National University of Malaysia

1

Groundwater (Our Hidden Asset)

Class: Special lecture II for Regular Course 5th grade students

Oct. 9th (WED) 15:35-16:20

28-Jan-14

Wan Zuhairi Wan Yaacob (Assoc. Prof, PhD) Faculty of Science and Technology

National University of Malaysia 43600 Bangi, Selangor, MALAYSIA.

National University of Malaysia

• What is Groundwater

• Groundwater as a resource

• Groundwater and Geotechnical Problems

• Groundwater movement in soil

• Conclusion

28-Jan-14 2

Content:

National University of Malaysia

28-Jan-14 3

What is Groundwater?

National University of Malaysia

4

Two Types of Water

28-Jan-14

Hydrogeology (Groundwater) Subsurface water

Hydrology (Surface water)

Unsaturated

Saturated

Water table

National University of Malaysia Groundwater

• Groundwater is a water that is found underground and is stored in the pore spaces (between grains) of porous geologic formation called an “aquifer”.

• The importance of groundwater is easily overlooked.

• Groundwater is a hidden asset, out-of-sight and out-of-mind.

Water Cycle

28-Jan-14 5

National University of Malaysia

Groundwater

6 28-Jan-14

Piezometric surface

• Aquifer (permeable) • Aquitard (Impermeable) • Artesian well • Water table • Piezometric surface

National University of Malaysia

28-Jan-14 7

Groundwater as a Resource

National University of Malaysia

Groundwater and the world’s freshwater supply

"...Altogether, (groundwater) aquifers store 97% of the planet's (available) freshwater."

8 28-Jan-14

National University of Malaysia

Water Usage in Large Cities in the World

9 28-Jan-14

National University of Malaysia

Water Usage in Malaysia

35

5

60

Groundwater utilization by sector

Industrial

Agricultural

Domestic

3

97

Water use by source

Groundwater

Surface water

10

Surface water

Ground water

• Japan (13%) • South Korea (32%)

28-Jan-14

National University of Malaysia

• Kelantan : 70% of its water source is from groundwater.

Groundwater

11

“Air Kelantan”

Production well

Crystal clear groundwater

Privately owned tube well

28-Jan-14

My hometown

National University of Malaysia

28-Jan-14 12

Surface water vs Groundwater

Slide from Dr. Saim Suratman (NAHRIM, Malaysia)

National University of Malaysia

13

Source: Dr Saim Suratman, NAHRIM

Sg. Langat, Selangor

Sg. Jeli, Kelantan

SW GW

SW GW

28-Jan-14

National University of Malaysia

28-Jan-14 14

Bank Infiltration

Fresh Water

River Water

Type of filtration that works by passing water to be purified for use as drinking water through the banks of a river or lake.

National University of Malaysia

Source: Dr Azuhan Mohamed, Groundwater Expert.

Groundwater !!

28-Jan-14 15

This is what people normally see This is what people should be able to see

National University of Malaysia

28-Jan-14 16

National University of Malaysia

17

Source: Dr Azuhan Mohamed, Groundwater Expert.

28-Jan-14

National University of Malaysia

28-Jan-14 18

Groundwater and Geotechnical Problems

National University of Malaysia

1. Groundwater & Mining

19 28-Jan-14

Groundwater to mining engineer (eg. Penjom Gold Mine)

PENJOM GOLD MINE, MALAYSIA

How to manage the influx of groundwater into the open pit mine?

National University of Malaysia

28-Jan-14 20

Vaiont Dam, Italy

2. Groundwater & Stability of Dam

Before After

National University of Malaysia

Trigger factor: the fluctuation of groundwater level

Vaiont Dam, Italy

28-Jan-14 21

Slip surface

Water level before

Water level after

National University of Malaysia

28-Jan-14 22

Trigger factor: the fluctuation of groundwater level

Ancient Slip surface

Water level before Water level after

Before

After

Dam Reservoir Old landslide area

National University of Malaysia

28-Jan-14 23

Groundwater & Foundation

Expensive house

Crack developed under the house and surrounding area Problem: The foundation of the house failed,

Resulting cracks and unstable foundation.

National University of Malaysia

28-Jan-14 24

Groundwater & Foundation

Reason for failure - Fill material = silt + gravel + boulder material - High K values - Channeling (old river) - Higher new water level/high water pressure

After development

Fill material

Retaining Wall

Before development

Original WT

Old river (diverted)

National University of Malaysia

28-Jan-14 25

Groundwater & Foundation

National University of Malaysia

28-Jan-14 26

Groundwater & Foundation Groundwater Modeling using Visual MODFLOW Pro

National University of Malaysia

28-Jan-14 27

Groundwater Contamination

Groundwater Remediation at Taman Beringin Landfill site Malaysia

Drilling (boreholes)

National University of Malaysia

28-Jan-14 28

Groundwater Contamination

Groundwater Remediation at Taman Beringin Landfill site Malaysia

National University of Malaysia

28-Jan-14 29

Groundwater Remediation at Taman Beringin Landfill site Malaysia

Groundwater Modeling using Visual MODFLOW Pro

National University of Malaysia

28-Jan-14 30

Groundwater Movement

National University of Malaysia

31

A measure of how easily a fluid (e.g., water) can pass through a porous medium (e.g., soils)

Loose soil

- easy to flow

- high permeability

Dense soil

- difficult to flow

- low permeability

water

Hydraulic conductivity

28-Jan-14

National University of Malaysia

Darcy’s Law

• Darcy’s experiment

• Henry Darcy

• French engineer

• 1856

28-Jan-14 32

National University of Malaysia

Darcy’s Law

Z = 0 (Datum) Z1, Z2 Elevation of manometer h1, h2 Elevation of fluid ∆𝒍 Distance of manometer

V (specific discharge) of cylinder

𝒗 =𝑸

𝑨

𝒗 𝜶 ∆𝒉

𝒗 𝜶 𝟏/∆𝒍

E1

𝒗 𝜶 (𝒉𝟏 − 𝒉𝟐)

28-Jan-14 33

National University of Malaysia

Darcy’s Law

𝑸 = V.A = (−𝒌 𝝏𝒉/𝝏𝒍) . 𝑨

𝒗 𝜶 − ∆𝒉 𝒗 𝜶 𝟏/∆𝒍

𝒗 𝜶 − ∆𝒉/∆𝒍

𝒗 = −𝒌 ∆𝒉/∆𝒍

𝒗 = −𝒌 𝝏𝒉/𝝏𝒍

If 𝝏𝒉/𝝏𝒍 (constant); 𝒗 𝜶 𝑲 ; 𝑲 = 𝒉𝒚𝒅𝒓𝒂𝒖𝒍𝒊𝒄 𝒄𝒐𝒏𝒅𝒖𝒄𝒕𝒊𝒗𝒊𝒕𝒚

E2

E2 E1

𝑸 = −𝒌 . 𝒊 . 𝑨

-ve sign: the direction of flow is towards the

decreasing hydraulic head

28-Jan-14 34

National University of Malaysia

Laboratory Field

- Manometer - piezometer

Borehole / Well

28-Jan-14 35

National University of Malaysia

• A confined aquifer has a source of recharge.

• The discharge, Q = 37500 m3/day

• The piezometric head in two wells 1000 m apart is 55 m and 50

m respectively, from a common datum.

• The average thickness of the aquifer is 30 m, and the average

width is 5 km.

Example of Darcy’s Law

28-Jan-14 36

National University of Malaysia Calculate:

(a) Calculate the hydraulic conductivity (K) ?

5 km

28-Jan-14 37

National University of Malaysia

28-Jan-14 38

Solution

Cross-Sectional area (A) = 30(5)(1000) = 15 x 104

m2

Hydraulic gradient (i) = (55-50)/1000 = 5 x 10-3 (No unit / unit less)

Q = 37,500 m3/day Darcy’s Law, Q = k.i.A k = Q / i.A = (37500) / (5 x 10-3)(15 x 10

4 )

= 50 m/day (0.000578703704 m/sec) = 5.79 x 10-4 m/sec

National University of Malaysia

28-Jan-14 39

50

National University of Malaysia

int xn dx = xn + 1/(n + 1)

logex = 2.303 log10 x

𝑘 = 2.3

𝑄𝑡 . 𝑙𝑜𝑔10

𝑟2

𝑟1

𝜋 (𝑧2 2 − 𝑧1

2 )

Determination of permeability in the field

National University of Malaysia

28-Jan-14 41

Example:

Pumping well Rate = Q

Observation well

Z1, Z2

r1,r2

𝑘 = 2.3

𝑄𝑡 . 𝑙𝑜𝑔10

𝑟2

𝑟1

𝜋 (𝑧2 2 − 𝑧1

2 )

National University of Malaysia

Groundwater is precious as a clean water resource

Groundwater has implication on engineering structures and stabilities

Groundwater can pollute – need for better understanding about the groundwater safety

Movement of groundwater is govern by Darcy’s Law.

28-Jan-14 42

Conclusions

National University of Malaysia

28-Jan-14 43

Thank you どうもありがとうございました