Measuring Aquifer Specific Yields With Absolute Gravimetry: Result in the Choushui River Alluvial Fan and Mingchu Basin, Central Taiwan

Abstract. Unusual decreases in water levels were consistently observed in 78% (=42/54) of the wells in the Choshuichi Alluvial Fan of central Taiwan roughly 150 days before the Chi-Chi earthquake (M = 7.6 on 20 September 1999) when the influences of barometric pressure, earth tides, precipitation and artificial pumping were removed. Variations in groundwater levels measured in the anomalous wells between 1 August 1997 and 19 September 1999, the time period covering the unusual decreases, were transferred into the frequency domain to examine anomalous frequency bands associated with the Chi-Chi earthquake. Analytical results show that amplitudes at the frequency band between 0.02 day−1 and 0.04 day−1 were generally maintained at the low stage and were enhanced in the few weeks before the Chi-Chi earthquake. Variations in amplitude within this particular frequency band were further examined in association with earthquakes (M > 6) between 1 August 1997 and 31 December 2009. Enhanced amplitude phenomena are consistently observed prior to the other two earthquakes (the Rei-Li and Ming-Jian earthquakes) during the 12.5 yr, which sheds a promising light on research into precursors of strong earthquakes when combined with other geophysical observations such as geomagnetic anomalies and crustal displacements.

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IoT technology and big data processing for monitoring and analysing land subsidence in Central Taiwan

Proceedings of the International Association of Hydrological Sciences ◽

10.5194/piahs-382-103-2020 ◽

2020 ◽

Vol 382 ◽

pp. 103-109

Author(s):

Wei-Chia Hung ◽

Yi-An Chen ◽

Cheinway Hwang

Keyword(s):

Land Subsidence ◽

High Speed ◽

Large Scale ◽

Alluvial Fan ◽

Monitoring Wells ◽

Multi Temporal ◽

Multiple Sensor Monitoring ◽

Large Scale Land ◽

Central Taiwan ◽

Subsidence Monitoring

Abstract. Over 1992–2018, groundwater overexploitation had caused large-scale land subsidence in the Choshui River Alluvial Fan (CRAF) in Taiwan. The Taiwan High Speed Railway (THSR) passes through an area of severe subsidence in CRAF, and the subsidence poses a serious threat to its operation. How to effectively monitor land subsidence here has become a major issue in Taiwan. In this paper, we introduce a multiple-sensor monitoring system for land subsidence, including 50 continuous operation reference stations (CORS), multi temporal InSAR (MT-InSAR), a 1000 km levelling network, 34 multi-layer compaction monitoring wells and 116 groundwater monitoring wells. This system can monitor the extent of land subsidence and provide data for studying the mechanism of land subsidence. We use the Internet of Things (IoT) technology to control and manage the sensors and develop a bigdata processing procedure to analyse the monitoring data for the system of sensors. The procedure makes the land subsidence monitoring more efficient and intelligent.

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Detect groundwater storage in an island watershed by GRACE gravimetry

10.5194/egusphere-egu2020-1827 ◽

2020 ◽

Author(s):

Chung-Chieh Huang ◽

Hong-Ru Lin ◽

Jyun-Lin Chen ◽

Shao-Yang Huang ◽

Jet-Chau Wen ◽

...

Keyword(s):

High Precision ◽

Large Scale ◽

Field Measurements ◽

Alluvial Fan ◽

Small Scale ◽

Groundwater Storage ◽

Satellite Gravimetry ◽

Grace Data ◽

Terrestrial Water ◽

Central Taiwan

&#160; &#160; &#160; &#160; &#160;Since the successful launch of the Gravity Recovery and Climate Experiment (GRACE) on March 17th, 2002, a number of scientists have adopted satellite gravimetry for the detection of variations on terrestrial water storage (TWS). Use of high-precision GRACE gravimetry presents advantages in hydrogeologic studies, such as providing accurate estimates of currents and gravity fields. Many studies have proven that the high-precision GRACE gravimetry can observe large-scale (over 50,000 km2) variations in groundwater storage (GWS). However, relatively few studies conducted using satellite gravimetry have focused on scales smaller than 5,000 km2.&#160;&#160;&#160;&#160;&#160;&#160;&#160; The purpose of this study is to investigate the potential for using GRACE gravimetry to observe small-scale variations in GWS specifically, this paper presents a case study of the Zhoushui River alluvial fan (~2,560 km2) in central Taiwan as an example of how well GRACE data compare to field-based data for ascertaining small-scale variations in GWS. Field measurements of groundwater level in 52 observation wells (2002-2017) were used to analyze variations in GWS. Results of this field-based analysis were compared to results obtained using the GWS data (2002-2017) obtained by GRACE gravimetry. This comparison allowed us to evaluate the similarities and differences in both methods as well as to prove the feasibility of using GRACE gravimetry in small-scale regions. Results of our comparative analysis indicate that water resources in small watershed can be successfully managed using gravimetric data collected by GRACE satellite.&#160;Keywords: Groundwater storage, GRACE, Watershed

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Stochastic delineation of well capture zones in aquifers of Choushui River alluvial fan in central Taiwan

2015 International Carnahan Conference on Security Technology (ICCST) ◽

10.1109/ccst.2015.7389722 ◽

2015 ◽

Author(s):

Chi-Ping Lin ◽

Chuen-Fa Ni ◽

I-Hsian Li ◽

Chih-Heng Lu

Keyword(s):

Alluvial Fan ◽

Capture Zones ◽

Central Taiwan

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Anomalous frequency characteristics of groundwater level before major earthquakes in Taiwan

Hydrology and Earth System Sciences ◽

10.5194/hess-17-1693-2013 ◽

2013 ◽

Vol 17 (5) ◽

pp. 1693-1703 ◽

Cited By ~ 22

Author(s):

C.-H. Chen ◽

C.-H. Wang ◽

S. Wen ◽

T.-K. Yeh ◽

C.-H. Lin ◽

...

Keyword(s):

Frequency Band ◽

Groundwater Level ◽

Barometric Pressure ◽

Frequency Characteristics ◽

Alluvial Fan ◽

Water Levels ◽

Earth Tides ◽

Groundwater Levels ◽

Surface Displacements ◽

Central Taiwan

Abstract. Unusual decreases of water levels were consistently observed in 78% (= 42/54) of wells in the Choshuichi Alluvial Fan of central Taiwan about 250 days before the Chi-Chi earthquake (M = 7.6 on 20 September 1999) while possible factors of barometric pressure, earth tides, precipitation as well as artificial pumping were removed. Variations in groundwater levels measured on anomalous wells from 1 August 1997 to 19 September 1999, which covers the 250 day unusual decreases, were transferred into the frequency domain to unveil frequency characteristics associated with the Chi-Chi earthquake. Analytical results show that amplitudes at the frequency band between 0.02 day−1 and 0.04 day−1 generally maintained at the low stage and were apparently enhanced a few weeks before the Chi-Chi earthquake. Variations of amplitude at this particular frequency band were further examined along with other Taiwan earthquakes (M > 6) from 1 August 1997 to 31 December 2009. Features of the enhanced amplitudes at the frequency band are consistently observed prior to the other two earthquakes (the Rei-Li and Ming-Jian earthquakes) during the 12.5 yr study period. In addition, surface displacements recorded from GPS, which provides insights into understanding stress status in subsurface during the Chi-Chi earthquake, are also inspected. The result confirms that abnormal rise and fall changes in groundwater level yield an agreement with forward and backward surface displacements around the epicentre prior to the Chi-Chi earthquake.

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Multiple sensors applied to monitorland subsidence in Central Taiwan

Proceedings of the International Association of Hydrological Sciences ◽

10.5194/piahs-372-385-2015 ◽

2015 ◽

Vol 372 ◽

pp. 385-391 ◽

Cited By ~ 1

Author(s):

W.-C. Hung ◽

C. Wang ◽

C. Hwang ◽

Y.-A. Chen ◽

H.-C. Chiu ◽

...

Keyword(s):

High Speed ◽

Large Scale ◽

Alluvial Fan ◽

Persistent Scatterer Interferometry ◽

High Speed Rail ◽

Aquifer System ◽

Multiple Sensors ◽

Persistent Scatterer ◽

Global Positioning ◽

Central Taiwan

Abstract. During 1992–2013, pumping of groundwater caused large-scale aquifer-system compaction and land subsidence in the Choshui River Alluvial Fan (CRAF) in Taiwan. The subsidence has already endangered the operation of Taiwan High Speed Rail (THSR). In this paper, we introduce the multiple sensors monitoring system to study the extent of subsidence in CRAF and its mechanism, including GPS (Global Positioning System), PSI (Persistent Scatterer Interferometry), leveling and multi-layer compaction monitoring well. These sensors complement each other in spatial and temporal resolutions.

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