Summary presentation slides referring to the groundwater system

1. Course Title: Engineering Geology
Course Code: CIEG 209
1
Unit 7
The Groundwater System
Dr. Suman Manandhar, Dr. Eng. & PostDoc
(Ksyushu University)
Visiting Faculty,
School of Engineering, Department of Civil & Geomatic Engineering, Kathmandu University, NEPAL
Visiting Associate Professor
Institute of Lowland and Marine Research (ILMR), Saga University, JAPAN
Former Secretary General cum Treasurer
International Association of Lowland Technology (IALT), JAPAN
Chief Guest Editor & Associate Editor
Lowland Technology International Journal (LTI), JAPAN

2. Unit 7 : The Groundwater System
2
Phases
Suman Manandhar, Dr. Eng. (Geotechnical Engineering)

3. Introduction to Hydrogeology, General Concept,
Groundwater in the Hydrologic Cycle
3
Hydrogeology:
Water that lies beneath the ground surface, filling the pore space
between grains in bodies of sediment and clastic sedimentary rock, and
filling cracks and crevices in all types of rock.
Source of ground water is rain and snow that falls to the ground a
portion of which percolates down into the ground to become ground
water.
General Concept: Porosity and Permeability:
Porosity (): the percentage of rock or sediment that consists of voids
(pores) or openings. It is also defined as the ratioo of volume of voids
(Vv) to the volume of total aquifer material (Vtotal).
 = Vv / Vtotal
Factors affecting porosity: Sorting & Grain shape
Suman Manandhar, Dr. Eng.
(Geotechnical Engineering)

4. 4
Suman Manandhar, Dr. Eng. (Geotechnical Engineering)
Permeability: The capacity of porous rock, sediment or soil to transmit a
fluid such as water or petroleum through pores and fractures.
Porous: a rock that holds much water.
Permeable: a rock that allows water to flow easily through it.
impermeable: a rock that does not allow water to flow through it easily.
Hydraulic Gradient (I): The difference between hydraulic head at two
points divided by the length (l) is said to be hydraulic gradient (I), i.e.
I = (h1-h2)/l
Hydraulic Conductivity (K): Hydraulic conductivity is defined as the flow
velocity (V) per unit hydraulic gradient (I), expressed as metres/day or
metres/sec.
K = V/I

5. 5
Suman Manandhar, Dr. Eng. (Geotechnical Engineering)
Darcy’s Law:
Darcy’s Law states the rate of
fluid flow (V) through any
porous medium is:
a. Directly proportional to the
differences in hydraulic
head (h1-h2), and
b. Inversely proportional to
the length of the column
(l).
V  (h1-h2)/l
V = K (h1-h2)/l
Where, K = hydraulic
conductivity
V = K (I)
Discharge (Q) = Flow Velocity X Cross-
sectional Area
Q = V.A
Q = KIA

6. 6
Suman Manandhar, Dr. Eng. (Geotechnical Engineering)
Aquifer
When a water-
bearing rock readily
transmits water to
wells and springs, it
is called an aquifer.
Aquifers come in
two types which
are shown below:
Unconfined and
Confined.
Confining Bed:
A confining bed is a layer of geologic material, which hampers the
movement of water into and out of an aquifer.
1. Aquiclude: A saturated but relatively impermeable material that
does not yield appreciable quantities of water to well, e.g. clay
2. Aquifuge: A relatively impermeable formation neither containing
nor transmitting water, e.g. granite.

7. 7
Suman Manandhar, Dr. Eng. (Geotechnical Engineering)
Types of Aquifers
Unconfined aquifer:
Unconfined aquifers are those into which water seeps from the
ground surface directly above the aquifer.
Confined aquifer:
Confined aquifers are those in which an impermeable dirt/rock layer
exists that prevents water from seeping into the aquifer from the
ground surface located directly above. Instead, water seeps into
confined aquifers from farther away where the impermeable layer
doesn't exist.

8. 8
Global Hydrologic Cycle
Domenico and Schwartz, 1990.
Suman Manandhar, Dr. Eng. (Geotechnical Engineering)

9. 9
Basin Hydrologic Cycle
Charbeneau, 2000.
Suman Manandhar, Dr. Eng. (Geotechnical Engineering)

10. 10
Basin Hydrologic Cycle – GW/SW Interaction
Suman Manandhar, Dr. Eng. (Geotechnical
Engineering)

11. 11
Suman Manandhar, Dr. Eng. (Geotechnical Engineering)
Can’t “see” groundwater so a lot more is done by inference and
interpretation than for surface water.
Site investigation:
• Conceptual model of geological environment and the flow system
through it.
• Field measurements (bore holes, pumping tests, geophysical
explorations)
• Hydrogeologic simulation model
Groundwater investigation:

12. 12
Suman Manandhar, Dr. Eng. (Geotechnical Engineering)
Groundwater investigation

13. Ground water occurrence and conservation
13
• Ground water occurs when water recharges the subsurface through
cracks and pores in soil and rock.
• Shallow water level is called the water table.
Suman Manandhar, Dr. Eng. (Geotechnical Engineering)
Recharge
Natural
• Precipitation
• Melting snow
• Infiltration by streams and lakes
Artificial
• Recharge wells
• Water spread over land in
pits, furrows, ditches
• Small dams in stream
channels to detain and deflect
water

14. 14
Example of Layered Aquifer System
Bedient et al., 1999.
Suman Manandhar, Dr. Eng.
(Geotechnical Engineering)

15. 15
Aquifer Features
Suman Manandhar, Dr. Eng. (Geotechnical Engineering)

16. Thank you for
your kind attention !!!