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Transcript of Groundwater
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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.
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National University of Malaysia
• What is Groundwater
• Groundwater as a resource
• Groundwater and Geotechnical Problems
• Groundwater movement in soil
• Conclusion
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Content:
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National University of Malaysia
28-Jan-14 3
What is Groundwater?
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National University of Malaysia
4
Two Types of Water
28-Jan-14
Hydrogeology (Groundwater) Subsurface water
Hydrology (Surface water)
Unsaturated
Saturated
Water table
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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
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National University of Malaysia
Groundwater
6 28-Jan-14
Piezometric surface
• Aquifer (permeable) • Aquitard (Impermeable) • Artesian well • Water table • Piezometric surface
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National University of Malaysia
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Groundwater as a Resource
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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
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National University of Malaysia
Water Usage in Large Cities in the World
9 28-Jan-14
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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%)
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National University of Malaysia
• Kelantan : 70% of its water source is from groundwater.
Groundwater
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“Air Kelantan”
Production well
Crystal clear groundwater
Privately owned tube well
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My hometown
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National University of Malaysia
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Surface water vs Groundwater
Slide from Dr. Saim Suratman (NAHRIM, Malaysia)
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National University of Malaysia
13
Source: Dr Saim Suratman, NAHRIM
Sg. Langat, Selangor
Sg. Jeli, Kelantan
SW GW
SW GW
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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.
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National University of Malaysia
Source: Dr Azuhan Mohamed, Groundwater Expert.
Groundwater !!
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This is what people normally see This is what people should be able to see
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National University of Malaysia
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National University of Malaysia
17
Source: Dr Azuhan Mohamed, Groundwater Expert.
28-Jan-14
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National University of Malaysia
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Groundwater and Geotechnical Problems
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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?
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National University of Malaysia
28-Jan-14 20
Vaiont Dam, Italy
2. Groundwater & Stability of Dam
Before After
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National University of Malaysia
Trigger factor: the fluctuation of groundwater level
Vaiont Dam, Italy
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Slip surface
Water level before
Water level after
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National University of Malaysia
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Trigger factor: the fluctuation of groundwater level
Ancient Slip surface
Water level before Water level after
Before
After
Dam Reservoir Old landslide area
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National University of Malaysia
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Groundwater & Foundation
Expensive house
Crack developed under the house and surrounding area Problem: The foundation of the house failed,
Resulting cracks and unstable foundation.
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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)
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National University of Malaysia
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Groundwater & Foundation
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National University of Malaysia
28-Jan-14 26
Groundwater & Foundation Groundwater Modeling using Visual MODFLOW Pro
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National University of Malaysia
28-Jan-14 27
Groundwater Contamination
Groundwater Remediation at Taman Beringin Landfill site Malaysia
Drilling (boreholes)
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National University of Malaysia
28-Jan-14 28
Groundwater Contamination
Groundwater Remediation at Taman Beringin Landfill site Malaysia
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National University of Malaysia
28-Jan-14 29
Groundwater Remediation at Taman Beringin Landfill site Malaysia
Groundwater Modeling using Visual MODFLOW Pro
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National University of Malaysia
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Groundwater Movement
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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
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National University of Malaysia
Darcy’s Law
• Darcy’s experiment
• Henry Darcy
• French engineer
• 1856
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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)
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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
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National University of Malaysia
Laboratory Field
- Manometer - piezometer
Borehole / Well
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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
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National University of Malaysia Calculate:
(a) Calculate the hydraulic conductivity (K) ?
5 km
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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
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National University of Malaysia
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50
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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
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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 )
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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.
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Conclusions
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National University of Malaysia
28-Jan-14 43
Thank you どうもありがとうございました