1. Groundwater Geol 1110 Newell guest lecture 3/28/16

2. The Hydrosphere

3. The water cycle

4. Water Cycle Precipitation Precipitation Infiltration Infiltration Runoff Runoff Evaporation Evaporation Transpiration Transpiration Evapotranspiration Evapotranspiration

5. Groundwater: Outline 1. What is groundwater? Terms. 2. Darcy’s Law and groundwater movement 3. Groundwater extraction and contamination problems

7. Surface water – groundwater connection

8. Porosity – percentage of rock or sediment volume that consists of void space (pores) 30 % 15% Porosity isolated – pores not connected

9. Permeability – rocks ability to transmit fluid Depends on - grain size/arrangement - interconnectedness of pore spaces High permeability: gravels, sands, limestones with dissolution channels, fractured rocks Low permeability: clays, unfractured metamorphic and igneous rocks, limestones without dissolution Possible to have high porosity and low permeability: Example: Clays

10. Aquifer : geologic unit that stores and is capable of transmitting significant water; moderate to high permeability (both permeable and porous) Aquaclude: rock formations that slow but do not prevent flow of water to or from an adjacent aquifer (low permeability)

11. Unconfined Aquifer At shallow depth Water table is the top boundary Recharged by precipitation infiltrating Confined Aquifer Deeper Confined on top by a less permeable layer Recharged slowly

12. Perched water table Above the main water table In unsaturated zones Due to lenses of less permeable rocks (e.g., shales or clays)

13. Springs

14. Hot Springs

15. Groundwater: Outline 1. What is groundwater? Terms. 2. Darcy’s Law and groundwater movement 3. Groundwater extraction and contamination problems

16. Groundwater movement Hydraulic gradient Hydraulic gradient – the groundwater elevation (or pressure) difference over a given distance – groundwater moves from high elevation (high pressure) to low elevation (low pressure)

17. Groundwater Movement High P to low P results in curved flow-paths in subsurface High P to low P results in curved flow-paths in subsurface

18. Groundwater Movement

19. Quantifying Flow: Darcy’s Law Henri Darcy – mid 1800’s Expression describing the discharge of groundwater flowing through an aquifer Q = k*A*(h2-h1)/d hydraulic conductivity (k)* cross sectional area (A) * hydraulic graient

20. Wells

21. Flowing Well Pressure surface elevation above ground surface Pressure surface elevation above ground surface

22. Groundwater: Outline 1. What is groundwater? Terms. 2. Darcy’s Law and groundwater movement 3. Groundwater extraction and contamination problems

23. Environmental Aspects of Groundwater Groundwater depletion Groundwater depletion Subsidence due to Groundwater (and other fluid) extraction Subsidence due to Groundwater (and other fluid) extraction Salt Water Intrusion Salt Water Intrusion Groundwater contamination Groundwater contamination

24. Groundwater extraction and subsidence

25. San Joaquin Valley USGS, 1984

26. Groundwater decline and subsidence, Tucson, AZ

27. If pumping > recharge Subsidence due to groundwater withdrawal in Pahrump Valley, Nevada

28. Earth Fissures – Cedar City, UT In addition to groundwater decline and damage to surface structures…subside nce can result in pathways for contaminated water to aquifers

29. Extraction of Hydrocarbons Signal Hill, Long Beach, CA: 1930’s (those are oil well derricks)

30. Subsidence – Oil Extraction Oil extraction caused subsidence Water flooding started in 50’s

31. Salt Water Intrusion

32. Contamination

33. Other Groundwater Features – Caverns and Karst Topography

34. Karst Topography and Sinkholes

35. Flow Systems