Mass Wasting and Water Resources

Factors that influence slope stability:

•Slope angle
• ______ is more likely on steeper slopes

•Weathering and climate
• disintegrates rock and decreases its cohesion

•Water content
• more water increases pore pressure and adds weight

•Vegetation
• absorbs water from pore spaces
• roots can stabilize slope but can also add weight

•Geology
• unconsolidated sediments are more likely to fail than coherent, crystalline rock
• _______ more likely if layering parallels slope
• jointing can contribute to slope failure

Natural mass wasting triggers

• Earthquakes
• Heavy Rains
• Snowmelt
• Freeze-thaw cycles
• Volcanoes
• Removal of Vegetation (e.g., as the result of fire)

Global distribution of freshwater

Ice= 69%

Groundwater= 30%

Surface water= 1.3%

Global distribution of water

Oceans= 96.5% of Earth’s water

All freshwater= 2.5% of Earth’s water

Global distribution of surface water

ice & snow= 73%

lakes= 20%

wetlands= 2.5%

rivers= 0.5%

True or False:

There is more groundwater than there is surface water
in all the streams and lakes on Earth.

True

Freshwater use highest to lowest

Highest

1.Thermoelectric Power 41%
2. Irrigation 37%
3. Public and Domestic 12.6%
4. Industrial Use 5.2%
5. Aquaculture 2.5%
6. Mining 1.1%
7. Livestock 0.6%

Lowest

These 3 uses make up about 90% of total freshwater use in the US

Thermoelectric power, irrigation, and public/domestic use

Reservoir (or pool)

A place where mass or energy is stored

Flux

A process that moves mass or energy from one reservoir to another

Aquifers

porous, permeable rock layers that transmit (or store) water

e.g.: Sandstone, sand, gravel, and fractured rocks

Groundwater

water stored underground in the pores (spaces) in rocks and sediment

Porosity

Percentage of volume that is open space (that can fill with water or oil/gas)

Permeability

Measure of how easily fluid flows through something;
Depends on porosity and the size and interconnectivity of the pores/fractures

Zone of aeration

region beneath Earth’s surface where pore space is filled with air

Zone of saturation

region beneath Earth’s surface where pore space is filled with water

Water table

surface that separates the zones of saturation and aeration

Aquicludes/Aquitards

- low permeability rock layers that prevent the passage of water

Examples: Shale, clay, unfractured igneous and metamorphic rocks

Recharge (Inflow)

• infiltration

– water seeps in through soil, depends on precipitation and ground cover

• streams

- water lost from streams (losing streams), lakes, & unlined canals

Discharge (Outflow)

• streams

– groundwater to “gaining” streams, equivalent to minimum stream flow

• springs

- where water table intersects land surface

Drainage basins or watersheds

areas of land that drain into a body of water.
Smaller _______ are nested within larger ________
Individual ____________ are separated by divides (topographic high points).

Infiltration capacity

the maximum rate at which materials can absorb water

What factors might influence _________?
• Vegetation
• Soil moisture
• Temperature
• Soil texture (porosity/permeability)
• Slope
• Intensity of precipitation

Once infiltration capacity is reached, _______ begins
________ occurs as:

• Sheet flow
• Channel flow

Stage

water level in a stream

Discharge (m³/s)

= width (m) x depth (m) x velocity (m/s)

Floodplain

the area typically covered by water during a major flood event.