Hydraulic head applications of flowmeter logs in karst aquifer studies
Hydraulic Head Presentation
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Transcript of Hydraulic Head Presentation
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Hydraulic Head
Hydraulic Head Measure of the potential energy available for
flow in groundwater. Indicated by the water level in a monitoring
well (piezometer). Total hydraulic head is a combination of
gravitational potential energy and fluid pressure energy.
Hydraulic head is measured using small monitoring wells (piezometer wells).
Head is measured as DTW (depth to water), which is then subtracted from the elevation of the well head.
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Datum (sea level)
Hydraulic Head
Depth to water (dtw)
Elevation of well head (e)
Elevation Head(z)
Pressure Head(hp) ht = hp + zTotal Head
(ht)
ht = e - dtw
Point water pressure head vs.Fresh water pressure head
Point water head: the actual measured hydraulic head.
Fresh water head: the equivalent hydraulic head that would be observed if the well was filled with fresh water.
If the aquifer contains fresh water, the two are the same.
Fresh
Brackish
Saline
Point water heads
Apparent hydraulic gradient
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Fresh
Brackish
Saline
Fresh water heads
Actual hydraulic gradient
Groundwater contours = equipotential / potentiometric contours
Groundwater flow lines cross equipotential lines at 90.
Groundwater flows from high to low equipotential.
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Groundwater divide - barrier to flow created by water table ridge (recharge) or gaining stream valley (discharge).
Groundwater Divide
Equipotential contour lines: cross section view All points along the same equipotential line have equal value of
hydraulic head. Hydraulic head = elevation of intersection of water table and
potentiometric contour.
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252015
Equipotential contour values
252015
30
Discharge
RechargeFlow lines and Recharge / Discharge
25
Hp=30
HT = 25Hp = 30z = -5
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25
HT = 10Hp = 20z = -10
Well 1
Well 2Well 3
3-Point Problem The hydraulic gradient across a local area of an aquifer can be determined if
three values of hydraulic head are known.
h=40 h=30 h=35
3-Point Problem
N
100 meters
h=40m
h=30m
h=35m
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3-Point Problem
N
100 meters
h=40m
h=30m
h=35m
dh=5
dh=5
dh=10
3-Point Problem
N
100 meters
h=40m
h=30m
h=35m
dh=5
dh=5
dh=10
3-Point Problem
N
100 meters
h=40m
h=30m
h=35m
32
34
36
38
3132
3433
36373839
-
3-Point Problem
N
100 meters
h=40m
h=30m
h=35m
32
34
36
38
3132
3433
36373839