1. Sculpting the Earth’s Surface Running Water AndGroundwater

2. The Hydrologic Cycle  Water Basics –Sea water 97.2% –Fresh Water 2.8%  Polar ice & glaciers 2.15%  Groundwater 0.62%  Lakes and Rivers 0.01%

3. The Hydrologic Cycle  The Three Fates of Precipitation –Infiltration  The movement of water into rocks or soil through cracks and pore spaces –Runoff  Water that flows over the land –Transpiration/Evapotranspiration  the release of water vapor to the atmosphere by plants

5. The Hydrologic Cycle  Infiltration capacity of the soil is controlled by: –Intensity and duration of rainfall –Soil saturation –Soil texture –Slope of the land –Nature of the vegetative cover

6. Main Sources of Water  Surface Water –Lakes, rivers, reservoirs  Ground Water –In the Earth, flows through fractures and pores

7. Surface 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)

8. Surface Water  Most important agent sculpturing Earth’s land surface –Begins as sheetflow –Sheetflow develops into tiny channels called rills –Eventually flows into streams, rivers & lakes

9. Profile of a Stream

10. Surface Water - Streams  Upstream –Higher velocity –Smaller discharge –Smaller channel  Downstream –Lower velocity –Greater discharge –Larger channel Upstream-downstream characteristics

11. Local and Ultimate Base Level

12. Surface Water - Streams  Erosion = transportation of sediments –AKA load  Dissolved load  Suspended load  Bed load

13. Surface Water - Streams  Erosion = transportation of sediments –Load is related to a stream's  Competence - maximum particle size  Capacity - maximum load  Capacity is related to discharge

14. Surface Water - Streams DepositionDeposition Caused by a decrease in velocityCaused by a decrease in velocity Competence is reducedCompetence is reduced Sediment begins to drop outSediment begins to drop out

15. Surface Water - Streams  Stream sediments –Known as alluvium –Well-sorted deposits

16. Surface Water - Streams  Features produced by deposition –Deltas –Natural levees –Back swamps –Yazoo tributaries

17. Surface Water – Streams  River Erosion –Vertical erosion  Upstream portion  Produces deep, V-shaped valleys with rapids –Lateral erosion  Downstream portion  produces broad valleys, flood plains, and meandering streams

18. Meanders

19. Oxbow Lakes

21. Surface Water – Stream Valleys  Drainage basins and patterns A divide separates drainage basin Types of drainage patterns

22. Surface Water – Stream Valleys  Flood Plains –Periodic floods deposit rich soils  Agricultural production on floods plains is followed by urbanization –Natural levees  Forms as floods deposit coarse detritus near the river  Naturally constraint the river except in the larger floods

23. Surface Water – Flooding  Floods and flood control –Floods are the most common geologic hazard –Causes of floods  Weather  Human interference with the stream system

24. What is Groundwater?  Water found in the pores and fractures of soil and bedrock  Largest reservoir of fresh water  Tends to be less polluted than surface water

25. What is Groundwater?  An important erosional agent –Groundwater is often mildly acidic –Contains weak carbonic acid –Forms caverns at or just below the zone of saturation –Karst topography on the surface

26. Groundwater Terminology

27.  How does water get from the stream to the water table? –Gaining streams – gain water from the inflow of groundwater through the streambed –Losing streams – lose water to the groundwater system by outflow through the streambed –Interactions - A combination of the first two

28. Groundwater Movement & Storage  Factors –Porosity  Percentage of total volume of rock or sediment that consists of pore spaces –Determines how much groundwater can be stored –Variations can be considerable over short distances –Permeability  The ability of a material to transmit a fluid

29. Groundwater Movement & Storage  Factors (continued) –Specific retention  The portion whish is retained as a film on particles, rock surfaces, and pore spaces –Specific yield  The portion which will drain under gravity –In general,  Porosity = Specific retention + Specific yield

31. Groundwater Movement & Storage  Factors (continued) –Aquifer - A zone of Earth material capable of supplying groundwater at a useful rate from a well

32. Groundwater Movement & Storage  Factors (continued) –Aquitard - A zone of Earth material that holds water but cannot transmit it fast enough to pump from a well

33. Getting Groundwater Out of the Ground  Extraction Methods –“Natural” Methods  Springs, Hot Springs, & Geysers

34. Getting Groundwater Out of the Ground  Extraction Methods (continued) –Man-made Methods  Wells

35. Getting Groundwater Out of the Ground  Artesian well/spring –A situation in which groundwater under pressure rises above the level of the aquifer –Types of artesian wells  Nonflowing – pressure surface is below ground level  Flowing – pressure surface is above the ground –Not all artesian systems are wells, artesian spring also exist

37. Getting Groundwater Out of the Ground  Problems with groundwater removal –Non-renewable resource –Subsidence –Contamination

38. Sources of Contamination  Natural Sources –Biologic activity / organisms  Bacteria and viruses –Naturally occurring elements  Uranium, radium, arsenic, and fluoride –Often naturally occurring in rock formations

39. Geologic Work of Groundwater  Groundwater dissolves rock –Groundwater is often mildly acidic –Contains weak carbonic acid  Forms when rainwater dissolves carbon dioxide from the air and from decaying plants  Carbonic acid reacts with calcite in limestone to form calcium bicarbonate, a soluble material –Forms caverns at or just below the zone of saturation

40. Geologic Work of Groundwater  Caverns –Composed of dripstone (travertine)  Calcite deposited as dripping water evaporates –Collectively, they are called speleothems –Includes:  Stalactites (hanging from the ceiling)  Stalagmites (form on the floor of a cavern)

41. Geologic Work of Groundwater  Karst topography –Landscapes that to a large extent have been shaped by the dissolving power of groundwater –Some common features include  Irregular terrain  Sinkhole or sinks (formed by groundwater slowly dissolving the bedrock often accompanied by collapse)  Striking lack of surface drainage (streams)

42. Karst Topography

44. ~ End ~