large‐scale sand body, a unique type of sandbars in a convergent estuary. Specifically, we analyze and simulate the sand deposition system (defined as an inside bar) in the Qiantang Estuary (QE) in China. The deposit is 130 km long and up to 10 m thick and is characterized by a dextral morphology in the lower QE. Numerical simulation is carried out using an idealized horizontal 2‐D morphodynamic model mimicking the present QE settings. Our results indicate that the morphological evolution is controlled by the combination of river discharge and tides. The seasonal and interannual cycles of river discharges play a major role on the inside bar evolution. The bar is eroding during high river discharge periods, but accretion prevails during low river discharge periods. Meanwhile, the highest part of the sand body can move downstream or upstream by several kilometers, modifying the seasonal sediment exchange patterns. We also show that the Coriolis force plays an important role on the dextral morphology patterns in wide, convergent estuaries. It induces a significant lateral water level difference and a large‐scale gyre of residual sediment transport. Subsequently, the seaward tail of the inside bar shifts southward to help create a condition for the development of tidal flats in the lower reach of the estuary. The lateral bed level differences induced by Coriolis force are up to several meters. Coriolis effects also modify the behavior of flood and ebb tidal channels.

Study on flow characteristics in vertical slot fishways regarding slot layout optimization

Design of effective fishways is becoming increasingly important. This paper focuses on the effect of the angle of deflection (α) between small and large baffles in a vertical slot fishway (VSF). A reliable depth-averaged two-dimensional numerical model PCFLOW2D was used to perform simulations of various VSF configurations, including six angles of deflection, two slot sizes, two large baffle sizes and four water level differences between adjacent pools. The results showed the important influence of α on depth-discharge curves and maximum velocities at the slot which both strongly affect the fishway efficiency. With larger α, up to 42% smaller discharges and up to 33% smaller maximum velocities were calculated. In cases with small α and larger slot sizes much greater maximum velocities than theoretically calculated using over simplified formula were modeled (up to 62%). The important effect of transverse displacement of the slot on discharge and maximum velocity was evaluated. As expected, the most important parameter that determines the discharge and maximum velocity in the fishway is water level difference between adjacent pools. With slot layout optimization it is possible to achieve the same discharge and maximum velocity even at larger water level differences between adjacent pools which obviously reduce fishway construction costs.

Analysis of Inland Immersed Tunnel Health Monitoring System

Based on Nanchang Hong-gu tunnel, which was the largest inland immersed tube tunnel besides it’s tremendous water level difference, large scale, complex geological conditions, different longitudinal gradients, and other characteristics, accompanied with structure analysis by finite element model, monitoring scheme of the real-time health monitoring program and tunnel health assessment system was analyzed, and the monitoring system was established, then emphasized on the monitoring methods of tube joints open and dislocation, tube uneven settlement, shear key pressure, health assessment indexes and method of index weight determining in health assessment system. This system can make tunnel displacements, internal forces and other health indicators be measured and transmitted automatic in real-time. Research result was applied to Nanchang Honggu tunnel health monitoring system and would be guidance for other tunnel projects as well.

Contamination and spatial distribution of heavy metals in soil of Xiangxi River water-level-fluctuating zone of the Three Gorges Reservoir, China

ABSTRACTThe Three Gorges Reservoir is the largest hydroelectric project in China. It forms water-level-fluctuating (WLF) zones with a water level difference which can reach 30 m and a total area of 349 km2 along the Yangtze River. To determine the pollution level and spatial distribution of heavy metals in WLF regions, Xiangxi River (XXR), the largest first-order tributary, was selected as the study area. Both single-factor and multi-factor evaluation methods were employed to assess the contamination indices of heavy metals in soil. The results showed that the pollution degree for sampling sites varied from slight to moderate pollution levels, where 64% were in slight pollution degree and 4% were in moderate pollution degree. Approximately 68% of the sites were polluted. The ranking of 6 different kinds of heavy metals according to pollution degree was Cd > Pb > Cr > Hg > Ni > Cu. While Cd and Pb contributed the most to the pollutions, the contributions of the other four remained minor. Furthermore, a spatial distribution map of the comprehensive contamination index for the XXR basin is generated. The concentrations of heavy metals in sediments along 4 transects showed an overall decreasing trend with increasing elevation.

Simulation and Analysis of Rain-flood routing under Multi-stage Sluices Regulation in Tuhai River Basin

A coupling model of rainfall-runoff model (NAM) and hydrodynamic model (HD) is established based on MIKE11 to simulate the rain-flood routing in Tuhai River basin under three dispatching principles of multi-stage sluices regulation: gates fully open, water level control and water level difference control. The results show that the simulations for typical cross sections were good and the flow was obviously affected by artificial regulation. This model can be used to provide an accurate hydrodynamic basis for effectively regulating sluices in river networks, and provide technical support for rain-flood forecasting in the Tuhai River Basin.

배후수위 저감효과를 가진 신기능 잠제의 개발

Typically, a submerged breakwater is one of the good scene-friendly coastal structures used to reduce wave energy and coastal erosion. However, sometimes, a submerged breakwater also has a negative aspect in that a strong rip current occurring around an open inlet due to a difference in mean water levels on the front and rear sides of the structure leads to scouring. Such scouring has a bad effect on its stability. In order to eliminate this kind of demerit, this study investigated four new types of submerged breakwaters with drainage channels. First, hydraulic experiments were performed the typical and new structures. Then, the wave height and mean water level distributions around the structures were examined using the experimental results. Finally, it was revealed that the new type of submerged breakwater could efficiently reduce the mean water level on its rear side. In particular, in the case of new-type submerged breakwater 2, an average reduction efficiency of 71.2% for the difference between the mean water levels at the front and rear sides was shown in comparison with the typical one.

Evaluation of Containment Performance from Viewpoints of Diffusion and Dispersion for Impervious Structures at Coastal Landfill Sites

The containment performance of impervious structures is considered the most important performance, which the toxic substances are enclosed in coastal landfill sites. The containment performance is evaluated generally by the hydraulic conductivity and the thickness of impervious structures to focus on an advection. However, the leakage of toxic substances is affected by a diffusion and a dispersion. The diffusion and the dispersion are considered to be easily distinguished on the impervious structure which has the low-hydraulic conductivity. Such phenomena should be considered due to evaluate the containment performance. This is because to improve the containment performance and comprehend leakage of the toxic substances. The containment performance is evaluated from the viewpoint of the diffusion and the dispersion in this research. Concretely, the influence which the toxic substances leaks from impervious structures on the diffusion and the dispersion is evaluated by the infiltration and advection–dispersion analysis on steel-made side impervious walls. In other word, The relation between the leaking amount of toxic substances and coefficient of molecular diffusion, the relation between the travel time or the flow velocity and the leaking amount and the change in the water-level difference are considered respectively. So, the leaking amount which is influenced by a diffusion and a dispersion is considered. Consideration about to secure the containment performance of impervious structure which is restrained leakage by a diffusion and a dispersion.

Current power potential of a sea strait: The Bosphorus

The annual current energy potential of a sea strait, Bosphorus in Turkey, is evaluated by the calibrated and validated three dimensional numerical model results. The numerical approach is based on a number of unstructured flexible meshes (triangle or quadrilateral elements) and uses a cell-centered finite volume solution technique. Three-dimensional incompressible Reynolds averaged Navier-Stokes equations are solved invoking the assumptions of Boussinesq and hydrostatic pressure. The turbulence closure was implemented by using Smagorinsky and k-ε models in the horizontal and vertical domains, respectively. Water level and density differences acting on the model open boundaries combined with the meteorological structure of the region (wind speed, direction and atmospheric pressure difference) are the main forcing mechanisms of the numerical model as inputs. The strait flow is a typical example of a stratified flow among the world's straits, with a possible exception of having a negligible tidal oscillation. The results show that the complex geometry (both horizontally and vertically) of the strait combined with highly variable hydrological and meteorological conditions of the adjacent seas, the Marmara Sea and Black Sea, result in a considerable fluctuation in the kinetic energy potential. Cross-sectional variability of the kinetic energy is also notable both horizontally and vertically with increasing energy upwards and towards the shore. In spatial domain, although it is not the narrowest part of the strait, the highest kinetic energies are calculated at the southernmost part of the strait due to both a decrease in cross-sectional area and the presence of a sill on the bottom, a geometrical feature likely seen in straits that mainly control the flow structure (e.g., flow velocities). For a given cross section taken from a meandering part of the strait, the kinetic energy of the strait is higher at the outer and inner banks of the strait for the upper and lower layer flows, respectively. In time scale, the most energetic time period spans from the late spring to the end of summer related to the increase in water level difference between both ends of the strait due to long-term effects that represent seasonal variations (mainly the river inflows toward the Black Sea) and short-term effects (southward storms in the same direction with the upper layer flow). In winter, however, due to the southerly storms acting opposite to the surface layer flow, the kinetic energy potential of the strait drops to considerably low values occasionally.

Analysis on the Preliminary Stability of Pillar Linking Adjacent Caverns under the Effect of Water Level Differences

This paper investigates the preliminary stability of pillar linking adjacent caverns under the effect of water level differences. By choosing homologous rocks, permeability tests and Brazilian tests in the laboratory are conducted. Then theoretical model and solutions are made. The results show that the rock permeability is extremely low. The tensile strength of the tuff in the laboratory tests is not very high, and its strength will dramatically reduce due to long-term water erosion. Under the comprehensive effect of joint and fissure, the pillar is prone to slab due to the typical lamellar structure. Especially, when the span of the pillar is narrower or the water level difference is more obvious, the pillar will become more instability. All these factors mentioned above may result in deformation even failure of the caverns. Therefore, the development of micro-crack and joint in the pillar should be monitored regularly.

Hydraulic and Structural Design of Navigational Locks

Navigation lock is a structure in the waterway provided to create a safe navigation passage between two water pools which are not at the same level. The reason for difference in water levels can be natural such as tidal variations or can be manmade such as construction of dam or barrage across the river. The main components of Navigation lock comprise of approach channels, lock pit, filling/emptying arrangement. Design of lock depends on lockage time, water level variations, Lock capacity requirements, design vessel size. filling/emptying system shall be designed to work under gravity flow without any pumping requirements. Filling/emptying system is chosen to get appropriate filling/ emptying time. The optimum time for filling and emptying is generally kept between 8.0-10.0 minutes. The size of filling culverts are so computed to attain the optimum time for filling/emptying. Every lock is unique in terms of its geology, location, size, requirements and water level differences. Here typical design aspects of a navigational Lock in inland waterway have been described.

Scale Effects on the Discharge Coefficient of Ogee Spillway with an Arc in Plan and Converging Training Walls

Dam spillways are the structures that lead rightly and safely the outflow downstream, so that the dam integrity can be guaranteed. Many accidents with dams have been caused by an inadequate spillway design or insufficient capacity. To accurately respond the hydraulic spillways, designers use physical modeling for designing this kind of structures. The scale effect in the spillway modeling, as a result, leads to the difference between the measured data and the prototype. In this study, an experimental model of Germi-Chay Mianeh dam spillway was made in three 1:100, 1:75, and 1:50 scales. Then, the water level in upstream of the spillway crest was measured in seven discharges and compared to 1:50 scale (basic scale), the percentage of water level difference on the crest was calculated in two physical models with 1:100 and 1:75 scales. Results revealed that as the scales of ogee spillway with an arc in plan and converging training walls decrease using Froude simulation, the effect of viscosity and surface tension increase in turn resulting in decreasing discharge coefficient. In this study, the scale effect in discharge coefficient ogee spillway was stated with K' equation. Using model family approved that the minimum Reynolds and Weber numbers which are 3.1×104 and 270, respectively indicated the minimum scale effect and thus, it is possible to avoid the effect of viscosity and surface tension in ogee spillway with an arc in plan and with converging training walls. Moreover, results obtained from the small scale which has been simulated using Froude simulation could be extrapolated to the prototype.

Do Water Level Fluctuations Influence Production of Walleye and Yellow Perch Young‐of‐the‐Year in Large Northern Lakes?

AbstractMany ecological processes depend on the regular rise and fall of water levels (WLs), and artificial manipulations to WL regimes can impair important ecosystem services. Previous research has suggested that differences in WL between late summer and early spring may alter the suitability of shoals used by Walleyes Sander vitreus for spawning. Other species, such as the Yellow Perch Perca flavescens, are unlikely to be affected in the same way by WL fluctuations because their spawning requirements are quite different. We used 11–23 years of data from six northern Minnesota lakes to assess the effects of WL fluctuations on the abundances of young‐of‐the‐year (age‐0) Walleyes and Yellow Perch. In two lakes (Rainy Lake and Lake Kabetogama), a change in WL management occurred in 2000, after which these lakes saw increased age‐0 Walleye abundance, while the other study lakes experienced decreases or no change. Rainy Lake and Lake Kabetogama also had increases in age‐0 Yellow Perch, but another study lake did also. We used partial least‐squares regression to assess whether WL metrics were associated with variation in age‐0 Walleye and Yellow Perch abundances, but WL metrics were seldom associated with age‐0 abundance for either species. Our analysis suggested a potential influence of WL regulation on age‐0 Walleye abundance, but we found no evidence that early spring access to spawning shoals was the mechanism by which this occurred.Received August 19, 2015; accepted July 15, 2016 Published online November 10, 2016