Dam Water Level Research Articles

Three-Dimensional Nonlinear Finite Element Analysis on the Concrete Face Cock-Fill Dam of TianChi Upper Reservoir

Taking the concrete face cock-fill dam upper reservoir of Tianchi as an example, the stress and deformation characteristics of concrete face rock-fill dam are studied in-depth in this paper. The article builds a fine three-dimensional finite element model of Tianchi upper reservoir by a nonlinear elastic model of the finite element software ADINA. The stress and deformation of the two conditions under completion and storage for the dam are calculated ,which will be analyzed to obtain stress - strain distribution of the dam in two conditions, comparing dam stress and deformation before and after impoundment to get impact of the water pressure on the dam stress and deformation: comparing after impoundment and completion , the dam water level displacement of upstream side from role of horizontal water pressure will increase , the dam upstream offsets to downstream , but the offset is little ; Due to dam is affected by vertical hydrostatic pressure and uplift pressure after impoundment , the dam settlement is slightly less than the completion in storage. KEY WORDS: Tianchi upper reservoir, The concrete face cock-fill dam, Three-dimensional finite element, Nonlinear elastic model, Analysis of stress and deformation

사연댐 운영수위 하강에 따른 반구대 암각화지점의 수리학적 특성 분석

본 연구는 세계적 문화유산인 반구대암각화의 침수방지를 위해 사연댐의 운영수위를 하강시키는 것이 반구대암각화 보존에 적정한지를 대곡천의 수리학적 특성을 분석하여 평가하였다. 이를 위해 1차원 하천해석 모형인 HEC-RAS를 이용하여 사연댐 수위 변화에 따른 반구대암각화의 침수높이를 분석 하였고, 반구대암각화 지점의 유속 및 흐름을 2차원 하천해석 모형인 RMA-2를 이용하여 대곡천의 영향을 분석하였다. 수치모의 결과 평수기 유량조건에서 사연댐의 수위변화에 따른 반구대암각화의 침수 높이는 사연댐의 수위가 EL.60.0 m에서 EL.56.5 m까지는 반구대암각화 전체가 침수되었으며, EL.52.5 m일 때는 반구대암각화는 침수되지 않는 것으로 분석되었다. 사연댐의 수위가 EL.52.5 m일 때 20년 빈도에서 반구대암각화는 2.7 m(73%)의 침수가 발생하였고, 200년 빈도시에는 3.47 m(93.8%)의 침수가 발생하는 것으로 분석되었다. 홍수기 유량조건일 때 반구대암각화 지점의 흐름특성 분석결과 사연댐의 수위를 EL.60.0 m에서 EL.52.5 m로 낮출 경우 유속이 약 2.5배 증가하였으며, 최대유속선이 반구대암각화를 지남으로써 유수에 의한 훼손을 증가시키는 것으로 분석되었다. Assesment of hydraulic Characteristics has been carried out of Daegokcheon because Sa-yeon dam water level decline operation for proper due to world cultural heritage edged Bangudae petroglyphs. Analyses on the Dae-gok stream were conducted by changing the water level of the Sa-yeon Dam by using the 1D HEC-RAS numerical model for the inundation of height variations and 2D RMA-2 model for the flow characteristics. As a result of the modeling, if the water elevation on the Sa-yeon Dam is higher than EL.52.5 m, the Bangudae Petroglyphs starts to be flooded. The Bangudae Petroglyphs starts submerging from EL.60.0 m to EL.56.5 m on Sa-yeon Dam. The Bangudae Petroglyphs water level increased by 2.7 m for 20year and 3.47 m for 200year flood frequencies, 73% and 93.8% of the inundation occurs, respectively. As a result of the change on the water level of the Sa-yeon Dam, from EL.52.5 m to EL.60.0 m, the flood flow characterization on the Bangudae Petroglyphs showed that the velocity multiplied by 2.5 times the normal flow. The maximum velocity directly approches the Bangudae Petroglyphs thus, causing damaged.

Erratum to: Daily Forecasting of Dam Water Levels: Comparing a Support Vector Machine (SVM) Model With Adaptive Neuro Fuzzy Inference System (ANFIS)

Reservoir planning and management are critical to the development of the hydrological field and necessary to Integrated Water Resources Management. The growth of forecasting models has resulted in an excellent model known as the Support Vector Machine (SVM). This model uses linearly separable patterns based on an optimal hyperplane, which are extended to non-linearly separable patterns by transforming the raw data to map into a new space. SVM can find a global optimal solution equipped with Kernel functions. These Kernel functions have high flexibility in the forecasting computation, enabling data to be mapped at a higher and infinite-dimensional space in an implicit manner. This paper presents a new solution to the expert system, using SVM to forecast the daily dam water level of the Klang gate. Four categories are identified to determine the best model: the input scenario, the type of SVM regression, the number of V-fold cross-validation and the time lag. The best input scenario employs both the rainfall R(t-i) and the dam water level L(t-i). Type 2 SVM regression is selected as the best regression type, and 5-fold cross-validation produces the most accurate results. The results are compared with those obtained using ANFIS: all the RMSE, MAE and MAPE values prove that SVM is a superior model to ANFIS. Finally, all the results are combined to determine the best time lag, resulting in R(t-2) L(t-2) for the best model with only 1.64 % error.

Revisiting the Timing and Events Leading to and Causing the Johnstown Flood of 1889

The Johnstown Flood of May 31, 1889, was responsible for more recorded deaths than any other disaster in the United States until the Galveston hurricane of 1900.1 An important difference between the two is that the Johnstown flood was not a natural disaster. Although the Johnstown region was in the midst of a particularly wet spring and the former boroughs that now form the city of Johnstown were already experiencing low-level flood-ing on May 31, the ultimate reason for the high death toll was the catastrophic failure of the South Fork Dam, located fourteen miles upstream from the outskirts of Johnstown on the South Fork of the Little Conemaugh River (see fig. 1). The millions of tons of water released by the failure of the dam caused devastation along the Little Conemaugh River drainage. As the water moved downstream it was temporarily impounded by debris dams behind two Pennsylvania Railroad bridges (Viaduct and Bridge no. 6), which caused "reformation of the lake" at these points. When Bridge no. 6 failed, the rejuvenated flood wave sped toward Johnstown. Most structures

Validation of the rainfall-runoff SCS-CN model in a catchment with limited measured data in Zimbabwe

An evaluation of available opportunities to revive irrigation on a long abandoned irrigation scheme in a dry region of Zimbabwe is presented by assessing water availability at catchment level. The aim is to enhance the livelihoods, income and nutrition of the communities that depend on the irrigation scheme through a sustainable management of revitalised irrigation infrastructure and ensure food security. Runoff generated in the catchment, with potential to flow into the dam that supplies water to the scheme, is estimated using the Soil Conservation Service curve number (SCS-CN) model. The model simulates runoff at catchment level using daily rainfall data. An overview of the methodology and the various steps followed are provided. Daily rainfall and dam water levels are the only measured data available for the catchment. The dam water levels are used to determine the dam water volumes using rating tables. The dam water volumes are used to calculate the daily water inflows into the dam and these are compared with simulated water discharge rates obtained from the model. The plotted hydrographs of both simulated and measured values coincided very well in shape with great precision validating the SCS-CN model for simulating runoff in ungauged catchments. Key words: Irrigation, water availability, curve number, water balance, runoff, dam level.

Predicting piezometric water level in dams via artificial neural networks

The safety control of dams is based on measurements of parameters of interest such as seepage flows, seepage water clarity, piezometric levels, water levels, pressures, deformations or movements, temperature variations, loading conditions, etc. Interpretation of these large sets of available data is very important for dam health monitoring and it is based on mathematical models. Modelling seepage through geological formations located near the dam site or dam bodies is a challenging task in dam engineering. The objective of this study is to develop a feedforward neural network (FNN) model to predict the piezometric water level in dams. An improved resilient propagation algorithm has been used to train the FNN. The measured data have been compared with the results of FNN models and multiple linear regression (MLR) models that have been widely used in analysis of the structural dam behaviour. The FNN and MLR models have been developed and tested using experimental data collected during 9 years. The results of this study show that FNN models can be a powerful and important tool which can be used to assess dams.

Macro-micromechanical approaches for non-coaxiality of coarse grained soils

For coarse grained soils, their principal stress directions may change when the water level of embankment dam varies instantaneously. In this loading case, the principal directions of stress and strain rate will become non-coaxial. In an effort to model non-coaxial behavior, a modified three-dimensional non-coaxial model is developed in the context of vertex yield (tangent plasticity) theory. Discrete Element Method (PFC) incorporating user-defined interparticle contact models is also employed to gain an insight into microscopic mechanism of non-coaxiality. The analysis focuses on non-coaxial behaviors under simple shear condition. It has been shown that the proposed non-coaxial model gives good predictions for non-coaxiality with reference to microscopic observations while the classical coaxial model fails to simulate the non-coaxial behaviors. In general, non-coaxiality as a result of the rotation of principal stress, is large at a small shear strain, and inclined to become negligible with increasing shear strain. For coarse grained soils, their non-coaxiality tends to largely depend on the initial normal pressure, where a larger degree of non-coaxiality can be observed at a higher pressure.

Modelling the effect of rainfall variability, land use change and increased reservoir abstraction on surface water resources in semi-arid southern Zimbabwe

The semi-arid areas of Zimbabwe receive low and erratic rainfall such that communities living and farming in these areas do not obtain adequate yields in most years forcing them to rely on surface and ground water resources during the dry season and dry years. Such water, which is a buffer during dry seasons and dry years should be managed appropriately. However, appropriate management of the limited water resources in such areas is hindered by inadequate knowledge of the changes in water resources due to rainfall, runin, evaporation, seepage and productive water use. Mutangi (5.7km2) and Romwe (4.7km2) micro-catchments that are in semi-arid Southern Zimbabwe were instrumented to enable measurements of all components of hydrology including rainfall, streamflow, dam water level, soil moisture and groundwater levels in the 1999/00 and 2000/01 season. Validation of the Agricultural Research Unit (ACRU) simulation model against field data revealed that ACRU adequately simulated measured streamflow, soil moisture and dam water storage changes. The model showed that removing all the remnant woodland and leaving all the cropped land fallow did not have a significant (P<0.01) effect on both catchment streamflow and dam water level over the 27year simulation period. However, planting trees over the whole catchment resulted in a significant decrease in streamflow by 51%. Construction of tied ridges significantly (P<0.05) decreased streamflow from the catchment by 19%. Water abstraction from the dam could be increased 2, 4, 6, 8 and 10-fold without the dam drying to unacceptable levels (10% of dam capacity) except for 7%, 7%, 11%, 22% and 30% of the 27 simulation years (1972–1999) respectively. This demonstrates that currently small dams are not adequately utilized and vegetable yields and income could be increased by increased surface water abstraction.

UTILIZATION OF THE STORAGE CAPACITY OF A BASIN FOR FLOOD CONTROL BY A DAM

Efficient flood control by a dam requires proper understanding of the basin storage capacity (BSC) in upstream area, because flood runoff depends on the water content there. Using a long-term water cycle model, this paper estimates the BSC to be used for flood control. Two methods (1) the runoff percentage calculation and (2) the BSC-based minimum dam water level that secures the necessary water supply are proposed and applied to the flooding events with different basin conditions (wet/dry). The application results suggest that the BSC obtained from the long-term water balance is useful for effective flood control by a dam.

저수지 수위 정밀 측정에 의한 댐 유입량 자료 개선

A accurate reservoir inflow is very important as providing information for decision making about the water balance and the flood control, as well as for dam safety. The methods to calculate the inflow were divided by the directed method to measure streamflow from upstream reservoirs and the indirected method to estimate using the correlation of reservoir water level and release. Currently, the inflow of multi-purpose dam is being calculated by the indirect method and the reservoir water level to calculate the storage capacity is being used by centimeters(cm) units. Corresponding to the storage volume of 1cm according to scale and water level of multi-purpose dam comes up to from several 10 thousand tons to several million tons. If it converts to inflow during 1 hour, and it comes to several hundred (CMS). Therefore, the inflow calculated on the hourly is largely deviated along the water level changes and is occurred minus value as the case. In this research, the water level gage has been developed so that it can measure a accurate water level for the improvement for the error and derivation of inflow, even though there might be various hydrology and meteorologic considerations to analyse the water balance of reservoir. Also, it is confirmed that the error and the standard derivation of data observed by the new gage is decreased by 89,6% and 1/3 & 87% and 2/3 compared to that observed by the existing gage of Daecheong and Juam multi-purpose dam.

Water quality and plankton dynamics in two small dams in Zimbabwe

Two small dams on the Munwahuku River was investigated in relation to the influence of hydrology on their water chemistry over the period January 2000–August 2001. The water level of the upper dam fluctuated more than that of the lower dam and their theoretical water retention times were nine days and 3.6 days, respectively. Seasonal fluctuations in conductivity, TDS, TSS and transparency were due to effects of the first rains, while increases in BOD and COD suggested increased organic matter at low water levels. There were no dramatic seasonal variations in pH, alkalinity or nutrients, although total nitrogen was higher in the upper dam. The N:P ratios ranged from 0.57–3.75 in the upper dam and 0.92–14 in the lower dam and generally reflect the high levels of phosphorus in the dams. This could make them susceptible to colonisation by Cyanophyta. There were significant differences (p < 0.05) between the dams in total phosphorus, reactive phosphorus, nitrites and chlorophyll a. Small differences observed in the water quality of the two dams could be due to short water residence times. Extremes in water quality conditions were experienced during the dry season, when water levels were low, and during the rainy season when levels were higher. Peaks in phytoplankton and zooplankton abundance occurred during summer in both dams, and differences observed between the plankton community of the period January–October 2000 and that of November 2000–August 2001 were unexpected. The changes in the plankton communities, especially in the lower dam, were remarkable. There were no significant differences in plankton abundances between the dams. Phytoplankton dynamics were weakly associated with environmental factors in both dams and, apart from predation by fish and grazing by zooplankton, washouts during the rainy season and unstable stratification regimes were considered to be contributory factors. Canonical Correspondence Analysis showed that temperature and water transparency (also linked with suspended solids) were important variables in zooplankton dynamics in both dams. Hydrological factors, such as water retention time, floods and water levels, are key determinants of plankton communities in small dams.

Fauna de Chironomidae e outros insetos aquáticos de açudes do semi-árido paraibano, Brasil

Com o objetivo de estudar a fauna de Chironomidae e outros insetos aquáticos dos açudes São Mamede - SM (06º 55' S e 37º 06' W) e São Gonçalo - SG (06º 50' S e 38º 19' W), do semi-árido paraibano, coletas qualitativas foram realizadas em agosto e dezembro/95 (período seco) e julho/96 (após o pico máximo de chuvas da região). Foram feitos arrastos junto a vegetação da margem, utilizou-se para isso um pegador manual com 0,50 mm de abertura de malha. Registrou-se a participação de 15 taxa, dos quais Chironomus gr. decorus foi à espécie de Chironomidae dominante e freqüente nos dois açudes, contribuindo com uma abundância máxima de 81,82% em SG (dezembro/1995). Já no mês de julho/1996, constatou-se também a ocorrência de Goeldichironomus gr. pictus (1,45% em SG), Aedokritus sp. (44,20% em SG e 0,89% em SM), Fissimentum sp. (5,07% em SG) e Asheum sp. (45,33% em SM). Uma maior abundância de insetos aquáticos em julho/96 pode estar relacionada com os valores mais baixos de condutividade elétrica da água, alcalinidade e dureza, e um elevado nível d'água dos açudes. Já nos meses de agosto e dezembro/95, principalmente em SM, constatou-se elevados valores de condutividade, alcalinidade, dureza e sulfato, e uma baixa abundância de insetos aquáticos. A acentuada escassez populacional e taxonômica nesses açudes são fortemente influenciadas pelas condições ambientais.

A Design Criterion for Dynamic Stability of Eccentric Tainter-Gates

Tainter gates used for regulating the back water level of dam may be designed so that the skinplate center is kept under the trunnion pin. Such gates may be called an “eccentric Tainter-gate”, which is statically stably but dynamically unstable. This study presents a design criterion for dynamic stability of eccentric Tainter gates, which is theoretically derived in a practical form, that is, in a non-dimensional expression of the Scruton number representing the mass-damping parameter vs. the Froude number representing the dynamic similarity of fluctuating flow in the back water. In addition, in-air and in-water free vibration tests are made for two of Tainter-gate models with different size and eccentricity, and the measured data of Scruton number is plotted over the tested Froude number, and the design criterion for dynamic stability of the eccentric Tainter gates is verified for its practical validity.

Mound springs in the Dawson River Valley, Queensland. Vegetation-environment relations and consequences of a proposed impoundment on botanical values

Boggomosses are perennial mound springs in the Dawson River Valley, Queensland, an area subject to seasonal and often more prolonged drought. The results of a vegetation survey of the boggomosses are presented and assessed in relation to an impoundment proposed for the area. A classification of site-species data defined four boggomoss communities having distinct associations with soil texture and fertility, landscape position and possibly the age of springs. A measure of biogeographic significance was assigned to the plant species on the basis of rarity, isolation, affinity with the coastal flora and latitudinal limits. An impoundment at the maximum proposed height of 185 m would: a) inundate about 58% of the total number of springs; b) inundate 62% of significant community 1 springs that have high conservation significance; c) inundate all boggomoss populations of 26% of native plant species; d) inundate 30% of the boggomoss populations of the species that currently have two or more boggomoss populations to a level of one or less boggomoss populations; e) inundate all boggomoss populations of two out of 25 biogeographically significant species; f) inundate six out of 12 boggomoss populations of the vulnerable species Arthraxon hispidus; g) not inundate the single population of the vulnerable species Thelypteris confluens although the population would be within 1 m altitude of the maximum water height; h) not inundate the two populations of the endangered species Eriocaulon carsonii and Myriophyllum sp. (Aramac B. Wilson 110). Substantial lessening of impact on community 1 sites are achieved at dam water levels down to 177 m altitude and this trend is reftected in a progessive increase in the security of individual species. For example at the latter level, 88% of species would remain intact in more than one population and all known populations of Arthraxonwould remain intact.

DIE GEBRUIK VAN DIE INSET-UITSETIEGNIEK OM DIE TOTALE EKONOMIESE GEVOLGE VAN WATERBEPERKINGS VIR GEBRUIKERS VAN VAALRIVIERWATER TE BEPAAL

Abstract Below average rainfall that occurred over wide-spread areas in the RSA during the second half of the seventies caused critically low water levels in certain storage dams. The Department of Water Affairs has therefore been compelled (since March 1983) to introduce water restrictions in various areas. The direct financial consequences of the water restrictions on several sectors and areas were determined during an initial study. In order to determine the total financial consequences of the water restrictions on all sectors within the Vaal River water supply area, the input-output technique was applied during a further study. With this technique, which takes into account the interdependency between sectors, the impact of water restrictions on the total region was determined. The regional input-output model is discussed in the paper. The composition of the total impact per sector and for the area as a whole is also analysed, and the value of water for the various sectors during water shortage situati...

Dams, earthquakes and the valley genesis

The author has collected much information obtained through exact geodetic measurements and geophysical methods on tectonic movements taking place in proximity of dams in different parts of the world. He brings examples of correlation between the origin of seismism and the positive as well as negative movements of blocks along fault-slopes at a change of water level in dams. In his opinion these phenomena are the best proof of the block faulting, and consequently of the tectonic origin of the valleys believed so far to be of purely erosional origin.

Water Waves and Structural Loads Caused by a Periodic Change of Discharge from a Sluice-Gate

Characteristics of water waves and structural loads induced by a forced and periodical change of discharge from a sluice-gate were theoretically analyzed, as the first approach for making clear dynamical characteristics of Tainter-gates which are being used with increased frequencies in order to control the water level of dam. It was concluded as follows: A basic parameter characterizing water waves and structural loads is the modified Froude number F0=√(d0/g)·ω(d0: the depth of the gate-opening, g: the gravitational acceleration, ω: the frequency of an oscillatory discharge). Characteristics of water waves are very analogous to the resonance characteristics of the forced oscillatory system consisting of a mass, a spring and a viscous damper. When F0 is equal to about 0.8, wave motions fall into a resonance state. Characteristics of fluid-induced structural loads suggest a possibility that Tainter-gates fall into a self-excited oscillatory state. These theoretically obtained results were proved by experiments.