Earth Science, 13e

1. Earth Science, 13e Tarbuck & Lutgens

2. Running Water and GroundwaterEarth Science, 13eChapter 5 Stanley C. Hatfield Southwestern Illinois College

3. Li River, China’s Guilin DistrictNote karst topography, in which groundwater has dissolved large volumes of limestone (more later).

4. 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

5. The hydrologic cycle

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

7. Drainage basins and divides

8. Drainage basins and divides exist for all streams, regardless of size.

9. River systems are divided into 3 zones.

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

11. Gradient (slope) • Parts of lower Mississippi: 10 cm/km • Mountain streams: 40 m/km • Steeper gradient has more energy,  more velocity

12. Discharge • Measured in m3 or ft3 per second • Changes over time due to amount of precipitation in drainage basin

13. Measuring stream velocity 1 kph – 30 kph Straight – highest at center Curved– highest at outer bank

14. 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

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

16. Longitudinal profile of a stream

17. Stream Properties – Headwaters to Mouth

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

19. 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

20. 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

21. 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 back swamps or yazoo tributaries

22. Formation of natural levees by repeated flooding

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

24. Adjustment of base level to changing conditions

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

26. 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

27. V-shaped valley of the Yellowstone River

28. Continued erosion and deposition widens the valley

29. Characteristics of a wide stream valley

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

31. A meander loop on the Colorado River

32. Running water • Drainage patterns • Networks of streams that from distinctive patterns • Types of drainage patterns • Dendritic • Radial • Rectangular • Trellis

33. Drainage patterns

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

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

36. Satellite view of the Missouri River flowing into the Mississippi River near St. Louis

37. Same satellite view during flooding in 1993

38. 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 stream flow

39. 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

40. 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

41. Features associated with subsurface water

42. Water beneath the surface (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 • Aquitard – an impermeable layer of material • Aquifer – a permeable layer of material

43. Water beneath the surface (groundwater) • Features associated with groundwater • Springs • Hot springs • Water is 6–9° C (10–15° F) 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

44. Old Faithful geyser in Yellowstone National Park

45. 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

46. Formation of a cone of depression in the water table

47. Artesian systems

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

49. 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

50. 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)