Peralta Colleges, Physical Geography
Rita D. Haberlin, Instructor
HYDROLOGIC CYCLE AND GROUNDWATER
PowerPoint Presentation Outline Notes
What You Learn
- The role of water in the global ecosystem
- Where the world’s water supply is stored
- The pathways of moisture in the hydrologic cycle
- The fate of precipitation on the land
- How groundwater moves in rocks beneath the earth’s surface
- Man’s impact on ground water: depletion and pollution
- Earth is called the blue planet. Why?
- Seventy percent (70%) of the earth’s surface is oceans - the hydrosphere.
- The hydrosphere connects with the three other spheres.
The World’s Water Supply
Water Takes Three Different Forms
- Water = Liquid Form
- Ice = Solid Form
- Water Vapor = Gas Form
The Hydrologic Cycle
- What is the driving force behind the hydrologic cycle?
- Gravity helps keep water moving.
- Water circulates between the:
Pathways of Moisture in the Hydrologic Cycle
All the world’s water comes from the oceans.
In the end, most of it returns to the oceans. HOW?
- Surface water runoff
- Groundwater flow
The Fate of Precipitation on Land
Distribution of Groundwater
- Zone of saturation
- All the pores and cracks filled with water
- Water table
- Top of the zone of saturation
- Zone of aeration
- Area above the water table mostly filled with air
How can water move underground?
Groundwater movement depends upon rock:
- Percentage of pore space available to hold water.
- Ability to transmit water through connected pore spaces.
- Some rocks have pore spaces but they do not allow water to pass through.
- Some rocks do not have pores - they consist of intergrown crystals
- Rocks that allow water to pass through them are called permeable.
- Rocks that do not allow water to pass through are called impermeable.
- The best aquifers (groundwater storage areas) are both:
- Sandstone is a good example of an aquifer.
Water Tables Rise and Fall
Ground Water Depletion
What is the impact of widespread pumping?
- Shallow wells dry up
- Rivers and lakes dry up between rains
- Land subsidence
- Saltwater intrusion
Falling Water Tables - High Plain States
Land Subsidence - Global Map
Land Subsidence in the San Joaquin Valley
- Western side of the valley subsided 9 meters (nearly 30 feet).
- Withdrawal of groundwater
- Compaction of sediments
- The water table near the coast drops.
- Saltwater seeps into the aquifer.
- Coastal wells draw brackish water.
Sources of Groundwater Pollution
Human Impact on Groundwater
- Which well will have the cleanest water?
- Why is Well D likely to be polluted?
- Will heavy pumping of Well A affect other wells?
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