Estimation of barometric responses of groundwater levels at ......Barometric Pressure 50 hPa 0 10 20...
Transcript of Estimation of barometric responses of groundwater levels at ......Barometric Pressure 50 hPa 0 10 20...
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Estimation of barometric responses of groundwater levels at observation stations of
the Geological Survey of Japan, AIST
Yuichi Kitagawa(Geological Survey of Japan, AIST)
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Aim of This Research
AIST has been measuring the groundwater levels of wells in order to detect crustal movements.
To exactly evaluate detection capability of the crustal movements, it needs to understand the hydraulic characteristics of the well and stratum.
This research tried to understand the hydraulic characteristics of the well and stratum, using the barometric responses of the groundwater levels.
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Scheme of Crustal Strain Response[e.g., Hsieh et al.(1987), Rojstaczer(1988)]
Phenomenon(1): Groundwater flow between the well and the aquifer
(1)
Phenomenon(2): Groundwater flow in the partial confining layer
(2)
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Scheme of Barometric Response
Phenomenon(1): Groundwater flow between the well and the aquifer
(1)
Phenomenon(2): Groundwater flow in the partial confining layer
(2)Phenomenon(3): Air flow in the unsaturated zone
(3)
[e.g., Rojstaczer(1988)]
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Scheme of Static ResponseResponse for step change of barometric pressure
Ideal conditions for static response situation of barometric response1. Very high permeability between the well and the aquifer
or No wellbore storage2. Perfect confining layer
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Static ResponseResponse for step change of barometric pressure in time domain
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Static Response of water levelResponse for step change of barometric pressure in frequency domain
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Characteristics of Static Response
• Amplitude ratio of water level change to barometric pressure change is constant at whole frequency range.
• Phase shift of water level change to barometric pressure change is in opposite phase at whole frequency range.
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Scheme of Phenomenon(1)Response for step change of barometric pressure
Conditions for phenomenon(1)1. Low permeability between the well and the aquifer
or Large wellbore storage2. Perfect confining layer
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Effect of Phenomenon(1)Response for step change of barometric pressure in time domain
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Effect of Phenomenon(1) to water level
Response for step change of barometric pressure in frequency domain
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Characteristics of Effect of Phenomenon(1)
• Phenomenon(1) is strongly related to the permeability between the well and the aquifer.
• The lower the permeability is, the larger the effect is.
• The effect is characterized as decrease of amplitude ratio and lag of phase shift.
• The effect is not noticeable at low frequency range.
• The higher the frequency is, the larger the effect is.
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Scheme of Phenomenon(2)Response for step change of barometric pressure
Conditions for phenomenon(2)1. Very high permeability between the well and the aquifer
or No wellbore storage2. Partial confining layer
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Effect of Phenomenon(2)Response for step change of barometric pressure in time domain
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Effect of Phenomenon(2) to water level
Response for step change of barometric pressure in frequency domain
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Characteristics of Effect of Phenomenon(2)
• Phenomenon(2) is strongly related to the permeability of the confining layer.
• The higher the permeability is, the larger the effect is.
• The effect is characterized as increase of amplitude ratio and lag of phase shift.
• The effect is not noticeable at high frequency range.
• The lower the frequency is, the larger the effect is.
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Scheme of Phenomenon(3)Response for step change of barometric pressure
Conditions for phenomenon(3)1. Very high permeability between the well and the aquifer
or No wellbore storage2. Partial confining layer
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Effect of Phenomenon(3)Response for step change of barometric pressure in time domain
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Effect of Phenomenon(3) to water level
Response for step change of barometric pressure in frequency domain
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Characteristics of Effect of Phenomenon(3)
• Phenomenon(3) is strongly related to the air diffusivity of the unsaturated zone.
• The higher the diffusivity is, the larger the effect is.
• The effect is characterized as decrease of amplitude ratio and ahead of phase shift.
• The effect is not noticeable at high frequency range.
• The lower the frequency is, the larger the effect is.
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General Barometric ResponseResponse for step change of barometric pressure in time domain
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General Barometric Response of water level
Response for step change of barometric pressure in frequency domain
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Analysis of observation data• The barometric response of the groundwater level was estimated using the calculation of the transfer function of the well-aquifer system with input (the barometric pressure) and output (the groundwater level).
• If need be, the rainfall response of the groundwater level was corrected using the Matumoto’s (1992) method.
• Using the tidal response and the barometric response, the paramters of the hydraulic characteristics of the well-aquifer system tried to be presumed.
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Observation stations in and around the Kinki district
26 wells at 21 observation stations
In this report, the results of 3 wells (red ellipses) are shown after this slide.
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Result of Well at YSK StationBarometric Pressure
50hPa
01020304050 Rainfallmm/hour
2000/5/1 2000/5/11 2000/5/21 2000/5/31 2000/6/10 2000/6/20 2000/6/30
1.0m Groundwater Level
Groundwater level responded to the tide, the barometric pressure and the long-term rainfall.
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Barometric Response of Well at YSK Station
0.00.20.40.60.81.0
Amplitude ratiocm/hPa
-360
-180
0Phase shift
lag
ahead
Degree
0.00.20.40.60.81.0
0.0 0.2 0.4 0.6 0.8 1.0 cycle/day
Coherency
Red means the calculated response.
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Model of Well at YSK Station
Da=10-1.2[m2/s]
Dv=10-1.0[m2/s]
The borehole is sealed.There is no wellbore storage.
135m
70m
α=0.85Strain sensitivity of the aquifer is 40.0[mm/10-8strain].
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Barometric Response of Well at YSK Station
0.00.20.40.60.81.0
Amplitude ratiocm/hPa
-360
-180
0Phase shift
lag
ahead
Degree
0.00.20.40.60.81.0
0.0 0.2 0.4 0.6 0.8 1.0 cycle/day
Coherency
0.00.20.40.60.81.0
Amplitude ratiocm/hPa
-360
-180
0Phase shift
lag
ahead
Degree
0.00.20.40.60.81.0
0.0 0.2 0.4 0.6 0.8 1.0 cycle/day
Coherency
Red means the calculated response.
Blue shows the predicted response based on the estimated parameters of well-aquifer system.
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Strain Sensitivity of Well at YSK Station
01020304050
Amplitude ratiomm/10-8strain
-180
0
180
0.0 0.5 1.0 1.5 2.0 2.5
Phase shift
lag
ahead
Degree
cycle/day
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Characteristics of Well at YSK Station
• At low frequency, amplitude ratio of the barometric response decreases.
• This fact means the leakage from the aquifer due to the partial confining layer.
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Result of Well at TNN StationBarometric Pressure
50hPa
01020304050 Rainfallmm/hour
2002/6/1 2002/6/11 2002/6/21 2002/7/1 2002/7/11 2002/7/21 2002/7/31
0.5m Groundwater Level
Groundwater level responded to the tide and the barometric pressure and did not respond to the rainfall in the short-term.
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Barometric Response of Well at TNN Station
0.00.20.40.60.81.0
Amplitude ratiocm/hPa
-360
-180
0Phase shift
lag
ahead
Degree
0.00.20.40.60.81.0
0.0 0.2 0.4 0.6 0.8 1.0 cycle/day
Coherency
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Model of Well at TNN Station
Da=10-5.0[m2/s]
Kv=10-10[m/s]
445m
r=0.1m
Kh=10-6.3[m/s]
Ss=10-6[1/m]
Ss=10-6[1/m]α=0.62
45m
Strain sensitivity of the aquifer is 5.5[mm/10-8strain].
17m
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Barometric Response of Well at TNN Station
0.00.20.40.60.81.0
Amplitude ratiocm/hPa
-360
-180
0Phase shift
lag
ahead
Degree
0.00.20.40.60.81.0
0.0 0.2 0.4 0.6 0.8 1.0 cycle/day
Coherency
0.00.20.40.60.81.0
Amplitude ratiocm/hPa
-360
-180
0Phase shift
lag
ahead
Degree
0.00.20.40.60.81.0
0.0 0.2 0.4 0.6 0.8 1.0 cycle/day
Coherency
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Strain Sensitivity of Well at TNN Station
02468
10Amplitude ratio
mm/10-8strain
-180
0
180
0.0 0.5 1.0 1.5 2.0 2.5
Phase shift
lag
ahead
Degree
cycle/day
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Characteristics of Well at TNN Station
• Amplitude ratio of the barometric response is roughly flat.
• This fact means little leakage from the aquifer due to the good confining layer.
• The wellbore storage slightly affects.
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Result of Well at HNO StationBarometric Pressure
50hPa
01020304050 Rainfallmm/hour
2000/6/1 2000/6/11 2000/6/21 2000/7/1 2000/7/11 2000/7/21 2000/7/31
0.5m Groundwater Level raw data
data after rainfall response correction
Groundwater level responded to the tide, the barometric pressure and the rainfall.
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Barometric Response of Well at HNO Station
0.00.20.40.60.81.0
Amplitude ratiocm/hPa
-360
-180
0Phase shift
lag
ahead
Degree
0.00.20.40.60.81.0
0.0 0.2 0.4 0.6 0.8 1.0 cycle/day
Coherency
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Model of Well at HNO Station
Da=10-2.5[m2/s]
Dv=10-2.0[m2/s]
The borehole is sealed.There is no wellbore storage.
230m
115m
α=0.75Strain sensitivity of the aquifer is 14.5[mm/10-8strain].
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Barometric Response of Well at HNO Station
0.00.20.40.60.81.0
Amplitude ratiocm/hPa
-360
-180
0Phase shift
lag
ahead
Degree
0.00.20.40.60.81.0
0.0 0.2 0.4 0.6 0.8 1.0 cycle/day
Coherency
0.00.20.40.60.81.0
Amplitude ratiocm/hPa
-360
-180
0Phase shift
lag
ahead
Degree
0.00.20.40.60.81.0
0.0 0.2 0.4 0.6 0.8 1.0 cycle/day
Coherency
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Strain Sensitivity of Well at HNO Station
05
101520
Amplitude ratiomm/10-8strain
-180
0
180
0.0 0.5 1.0 1.5 2.0 2.5
Phase shift
lag
ahead
Degree
cycle/day
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Characteristics of Well at HNO Station
• The rainfall response of the groundwater level was not enough corrected.
• At low frequency, amplitude ratio of the barometric response slightly decreases.