Observation of gravity fluctuations due to tide-induced groundwater table fluctuations with two superconducting gravimeters

2020 ◽  
Author(s):  
Hiroki Goto ◽  
Mituhiko Sugihara ◽  
Yuji Nishi ◽  
Hiroshi Ikeda
Keyword(s):  
Groundwater Level ◽  
Hydraulic Properties ◽  
Groundwater Resources ◽  
Groundwater Table ◽  
Surface Gravity ◽  
Superconducting Gravimeters ◽  
Loading Effects ◽  
Ocean Loading ◽  
Aquifer Properties ◽  
The Difference

<p>Estimation of aquifer hydraulic properties is necessary for predicting groundwater flow and hence managing groundwater resources. Analysis of tide-induced groundwater table fluctuations in unconfined aquifers is one of the methods to estimate aquifer properties. Changes in groundwater level affect surface gravity. Consequently, surface gravity in coastal regions is expected to fluctuate due to the groundwater table fluctuations and is potentially useful for estimating aquifer properties. Moreover, gravity measurements are sensitive to mass redistribution around the observation location and therefore are useful for estimating the storage coefficient of an aquifer. In this study, surface gravity and unconfined groundwater level were measured continuously near the coast of Japan to observe gravity fluctuations due to the tide-induced groundwater table fluctuations. Groundwater level measured in two wells at 60 and 90 m distances from the coastline fluctuated in response to ocean tides. Two superconducting gravimeters (SGs) were installed at 70 and 80 m distances from the coastline and at an elevation of 8 m. After taking the difference between gravity values recorded with the two SGs and then correcting the gravity difference for ocean loading effects, diurnal and semi-diurnal gravity fluctuations, which are possibly due to tide-induced groundwater table fluctuations, were recognized. These results suggest that gravity monitoring with two SGs at different distances from the coastline can be useful for observing gravity fluctuations due to tide-induced groundwater table fluctuations and possibly for estimating aquifer hydraulic properties.</p>

scholarly journals Artificial Neural Network Optimized with a Genetic Algorithm for Seasonal Groundwater Table Depth Prediction in Uttar Pradesh, India

2020 ◽  
Vol 12 (21) ◽  
pp. 8932
Author(s):  
Kusum Pandey ◽  
Shiv Kumar ◽  
Anurag Malik ◽  
Alban Kuriqi
Keyword(s):  
Neural Network ◽  
Genetic Algorithm ◽  
Artificial Neural Network ◽  
Groundwater Level ◽  
Groundwater Resources ◽  
Uttar Pradesh ◽  
Groundwater Table ◽  
Post Monsoon ◽  
Groundwater Table Depth ◽  
Ann Models

Accurate information about groundwater level prediction is crucial for effective planning and management of groundwater resources. In the present study, the Artificial Neural Network (ANN), optimized with a Genetic Algorithm (GA-ANN), was employed for seasonal groundwater table depth (GWTD) prediction in the area between the Ganga and Hindon rivers located in Uttar Pradesh State, India. A total of 18 models for both seasons (nine for the pre-monsoon and nine for the post-monsoon) have been formulated by using groundwater recharge (GWR), groundwater discharge (GWD), and previous groundwater level data from a 21-year period (1994–2014). The hybrid GA-ANN models’ predictive ability was evaluated against the traditional GA models based on statistical indicators and visual inspection. The results appraisal indicates that the hybrid GA-ANN models outperformed the GA models for predicting the seasonal GWTD in the study region. Overall, the hybrid GA-ANN-8 model with an 8-9-1 structure (i.e., 8: inputs, 9: neurons in the hidden layer, and 1: output) was nominated optimal for predicting the GWTD during pre- and post-monsoon seasons. Additionally, it was noted that the maximum number of input variables in the hybrid GA-ANN approach improved the prediction accuracy. In conclusion, the proposed hybrid GA-ANN model’s findings could be readily transferable or implemented in other parts of the world, specifically those with similar geology and hydrogeology conditions for sustainable planning and groundwater resources management.

Revisiting non-tidal ocean loading corrections for high precision terrestrial gravimetry

2021 ◽  
Author(s):  
Ezequiel D. Antokoletz ◽  
Hartmut Wziontek ◽  
Henryk Dobslaw ◽  
Claudia N. Tocho
Keyword(s):  
Time Series ◽  
High Precision ◽  
Ocean Circulation ◽  
Ocean Dynamics ◽  
Atmospheric Effects ◽  
Satellite Gravity ◽  
Simple Assumption ◽  
Superconducting Gravimeters ◽  
Loading Effects ◽  
Ocean Loading

<p>In modelling of atmospheric loading effects in terrestrial gravimetry by numerical weather models, often the Inverse Barometer (IB) hypothesis is applied over oceans. This simple assumption implies an isostatic compensation of the oceans to atmospheric pressure changes, causing no net deformation of the seafloor. However, the IB hypothesis is in general not valid for periods shorter than a few weeks and, consequently, the ocean dynamics cannot be neglected. In particular, for the correction of high precision gravity time series as e.g. obtained from superconducting gravimeters, it is essential to model even small contributions in order to separate different effects. When including non-tidal ocean loading effects from ocean circulation models into atmospheric models, special care has to be taken of the interface between the atmosphere and the oceans in order not to account contributions twice.</p><p>The established approach for modelling non-tidal ocean loading effects is revised in this study. When combining it with the modelling of atmospheric effects for terrestrial gravimetry, it is shown that Newtonian attraction contributions from the atmosphere may be accounted twice. To solve this problem, an alternative is proposed and tested which further reduces the variability of the gravity residuals, as shown for a set of four superconducting gravity meters globally distributed.</p><p>The improvement is achieved by a different treatment of the Newtonian attraction component related to the IB effect. Discrepancies up to the μGal level are demonstrated, depending on the location of the station. With several simplifications, the approach can be made operational and included in existing services, further improving the compatibility of terrestrial gravity time series with satellite gravity observations.</p>

scholarly journals Seismically induced changes in groundwater levels and temperatures following the ML5.8 (ML5.1) Gyeongju earthquake in South Korea

2021 ◽  
Author(s):  
Soo-Hyoung Lee ◽  
Jae Min Lee ◽  
Sang-Ho Moon ◽  
Kyoochul Ha ◽  
Yongcheol Kim ◽  
...  
Keyword(s):  
South Korea ◽  
Groundwater Level ◽  
Seismic Waves ◽  
Groundwater Resources ◽  
Fluid Pressure ◽  
Water Levels ◽  
Aquifer System ◽  
Groundwater Levels ◽  
Monitoring Wells ◽  
Gyeongju Earthquake

AbstractHydrogeological responses to earthquakes such as changes in groundwater level, temperature, and chemistry, have been observed for several decades. This study examines behavior associated with ML 5.8 and ML 5.1 earthquakes that occurred on 12 September 2016 near Gyeongju, a city located on the southeast coast of the Korean peninsula. The ML 5.8 event stands as the largest recorded earthquake in South Korea since the advent of modern recording systems. There was considerable damage associated with the earthquakes and many aftershocks. Records from monitoring wells located about 135 km west of the epicenter displayed various patterns of change in both water level and temperature. There were transient-type, step-like-type (up and down), and persistent-type (rise and fall) changes in water levels. The water temperature changes were of transient, shift-change, and tendency-change types. Transient changes in the groundwater level and temperature were particularly well developed in monitoring wells installed along a major boundary fault that bisected the study area. These changes were interpreted as representing an aquifer system deformed by seismic waves. The various patterns in groundwater level and temperature, therefore, suggested that seismic waves impacted the fractured units through the reactivation of fractures, joints, and microcracks, which resulted from a pulse in fluid pressure. This study points to the value of long-term monitoring efforts, which in this case were able to provide detailed information needed to manage the groundwater resources in areas potentially affected by further earthquakes.

scholarly journals Hydraulic Tomography for Estimating the Diffusivity of Heterogeneous Aquifers Based on Groundwater Response to Tidal Fluctuation in an Artificial Island in Taiwan

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Jet-Chau Wen ◽  
Hong-Ru Lin ◽  
Tian-Chyi Jim Yeh ◽  
Yu-Li Wang ◽  
Keng-Li Lin ◽  
...  
Keyword(s):  
Groundwater Level ◽  
Hydraulic Properties ◽  
Tidal Fluctuation ◽  
Heterogeneous Aquifers ◽  
Hydraulic Diffusivity ◽  
The Real ◽  
Groundwater Levels ◽  
Hydraulic Tomography ◽  
Groundwater Response ◽  
Spectrum Ratio

This study investigated the hydraulic properties of the heterogeneous aquifers of an artificial island (Yunlin Offshore Industrial Park) in Taiwan. The research was based on the groundwater level response affected by tidal fluctuation using the hydraulic tomography (HT) to analyze the hydraulic diffusivity (α). Specifically, the power spectrum ratio of groundwater and tidal fluctuations derived from the Gelhar solution was used to estimate α in homogeneous aquifers; this, however, could not be applied in the artificial island. Next, the spatial distribution of the groundwater level response affected by tidal fluctuation was analyzed and found to be irregular, proving the existence of hydrogeological heterogeneity in the artificial island. Furthermore, the results of the estimated α using the HT showed low error and high correlation, 0.41 m2/hr and 0.83, respectively, between the optimal estimated heterogeneous and reference α fields in the synthetic aquifer. Last, the HT was used in the real tested scenario. By comparing the predicted groundwater levels of the optimal estimated heterogeneous α field and the observed groundwater levels of the real aquifer, it was found that the correlation was higher than 0.99. Therefore, the HT can be used to obtain the optimal estimated heterogeneous α field in the artificial island.

scholarly journals Quantifying aquifer properties and freshwater resource in coastal barriers: a hydrogeophysical approach applied at Sasihithlu (Karnataka state, India)

2012 ◽  
Vol 16 (11) ◽  
pp. 4387-4400 ◽  
Author(s):  
J.-M. Vouillamoz ◽  
J. Hoareau ◽  
M. Grammare ◽  
D. Caron ◽  
L. Nandagiri ◽  
...  
Keyword(s):  
Sea Level ◽  
Groundwater Resources ◽  
Time Lapse ◽  
Unconfined Aquifer ◽  
Spatial Knowledge ◽  
Western India ◽  
Transient Electromagnetic ◽  
Freshwater Resource ◽  
Aquifer Properties ◽  
Rainfall Patterns

Abstract. Many human communities living in coastal areas in Africa and Asia rely on thin freshwater lenses for their domestic supply. Population growth together with change in rainfall patterns and sea level will probably impact these vulnerable groundwater resources. Spatial knowledge of the aquifer properties and creation of a groundwater model are required for achieving a sustainable management of the resource. This paper presents a ready-to-use methodology for estimating the key aquifer properties and the freshwater resource based on the joint use of two non-invasive geophysical tools together with common hydrological measurements. We applied the proposed methodology in an unconfined aquifer of a coastal sandy barrier in South-Western India. We jointly used magnetic resonance and transient electromagnetic soundings and we monitored rainfall, groundwater level and groundwater electrical conductivity. The combined interpretation of geophysical and hydrological results allowed estimating the aquifer properties and mapping the freshwater lens. Depending on the location and season, we estimate the freshwater reserve to range between 400 and 700 L m−2 of surface area (± 50%). We also estimate the recharge using time lapse geophysical measurements with hydrological monitoring. After a rainy event close to 100% of the rain is reaching the water table, but the net recharge at the end of the monsoon is less than 10% of the rain. Thus, we conclude that a change in rainfall patterns will probably not impact the groundwater resource since most of the rain water recharging the aquifer is flowing towards the sea and the river. However, a change in sea level will impact both the groundwater reserve and net recharge.

scholarly journals Youth Development in Albania

2014 ◽  
Vol 1 (1) ◽  
pp. 43
Author(s):  
Armanda Keqi ◽  
Bora Kokalari ◽  
Sabina Beqiri
Keyword(s):  
Young People ◽  
Youth Development ◽  
Rural Areas ◽  
Transition Period ◽  
Labour Force ◽  
Groundwater Resources ◽  
Small Towns ◽  
The State ◽  
The Difference ◽  
Legal Immigration

Young generations are those who make lives livelier and happier, who design the future and make the change, the ones with full hope and enthusiasm to go further and make the impossible possible. As every country of Europe, Asia or America, Albania as well is surrounded by a very fruitful young ladies and gentlemen's. This paper aims to analyse the changes of the youth development in Albania during the transition period. The young development in Albania has faced many problems, such as the difference between the levels of development of the youths that live in the other cities of Albania with the ones of the capital. Rural areas and small towns are closed where a portion of youth in minor are totally dependent from family, and they are exactly that with their weak hands are inclined to do the heavy work to keep their family one more day alive. Youth at the opening of the borders, generally tended to leave towards legal immigration either as tourist or in illegal opportunities addressing major countries like Britain, Greece, Italy, Belgium etc. Albania needs to make arrangements which will be financed by businessmen, private universities in cooperation with the state to offer young people opportunities to work together and to be closer to each other and to show their skills in conversation competitions. At the same time the state has other open universities in backward areas which will provide young entrepreneurs' with more opportunities for young people to graduate and to serve different areas. Meanwhile, there is needed a strategy to separate the fields in which there is a need to have more expert in the field which is required to work also which would come more to help the country's economy with the addition of experts. Albania is a country blessed where high mountains finish in seas, where groundwater resources are numerous, and with a conductive climate to produce almost all kinds of fruits and where vegetation is very diverse. If the youth will be directed towards learning of foreign languages and in recognition of their territories, traditions and customs, thus, we would make a big step because tourism market is precisely the kind of market where young people will find themselves more comfortable than ever, where the labour force will be insufficient paid and where the demand for products would be required as the number of tourists would be great and just the requirements would change in terms of application areas during the summer as it would be for beaches and seasonal fruits, while during the winter for skiing and mountain tourism.

scholarly journals Assessing the long-term sustainability of the groundwater resources in the Bacchiglione basin (Veneto, Italy) with the Mann–Kendall test: suggestions for higher reliability

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Mara Meggiorin ◽  
Giulia Passadore ◽  
Silvia Bertoldo ◽  
Andrea Sottani ◽  
Andrea Rinaldo
Keyword(s):  
Groundwater Level ◽  
Water Cycle ◽  
Groundwater Resources ◽  
Sustainable Use ◽  
Kendall Test ◽  
Groundwater System ◽  
Aquifer System ◽  
Mann Kendall Test ◽  
Status Assessment

The social, economic, and ecological importance of the aquifer system within the Bacchiglione basin (Veneto, IT) is noteworthy, and there is considerable disagreement among previous studies over its sustainable use. Investigating the long-term quantitative sustainability of the groundwater system, this study presents a statistical methodology that can be applied to similar cases. Using a combination of robust and widely used techniques, we apply the seasonal Mann–Kendall test and the Sen’s slope estimator to the recorded groundwater level timeseries. The analysis is carried out on a large and heterogeneous proprietary dataset gathering hourly groundwater level timeseries at 79 control points, acquired during the period 2005–2019. The test identifies significant decreasing trends for most of the available records, unlike previous studies on the quantitative status of the same resource which covered the domain investigated here for a slightly different period: 2000–2014. The present study questions the reason for such diverging results by focusing on the method’s accuracy. After carrying out a Fourier analysis on the longest available timeseries, for studies of groundwater status assessment this work suggests applying the Mann–Kendall test to timeseries longer than 20 years (because otherwise the analysis would be affected by interannual periodicities of the water cycle). A further analysis of two 60-year-long monthly timeseries between 1960 and 2020 supports the actual sustainable use of the groundwater resource, the past deployment of the groundwater resources notwithstanding. Results thus prove more reliable, and meaningful inferences on the longterm sustainability of the groundwater system are possible.

Characteristics of Rainfall- Groundwater Level Response in Taipei City, Taiwan

2021 ◽  
Author(s):  
Shih-Kai Chen ◽  
Yuan-Jie Lin ◽  
Yuan-Yu Lee
Keyword(s):  
Climate Change ◽  
Groundwater Level ◽  
Groundwater Table ◽  
Soil Liquefaction ◽  
Mitigation Strategies ◽  
Disaster Mitigation ◽  
Limiting Factor ◽  
Sponge City ◽  
Cumulative Rainfall ◽  
Taipei Basin

<p>The Taipei Basin, Taiwan has been densely populated and highly economically developed in recent decades. Global climate change has led to frequently flooding and drought events in recent years, formulating suitable measures to mitigate climatic disaster has become a crucial issue in this city. The sponge city concept is one of the most important options for disaster mitigation in highly urbanization areas. However, the city is also potentially threatened by soil liquefaction due to its sedimentary geology and increasing groundwater level. High groundwater level might be a key limiting factor in the promotion of sponge city. The aim of this study was to understand the relationship between rainfall and groundwater level and the impacts of cumulative rainfall, depth to groundwater table, and impervious pavement ratio on the rainfall/groundwater level response in study area. The cross-correlation function (CCF) was applied to analyze the correlation between rainfall and groundwater level data obtained from 20 observed wells and nearby rainfall gages during dry and wet seasons from 2012 to 2017. The significance groundwater recharge response can be found in 61% and 37% of the observation wells during the wet and dry seasons, respectively. Compared with the factors such as cumulative rainfall, and depth to groundwater table, the ratio of surface impervious pavement is the primary affecting factor behind the correlation between rainfall and groundwater level response. The analysis results also show the areas with shallow groundwater level, high imperious pavement ratio, and the groundwater level with no significant response to rainfall, are almost overlapped with the middle and high level liquefaction potential areas in this city. Measures such as the application of the sponge city concept to increase infiltration should be carefully reevaluated in this city. The research results can provide a reference for the future development of urban water resources management and disaster mitigation strategies under the challenge of globe climate change.</p>

Improving corrections in microgravimetric surveys through modelling of ocean loading effects

1998 ◽  
Author(s):  
M. Llubes ◽  
J. Hinderer ◽  
M. Amalvict ◽  
M. F. Lalancette-Le Quentrec
Keyword(s):  
Loading Effects ◽  
Ocean Loading
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