Water Level Amplitude Research Articles

Simulation of Storm Surges in the South Central Coast of Vietnam Under Climate Change

The research was supported by National Research Project Program of Vietnam: science and technology in response to climate change, natural resources and environmental management in the 2016-2020 period (program number: BĐKH/16-20), Developing a sustainable socio-economic model adapting to extreme natural disasters under climate change in the South Central region of Viet Nam. A case study of Ninh Thuan province (grant number: BĐKH.04/16-20). Abstract This paper presents the results of storm surge simulation in the South Central region of Vietnam using the Mike 21-FM HD model. Wind pressure fields of typical storms were first identified in period of 1986-2005 using the parametric wind field model. Storm surge risk was then simulated based on the rare 10, 50 and 100-year frequency corresponding to 2030, 2050, and 2100 scenarios. Storm surge model was finally calibrated and validated using the level of water measured in the November 2009 Typhoon Mirinae and October 2013 Typhoon Nari. The results show that storm surges were consistent with water level variation and amplitude; the maximum and minimum storm surges were 2.34m in the Binh Thuan coastal area and 0.78m in the Khanh Hoa coastal area, respectively. The results of this study demonstrated the use of MIKE 21-FM HD model for the simulation of storm surges in the future plays an important role in damage risk reduction caused by storm surges. Keywords: storm surge simulation, climate change, Mike 21-FM HD model, South Central coast of Vietnam. DOI : 10.7176/JEES/9-6-08 Publication date :June 30 th 2019

Study on Effects of Water Drop for High Concrete Face Rockfill Dams in Narrow Valley

In order to analyze the influence of sudden drawdown of dam water level of high concrete face rockfill dam (CFRD), the paper took a narrow valley high CFRD project for example and conducted a comparative study of stress and deformation of panel and dam between different drop amplitude of dam water level. An elastoplastic hardening soil (HS) constitutive model was used to predict the behavior of CFRD. Then, through analyzing the calculation result of six calculation Cases, the paper summarized the effect of dam water level drawdown speed and amplitude on deformation and stress respectively of panel and rockfill zones. The results showed that owing to the arching effect of the CFRD in narrow valley, total deformation of concrete face slab occurring near the dam crest. However, the pressure and tensile stress of concrete face slab along the dam axial direction have a significant influence on the separation of the slab pieces, and potential seepage at the joints in the slab. The study indicates that the hardening soil model could better to analysis of the behavior of high CFRDs and to predict the performances of high CFRDs.

A SEMI-ANALYTIC MODEL OF TIDAL INLETS AND THEIR EVOLUTION

The water exchange between the sea and a lagoon or bay through an inlet due to tides is a classical topic that has been investigated in a large number of studies (Keulegan, 1967; O’Brien and Dean, 1972; O’Brien and Clark, 1974; Escoffier, 1977). In this paper, a simple semi-analytic model of the flow induced by tides through an inlet connecting the sea to a lagoon or bay is developed. The model is employed to derive explicit expressions for key parameters associated with inlet flows such as bay water level amplitude, tidal prism, maximum inlet velocity, and mixing (retention) time. Also, the inlet flow model is combined with a sediment transport model to determine the conditions for equilibrium as well as the evolution of the inlet cross-sectional area towards equilibrium or closure.

Application of 1D–2D coupled modeling in water quality assessment: A case study in Ca Mau Peninsula, Vietnam

A few 1D and 2D models are used to simulate and calculate the water level and water quality regarding four state variable (DO, NH4, NO3, and BOD) observations in the main rivers and coastal estuaries on the Ca Mau peninsula. This study calibrates and validates 1D and 2D models during the dry and flood seasons for 2014 and 2015, as well as assesses water quality in coastal estuaries during the dry and flood season of 2016 by using a 2D model. The calibration and validation results of the hydrodynamic 1D and 2D models show that there is a high degree of conformity regarding the phase and amplitude of water level at observing stations with mean absolute error (MAE) ranges from 0.05 m to 0.37 m. The RMSE–observation standard deviation ratio (RSR) vary from 0.12 to 0.64, and the percent bias (PBIAS) is from −8.9% to 3.2%. Calibration and validation of water quality parameter (DO, NH4, NO3, and BOD5 concentration) results have a high correlation coefficient during both the dry and flood season of 2014 and 2015. The standards, originating from the National Technical Regulation on Surface Water quality and on Coastal Water Quality, are used to evaluate pollutant concentrations in estuaries in the study area during the dry and flood seasons of 2016. The water quality parameters contain DO (4.6 mg/l–7.9 mg/l) and BOD (4.6 mg/l–10.7 mg/l) concentrations over the National Technical Regulation on Surface and Coastal Water Quality and the A1 limit with DO (>4 mg/l) and BOD5 (4 mg/l) on surface water quality for domestic water use in the dry and flood seasons. The calculated results will help managers make better plans for aquaculture and aquatic conservation zones in coastal estuaries in the future.

Variability of Short-Term Diel Water Temperature Amplitudes in a Mountain Lake

This paper presents an analysis of the variability of short-term water temperature amplitudes in Lake Morskie Oko, situated in the Tatra Mountains National Park, which makes the human impact on the lake very limited. The objective of the study was to determine to what extent an increase in depth contributes to suppressing daily water temperature amplitudes. It was shown, among other things, that water temperature amplitudes were the lowest in the period of occurrence of the ice cover, higher in the period of occurrence of other (than ice cover) ice phenomena, and the highest in the case of their lack. The analysis of profiles of water temperature amplitudes (in the case of lack of ice phenomena) resulted in determination of their six types. A strong correlation was observed in which the effect of mean daily air temperature and the effect of wind on water level amplitudes are considerably lower during the occurrence of ice phenomena in comparison to the period when the water surface is free from such phenomena. It was demonstrated that the near-bottom waters in Lake Morskie Oko are very stable in terms of temperature. The short transition period from ice cover to free water surface was determined to be very important, because it constitutes a threshold in the effect of air temperature and wind on changes in thermal dynamics of water (in this case expressed in amplitude values). Finally, proposals are presented for future expansion of the scope of research on water temperature amplitudes. This work is important, because the amplitudes were investigated not only at the surface of the lake, but also at its bottom, and also during the ice cover period, when the lake was isolated from the atmospheric influences. This study may contribute to better understanding of the lake water temperature responses to climate change and thus to more accurate prediction these patterns in lake globally. Moreover, understanding of changes in water temperature is closely related to the variability of its heat resources, and these in the future may be used on a large scale. In the case of a mountain lake such as Morskie Oko, the heat of water may be used, for example, for heating tourist shelters.

Bog surface oscillation (mire breathing): A useful measure in raised bog restoration

AbstractOscillation of the peat surface is an important mechanism for hydrological self‐regulation in bogs. As the water table rises in the wet season, the peat body expands, raising the bog surface and increasing water storage. With seasonal drying, the water table declines, the peat loses volume, and the bog surface drops, thereby keeping Sphagnum mosses in close contact with the water table. The oscillation of surface elevation in a Pacific coastal temperate raised bog was monitored at multiple sites for 4–12 years in 8 different plant communities of both peat‐harvested and unharvested sites to determine how bog surface oscillation relates to site conditions. The multiyear averages of bog surface oscillation for the different sites ranged from 2 to 34 cm (mean: 10.8 cm). In harvested sites, surface oscillation was linked to a larger water level amplitude and a shallower water table. In unharvested sites, a shallow water table was also a strong predictor of surface oscillation, but water level amplitude was negatively correlated to surface oscillation. This discrepancy was attributed to rewetting and regeneration of harvested sites, as well as historic drainage in many of the unharvested sites that reduced the elasticity of the peat. Surface oscillation differed significantly between some of the plant communities, generally between drier and wetter sites. In disturbed bogs, regeneration of a more elastic surface peat can increase the magnitude of peat volume change and bring about the return of self‐regulating mechanisms. Bog surface oscillation may be an important metric for assessing the restoration success or storage capacity of raised bogs in similar climatic settings.

Study on the Influence and Rapid Prediction of Wind on water level for Open Channel Water Transfer Project

Taking the typical main canal of the Middle Route of South-to-North Water Transfer project as an example, the numerical simulation study on the variation law of water level before sluice under different wind conditions is carried out. First, based on numerical simulation, mathematical induction, and statistical analysis method, the influences of wind speed, wind duration and wind direction on water level fluctuation are put forward and the fast prediction formula of maximum water level fluctuation under wind influence is extracted. Then, the feasibility of the fast prediction formula is verified by the actual monitoring data. The results show that: (1) the duration of wind has little influence on the maximum water level variation, and the maximum error is 9.83 %; (2) the maximum water level amplitude increases with increasing wind speed and decreases with increasing wind source distance; (3) the whole water level variation is symmetrical about the angle α=180°, and 0° to 90° is a period of maximum water level variation; (4) the error between the calculation result of the fast prediction formula and the measured result is 1.25 %, which shows that the maximum water level prediction formula is relatively applicable to open channel water transfer project. These research results provide a scientific basis for routine dispatching of water conveyance projects.

Monitoring Recent Fluctuations of the Southern Pool of Lake Chad Using Multiple Remote Sensing Data: Implications for Water Balance Analysis

The drought episodes in the second half of the 20th century have profoundly modified the state of Lake Chad and investigation of its variations is necessary under the new circumstances. Multiple remote sensing observations were used in this paper to study its variation in the recent 25 years. Unlike previous studies, only the southern pool of Lake Chad (SPLC) was selected as our study area, because it is the only permanent open water area after the serious lake recession in 1973–1975. Four satellite altimetry products were used for water level retrieval and 904 Landsat TM/ETM+ images were used for lake surface area extraction. Based on the water level (L) and surface area (A) retrieved (with coinciding dates), linear regression method was used to retrieve the SPLC’s L-A curve, which was then integrated to estimate water volume variations ( Δ V ). The results show that the SPLC has been in a relatively stable phase, with a slight increasing trend from 1992 to 2016. On annual average scale, the increase rate of water level, surface area and water volume is 0.5 cm year−1, 0.14 km2 year−1 and 0.007 km3 year−1, respectively. As for the intra-annual variations of the SPLC, the seasonal variation amplitude of water level, lake area and water volume is 1.38 m, 38.08 km2 and 2.00 km3, respectively. The scatterplots between precipitation and Δ V indicate that there is a time lag of about one to two months in the response of water volume variations to precipitation, which makes it possible for us to predict Δ V . The water balance of the SPLC is significantly different from that of the entire Lake Chad. While evaporation accounts for 96% of the lake’s total water losses, only 16% of the SPLC’s losses are consumed by evaporation, with the other 84% offset by outflow.

Groundwater Level Changes since 1978 in an African City on Basement Rocks: The Case of the CIEH Borehole in Ouagadougou (Burkina Faso)

The CIEH piezometer, located in the center of Ouagadougou city presents a water level record spanning the West African Drought which peaked during the 80s and 90s. Its water level is investigated as a potential proxy for groundwater water resources in West African basement rock aquifers submitted to climate changes. 23 boreholes and wells in various land uses and within a 2 km radius around the CIEH piezometer were monitored during the 2013-2014 hydrologic year. The minimum water level occurred in May, at the end of the dry season, while the maximum took place in October, one month after the end of the rainy season. The mean water level amplitude is 3 m, the minimum amplitude being reached at the CIEH piezometer (0.76 m). Moreover, the CIEH piezometer is located in a 2 m amplitude water table depression either in May or in October. Simplified 2d modeling using a general basement aquifer structure shows that (i) the water level in the piezometer is under ongoing influence of the spillway raise of the nearby dam#3 lake in 2002, (ii) the whole 1978-2004 period cannot be modelled with constant parameters. A 3% decrease of water uptake is adopted after 1985, presumably resulting from land use changes in the Ouagadougou city. The water table at the CIEH piezometer is presently at its 1978 level, which can considered as a pre-drought value. However this includes a 1.5 m contribution of the two abovementioned anthropic effects Further quantitative interpretations of the CIEH piezometer record will require additional geophysical and hydrological investigations.

An investigation of water level fluctuations in Polish lakes in various phases of the winter North Atlantic Oscillation

The North Atlantic Oscillation is a macroscale type of circulation determining climate and hydrological conditions in Europe. The paper presents water level fluctuations in 19 Polish lakes in various phases of NAO of the winter season in the years 1976-2010. Correlations of the winter NAO index with monthly, seasonal, maximum, and minimum water stages, and annual water level amplitudes in lakes were calculated. Approximately 20% of the performed tests showed statistical significance. Lakes were recorded where the correlations were significant in a major part of the year, as well as lakes showing no significant correlations in any month. Deviations of mean water stages in the positive and negative phase of NAO from mean water stages were calculated for each of the lakes. This permitted classifying the lakes into two groups by Ward’s method based on deviations of water stages in the positive and negative phase of NAODJFMfrom average values. This resulted in the designation of 4 and 5 typological classes of lakes, respectively. Deviations of water stages in lakes in various phases of NAODJFMfrom mean values were determined to even exceed 20 cm. The study results can find practical applications in reference to water retention. In view of the observed environmental changes, it is possible that the hydrotechnical infrastructure on lakes will have to be developed in the future. Such a situation will permit the precise control of water level fluctuations for the purpose of the optimal adaptation of lakes for economic purposes.

Co-seismic response of water level in the Jingle well (China) associated with the Gorkha Nepal (Mw 7.8) earthquake

Changes in co-seismic water levels associated with the Gorkha Nepal earthquake (25 April 2015, Mw 7.8) were recorded in the Jingle well in Shanxi Province China (longitude E112.03°, latitude N38.35°, about 2769km from epicenter). Based on the observed water levels, we clearly identified signals relating to P, S and surface waves. However, the water temperature recorded at a depth of 350m shows no co-seismic changes. A spectrum analysis of co-seismic variations of water level shows that the oscillation frequency and amplitude of water level in the borehole are determined by the natural frequency of the borehole, which is not associated with the propagation of seismic waves. The borehole-aquifer system shows a large amplification associated with ground vibrations generated by earthquakes. Considering the local hydro-geological map and the temperature gradient of the Jingle well, a large volume “groundwater reservoir” model can be used to explain these processes. Due to seismic wave propagation, the volume of a well-confined aquifer expands and contracts forming fractures that change the water flow. In the well-confined aquifer, water levels oscillate simultaneously with high amplitude ground shaking during earthquakes. However, the water in the center of the “underground reservoir” remains relatively stationary, without any changes in the water temperature. In addition, a possible precursor wave is recorded in the water level at the Jingle well prior to the Gorkha earthquake.

Simulations of nutrient emissions from a net cage aquaculture system in a Brazilian bay.

Hydrodynamics and transport simulations were conducted with the modeling software TELEMAC-2D on Icó-Mandantes bay, a branch of the Itaparica reservoir. The bay has a maximal operational water level amplitude of 5 m and is suffering from eutrophication and algae bloom. Therefore, we investigated low and high water level scenarios with two different high resolution meshes, with the purpose to deeper understand their impact on transport of substances and to improve the watershed management. In particular, nutrient emissions from a hypothetical net cage aquaculture system located in the bay were investigated on half-year cycles. We observed a relevant impact on water quality for a tilapia production of 130 t y(-1); i.e. after 6 months' simulation we obtained around 8 μgP L(-1) and 6 μgP L(-1) at the source of emissions, for low and high water scenarios, respectively.

The Ecological Amplitude ofAcorus calamusYoung Shoots Under Water Level Gradient

ABSTRACT This paper analysed the influence of the gradient of water levels (-54–120 cm) on Acorus calamus (A. calamus) young shoots in terms of their growth characteristics (germination rate, basal stem, height and biomass), leaf characteristics (number, area and moisture content), chlorophyll (chl) fluorescence parameters (Fv/ Fm, ETR, qP and qN) and other indicators. Based on a Gaussian model, we determined and quantified the response relationship between A. calamus young shoots and water level. The results showed that the ecological amplitude of water level for A. calamus young shoots was -52.3−141.8 cm, and the optimum range was -3.5−69.3 cm; a variety of indicators suggested that the optimum depth for A. calamus young shoots was from18.8 cm to 49.6 cm. The A. calamus seedling growth characteristics which were sensitive to changes in the water level were the germination rate and biomass. The germination rate was more sensitive to the submergence water depth, but the biomass was obviously influenced by...

Research on critical groundwater level under the threshold value of land subsidence in the typical region of Beijing

Abstract. Groundwater in Beijing has been excessively exploited in a long time, causing the groundwater level continued to declining and land subsidence areas expanding, which restrained the economic and social sustainable development. Long years of study show good time-space corresponding relationship between groundwater level and land subsidence. To providing scientific basis for the following land subsidence prevention and treatment, quantitative research between groundwater level and settlement is necessary. Multi-linear regression models are set up by long series factual monitoring data about layered water table and settlement in the Tianzhu monitoring station. The results show that: layered settlement is closely related to water table, water level variation and amplitude, especially the water table. Finally, according to the threshold value in the land subsidence prevention and control plan of China (45, 30, 25 mm), the minimum allowable layered water level in this region while settlement achieving the threshold value is calculated between −18.448 and −10.082 m. The results provide a reasonable and operable control target of groundwater level for rational adjustment of groundwater exploited horizon in the future.

Sustainability aspects of water regulation and flood risk reduction in Lake Vänern

A modern feature of flood risk management is to integrate ecological, economic and social aspects in risk prevention and mitigation. Risk-reducing measures can be in conflict with ecosystem functions and complicate upstream/downstream relations. Flood risks are also influenced by processes in the catchment, such as changes in climate and land-use, or increases of vulnerable urban areas. Lake Vänern in Sweden has high ecological and social values but is also flood-prone, which in this article has been analyzed from a perspective of sustainable development. Lake Vänern and the Göta älv River are used for drinking water supply, shipping, hydropower production, fishing, tourism, as a recipient for industries and wastewater plants, etc. The flood risks are connected to landslide and industrial risks. One interest at stake is the drinking water supply for 800,000 persons in the Gothenburg region. According to climate scenarios, flood risks will increase in the 21st century due to increased precipitation. Recent studies in the region were used to identify relevant interests and values connected to Lake Vänern. The study reveals differing interests in relation to water level regimes. From a flood protection perspective (risks around the lake and downstream to Gothenburg) a low and stable water level is beneficial. For shipping and hydropower, a stable medium-high water level is wanted, whereas from an ecosystem and landscape development perspective larger water level amplitudes are optimal. One out of a few reasons for this is the need to prevent a massive increase in vegetation in coastal areas. There are good reasons to have a broad decision-support, representing different values and interests, when the permanent water regulation scheme will be decided. This study also addresses the potential to reconcile the concept of flood risk management with that of a sustainable development.

Unsteady Flow Impact on Downstream Waterways and Control Measures Research of Pingban Hub in Nanpanjiangjiang River of Guizhou

After the completion of the hub on river, its scheduling unsteady flow generated an adverse impact on the downstream navigation. In this paper, according to the unsteady flow data of PingBan hub in Nanpanjiangjiang River in Guizhou province, researched unsteady flow spread characteristics and rule in hub downstream channel. Studies have shown that: unlike general water level changes in hub downstream, the waterlevel amplitude attenuation along is not obvious in researched reach; Clear the concept of unsteady flow additional velocity、additional slope,through this theory reveals the ship ascending rapids mechanism difficultly under unsteady flow condition. On this basis, proposed channel regulation methods and measures in hub downstream, which provided support for the hub downstream channel regulation.

Infragravity currents in a small ría: Estuary-amplified coastal edge waves?

Observations are presented of estuarine infragravity oscillations in a very small estuary, the Ría de Santiuste, northern Spain, that discharges into a bay. Time-scale calculations and measurements indicate that the most likely source of amplified infragravity waves within the estuary are coastal edge waves, which appear to be resonating between the headlands of the bay, and onshore-offshore seiching of waters that may be resonating between the beach and the bay's seaward limit. Infragravity waves in the estuary have a narrow, power-dominant periodicity range of 4.3–4.8 min. Generally, only very weak waves, and at other periodicities, occur within the tidal river when it is unaffected by the tide. Although infragravity water-level amplitudes are small in the tidal river, typically ∼0.01 m during high water, the corresponding velocity amplitudes are significant, typically ∼0.1 m s−1, despite the occurrence of high runoff conditions during these measurements. Within the estuary and close to the mouth, near-bed salinity shows considerable variability that is a consequence of salt wedge oscillations with periodicities that are within the range of 4.3–4.8 min. Model results for simulated neap to spring high-water water levels show that wave periodicities in the range 3.5–4.5 min correspond approximately to 3λ/4 resonances. The model also indicates that an effect of low runoff is to greatly enhance resonant behaviour within the estuary, such that water level amplitudes of 0.02 m at the mouth can produce wave currents as fast as 0.4 m s−1 within the estuary, compared with ∼0.1 m s−1 during high runoff.

Unidirectional power extraction from a channel connecting a bay to the open ocean

Bays connected to the open ocean by a channel can give rise to large tidal currents which might be suitable for tidal stream turbines. The maximum power extractable from such a geometry was found by Blanchfield et al . (The extractable power from a channel linking a bay to the open ocean. Proc IMechE, Part A: J Power and Energy 222(3):289–297) to be given to within approximately 15%, as [Formula: see text], where a is the water level amplitude of the dominant tidal constituent in the open ocean and Q0 is the maximum volumetric flow rate in the undisturbed state. This analysis is based on turbines operating on both flood and ebb tides. In the present paper, we show that for sites with relatively small bays greater power can be extracted by only operating the turbines in one direction. The pros and cons of this alternative strategy are briefly discussed.

River flow controls on tides and tide‐mean water level profiles in a tidal freshwater river

Tidal rivers feature oscillatory and steady gradients in the water surface, controlled by interactions between river flow and tides. The river discharge attenuates the tidal motion, and tidal motion increases tidal‐mean friction in the river, which may act as a barrier to the river discharge. Time series of tidal water level amplitudes at five gauge stations along the River Mahakam in Indonesia, and tidal flow velocity amplitudes at a discharge monitoring station were obtained applying wavelet analysis. Temporal variations in tidal damping coefficients for quaterdiurnal, semidiurnal, and diurnal tidal species were quantified from the observed amplitude profiles. The analysis shows that tidal damping during the rising limb of a discharge wave differs from damping during the falling limb. Wavelet cross‐correlations between surface levels yielded empirical estimates of wave numbers. An empirical relation between tidal damping and river flow is derived to describe subtidal bottom friction along an idealized tidal river resembling the Mahakam. The subtidal friction is decomposed into contributions from the river flow only, from river‐tide interaction, and from tidal asymmetry. Even for high river flow and low tidal velocity, river flow enhances friction attributed to river‐tide interaction, causing subtidal water level setup. A simple multilinear regression model using subtidal bottom friction is employed to predict subtidal water levels at locations upstream, with a relatively good agreement between predictions and observations. The explicit expression shows the nonlinear dependence of subtidal friction on river flow velocity, explaining the complex behavior of tidal‐mean surface level profiles.

Influence of Hydraulic Factor of Vertical-Slot Fishway on Swimming Ability of Fish

Vertical-slot fishway is widely used in different shape of fish-way due to the adaptability to water level amplitude, the hydraulic characteristics of the vertical-slot fish-way of different scale has been extensively researched by researcher domestic and overseas, the energy dissipation mechanism and hydraulic characteristics of the fish-way in different scale under different inflow has been acquainted now. In this paper, the hydraulic characteristics of Vertical-slot fish-way of different size under water depth, inflow and slope is analyzed , influence of water depth, flow velocity, dissipation rating per unit volume and turbulent energy etc. On fish swimming ability is discussed, and design of fish-way is evaluated by relevant hydraulic factor of fish swimming characteristics. Finally the research method and experience abroad is summarized in the paper.