1. GROUNDWATER

2. GROUNDWATER
Groundwater is subsurface water that fully saturates pore spaces of bedrock.
The rate of movement of groundwater is gravity driven, varying between 0.6 inches per day (in sandstones) to several inches per year (in granites)
The source of groundwater is rain and melt water infiltrating and percolating through fractures/pores in soil and bedrock.
Groundwater can range in age from recent to ancient
Some groundwater is thousands of years old

3. GROUNDWATER MOVEMENT AND SOURCES

4. How much groundwater is there?
Estimates of up to 4 million km3 for groundwater
Surface water – 160,000 km3
Extraction of groundwater measured in ‘acre-feet’ (the amount of water that covers one acre of land, one foot deep)
California extracts million acre-feet (maf) per year
The Ogallala Aquifer in central United States produces 110 maf per year (317 billion gallons of water per year)

5. GROUNDWATER USAGE

6. WHO USES GROUNDWATER?
Almost all humans will use groundwater – either directly pumping it into their own cistern or through major metropolitan water transportation systems.

7. Where is Groundwater Stored?
Groundwater is stored in rock bodies called aquifers.
A good aquifer provides both storage and transmittal of groundwater
Characteristics of aquifers:
Porosity
The number and size of pore spaces, fractures, joints, in bedrock
Provides Storage for groundwater
Permeability
The connectedness of pore spaces, fractures, joints in bedrock
Provides Transmittal for groundwater

8. What Bedrock makes a Good Aquifer?
Any bedrock with both good porosity and good permeability
Unconsolidated sedimentary rock
The San Fernando Valley floor, for example
Sandstones
Fractured igneous rocks (basalt) or jointed limestone

9. POROSITY and PERMEABILITY

10. What if bedrock only has good porosity or only permeability?
Bedrock with good porosity but poor permeability are call aquicludes or aquitards
These types of bedrock may store water, but cannot transmit it.
Unfractured igneous rock
Metamorphic rock
Bedrock with high amounts of clay
Shales, claystones, mudstones, siltstones

11. What Is An Unconfined Aquifer?
An unconfined aquifer has little to no overlying sedimentary layers.
There is no confining layer of clay or other impermeable sedimentary layers
The largest unconfined aquifer in the United States is the Ogallala Aquifer which extends from Texas through Oklahoma, Kansas, Nebraska and North Dakota, plus parts of Wyoming, Colorado and New Mexico.

12. UNCONFINED AQUIFER

13. OGALLALA AQUIFER

14. What is a Confined Aquifer?
Confined Aquifers are usually sandwiched between two non-permeable layers.
The confining layers provide pressure on the aquifer, allowing the groundwater to rise to the surface under its own energy – no pumping required: Artesian Wells
Largest Artesian well in United States is the Big Spring in Missouri
Produces million gallons of water/day

15. CONFINED AQUIFER

16. ARTESIAN WELLS

17. Decorative Waterwheel placed over original Artesian Wells in SFV (Sportsman’s Lodge)
Historic springs exist many places along Ventura Boulevard.
This is why the Spaniards established California's first highway, El Camino Real, along this long used pathway.
Photo in Archives of The Museum of the San Fernando Valley Photo by Gerald Fecht

18. Big Spring, Missouri

19. AQUIFER ZONES The Vadose Zone: Zone of Aeration
This is the upper zone of an aquifer
Between each pore space and within each joint or fracture, both air and water can be stored
The Phreatic Zone: Zone of Saturation
This is the lower zone of an aquifer
Between each pore space and within each joint or fracture, only water is stored.
Represents the zone within the aquifer designated as ‘true groundwater’
Water Table
This is the upper limit of the Phreatic Zone within an aquifer
This is the boundary between the Vadose and Phreatic Zone
Depth of water table determined by wells – they will fill to the level of the water table
Lakes, springs, streams are ‘surface expressions’ of the water table

20. VADOSE AND PHREATIC ZONES

21. DIAGRAM OF AN AQUIFER

23. California
Statewide Aquifers

24. LOS ANGELES GROUNDWATER BASINS

25. San Fernando Valley/San Gabriel Valley Groundwater

26. San Francisco Area Groundwater

27. Ventura County Groundwater

28. GROUNDWATER MANAGEMENT CHALLENGES
Laws
Water Table Depletion
Ground Subsidence
Contamination

29. Laws on Groundwater Usage
Only two states of USA have no laws regarding the use of groundwater: Texas and California
The only requirement for the water to be of “beneficial use”
Recent attempts in California’s Legislature to regulate groundwater have been met with strong resistance from many groups: farmers, municipalities included
Most recent ‘water bill’ passed has some restrictions, but groundwater still not regulated

30. GROUNDWATER WITHDRAWALS

31. WATER TABLE DEPLETION
Water table depletion can be the result of natural droughts as well as human activity
Over-pumping wells can result in temporary and permanent lowering of the water table

32. NORMAL CONDITIONS FOR WATER TABLE

33. CONDITIONS FOR WATER TABLE DEPLETION

34. DRAWDOWN EFFECT AND CONE OF DEPRESSION WITH RECOVERY

35. DRAWDOWN – NO RECOVERY
lowered

36. GROUND SUBSIDENCE
Over pumping groundwater can result in the sinking of overlying layers.
Groundwater acts to ‘buoy’ up overlying sedimentary layers – remove the water and all the pore spaces, fractures, and joints can collapse

37. SUBSIDENCE
Picture from the San Joaquin Valley showing the amount of land subsidence since 1925 due to aggressive groundwater pumping

38. SUBSIDENCE IN CALIFORNIA

39. SUBSIDENCE IN CALIFORNIA

41. SUBSIDENCE IN TEXAS

42. Subsidence in Venice, Italy
Parts of Venice have sunk more than 23 cm (approximately 9.2 inches) causing concern

43. CONTAMINATION Groundwater contamination comes in several ways
Landfills and septic tanks
Agriculture
Industrial
Urban
Toxic wastes
Salt water intrusion

44. SOURCES OF CONTAMINATION

45. LANDFILL CONTAMINATION

46. Hazardous Wastes in Landfill

47. GAS TANK CONTAMINATION

48. Septic Tank Contamination
Groundwater

49. AGRICULTURE CONTAMINATION
Pesticides
Insecticides
Herbicides
Fertilizers
Animal Waste

50. AGRICULTURAL CONTAMINATION

51. INDUSTRIAL CONTAMINATION

52. San Fernando Valley/San Gabriel Valley Groundwater contamination
TCE – Trichloroethylene – a degreaser for cleaning metal

53. San Francisco Area Groundwater Basin Contamination
Arsenic used in gold processing; many northern California rivers are contaminated; even rivers used for municipal water supply

54. SALT WATER INTRUSION