Earth Science, 13e

Tarbuck & Lutgens

Running Water and GroundwaterEarth Science, 13eChapter 5

Stanley C. Hatfield Southwestern Illinois College

Earth as a system: the hydrologic cycle • Illustrates the circulation of Earth’s water supply • Processes involved in the cycle• Precipitation• Evaporation• Infiltration• Runoff• Transpiration

The hydrologic cycle

Running water • Drainage basin• Land area that contributes water to a river system• A divide separates drainage basins

Drainage basins and divides

Running water

• Streamflow • Factors that determine velocity

• Gradient, or slope • Channel characteristics • Shape• Size• Roughness

• Discharge – volume of water flowing in the stream (generally expresses as cubic feet per second)

• Discharge = Depth x Width x Velocity

Running water• Upstream-downstream changes • Profile

• Cross-sectional view of a stream • From headwaters (source) to mouth • Profile is a smooth curve • Gradient decreases from the headwaters to the mouth

• Factors that increase downstream • Velocity• Discharge• Channel Size

Running water • Upstream-downstream changes • Profile

Factors that decrease downstream• Gradient, or slope • Channel roughness

Longitudinal profile of a stream

Running water • The work of streams • Erosion• Transportation

• Transported material is called the stream’s load• Dissolved Load – minerals (oxygen, salts, nitrogen carbon dioxide)

• Discussed in ppm (parts per million)• Velocity has little to no effect on

• Suspended Load - silt/clay• Usually the largest load of a stream • Settling velocity

• Bed Load –move material via saltation

Running water • The work of streams • Transportation

• Load is related to a stream’s • Competence – maximum particle size• Capacity – maximum load • Capacity and Competence are related to discharge

• Greater the discharge the greater the capacity competence• Gradient • Examples – Low Mississippi Delta High Colorado River going through the

grand canyon (drops 10ft/mi)

Running water • The work of streams • Transportation

• Deposition• Caused by a decrease in velocity• Competence is reduced • Sediment begins to drop out

• Stream sediments • Known as alluvium• Well-sorted deposits

Running water • The work of streams • Transportation

• Features produced by deposition • Deltas – exist in ocean or lakes• Natural levees – form parallel to the stream channel • Area behind the levees may contain back swamps or Yazoo tributaries

Running water • 5.6 Base level

• Point at which a stream deposits into a larger body of water that is usually lentic or lotic.• Lentic standing water • Lotic Running water • Estuaries are the more common end point.

• Two general types • Ultimate – sea level• Erosion and transport processes becomes weaker and depositional

process takes over.• Temporary – Local • Includes lakes, resistant layers of rock, and point at which tributaries enter

a larger stream

• What happens to the velocity of a stream as it enters a lake?• Changing causes readjustment of the stream – depositional or

erosional processes will change.

Adjustment of base level to changing conditions

Running water • Stream valleys • Types of Stream Valleys

• Narrow, Steep, Wide

• Consists of the channel and the surrounding terrain of that contributes water to the stream.

• Most stream valleys are wider at the top than the bottom.• Is the stream the only agent working on the stream valley?• Valley sides are shaped by

• Weathering• Work of wind and water on the surface

• Overland flow • Runoff

• Mass wasting • Large and sudden movements of land mass

Running water • Characteristics of narrow valleys

• V-shaped • Created by the hydraulic powers if the stream moving bed load across the

bed of the channel in turbulent water.

• Down cutting toward base level is the dominant activity • Features often include: • Rapids –result of resistant rock acting as a temporary base level

• Down cutting continues downstream

• Waterfalls – Places where the stream makes an abrupt drop• Both are a result of a variation in erodability of the bedrock • Highest water fall in the world is Angel Falls

V-shaped valley of the Yellowstone River

Running Water • Characteristics of wide valleys

• Stream is near base level• Downward erosion is less dominant • Stream energy is directed from side to side

• Floodplains• http://www.youtube.com/watch?v=qEz4MiOVTMMOver time floodplains will widen

Mississippi River has areas w/ 100mi between divides

• Features often include • Meanders

• Incised Meanders – Found in steep narrow valleys • Created by a shifting in base level.

• Cutoffs plays a major part in the shifting of deltas • Oxbow lakes

Continued erosion and deposition widens the valley

Characteristics of a wide stream valley

A meander loop on the Colorado River

5.8 Depositional Landforms • Streams can create depositional features through out the

course of the stream. • Small-scale/short-term features• Deposits are referred to as bars• Often consist of both medium and fine grained material.• Temporary feature of the stream channel• Relocated as streams transport material toward the ocean.Large-scale/long-term features

Deltas, natural levees and alluvial fans • All of the features are found most often where flow velocity has

______.• decreased

Depositional Landforms• Deltas• Formed where streams enter a lentic body of water

• Ex. Lakes, in-land sea, or ocean

• Depositional processes take over at this point and start to convert the main stream into distributaries• Distributaries take water away from the main stream.

• Natural Levees• Form where streams have overflowed their banks • Once the stream leaves it’s channel the velocity decreases quickly

resulting in the deposition of sediment.• Over time the consistent flooding may result in the large levees

• Levees of the Mississippi can reach up to 20ft (6m)

• Areas behind levees tend to drain poorly and are often result in Yazoo tributaries and back swamps

• Alluvial Fans• Result of streams w/ high flow velocity entering a broad flat plain

Formation of natural levees by repeated flooding

Running water • 5.9 Drainage patterns• Networks of streams that form distinctive patterns• Types of drainage patterns

• Dendritic- the most common type of drainage pattern• Schuylkill river and Delaware • Characterized by its tree-like branching • Underlying geology is generally uniform and resistant to erosional

processes

• Radial – spokes on a wheel• Affiliated w/ volcanoes

• Rectangular- forms as a result of crisscrossing of joints and/or faulting • Characterized by 90degree angles

• Trellis - rectangular pattern in which tributaries are parallel to each other

Drainage patterns

Running water • Floods and flood control • Floods are the most common geologic hazard • Causes of floods

• Weather• Human interference with the stream system

• Flood Videos • NASA Mississippi Flooding 2011

http://www.youtube.com/watch?v=5ju1boh5bq8 Mississippi Flooding June 2012http://www.youtube.com/watch?v=QQH4IlSvlu0

Running water • Floods and flood control • Engineering efforts

• Artificial levees• Flood-control dams• Channelization

• Nonstructural approach through sound floodplain management

Satellite view of the Missouri River flowing into the Mississippi River near St. Louis

Same satellite view during flooding in 1993

Water beneath the surface (groundwater) • Largest freshwater reservoir for humans • Geological roles• As an erosional agent, dissolving by groundwater produces

• Sinkholes• Caverns

• An equalizer of stream flow

Water beneath the surface (groundwater) • Distribution and movement of groundwater • Distribution of groundwater

• Belt of soil moisture • Zone of aeration • Unsaturated zone • Pore spaces in the material are filled mainly with air

Water beneath the surface (groundwater) • Distribution and movement of groundwater • Distribution of groundwater

• Zone of saturation • All pore spaces in the material are filled with water • Water within the pores is groundwater

• Water table – the upper limit of the zone of saturation

Features associated with subsurface water

Water beneath the surface (groundwater) • Distribution and movement of groundwater • Distribution of groundwater

• Porosity • Percentage of pore spaces • Determines storage of groundwater

• Permeability• Ability to transmit water through connected pore spaces • Aquitard – an impermeable layer of material • Aquifer – a permeable layer of material

Water beneath the surface (groundwater) • Features associated with groundwater• Springs

• Hot springs • Water is 6–9° C (10–15° F) warmer than the mean air temperature of the

locality • Heated by cooling of igneous rock

• Geysers • Intermittent hot springs • Water turns to steam and erupts

Old Faithful geyser in Yellowstone National Park

Water beneath the surface (groundwater) • Features associated with groundwater• Wells

• Pumping can cause a drawdown (lowering) of the water table• Pumping can form a cone of depression in the water table

• Artesian wells• Water in the well rises higher than the initial groundwater level

Formation of a cone of depression in the water table

Artesian systems

Water beneath the surface (groundwater) • Environmental problems associated with groundwater • Treating it as a nonrenewable resource • Land subsidence caused by its withdrawal • Contamination

Water beneath the surface (groundwater) • Geologic work of groundwater • Groundwater is often mildly acidic

• Contains weak carbonic acid • Dissolves calcite in limestone

• Caverns • Formed by dissolving rock beneath Earth’s surface • Formed in the zone of saturation

Water beneath the surface (groundwater) • Geologic work of groundwater • Caverns

• Features found within caverns • Form in the zone of aeration • Composed of dripstone • Calcite deposited as dripping water evaporates • Common features include stalactites (hanging from the ceiling) and

stalagmites (growing upward from the floor)

Cave features in Carlsbad Caverns National Park

Water beneath the surface (groundwater) • Geologic work of groundwater • Karst topography

• Formed by dissolving rock at, or near, Earth’s surface • Common features • Sinkholes – surface depressions• Sinkholes form by dissolving bedrock and cavern collapse• Caves and caverns

• Area lacks good surface drainage

Features of karst topography

End of Chapter 5