Lecture 3

LANDSCAPES FASHIONED BY WATER

Surface Water

Water Cycle

The unending circulation of Earth's water supply powered by the energy from the sun in which the atmosphere provides the vital link between the oceans and continents.

Please refer to hydrologic cycle figure.

Surface Water

Surface water flow makes its way to sea under the influence of gravity. The time required for the journey depends on the velocity of the stream. Velocity is the distance that water travels in a unit of time. Some streams are slow and sluggish; some are fast.

Surface water flow can best be described as follows.

1. 1. Along straight stretches of streams the highest velocities are near the center of the channel just below the surface where channel friction is the least.

2. 2. When a stream curves the zone of high velocity is towards its outer bank.

3. 3. The gradient is the slope of a stream's channel, expressed as the vertical drop of a stream over a specified distance; the steeper the gradient the more energy available for stream flow.

4. 4. Friction affects a stream's flow. The shape, size and roughness of the channel affects the amount of friction encountered by the water as it flows through the channel.

5. 5. Discharge is the volume of water flowing past a certain point in a given unit of time. It is controlled by the amount of rainfall and snowmelt.

Stream Profile

The stream profile is a cross sectional view of a stream channel from its source (headwaters/head) to its mouth (the point where the river ends).

Stream gradient decreases downstream and increases upstream.

Where the gradient is great, discharge is small.

Where discharge is great, gradient is small.

Base Level

There is a lower limit to how deep a stream can erode and that limit is the stream's base level.

Base level is the lowest point to which a stream can erode its channel.

Two general types of base level are:

1. 1. Ultimate base level is sea level It is the lowest level to which steam erosion could lower the land, and

2. 2. Temporary or local base level, which includes lakes, resistant layers of rock and main streams, that act as base level for their tributaries when a stream enters a lake the velocity of the stream decreases and its ability to erode decreases).

Stream Activities.

Erosion is the removal of rock and soil by the stream.

Transportation is the stream's way of moving their load. Transportation occurs in three ways: 1) dissolved load, 2) suspended load, and 3) bed load.

Deposition occurs when ever a stream slows down; the sediment or load begins to drop out or settle at the bottom of the stream.

Stream Valleys

There are two types of valleys:

· · narrow "V" shaped valleys;

· · wide valleys with flat floor.

· · Narrow valleys indicate that the primary work of the stream has been down cutting toward base level.

· · Wide valleys are due to a stream cutting its channel closer to base level. Downward erosion becomes less dominant; the stream begins to focus its energy from side to side.

o o The result of above action is a widening of the valley as the stream cuts away at one bank then the other (a. floodplain is produced when the above action occurs, most of the time the stream is confined to its channel except during flood time when the stream inundates the floodplain, and b. meanders: streams that flow on floodplains move in sweeping bends called meanders).

Stream Morphology: Below are some stream features: look these up in the text or Internet.

· · Floodplain,

· · Point bar,

· · Cut bank,

· · Channel,

· · Drainage basin

Ground Water

Ground Water

Ground water is defined as water located in the pores of rocks and soil.

Porosity and permeability control the flow of ground water in the ground.

· · Porosity is the pore space in the soil or rock.

· · Permeability is the amount or pores that are interconnected.

Aquifers

Saturation zone is the zone of rock or soil that is saturated with water.

A confined aquifer is when water is entrapped between two confining layers, such as clay.

· · Confined aquifers are not affected by precipitation.

· · Confined aquifers are not as vulnerable to contamination and pollution.

· · Clay on top of confined aquifer systems protect the aquifer.

· · Confined aquifers are under pressure.

· · Edwards Aquifer-San Antonio’s drinking water aquifer.

· · Mesilla Bolson and Hueco Bolson- El Paso’s drinking water aquifer.

An Unconfined aquifer (water table) is an aquifer that is only confined at the bottom, not the top.

· · This aquifer is affected by the amount of precipitation. That is lots of rain=increase in aquifer level.

Lecture 3

LANDSCAPES FASHIONED BY WATER

Surface Water

Water Cycle

The unending circulation of Earth's water supply powered by the energy from the sun in which the atmosphere provides the vital link between the oceans and continents.

Please refer to hydrologic cycle figure.

Surface Water

Surface water flow makes its way to sea under the influence of gravity. The time required for the journey depends on the velocity of the stream. Velocity is the distance that water travels in a unit of time. Some streams are slow and sluggish; some are fast.

Surface water flow can best be described as follows.

1. 1. Along straight stretches of streams the highest velocities are near the center of the channel just below the surface where channel friction is the least.

2. 2. When a stream curves the zone of high velocity is towards its outer bank.

3. 3. The gradient is the slope of a stream's channel, expressed as the vertical drop of a stream over a specified distance; the steeper the gradient the more energy available for stream flow.

4. 4. Friction affects a stream's flow. The shape, size and roughness of the channel affects the amount of friction encountered by the water as it flows through the channel.

5. 5. Discharge is the volume of water flowing past a certain point in a given unit of time. It is controlled by the amount of rainfall and snowmelt.

Stream Profile

The stream profile is a cross sectional view of a stream channel from its source (headwaters/head) to its mouth (the point where the river ends).

Stream gradient decreases downstream and increases upstream.

Where the gradient is great, discharge is small.

Where discharge is great, gradient is small.

Base Level

There is a lower limit to how deep a stream can erode and that limit is the stream's base level.

Base level is the lowest point to which a stream can erode its channel.

Two general types of base level are:

1. 1. Ultimate base level is sea level It is the lowest level to which steam erosion could lower the land, and

2. 2. Temporary or local base level, which includes lakes, resistant layers of rock and main streams, that act as base level for their tributaries when a stream enters a lake the velocity of the stream decreases and its ability to erode decreases).

Stream Activities.

Erosion is the removal of rock and soil by the stream.

Transportation is the stream's way of moving their load. Transportation occurs in three ways: 1) dissolved load, 2) suspended load, and 3) bed load.

Deposition occurs when ever a stream slows down; the sediment or load begins to drop out or settle at the bottom of the stream.

Stream Valleys

There are two types of valleys:

· · narrow "V" shaped valleys;

· · wide valleys with flat floor.

· · Narrow valleys indicate that the primary work of the stream has been down cutting toward base level.

· · Wide valleys are due to a stream cutting its channel closer to base level. Downward erosion becomes less dominant; the stream begins to focus its energy from side to side.

Stream Morphology: Below are some stream features: look these up in the text or Internet.

· · Floodplain,

· · Point bar,

· · Cut bank,

· · Channel,

· · Drainage basin

Ground Water

Ground water is defined as water located in the pores of rocks and soil.

Porosity and permeability control the flow of ground water in the ground.

· · Porosity is the pore space in the soil or rock.

· · Permeability is the amount or pores that are interconnected.

Aquifers

Saturation zone is the zone of rock or soil that is saturated with water.

A confined aquifer is when water is entrapped between two confining layers, such as clay.

· · Confined aquifers are not affected by precipitation.

· · Confined aquifers are not as vulnerable to contamination and pollution.

· · Clay on top of confined aquifer systems protect the aquifer.

· · Confined aquifers are under pressure.

· · Edwards Aquifer-San Antonio’s drinking water aquifer.

· · Mesilla Bolson and Hueco Bolson- El Paso’s drinking water aquifer.

An Unconfined aquifer (water table) is an aquifer that is only confined at the bottom, not the top.

· · This aquifer is affected by the amount of precipitation. That is lots of rain=increase in aquifer level.

· · This aquifer is vulnerable to pollution and contamination.

· · This aquifer is not under pressure.

Springs are where the ground water intersects the land surface.

Some landscapes produced by ground water are:

o o Caverns;

o o Sink holes

o o Karst.