Surface Water - Unit 2

Hydrologic cycle (water cycle)

Repeated circulation of water through the different Earth environmental components

- Geosphere

- Hydrosphere

- Atmosphere

- Biosphere

Geosphere

the solid part of the earth consisting of the crust and outer mantle

Hydrosphere

All the water at and near the surface of the earth, 97% of which is in oceans

Atmosphere

the envelope of gases surrounding the earth or another planet.

Biosphere

part of Earth in which life exists including land, water, and air or atmosphere

ways water vapor enters atomosphere

Evaporation, Sublimation, and Transpiration

Evaporation

The change of a substance from a liquid to a gas

Sublimation

A change directly from the solid to the gaseous state without becoming liquid

Transpiration

Evaporation of water from the leaves of a plant

Precipitated water can move to many places including...

- Re-enter atmosphere

- Move into the ground

- Stay on the surface

What percent of earths fresh water is surface water?

1.3%

sheet flow

runoff moving in unconfined thin sheets

channelized flow

Water flow restricted to channels. Compare with sheet flow.

Drainage basins

Areas drained by a given stream or stream system; Also called watersheds

Drainage divides

Define boundaries of specific drainage basins

Continental divides

Special type of drainage divides

- Mark where surface water flows into specific oceans/seas/bays or an isolated basin

Water flow in a stream channel

Driven by gravity; Can be one of two types

- Laminar flow

- Turbulent flow

Laminar flow

a smooth pattern of flow

Turbulent flow

Irregular flow with random variations in pressure.

Channel slope (gradient)

Steeper gradient means more gravitational

energy to drive flow

Channel shape

For comparable channels, water flows

faster in narrow and deep channels and

slower in wide and shallow channels

What kinds of channels does water more more efficiently through?

Water moves more efficiently through...

o Larger channels

o Smoother channels

How do channel properties change along the stream length

Generally, from head to mouth...

- Channel slope (gradient) decreases

- Channel size increases

- Channels become smoother

Types of work by flowing surface water

Erosion, transport, deposition

Work of a specific stream is governed by...

Stream flow velocity, Stream discharge, and Properties of channel bed and channel banks

What are the 3 zones of a stream

- Sediment production (erosion) zone (Headwaters region)

- Sediment transport zone (Main trunk of stream)

- Sediment deposition zone (Mouth region)

What are the 3 sizes of sediment eroded by streams

- Easily eroded...

o Sand-sized sediments

- Not as easily eroded...

o Silt- and clay-sized sediments

o Gravel-sized sediments

What are the 3 types of erosion by streams (bedrock)

Quarrying, Abrasion, and Corrosion

Quarrying

Removing large bedrock blocks from the channel bed

Abrasion

Scraping, bumping and rubbing action of sediment carried in stream

Corrosion

Bedrock dissolution

Streams transport material in one of three ways

- In solution (Dissolved load)

- In suspension (Suspended load)

- Along the bed (Bed load)

Dissolved load

Materials dissolved in the water

Suspended load

Materials carried along in suspension; Mostly small sediment particles

o Fine sand and silt

Bed load

Materials transported along channel bed; Larger sediment particles

o Coarse sands

o Gravel

o Boulders

Ability of a stream to carry solid particles often

described by two properties

competence and capacity

Competence

Maximum sediment size a stream can transport

Capacity

Maximum sediment load a stream can transport

o Total mass per unit time

When does deposition of sediments from streams occur

Deposition occurs when the stream flow rate decreases

- Stream capacity decreases

- Largest suspended sediments are deposited

- Results in well sorted sediment deposits

Deltas

Sediment deposits accumulated where

streams empty into a large body of water

- Sediment deposits form a delta

Alluvial fans

Fan-shaped sediment deposits at base of mountain fronts

- Mountain stream emerges onto a flat lowland

- Stream channel slope decreases

Natural levees

- Raised areas adjacent to the channel

- Form during flood events

Bedrock channels

- Channels cut into bedrock

- Typically form in headwater region

Alluvial channels

- Channels cut into previously deposited steam sediments

- Channels progressively change shape and location (meander)

- Typically form in floodplains

What parts of a meandering channel erode vs deposit?

- Outside of a meander is a zone of active erosion

- Inside of a meander is a zone of deposition

Oxbow lake

A meander that has been cut off from the river

Base level

The lowest level to which a stream can erode its channel

Graded stream

A stream that maintains a minimum flow rate necessary to transport the sediment that is delivered to it

- No net erosion or deposition of sediment

When does stream valley widening occur?

As a stream approaches a graded condition...

- Downcutting is less important

- Erosion mostly occurs laterally

- Produces flood plain

Incised meanders

Meanders flowing through steep, narrow

bedrock valleys

Stream drainage patterns

Network of stream valleys creates a drainage pattern