Chapter 11 – WATER ON THE GROUND

1. Chapter 11 – WATER ON THE GROUND

2. The Hydrologic Cycle Hydrologic cycle How water moves through 4 spheres Evaporation Change from liquid to vapor Transpiration Water from plants passes into atmosphere Condensation Change from vapor to liquid

3. The Hydrologic Cycle Water in Earth system Deposition Changes from vapor to solid Precipitation Condensed water falls back to surface (rain, snow, hail) Surface runoff Excess precipitation drains over land or via stream channels Infiltration Water soaks into ground via small soil openings

4. The Hydrologic Cycle • Water in Earth system • 97.5% of water in hydrologic cycle found in oceans • 75% of freshwater is found in glaciers/ice caps • 98.5% unfrozen freshwater is found underground

5. How Water Affects Land Streams and stream flow Overland flow vs. stream flow Runoff Stream Body of water that flows downslope along clearly defined natural passageway

6. Streams and stream flows Gradient Steepness of stream channel Change in elevation divided by distance Discharge Amount of water passing by point on channel’s bank during unit of time Width x Depth x Velocity Bed texture Material that makes up streambed How Water Affects Land

7. Streams and stream flows Load Sediment carried or by stream Bedload Saltation vs. Traction Suspended load Dissolved load Capacity vs. Competence Base level Lowest elevation stream can erode its channel Ultimate vs. local base level How Water Affects Land

8. Streams and stream flows Niagara Falls Knick point = rapids & waterfalls How Water Affects Land

9. How Water Affects Land Streams and stream flow Channel Clearly defined passageway where stream flows Straight Rare Braided Interwoven channels Meandering Curving channel Cut bank Point bar Oxbow lake

10. How Water Affects Land Streams and stream flow Meandering streams Cut bank (outside) Point bar (inside) Early vs. Mature vs. Old Age

11. How Water Affects Land Streams and stream flow Stream drainage patterns Controlled by topography Dendritic Radial Controlled by underlying geology Centripetal Rectangular Trellis

12. Stream deposit Floodplain Flat valley floor adjacent to stream channel Inundated when stream overflows Alluvium Stream sediment Natural levee Alluvial fan How Water Affects Land

13. Stream deposit Delta Sediment build-up where stream flows into standing water Triangular shape How Water Affects Land

14. Drainage basin Total area from which water flows into stream Divide Topographic high separating adjacent drainage basins How Water Affects Land

15. Tributaries Smaller channels that feed into larger streams More numerous around headwaters Distributaries Smaller channels that distribute water near mouth of stream Form due to excess sediment in main stream channel How Water Affects Land

16. Lakes Standing bodies of open water surrounded by land Ephemeral lakes How Water Affects Land

17. Water as a Hazard & a Resource Floods Event in which body of water overflows its banks Storm runoff Storm surge

18. Hydrographs of stream discharge Crest Hydrologic station Water as a Hazard & a Resource

19. Flooding and urban development Impermeable surfaces Water as a Hazard & a Resource

20. Water as a Hazard & a Resource Flood prediction and prevention Flood frequency curve Recurrence interval Channelization Artificial levees Flood control dams Diversion channels Floodplain zoning

21. Surface water resources Reliable water supply critical to human survival & health, agriculture & other economic activities Nearly 250 million people are water-scarce Water as a Hazard & a Resource