water level changes
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Author(s):  
Iran E. Lima Neto ◽  
Pedro H.A. Medeiros ◽  
Alexandre C. Costa ◽  
Mario C. Wiegand ◽  
Antônio Ricardo M. Barros ◽  
...  

Author(s):  
Timothy H. Morin ◽  
William J. Riley ◽  
Robert F. Grant ◽  
Zelalem Mekonnen ◽  
Kay C. Stefanik ◽  
...  

2021 ◽  
Author(s):  
Fuyu Yan ◽  
Lianrong Wu ◽  
Xining Sun ◽  
Qiwu Shen ◽  
Qiaofeng Dong ◽  
...  

Abstract The normal operation of Yulangpei tailings reservoir is affected by landslide stability. In this paper, taking the main and side slopes near the dam bank of the Yulangpei ditch as an example, water-soil coupling theory is applied to comprehensively evaluate the reliability of the side slopes of the tailings reservoir. Grading and seepage prevention (GSP) measures and the suction of the substrate are considered, as well as the infiltration of different rainfall and reservoir water levels. We numerically simulate the typical three forms of side slopes under the coupling conditions and conduct a reliable and comprehensive evaluation of tailings reservoir side slopes. The study shows that under six reservoir water level changes, the factor of safety (FS) of the bank slope shows a hysteresis effect. According to nine rainfall infiltration conditions and during rainfall, the greater the rainfall intensity, the greater the weakening effect. When rainfall stops, the FS rebounds. After GSP measures, the initial stability of the bank slope under different conditions is improved, but the main slope is more sensitive to changes in rainfall and water levels.


2021 ◽  
Vol 13 (24) ◽  
pp. 5087
Author(s):  
Jianfeng Liu ◽  
Qiushi Zou ◽  
Qingwu Hu ◽  
Changping Zhang

The landscape of ancient sites has changed greatly with the passage of time. Among all of the factors, human activities and the change in natural environment are the main factors leading to the change in site landscape. The Panlongcheng site, which is located in Hubei Province, China, has a history of 3500 years with the most abundant relics in the Yangtze River Basin during the Shang Dynasty. As a near-water site, the landscape of the Panlongcheng site is greatly affected by water level changes and water conservancy activities. In this paper, by using spatial information technology, the data obtained from land and underwater archaeological exploration were integrated to restore landscapes of Panlongcheng sites in different periods. After removing modern artificial features and topsoil, the landscapes of the sites before the Shang Dynasty, in the Shang Dynasty and modern time were reconstructed. Combining historical records of water level changes, the landscape and water–land distribution of the Panlongcheng site were compared. The analysis results reflect the interaction between water level changes and human activities in this region for thousands of years, and support the archaeological findings in the near-water area of the Panlongcheng site, which provides a new idea for the landscape reconstruction and analysis of near-water sites.


2021 ◽  
Author(s):  
◽  
Konrad Cedd Weaver

<p>Earthquakes redistribute fluids and change associated flow paths in the subsurface. Earthquake hydrology is an evolving discipline that studies such phenomena, providing novel information on crustal processes, natural hazards and water resources. This thesis uses the internationally significant New Zealand "hydroseismicity" dataset, in a regional-scale multi-site multi-earthquake study which includes the occurrence and the absence of responses, spanning a decade. Earthquake-induced groundwater level and tidal behaviour changes were examined in a range of aquifers, rock types and hydrogeological settings. Monitoring wells were within one (near-field) to several (intermediate- field) ruptured fault lengths of a variety of earthquakes that had a range of shaking intensities. This thesis presents three studies on the seismic and hydrogeological controls on earthquake-induced groundwater level changes.  Water level changes were recorded New Zealand-wide within compositionally diverse, young shallow aquifers, in 433 monitoring wells at distances between 4 and 850 km from the 2016 Mw 7.8 Kaikoura earthquake epicentre. Water level changes are inconsistent with static stress changes, but do correlate with peak ground acceleration (PGA). At PGAs exceeding ~2 m/s2, water level changes predominantly increased persistently, which may have resulted from shear-induced consolidation. At lower PGAs there were approximately equal numbers of persistent water level increases and decreases, which are thought to have resulted from permeability enhancement. Water level changes also occurred more frequently north of the epicentre, due to the northward directivity of the Kaikoura earthquake rupture. Local hydrogeological conditions also contributed to the observed responses, with larger water level changes occurring in deeper wells and in well-consolidated rocks at equivalent PGA levels.  Earthquakes have previously been inferred to induce hydrological changes in aquifers on the basis of changes to well tidal behaviour and water level, but the relationship between these changes have been unclear. Earthquake-induced changes to tidal behaviour and groundwater levels were quantified in 161 monitoring wells screened in gravel aquifers in Canterbury, New Zealand. In the near-field of the Canterbury earthquake sequence of 2010 and 2011, permeability reduction detected by tidal behaviour changes and increased water levels supports the hypothesis of shear-induced consolidation. Water level changes that occurred with no change in tidal behaviour re-equilibrated at a new post-seismic level within ~50 minutes possibly due to high permeability, good well-aquifer coupling, and/or small permeability changes in the local aquifer. Water level changes that occurred with tidal behaviour changes took from ~240 minutes to ~10 days to re-equilibrate, thought to represent permeability changes on a larger scale. Recent studies commonly utilise a general metric for earthquake-induced hydrological responses based on epicentral distance, earthquake magnitude and seismic energy density. A logistic regression model with random effects was applied to a dataset of binary responses of 495 monitoring well water levels to 11 Mw 5.4 or larger earthquakes. Within the model, earthquake shaking (represented by peak ground velocity), degree of confinement (depth) and rock strength (site average shear wave velocity in the shallow subsurface) were incorporated. For practical applications, the probabilistic framework was converted into the Modified Mercalli (MM) intensity scale. The model shows that water level changes are unlikely below MM intensity VI. At an MM intensity VII, water level changes are about as likely as not to very likely. At MM intensity VIII, the likelihood rises to very likely to virtually certain. This study was the first attempt we are aware of worldwide at incorporating both seismic and hydrogeological factors into a probabilistic framework for earthquake-induced groundwater level changes. The framework is a novel and more universal approach in quantifying responses than previous metrics using epicentral distance, magnitude and seismic energy density. It has potential to enable better comparison of international studies and inform practitioners making decisions around investment to mitigate risk to, and to increase the resilience of, water supply infrastructure.</p>


2021 ◽  
Author(s):  
◽  
Konrad Cedd Weaver

<p>Earthquakes redistribute fluids and change associated flow paths in the subsurface. Earthquake hydrology is an evolving discipline that studies such phenomena, providing novel information on crustal processes, natural hazards and water resources. This thesis uses the internationally significant New Zealand "hydroseismicity" dataset, in a regional-scale multi-site multi-earthquake study which includes the occurrence and the absence of responses, spanning a decade. Earthquake-induced groundwater level and tidal behaviour changes were examined in a range of aquifers, rock types and hydrogeological settings. Monitoring wells were within one (near-field) to several (intermediate- field) ruptured fault lengths of a variety of earthquakes that had a range of shaking intensities. This thesis presents three studies on the seismic and hydrogeological controls on earthquake-induced groundwater level changes.  Water level changes were recorded New Zealand-wide within compositionally diverse, young shallow aquifers, in 433 monitoring wells at distances between 4 and 850 km from the 2016 Mw 7.8 Kaikoura earthquake epicentre. Water level changes are inconsistent with static stress changes, but do correlate with peak ground acceleration (PGA). At PGAs exceeding ~2 m/s2, water level changes predominantly increased persistently, which may have resulted from shear-induced consolidation. At lower PGAs there were approximately equal numbers of persistent water level increases and decreases, which are thought to have resulted from permeability enhancement. Water level changes also occurred more frequently north of the epicentre, due to the northward directivity of the Kaikoura earthquake rupture. Local hydrogeological conditions also contributed to the observed responses, with larger water level changes occurring in deeper wells and in well-consolidated rocks at equivalent PGA levels.  Earthquakes have previously been inferred to induce hydrological changes in aquifers on the basis of changes to well tidal behaviour and water level, but the relationship between these changes have been unclear. Earthquake-induced changes to tidal behaviour and groundwater levels were quantified in 161 monitoring wells screened in gravel aquifers in Canterbury, New Zealand. In the near-field of the Canterbury earthquake sequence of 2010 and 2011, permeability reduction detected by tidal behaviour changes and increased water levels supports the hypothesis of shear-induced consolidation. Water level changes that occurred with no change in tidal behaviour re-equilibrated at a new post-seismic level within ~50 minutes possibly due to high permeability, good well-aquifer coupling, and/or small permeability changes in the local aquifer. Water level changes that occurred with tidal behaviour changes took from ~240 minutes to ~10 days to re-equilibrate, thought to represent permeability changes on a larger scale. Recent studies commonly utilise a general metric for earthquake-induced hydrological responses based on epicentral distance, earthquake magnitude and seismic energy density. A logistic regression model with random effects was applied to a dataset of binary responses of 495 monitoring well water levels to 11 Mw 5.4 or larger earthquakes. Within the model, earthquake shaking (represented by peak ground velocity), degree of confinement (depth) and rock strength (site average shear wave velocity in the shallow subsurface) were incorporated. For practical applications, the probabilistic framework was converted into the Modified Mercalli (MM) intensity scale. The model shows that water level changes are unlikely below MM intensity VI. At an MM intensity VII, water level changes are about as likely as not to very likely. At MM intensity VIII, the likelihood rises to very likely to virtually certain. This study was the first attempt we are aware of worldwide at incorporating both seismic and hydrogeological factors into a probabilistic framework for earthquake-induced groundwater level changes. The framework is a novel and more universal approach in quantifying responses than previous metrics using epicentral distance, magnitude and seismic energy density. It has potential to enable better comparison of international studies and inform practitioners making decisions around investment to mitigate risk to, and to increase the resilience of, water supply infrastructure.</p>


Water ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 3427
Author(s):  
Qingqing Tang ◽  
Daming Tan ◽  
Yongyue Ji ◽  
Lingyun Yan ◽  
Sidong Zeng ◽  
...  

The dynamics of the mid-channel bars (MCBs) in the Three Gorges Reservoir (TGR) were substantially impacted by the large water-level changes due to the impoundments of the TGR. However, it is still not clear how the morphology of the MCBs changed under the influence of water level and hydrological regime changes induced by the impoundments and operation of the TGR. In this work, the MCBs in the TGR were retrieved using Landsat remote sensing images from 1989 to 2019, and the spatio-temporal variations in the number, area, morphology and location of the MCBs during different impoundment periods were investigated. The results showed that the number and area of MCBs changed dramatically with water-level changes, and the changes were dominated by MCBs with an area less than 0.03 km2 and larger than 1 km2. The area of MCBs decreased progressively with the rising water level, and the number generally showed a decreasing trend, with the minimum number occurring at the third stage when the water level reached 139 m, resulting in the maximum average area at this period. The ratio of length to width of the MCBs generally decreased with the changes in hydrological and sediment regimes, leading to a shape adjustment from narrow–long to relatively short–round with the rising of the water level. The water impoundments of the TGR led to the migration of the dominant area from the upper section to the middle section of the TGR and resulted in a more even distribution of MCBs in the TGR. The results improve our understanding of the mechanisms of the development of MCBs in the TGR under the influence of water impoundment coupled with the annually cyclic hydrological regime and longer periods of inundation and exposure.


2021 ◽  
Vol 9 ◽  
Author(s):  
Luqi Wang ◽  
Jiahao Wu ◽  
Wengang Zhang ◽  
Lin Wang ◽  
Wei Cui

Embankments are widespread throughout the world and their safety under seismic conditions is a primary concern in the geotechnical engineering community since the failure events may lead to disastrous consequences. This study proposes an efficient seismic slope stability analysis approach by introducing advanced gradient boosting algorithms, namely Categorical Boosting (CatBoost), Light Gradient Boosting Machine (LightGBM), and Extreme Gradient Boosting (XGBoost). A database consisting of 600 datasets is prepared for model calibration and evaluation, where the factor of safety (FS) is regarded as the output and four influential factors are selected as the inputs. For each dataset, the FS corresponding to the four inputs is evaluated using the commercial geotechnical software of Slide2. As an illustration, the proposed approach is applied to the seismic stability analysis of a hypothetical embankment example subjected to water level changes. For comparison, the predictive performance of CatBoost, LightGBM, and XGBoost is investigated. Moreover, the Shapley additive explanations (SHAP) method is used in this study to explore the relative importance of the four features. Results show that all the three gradient boosting algorithms (i.e., CatBoost, LightGBM, and XGBoost) perform well in the prediction of FS for both the training dataset and testing dataset. Among the four influencing factors, the friction angle φ is the most important feature variable, followed by horizontal seismic coefficient Kh, cohesion c, and saturated permeability ks.


2021 ◽  
Author(s):  
A.E. Hmelnov ◽  
A.S. Gachenko

For the tasks considering changes of water level it is required to have a combined (above water and underwater) elevation model. And the highest accuracy requirements are imposed on the parts of the model, which produce the contour lines in the range of the actual water level changes, while the information about the underwater elevation is usually very scarce and rough. In the article we consider the possibility to obtain this part of the elevation model using open high resolution (10 m/pixel) satellite images corresponding to different water levels. Here we describe the technique, which allows us to obtain the subpixel accuracy of the resulting contour lines. And we consider the problems in the quality of the satellite images that the contour lines reveal, and some ways to deal with the problems.


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