1. Ch 15 and 16-River Systems and Groundwater
Objectives
Stages of the water cycle
Factors that affect a water budget
List approaches to water conservation
Summarize how a river develops
Describe the parts of a river system
Explain factors that affect the erosive ability of a river
Describe how erosive factors affect the evolution of a river channel
Explain the types of stream deposition
Describe advantage and disadvantage of living in floodplain
Identify the methods of flood control
Describe the life cycle of a lake

2. Movement of Water on Earth
Water vapor-water that occurs as invisible gas in atmosphere
Water cycle-continuous movement of water between the atmosphere, land, oceans
Evapotranspiration-total loss of water from an area
Evaporation-liquid water changes into water vapor. Where does the most evaporation take place at?
Transpiration-plants release water vapor
Condensation-gas to liquid
Water on outside of glass
Tiny liquid water droplets and forms clouds
Precipitation-water falls from clouds
75% falls on oceans
Examples

4. Water Budget/Use Water budget established by water cycle
Factors that affect it include; temperature, vegetation, wind, and amount and duration of rainfall. How are these factors?
Average person uses 95,000 L each yr. What is it used for? 90% of water used in cities, returned to rivers and oceans as wastewater
Some may contain harmful materials

5. Water Conservation What is water conservation?
The wise use of water resources
How can people conserve water?
How can governments conserve?
Enforcing conservation laws and antipollution laws that prohibit dumping of waste into bodies of water
Finding alternative ways to obtaining fresh water
Desalination-process of removing salt from ocean water
Expensive and impractical

6. Stream Erosion How does a river develop? Parts of River System
Soil collects water, runoff begins from excess water, erodes rock and soil, forms narrow ditch. Precipitation and erosion form valley w/ permanent stream
Parts of River System
Tributaries-feeders streams into main stream
Watershed-land that is drained by river system
Divides-ridges or elevated regions, separate water sheds
Channel-narrow depression stream follows downhill
Banks-edges of stream above water level
Bed-the part of stream channel below water level

7. Channel Erosion
Stream Load-materials other than water carried by stream
Suspended load, bed load, dissolved load
Stream Discharge-volume of water that flows w/in given time
Stream Gradient-change in elevation over given distance. Velocity depends on gradient

8. Evolution of River Channels
As the stream’s load, discharge, and gradient decrease, the erosive power of the stream decreases
Channels erode, become wider and deeper=rivers
Meander- one of the bends, twists, or curves in low-gradient stream or river.
More energy directed to banks than beds.
Faster on outside of curve, sediment deposited to form sand bars
Oxbow Lake-the meander becomes isolated from river
Braided Streams-multiple channels, divide or rejoin around sediment bars
Large sediment load, coarse sand and gravel
Build up on channel floor

9. Oxbow Lake

10. Stream Deposition Types of stream deposition
Deltas-fan shaped mass of rock material deposited at mouth of stream
Waves, tides, offshore depths, sediment load
Alluvial fan-fan shaped mass of rock material deposited by stream when slope of land decreases sharply
Form when streams flow from mts to flat land

11. Floodplains What is a floodplain? Advantage Disadvantage
Area along river that forms from sediments deposited when river overflows its banks
Natural levees
Advantage
Convenient access to river for shipping, fishing, transportation
Rich soils, good for farming
Disadvantage
Swampy areas
Flooding homes

12. Flood Control Name some things that could prevent flooding
Forest and soil conservation measures
Artificial structures
Dams
Artificial levees, artificial lakes
Permanent overflow channels or floodways

13. Life Cycle of Lake
Most lakes located in high latitudes and mountainous areas
What are some sources of lakes?
Springs, rivers, runoff
Most comes from precipitation and melting of ice and snow
Short in geologic terms. Why?

14. Properties of Aquifers
Groundwater-water beneath the Earth’s surface, fills fractures and cavities in rock
What is an aquifer?
Body of rock or sediment in which large amounts of water can flow and be stored
Factors that affect flow of water-porosity and permeability
Porosity
Percentage of total volume of a rock or sediment that consists of open spaces
Sorting, particle packing and grain shape
Permeability
Ability of rock or sediment to let fluids pass through its open spaces or pores
Size and sorting, open spaces must be connected

15. Zones of Aquifers
Zone of saturation-layer of aquifer in which the pore space is completely filled w/ water
Zone of aeration-lies between the water table and Earth’s surface
Top layer holds soil moisture
Bottom region above water table is capillary fringe
Dry area in between fills w//water when it rains
Water table-upper surface of underground water
Recharge zone- anywhere that water from the surface can travel through permeable rock to reach an aquifer

16. Wells and Springs
Well-hole that is dug to below level of water table and through which groundwater is brought to Earth’s surface
Cone of depression- water table lowers below the well, it goes dry
Spring-Natural flow of groundwater to Earth’s surface in places where ground surface dips below water table
Artesian formation-sloping layer of permeable rock sandwiched between 2 layers of impermeable rock and exposed at surface
Source of water for some springs
Artesian well-well through which water flows freely w/out being pumped

17. Hot Springs and Geysers
Hot springs-groundwater is heated when it passes through rock that has been heated by magma
At least 37 deg C and rises to surface before cooling
Geysers-hot springs that periodically erupt from surface pools or through small vents
Narrow vent that connects 1 or more underground chambers w/ surface

18. Results of Weathering by Groundwater
Caverns-large cave that may consist of many smaller connecting chambers
Carbonic acid slowly dissolves the limestone and enlarges cracks in the rock
Stalactites-suspended cone-shaped deposit of calcite on ceiling of cavern
Stalagmites-upward pointing cone of calcite on floor of cavern
Sinkholes-circular depression that forms at the surface when rock dissolves, when sediment is removed, or when caves or mines collapse
Natural bridges-uncollapsed rock between each pair of sinkholes forms an arch of rock