Kuliah Kuliah Oleh Oleh ALIRAN AIR TANAH

ALIRAN AIR TANAH
(Jurusan Teknik Sipil S-1)
TTM-2
TTMBASIC CONCEPT

Kuliah Oleh : Dr.. Eng. Sigit Sutikno,
Sutikno, ST.,MT



GROUNDWATER
1.
2.
3.
4.
5.

Introduction
General Concept
Flow Net
Darcy’s Law

Hydraulic Conductivity Test

Kuliah Oleh : Dr. Eng. Sigit Sutikno,
Sutikno, ST.,MT

1. Introduction
• Movement of ground water
through pores and fractures is
relatively slow (meters/day)
compared to flow
of water in surface streams

• Flow velocity depends upon:
– Slope of the water table
– Permeability of the rock or
sediment

Kuliah Oleh : Dr. Eng. Sigit Sutikno,
Sutikno, ST.,MT

2. General concept

 The water table is actually a sloping surface.

 Slope (gradient) is determined by the difference in water table
elevation (h) over a specified distance (L).

 Direction of flow is downslope.

 Flow rate depends on the gradient and the properties of the aquifer.

Kuliah Oleh : Dr. Eng. Sigit Sutikno,
Sutikno, ST.,MT

2. General concept
• Hydraulic gradient for an
unconfined aquifer =
approximately the slope of the
water table.

•Hydraulic conductivity = ability of material to allow water to move
through it, expressed in terms of m/day (distance/time). It is a
function of the size and shape of particles, and the size, shape, and
connectivity of pore spaces.

K

= length/time (m/day)

Movement of groundwater depends on rock and sediment properties
and the groundwater’s flow potential. Porosity, permeability, specific
yield and specific retention are important components of hydraulic
conductivity.
S. Hughes,
2003
Kuliah Oleh : Dr. Eng. Sigit Sutikno,
Sutikno
, ST.,MT

3. Flow Net

Water table contour lines are similar to topographic lines on a map.
They essentially represent "elevations" in the subsurface. These
elevations are the hydraulic head mentioned above.

Kuliah Oleh : Dr. Eng. Sigit Sutikno,
Sutikno, ST.,MT

S. Hughes, 2003

3. Flow Net
Water table contour lines can be used to
determine the direction groundwater
will flow in a given region.
Water table contours (called
equipotential lines) are constructed to
join areas of equal head.
A map of groundwater contour lines
with groundwater flow lines is called a
flow net.

Remember: groundwater always
moves from an area of higher hydraulic
head to an area of lower hydraulic
head.

S. Hughes, 2003

3. Flow Net
A simple flow net
Cross-profile view
100

Qal

50

WT

Aquitard (granite)

Qal

Aquitard
Qal
well

Kuliah Oleh : Dr. Eng. Sigit Sutikno,
Sutikno, ST.,MT

4. Darcy’s Law
Henry Darcy, 1856, studied water flowing through porous material.
His equation describes groundwater flow.
Darcy’s experiment:

• Water is applied under
pressure through end A, flows
through the pipe, and
discharges at end B.
• Water pressure is measured
using piezometer tubes

Kuliah Oleh : Dr. Eng. Sigit Sutikno,
Sutikno, ST.,MT

4. Darcy’s Law
Hydraulic head = dh (change in height between A and B)
Flow length = dL (distance between the two tubes)
Hydraulic gradient (I) = dh / dL

The velocity of groundwater is
based on
a) hydraulic conductivity (K),
b) hydraulic gradient (I).

Kuliah Oleh : Dr. Eng. Sigit Sutikno,
Sutikno, ST.,MT

4. Darcy’s Law
The equation is

Q = KIA
Q = Discharge = volumetric
flow rate, volume of water
flowing through an aquifer per
unit time (m3/day)
A = Area through which the
groundwater is flowing, crosssectional area of flow (aquifer
width x thickness, in m2)
Kuliah Oleh : Dr. Eng. Sigit Sutikno,
Sutikno, ST.,MT

5. Hydraulic Conductivity Test

Kuliah Oleh : Dr. Eng. Sigit Sutikno,
Sutikno, ST.,MT

That’s all for this class today,
any questions..???

Kuliah Oleh : Dr.. Eng. Sigit Sutikno,

Sutikno, ST.,MT