1 / 19

Groundwater

Groundwater. Importance of Groundwater. Supplies 40% of U.S. public drinking water. Almost all rural residents Agriculture can be dependent on groundwater for irrigation. Shapes the land surface (e.g. sinkholes, mudslides). Fig. 17.3. Occurrence of Groundwater.

krystal
Download Presentation

Groundwater

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Groundwater

  2. Importance of Groundwater • Supplies 40% of U.S. public drinking water. • Almost all rural residents • Agriculture can be dependent on groundwater for irrigation. • Shapes the land surface (e.g. sinkholes, mudslides). Fig. 17.3

  3. Occurrence of Groundwater • Found everywhere below the surface, in all rock/sediment types. • Stored in and flows through pores spaces. Fig. 17.5 Fig. 17.5

  4. Occurrence of Groundwater • The watertable is the boundary between the unsaturated and saturated zones. Unsat. – pores filled with air and water Sat. – pores filled with only water Fig. 17.6

  5. Occurrence of Groundwater • Most surface water bodies (i.e. streams, lakes) occur where water table insects the land surface. Quarries/mines must be dewatered while operating. Fig. 17.4

  6. Movement of Groundwater • Precipitation infiltrates, flows through unsat. zone to water table. • Groundwater flows from higher to lower elevations (velocity – cm to m per day). Fig. 17.17

  7. The Water Table and Groundwater Flow

  8. Water Table Fluctuations • The water table is continually rising and falling. • rises when precipitation infiltrates • falls as water discharges to streams Fig. 17.13

  9. The water table also drops when water is pumped from wells. Water Table Fluctuations • Shallow wells go dry during dry periods. • water table drops below bottom of the well.

  10. Effects of Pumping Groundwater

  11. Effects of Pumping Groundwater • Groundwater can be pumped out faster than it recharges. • water table drops, aquifer yields less water Fig. 17.13

  12. Effects of Pumping Groundwater Fig. 17.14 • High Plains Aquifer: • Low recharge rate • High pumping rate (agriculture) • Max. water table drop is >50 m (160 ft.) • Half of aquifer has been drained

  13. Effects of Pumping Groundwater Fig. 17.33 • Land subsidence: • Water in pores supports grains, resists compaction. • Dewatering pores allows compaction. • Compaction lowers land surface elevation (subsidence).

  14. Effects of Pumping Groundwater • Land subsidence fissures in Arizona caused by groundwater pumping. Fig. 17.15

  15. Effects of Pumping Groundwater Fig. 17.33 • Salt water intrusion: • Near coasts, groundwater at depth is salty. • Pumping fresh water may eventually draw salt water into a well.

  16. Groundwater and Landscapes • Limestone is easily dissolved by groundwater. • Sinkholes – where surface rocks collapse into the void left after limestone dissolves. Fig. 17.36

  17. Groundwater and Landscapes • Groundwater flows along joints, dissolves limestone. • Eventually, caves form and sinkholes form when cave roof collapses. Fig. 17.36

  18. Groundwater and Landscapes • Sinkhole damage in Florida.

  19. Groundwater and Landscapes • Areas in the U.S. where rocks are easily dissolved. Fig. 17.36

More Related