1. Running Water and Groundwater Chapter 5
Earth Science
Running Water and Groundwater Chapter 5

2. Earth as a system: the hydrologic cycle
Illustrates the circulation of Earth’s water supply
Processes involved in the cycle
Precipitation
Evaporation
Infiltration
Runoff
Transpiration

3. Sources of Earth’s water
Figure 5.2

4. Running Water Surface water is crucial for humans.
Running water is surface water – rivers, lakes, etc.
Surface water is crucial for humans.
Drinking water
Agricultural irrigation
Fertile soils
Transportation
Waste disposal

5. Running water Drainage basin
Land area that contributes water to a river system
A divide separates drainage basins

6. Running water Streamflow Factors that determine velocity
Gradient, or slope
Channel characteristics
Shape
Size
Roughness
Discharge – volume of water flowing in the stream (generally expressed as cubic feet per second)

7. Running Water
Gradient (slope) – Vertical drop over a unit horizontal distance.
“Rise over run”
Example: Fall of 91 feet over 22 miles
= 91 feet = 91 feet
22 x 5280 feet feet
= a gradient of

8. Running Water Channel characteristics - shape, size, roughness.
Higher velocities with…
Uniform channel shape.
Smallest channel perimeter.
Smooth channels.

9. Running water Upstream-downstream changes Profile
Cross-sectional view of a stream
From head (source) to mouth
Profile is a smooth curve
Gradient decreases from the head to the mouth
Factors that increase downstream
Velocity
Discharge

10. Running Water
Discharge – The volume of water moving past a given point per unit time (cfs).
Measured by
Cross-sectional area
Flow velocity
Discharge changes due
to seasonal variation in
precipitation and runoff.

11. Running water Upstream-downstream changes Profile
Factors that increase downstream
Channel size
Discharge
Factors that decrease downstream
Gradient, or slope
Channel roughness

12. Running water The work of streams Erosion Transportation
Transported material
The stream’s load
Dissolved load
Suspended load
Bed load

13. Running water The work of streams Transportation
Load is related to a stream’s
Competence – maximum particle size
Capacity – maximum load
Capacity is related to discharge

14. Running water The work of streams Transportation Deposition
Caused by a decrease in velocity
Competence is reduced
Sediment begins to drop out
Stream sediments
Known as alluvium
Well-sorted deposits

15. Running water The work of streams Transportation
Features produced by deposition
Deltas – exist in ocean or lakes
Natural levees – Form parallel to the stream channel
Area behind the levees may contain backswamps or tributaries

16. Formation of natural levees by repeated flooding
Figure 5.21

17. Formation of a Delta

18. Running water Base level Lowest point to which a stream can erode
Two general types
Ultimate – sea level
Temporary, or local
Changing causes readjustment of the stream – deposition or erosion

19. Adjustment of base level to changing conditions
Figure 5.15

20. Base Level
W. W. Norton

21. Raised Base Level
W. W. Norton

22. Lowered Base Level
W. W. Norton

23. Stream Terraces Remnants of a former floodplain.
Rivers adjust to a relative drop in base level by downcutting.
Many US streams
preserve terraces
formed during
glacial maximum.

24. Running water Stream valleys Characteristics of narrow valleys
Valley sides are shaped by
Weathering
Overland flow
Mass wasting
Characteristics of narrow valleys
V-shaped
Downcutting toward base level

25. A narrow, V-shaped valley
Characteristics of narrow valleys
Rapids
Waterfalls
Figure 5.17 A

26. Continued erosion and deposition widens the valley
Figure 5.17 B

27. A wide stream valley is characterized by meandering on a well-developed floodplain
Stream is near base level
Downward erosion is less dominant
Stream energy is directed from side to side
Figure 5.17 C

28. Running water Stream valleys Characteristics of wide valleys
Floodplain
Features often include
Meanders
Cutoffs
Oxbow lakes

29. Erosion and deposition along a meandering stream

30. A meander loop on the Colorado River
Figure 5.18

31. Running water Drainage patterns
Networks of streams that form distinctive patterns
Types of drainage patterns
Dendritic
Radial
Rectangular
Trellis

32. Drainage patterns
Figure 5.22

33. Running water Floods and flood control
Floods are the most common geologic hazard
Causes of floods
Weather
Human interference with the stream system

34. Running water Floods and flood control Engineering efforts
Artificial levees
Flood-control dams
Channelization
Nonstructural approach through sound floodplain management

35. What is Ground Water? Water that infiltrates the surface.
A component of the hydrologic cycle.

36. Groundwater Distribution and movement of groundwater
Distribution of groundwater
Belt of soil moisture
Zone of aeration
Unsaturated zone
Pore spaces in the material are filled mainly with air

37. Groundwater Largest freshwater reservoir for humans Geological roles
As an erosional agent, dissolving by groundwater produces
Sinkholes
Caverns
An equalizer of streamflow
Gaining
Losing

38. Groundwater Distribution and movement of groundwater
Distribution of groundwater
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

39. Groundwater Distribution and movement of groundwater
Distribution of groundwater
Porosity
Percentage of pore spaces
Determines storage of groundwater
Permeability
Ability to transmit water through connected pore spaces

40. Groundwater Permeability Aquitard – an impermeable layer of material
Aquifer – a permeable layer of material

41. Water beneath the surface (groundwater)
Features associated with groundwater
Springs
Hot springs
Water is 6–9°C warmer than the mean air temperature of the locality
Heated by cooling of igneous rock
Geysers
Intermittent hot springs
Water turns to steam and erupts

42. Old Faithful geyser in Yellowstone National Park
Figure 5.29

43. Water beneath the surface (groundwater)
Features associated with groundwater
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

44. Formation of a cone of depression in the water table
Figure 5.31

45. Artesian systems
Figure 5.32

46. Water beneath the surface (groundwater)
Environmental problems associated with groundwater
Treating it as a nonrenewable resource
Land subsidence caused by its withdrawal
Contamination

47. Water beneath the surface (groundwater)
Geologic work of groundwater
Groundwater is often mildly acidic
Contains weak carbonic acid
Dissolves calcite in limestone
Caverns
Formed by dissolving rock beneath Earth’s surface
Formed in the zone of saturation

48. Caverns
Most caverns are created by limestone dissolution at or just below the water table.

50. Cavern Features
Composed of dripstone (travertine) calcite deposited as dripping water evaporates.
Collectively, they are called speleothems.
Stalactites (ceiling) and stalagmites (floor).