1. Running Water and Groundwater
Earth Science, 1
Running Water and Groundwater

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. The hydrologic cycle
Figure 5.3

4. Sources of Earth’s water
Figure 5.2

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

6. Drainage basins and drainage divides
Figure 5.4

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

8. Longitudinal profile of a stream
Figure 5.7

9. Running water The work of streams Erosion Transportation
Transported material is called the stream’s load
Dissolved load
Suspended load
Bed load

10. 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

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

12. 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 yazoo tributaries

13. Formation of natural levees by repeated flooding
Figure 5.21

14. 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

15. Adjustment of base level to changing conditions
Figure 5.15

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

17. Running water Stream valleys Characteristics of narrow valleys
Features often include
Rapids
Waterfalls
Characteristics of wide valleys
Stream is near base level
Downward erosion is less dominant
Stream energy is directed from side to side

18. A narrow, V-shaped valley
Figure 5.17 A

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

20. A wide stream valley is characterized by meandering on a well-developed floodplain
Figure 5.17 C

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

22. Erosion and deposition along a meandering stream
Figure 5.10

23. A meander loop on the Colorado River
Figure 5.18

24. Formation of a cutoff and oxbow lake
Figure 5.11

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

26. Drainage patterns
Figure 5.22

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

28. Satellite view of the Missouri River flowing into the Mississippi River near St. Louis
Figure 5.23 top

29. Same satellite view during flooding in 1993
Figure 5.23 bottom

30. Water beneath the surface (groundwater)
Largest freshwater reservoir for humans
Geological roles
As an erosional agent, dissolving by groundwater produces
Sinkholes
Caverns
An equalizer of streamflow

31. Water beneath the surface (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

32. Water beneath the surface (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

33. Features associated with subsurface water
Figure 5.26

34. Water beneath the surface (groundwater)
Distribution and movement of groundwater
Permeability
Ability to transmit water through connected pore spaces
Aquitard – an impermeable layer of material
Aquifer – a permeable layer of material

35. Artesian systems
Figure 5.32

36. 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

37. Water beneath the surface (groundwater)
Geologic work of groundwater
Caverns
Features found within caverns
Form in the zone of aeration
Composed of dripstone
Calcite deposited as dripping water evaporates
Common features include stalactites (hanging from the ceiling) and stalagmites (growing upward from the floor)

38. Cave Features in Lehman Caves, Great Basin National Park, and Carlsbad Caverns National Park
Figure 5.38

39. Karst topography
Formed by dissolving rock at, or near, Earth’s surface
Sinkholes – surface depressions
Sinkholes form by dissolving bedrock and cavern collapse
Caves and caverns
Area lacks good surface drainage

40. Features of karst topography
Figure 5.39 C