River Systems

Earth Space Science

Mr. Coyle

The Hydrologic Cycle

• Infiltration = Groundwater System• Runoff = Surface Water System

• Runoff = Precipitation - Evapotranspiration

Where is the Water ?

RIVERS & STREAMS• Water Reservoirs

• The Hydrologic Cycle

• Surface Water Systems

• Meandering

• Deltas/Alluvial Fans

• Floods and flooding

• Rivers:– Provide water and nutrients for agriculture

– Provide habitat to diverse flora and fauna

– Provide routes for commerce

– Provide recreation

– Provide electricity

www.aquatic.uoguelph.ca/rivers/chintro.htm

Importance of rivers

• Discharge- volume of water

• Velocity- rate of water movement

• Gradient- slope of inclined surface

Natural Watercourses

• The shape, size and content of a river are constantly changing, forming a close and mutual interdependence between the river and the land it traverses.

Variation in time and space

What is a Watershed?

www.aquatic.uoguelph.ca/rivers/chwater.htm

www.dec.state.ny.us/website/2000/watersheds.gif

www.epa.gov/watertrain/ecology/ecology21.html

The Worlds Largest Rivers

Largest Rivers of the World   

River Outflow mi. kmNile Mediterranean Sea 4,180 6,690

Amazon Atlantic Ocean 3,912 6,296

Mississippi-Missouri Gulf of Mexico 3,710 5,970

Yangtze Kiang China Sea 3,602 5,797

Ob Gulf of Ob 3,459 5,567

Huang Ho (Yellow) Gulf of Chihli 2,900 4,667

Yenisei Arctic Ocean 2,800 4,506

Paraná Río de la Plata 2,795 4,498

Irtish Ob River 2,758 4,438

Zaire (Congo) Atlantic Ocean 2,716 4,371

Heilong (Amur) Tatar Strait 2,704 4,352

Lena Arctic Ocean 2,652 4,268

Mackenzie Beaufort Sea (Arctic Ocean) 2,635 4,241

Niger Gulf of Guinea 2,600 4,184

Mekong South China Sea 2,500 4,023

Mississippi Gulf of Mexico 2,348 3,779

Missouri Mississippi River 2,315 3,726

Volga Caspian Sea 2,291 3,687

Madeira Amazon River 2,012 3,238

Purus Amazon River 1,993 3,207

São Francisco Atlantic Ocean 1,987 3,198

Yukon Bering Sea 1,979 3,185

St. Lawrence Gulf of St. Lawrence 1,900 3,058

Rio Grande Gulf of Mexico 1,885 3,034

Brahmaputra Ganges River 1,800 2,897

Indus Arabian Sea 1,800 2,897

Danube Black Sea 1,766 2,842

Euphrates Shatt-al-Arab 1,739 2,799

Darling Murray River 1,702 2,739

Zambezi Mozambique Channel 1,700 2,736

Tocantins Pará River 1,677 2,699

Approx. length

Discharge

River m 3̂/sec mm/yr % of total entering oceans

Runoff Ratio

1 Amazon, Brazil 190,000 835 13.0 0.472 Congo, Zaire 42,000 340 2.9 0.253 Yangtse Kiang, China 35,000 560 2.4 0.504 Orinoco, Venezuela 29,000 845 2.0 0.465 Brahmaputra, Bangladesh 20,000 1070 1.4 0.656 La Plata, Brazil 19,500 235 1.3 0.207 Yenissei, Russia 17,800 215 1.2 0.428 Mississippi, USA 17,700 175 1.2 0.219 Lena, Russia 16,300 210 1.1 0.4610 Mekong, Vietnam 15,900 630 1.1 0.4311 Ganges, India 15,500 455 1.1 0.4212 Irrawaddy, Burma 14,000 1020 1.0 0.6013 Ob, Russia 12,500 135 0.9 0.2414 Sikiang, China 11,500 840 0.8 -15 Amur, Russia 11,000 190 0.8 0.3216 St. Lawrence, Canada 10,400 310 0.7 0.33

U.S. Precipitation Map

U.S. Runoff Map

Notice the effect of the Rocky Mountains

Laminar vs. Turbulent Flow

Turbulent flow in the headwaters of a rushing mountain stream

Near-Laminar flow in the center of a river channel

So Where Does The Stream Move Fastest?

• Headwaters move slowest• Mouth of stream moves

fastest • Laminar flow is more

efficient than turbulent flow.

• Deeper stream move faster than shallow streams

Sediment Load

Movement of Bedload by Saltation

Sedimentation

Longitudinal Stream ProfileCan be divided into 3 main parts

Drainage (Tributary) System

Transport System Distributary System

Drainage System

• Stream energy is spent eroding downward into the basement rock and...

• Moving sediment

• Creates “V” shaped canyon and valleys

• When streams emerge from the mountain front, they often deposit some of this sediment forming alluvial fans.

Alluvial FansTransition from Tributary to Transport

Aging Rivers: How Old Is It?

• Young- rapid bed erosion, waterfalls, rapids, v-shaped valleys, few tributaries, low volume

• Mature- well established tributaries, larger volume of water, erode banks and not the bed (bottom), meanders, oxbow lakes

Flash Flooding & Sheetwash

Braided Pattern = high slope + high stream power + coarse bed materials

Braided Streams & Rivers

• High sediment load

• Constantly changing course

• Floodplain is completely occupied by channels

• Many small islands called mid-channel bars

• Usually coarse sand and gravel deposits.

Meandering Rivers

Meandering Rivers

• Constantly erode material - Cut bank

• Constantly deposit material - Point bar

• Change their channel course gradually

• Create floodplains wider than the channel– Very Fertile soil– Subjected to seasonal flooding

Formation of Meanders

Point bar deposits

Point Bar Deposits

Point bar deposits grows laterally through time

Cut bank erosion

Point bar deposits }Meander

loop

Formation of an Oxbow

Meandering streamflowing fromtop of screento bottom

Maximum erosion

Maximum deposition

Oxbow Lake

Oxbow cuttoff

Meander scars

1993 Mississippi Flood

Flooding & Sedimentation

Deltas - Distribution Systems

If the Mississippi

changes course again, what

will happen to the City of

New Orleans?

Things to Remember

• Rivers are part of a larger hydrologic system

• The have three main components:

• Drainage (Tributary) systems - collect water

• Transport Systems - move water along– Alluvial fans, braided streams, meandering streams

• Rivers exceed their capacity during floods

• Distributary systems - return water to the sea– Deltas.