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Water
Water Cycle• Evaporation is the process in which liquid bodies of water, such as ponds,
lakes, rivers, and oceans, change into water vapor.• Transpiration is the evaporation of water from plant leaves.• Condensation is the next process. In condensation the water vapor
changes to liquid water or ice. The clouds are formed due to condensation.• Precipitation is when the water condenses so much that it falls to the
ground in the form of rain, snow, or hail.• Once the precipitation falls to the ground, the water may infiltrate
(infiltration) into the ground OR• Once the precipitation falls to the ground, the water may flow onto the
ground (runoff) into lakes, streams, rivers oceans, or ponds.• Once in these bodies of water, evaporation occurs and the process starts all
over again.
Distribution of Groundwater
Groundwater: Belt of soil moisture
Zone of aeration • Unsaturated zone • Pore spaces in the material are filled mainly with air
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
Porosity vs Permeability
Porosity • Amount of pore space available• Determines how much groundwater can be
stored • Depends on:
• Shape, packing and arrangement of grains• Well-sorted: all grains are the same size (high
porosity), examples: sand, poorly cemented coquina.
• Poorly-sorted: finer grains fill spaces between larger grains (low porosity), examples: well-cemented sandstone, shale, mudstone, and limestone.
Porosity vs Permeability
Permeability• Ability to transmit water through connected pore
spaces • How easily water can flow through a rock or sediment
• Depends on:• Grain size (Coarser-grained sediments are
more permeable than fine-grained sediments because the pores between the grains are larger)
• Grain shape and packing (sorting)
Groundwater Features
• 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
Aquifers•Aquitard – formed by impermeable materials that create a zone of saturation above it•Aquifer – permeable layers that allow water to flow freely through
The source of most water wells
Two Types of Aquifers
• Unconfined: water level rises freely as the aquifer recharges
• Confined: rising water reaches impermeable layer, becomes pressurized
• Use aquifer coloring sheet for pictures
Groundwater Overuse
• Groundwater is replenished mostly by rain– If there is less
rain than use of the water, the water level will decrease
Groundwater Overuse• Cone of depression – lowering of the water
table around a well due to large amounts of water being pumped out
Groundwater Overuse
• Ground subsidence (sinking) can occur if water is used faster than it is replenished– Creates
depressions or sinkholes
Sources of Groundwater Contamination
• Sewage from septic tanks, farm wastes, inadequate or broken sewers
• Fertilizers and pesticides from agriculture• Residential runoff• Highway salts• Chemical and industrial materials that
leak from pipelines, storage tanks, landfills, or holding tanks
• Saltwater in coastal areas• Minerals and nutrients from dissolved
rock and other natural materials
Groundwater Pollution
• Point Source Pollution – contaminants have an identifiable source– Smokestacks, car tailpipe
• Nonpoint Source Pollution – contaminant source cannot be found– Several farmlands in the same area
• Flow downhill – contaminants leaked into the ground at the top of a hill will flow downhill
• Rainwater – runs through the contaminant, absorbs it, and transfers it to another area
Groundwater Cleaning
• If water travels slowly through sand or permeable sandstone, the water is purified
• Sometimes contaminated water is pumped out of an aquifer and treated; the aquifer is replenished naturally or with the treated water
River Basins
• Encompasses all the land surface that drains surface water from many finger-like streams and creeks which flow downhill into one another and eventually into one large river which takes the water to the ocean.
River Basins
• Watersheds (river basins) are separated from each other by areas of higher elevation (ridge lines/divides).
• Water channels at ridge lines will be narrow with fast-moving water.
• As channels combine, the width of the stream will increase.
• Watersheds have a branching appearance due to the tributaries (small streams branching from larger streams and rivers)
NC River Basins
Wetlands
• Land that is covered by water all or part of the year.
• Includes swamps, marshes and bogs
Wetlands
3 Functions:1. Provide flood protection during storms2. Filter pollution and urban runoff3. Habitat for many animals
Wetlands
SwampMostly trees and bushes
MarshTall grasses, some trees and bushes
Carolina BaysUnique to East CoastOval-shaped lakes that often fill with plants and sediment