1. Groundwater
P = Q + ET + G + DS

2. What is an Aquifer? Rocks and sediments have pores (spaces)
Rock (limestone, granite, sandstone etc.)
Sand and gravel
When pores are full of water that media is saturated
Contiguous areas of saturated media form an aquifer
Aquifers can be layered
Confined vs. Unconfined
Aquifers have the capacity to transmit water through interconnected pores

3. Floridan Aquifer Extent

4. High Plains Aquifer (Ogalalla)

5. Confinement

6. Cross-Section– Floridan Aquifer

7. Transmissivity How much water can be moved horizontally
Function of thickness and Ksat
Good measure of well productivity
Floridan is the most transmissive aquifer in the world

9. Loss of Potential

11. Artesian Springs
Where a confining layer exists, there may be a pressure potential in the aquifer HIGHER than the gravity potential of the surface.
When tapped, water flows upwards

12. Potentiometric Surface
Elevation of “free water surface”
Where this surface and the ground intersect (and there’s no confinement) water seeps

15. Relevant Questions Where is the water going?
Potentiometric (piezometric) surface
How much water is moving? How quickly?
Potentiometric surface and Darcys Law
What level of natural assimilation is occuring?
Water quality modeling

16. Gainesville’s Well Field
Geology
Land use
Conservation Easement
Also Lake City
Jasper

17. Murphree Wellfield Cone of Depression
1988 (Observed)
2010 (Predicted)

18. How to make a sinkhole
Pray for lots of Rain
Suck a lot of water

19. Freeze Protection
To protect strawberry yield during a January freeze in 2010, ~ 2 billion gallons per day of water pumped over a 5 day period. Voila.

20. Subsidence
Invasion
Fire
Degraded wildlife habitat

21. P=Q+ET+G+ΔS Qgroundwater= K A ΔH/L
Soil water movement across a watershed boundary.
Qgroundwater= K A ΔH/L
Darcy’s Law
Q is water crossing the defined area of the boundary in m3/day
Darcy’s law can calculate vertical leakage through a clay layer AND lateral flow through a seepage face.

22. Q= K A ΔH/L
K is hydraulic conductivity, or the capacity of the media to transmit water
Most meaningful as saturated hydraulic conductivity Ksat (m/day). Why?

23. Measuring Ksat Constant Head Method
Constant depth of water (~50mm) on top of a saturated soil column with known dimensions (diameter, length)
Outflow volume collected over a period of time (e.g., 5 hrs)
Darcy’s Law to solve for Ksat

24. Measuring Ksat Hvorslev Method Field measurement in screened wells Le
Log scale
K only determined .1 1 .2 .3 .4 .5 .6 .7 .8
H/Ho
casing
H/Ho=.37 Le
Le/R must be >8
Gravel pack
Screen
t37 2 4 6 8 10
minutes R
high K material
Linear scale

25. Approximate Ksat and Uses
Ksat (cm/h)
Comments
>50
Beach sand/Golf Course Greens 5
Very sandy soils, cannot filter pollutants
0.5
Suitable for most agricultural, recreational, and urban uses
0.05
Clayey, Too slow for most uses
<0.005
Extremely slow; good if compacted material is needed

26. ΔH is the difference in H between two points
Water flows from high pressure to low pressure (could be “up”)
H = level of water in an open well above some datum
HA = ? HB = ? ΔH = ?
Flow Direction?!?

27. D?
ΔH?
Direction? 10 9 8 7 6 5 4 3 2 1

28. ΔH AD? Dir?
ΔH BF? Dir?
ΔH AF? Dir?
ΔH/L BF?

29. Vertical leakage problem
Ksat=0.001m/d
Watershed=100 ha 1 2 3 4 5 6
Datum
Q=K A ΔH/L K? A?
ΔH? L?

30. Q = K * A * ΔH/L Q = 0.001m/d x 1,000,000m2 x 2m / 2m
K = m/d
A = 100ha = 1,000,000 m2
ΔH = 5-3 = 2m
L = 2m
Q = 0.001m/d x 1,000,000m2 x 2m / 2m
Q = 1,000 m3/day or 365,000 m3/year
Q surface depth = 365,000 m3 / 1,000,000 m2= 0.365m

31. Lateral leakage problem Q=K A ΔH/L
K=0.1m/d
A=100m x 50m
=5,000m2
ΔH=108m-105m
=3m
L=1,000m
Qm3/d=
0.1m/d * 5,000m2 *0.003 = 1.5m3/d

32. Groundwater Flowpaths at Streams

33. Groundwater Discharges

34. Groundwater Flowpaths

35. Next Time…
Soil Water Storage