lec 15 water hydrology and streams

8/19/2019 Lec 15 Water Hydrology and Streams

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An Example of Clay Mineral Formation

Clay minerals are the most abundant product of weathering and

they are formed when Silicate minerals decompose by hydrolysis

GEO 1111 - Streams 3

2KAlSi3O8 + 2H+ + 9H2O >> Al2Si2O5(OH)4 + 2K+ + 4H4SiO4

Orthoclase feldspar+ acid + water>> clay + potassium + soluble silica

The ions released from silicate minerals in the weathering process aresodium, potassium, calcium, iron, and magnesium ions. They are carriedaway by rain and river waters or become important soil nutrients.


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Mineral Stability


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Water, Hydrology, Streams, and Rivers



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Learning Objectives

1. Hydrologic cycle2. Residence time of water in a system3. Streams and rivers

4. Stream’s functions; hydraulic parameters and load5. Particle Transport and Stokes Law6. Base level and graded steam concepts7. Floods and flood control



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Annual Water Balance

• Stream Runoff = Input – Losses

– Input = rain and snow

– Losses =evapotranspiration

• Storage

– changes in volume of soil water

or lake or river water



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Why is residence time important?



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Annual Water Balance

• What is the average discharge of the Ottawa

River at the Carillon Dam (~Montreal)?

– Flow = 1940 m3 sec-1

– Drainage Area = 146,300 km 2

– Unit Discharge = Flow / Drain area= 0.42 m a-1

• How does the annual discharge compare with

the Mackenzie? The Fraser? The Amazon?

• How does the unit discharge compare?



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Residence Time of Water in Pink

Lake, Gatineau Park?

• Catchment Area = 2km2

• Precipitation = 800 mm/a

•

Evaporation = 500 mm/a• Lake Volume = 1*107m3

• Residence time = Volume /Input



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Lake, Gatineau Park

• Catchment Area = 2km2 = 2*106 m2

• Precipitation = 800 mm/a =0.8 m/a

•

Evaporation = 500 mm/a= 0.5 m/a• Lake Volume (V) = 1*107m3

ALWAYS CHECK YOUR UNITS!

Do a dimensional analysis



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Lake, Gatineau Park

• Catchment Area = 2km2 = 2*106 m2

• Precipitation = 800 mm/a =0.8 m/a

•

Evaporation = 500 mm/a= 0.5 m/a• Lake Volume (V) = 1*107m3

• Residence time = Volume /Input

• Input (I) = (Precip-Evap)*Catchmt Area• Input = (0.8m-0.5m)*2*106 m2 =0.6*106 m3

• Residence time = V/I = (10/0.6)=16.6 a



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What happens when ….

• Water input greater than output?

– Water level in river / lake rises

• Flooding

• Ships can hold more cargo and do not ground in channels

• Water loss greater than precipitation input?

– Water levels drop, salinity rises,

– Soil dries up and wind-born soil transport increases• Agricultural crop failure



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A Drought Example

• Average Precipitation is 80 cm/a & Evaporation

is 60 cm/a

• What is the runoff?

• The soil water contains 20 cm water equivalent

• How many years will the water in the soil last if

the temperature rises 5oC and P is 80 and E is 85

cm/a?



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Streams and Rivers• Streams are any flowing body of water

• Rivers are major branches of a stream system

Fraser River, BC Stoney Creek, Texas

• Stream distribution→ f (plate tectonics, climate system)



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Hydrologic Cycle

Distribution of Earth’s water

1. Oceans:

2. Freshwater:

2a.

2b.

2c.

97.2%

2.8%

glaciers:

groundwater:

other lakes:

streams:atmosphere:soil moisture:

2.15%

0.62%

0.009%0.005%

0.0001%0.001%

So, why do we care?



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Streams are major geological agents of

change in landscapes (transfer materialfrom the highs to the lows – plane outrelief)

Importance

Most cities are built onfloodplains of riversSource of drinking water

Streams provide pathways for

inland colonization of continentse.g. Jacques Cartier

Lewis and Clark

Agriculture



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Stream system components



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Drainage basins

Drainage basin: total area drained bya stream and its tributaries

Drainage divide: ridge of high grounddividing one drainage basin from another

(red line – imaginary!)

Tributary: small stream flowing into a

larger one (contribut es)

Some terminology:



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Drainage basins

Largest drainage

basin of N. Am.?

Ottawa River drainage basin



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Stream system components Headwaters

Mouth

Longitudinal profile: cross-sectionalview of the stream bed (red line)



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1. valleys: sloping area aroundthe stream

Stream system components

2. channels: bottom of valley,where water flows

3. floodplains: flat area in valley

level with top of channel. Portionof the valley that can be flooded

Headwaters

MouthThe three basic parts of a stream:



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From upstream to downstream

discharge m3/s

v e l o c i t y m / s

d e p t h m

w i d t h m

Hydraulics and channel geometry

b) discharge (Q): Q (m3/s) = U (m/s) x A (m2)

Q ↑ downstr . - from collection of tributaries

a) gradient (L): height/distance (cm-m/km)↓ in L downstream.

d) velocity (U): average U ↑ downstr .; less bedroughness, higher Q, larger channels(overcome the lower L)

c) depth (d) & width (w): channel size ↑ downstr .;also, ↑ A = ↓ friction; larger streams have higher U



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Stream Processes

1. erosion

2. transport

3. Deposition …

Stream’s “job” = plane out relief

Accomplished through:

via channelized flow (most efficient)



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What controls erosion vs. transport vs. deposition?

a) hydraulic parameters

b) stream morphology

c) material (eroding intoand/or transporting)



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What keeps a particle suspended?Stokes Law describes the forces


Force of (1) buoyancy and (2) frictional and form drag due to flow

Force of gravity


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Particles settle when FG>(FB+FD)


Force of Buoyancy and Force of drag due to flow

Force of gravity


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Forces on a Particle in Flowing Water


Force Difference betweengravity and buoyancy

Force of Gravity on Particle ‘p’

Gravity Force = mpg = Vp Dpg

Fluid Buoyancy Force = VpDf g

Force G-B = Vp(Dp-Df )g


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Particle settling in Flowing Water


Force of Frictional drag due to flow

Fluid Drag Force

Drag = 0.5 C Df Rp2 W2

Df is fluid density

Rp is particle radius

W is water velocity

C Drag coefficient

Particle is dragged along by

flow so drag force is in the

direction of flow velocity


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Water Velocity and Particle Transport


Particles settle when FG>(FB+FD)


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Base level and graded streams

Distance from headwaters of river (km)

A l t i t u d e a b o v e

s e a l e v e l ( m )

MouthSource

Longitudinalprofile

Base level: level below which astream cannot erodee.g. sea level, lake level, dam

Graded stream: equilibrium statewhere channel geometry andhydraulic parameter enable thestream to transport its load withneither deposition nor erosion.

Interplay between erosion, transport, and deposition → f(base level)



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Base level and graded streams

Changes in base level result in an

adjustment in the longitudinal profile

1) Increase in base level

longitudinal prof. adjusts by:

2) Decrease in base level

longitudinal prof. adjusts by:

↑ deposition

↑ erosion↑ transport



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Channel pattern

Braided rivers

rapid and irregular dischargehigher slopeserodible banks

rapid channel migrationabundant coarse sedimentin-channel bars (lense of sediment)

Braided if interlacing network of channels


http://gsc.nrcan.gc.ca/landscapes/photos/photographs/alberta/jaspernationalpark/img11_03_02.jpghttp://gsc.nrcan.gc.ca/landscapes/photos/photographs/alberta/jaspernationalpark/img11_03_02.jpg


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Channel pattern

Meandering rivers

lower and more regular dischargelower slopescohesive banksslower more regular channel migration

abundant fine sediment



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Channel pattern

well developed levees

build-up of river banks →floods



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Channel pattern

Flow in meanderingchannels

Downstream flow

Helicoidal flow pattern

Cross-channel flow(secondary flow)

+



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point bar depositsalong inner bank

Channel pattern

Flow in meanderingchannels

Downstream flow

Helicoidal flow pattern

Cross-channel flow(secondary flow)

+



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Floods when streams leave their beds


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Flood – when discharge > stream capacity

→ stream overflows its banksNATURAL process

Floods - when streams leave their beds

Causes -

Contributing factors:• low infiltration rate

• topography

• ice-jam• rapid snow melt

• ...



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Floods - when streams leave their beds

Ice-jam Artificial levee breach – New Orleans(Hurricane Katrina, August 2005)


Impacts – One of the mostdeadly and destructive geologichazards; Why?


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Floods

Flood consequences –

• life loss, disease, water contamination

HUMAN impact

MATERIAL impact

• destruction or damage ofproperty and infrastructures

LANDSCAPE modification

• erosion (high discharge)

• sedimentation (reduced velocity →

channel invades floodplain)

• channel avulsion



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Alberta FloodsJune 19-22 2013

• >200mm rain in two days• Snow cover & Saturated ground• Steep watershed – no storage• 4 deaths, 100k evacuees• $>1B flood damage


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Flood Control Techniques

Controls -

Winnipeg, Manitoba –floodplain of Red River

• artificial levees

• dams

• channelization

• Natural Storage Areas• Live elsewhere



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Video Reviewing Hydrologic Cycle

• https://www.youtube.com/watch?v=ts19O41k

wDA


Summary of Key Concepts

https://www.youtube.com/watch?v=ts19O41kwDAhttps://www.youtube.com/watch?v=ts19O41kwDAhttps://www.youtube.com/watch?v=ts19O41kwDAhttps://www.youtube.com/watch?v=ts19O41kwDA


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Summary of Key Concepts

1. Streams / Rivers transport water, solutes and sediment

2. Water runoff (Flow) is the difference between water inputs andevapotranspiration (if at steady state)

3. Unit runoff allows discharge to be calculated and flows to be

scaled in different catchments

4. Water Residence time is average time a water molecule is in the

lake, river, stream, atmosphere etc

5. Stokes Law describes the settling of particles in streams and

other moving fluids. (gravity vs buoyancy and drag)

6. Flooding is the most damaging and dangerous direct impact of

excess flow• Streams are loci of human habitation.

• Extreme events are difficult to predict and control.



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N L


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Next Lecture

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lec 15 water hydrology and streams

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