1. Site Instrumentation Methodsby
Jim Richardson and
Mike Vepraskas
Modified 9/08

2. Overview Criteria for picking monitoring sites
Selection of equipment and installation
Data collection & interpretation
Rainfall measurements

3. Selecting Sites to Monitor
Pick sites that are representative of a large area--both in terms of landscape position and microtopography
Pick at least one site in an area known to be hydric, and one site in the upland (transect).
Replicate sites at the same landscape position (traverse).

4. Boundaries
In many cases you want to monitor across boundaries between:
Wetland vs. Non-Wetland
Hydric vs. Non-Hydric Soils

5. Think Shallow
Hydric soils are saturated either on the surface or within 12 in. of the surface.
Do not focus too deeply
Be sure to monitor within 12 in. of
surface

6. Upland (Not hydric) Hydric Boundary?
PIEZOMETER AND WELL NESTS
TRAVERSE
TRANSECT
Upland
(Not hydric)
Hydric
Boundary?
Hydric

7. Microtopography should be similar at an installation
10 ft
Piezometers or wells
will give different
readings
SOIL

8. Where do you place your Instruments? Potential hydric soil zone

9. Where do you place your Instruments?
Monitoring Sites
Hydric soil boundary

10. Where do you place your instruments?
Backswamp
Backplain
flat
Levee
Flood Plain
Till
Alluvium

11. Flooding Depth and Duration are Important too
Flooded and ponded
For long duration—
Hydric soils
Flooded for
Short duration
(not hydric?)
Alluvium
Till

12. Use Transects Across Hydric Boundaries
Wells and piezometers
Possible Boundaries

13. Soils Considerations
Complete a profile description for each plot where equipment will be installed.
Estimate the depth to any layers that may perch water for long periods, and any sand deposits.
From the description, estimate the depths that wells and piezometers will be installed.

14. Well Piezometers Sand Perched Water Table Clay Sand Shallow piezometer
contains water, but lower
piezometer does not. Perched water table detected.
Water drains
down well,
Saturation undetected

15. A Bw Bk Btg Soil Descriptions Suggest Boundaries Upland Boundary
Hydric Soil A Bw
Fig Based on Knuteson et al. 1989, Seelig and Richardson, 1992 and Richardson et al we developed a generalized soil-landscape model with Simmonson’s (1959) generalized theory of soil genesis conditions or losses, gains, and translocations marked. Bk
Btg

16. Overview Criteria for picking monitoring sites
Selection of equipment and installation
Data collection & interpretation
Rainfall measurements

17. Finding the Water Table
Wells should be used to identify water tables.
Piezometers measure pressure, and not the free water surface.
Wells work best when they don’t penetrate a layer that is perching water or intersect large cracks

18. Wells and Piezometers Wells are Piezometers tubes that contain
many holes
to let water
in.
Piezometers
contain few
holes, and let water in mainly at their
bottom.
Wells show
the depth
to the water
table
Piezometers show
if soil around
holes is saturated

19. Piezometers vs. Wells
We suggest placing one well at each site whenever you need to know where the water table is.
Piezometers should be used to conform to the technical standard (one in the upper 10 in.)
Do not use wells in Vertisols or any other clayey soil where bypass (crack) flow can occur

20. Wells have many holes, and some holes will be next to cracks
Vertisols have large, continuous cracks that carry water deep into the soil when soil is dry
Water flow
Wells have
many holes,
and some holes
will be next
to cracks
Dry
Ped
Fig. 3.7 By-Pass flow based on Bouma ( ). The factors influencing by pass flow are listed above the figure. High rain intensity, low water quality, steep relief, silt loams versus sands, water repellent soils, and wet soils have lower by pass flow than their counterparts.
Water in well is
from “Crack Flow”.
Soil is not saturated
Dry
PED

21. AQUIFERS CONFINED & UNCONFINED
Aquifer- in soil
SATURATED
ZONE
Confining aquitard (clay)
Confined aquifer- sand

22. “Domed” Organic Soil Piezometer Muck Clay Sand Mucky Mineral -75 Sand
Mucky Mineral
-75
Sand
-169
-170

23. “Domed” Organic Soil forms over point of upwelling water?
Sand
Clay
Muck
Surface
Organic
Mucky Mineral
-75
Break in clay
allows water
through
Sand
-169
-170

24. Suffolk Scarp

25. Dismal Swamp
Scarp

26. Suffolk Scarp
Stream
Sandy loam
Clay confining layer
Saturated Sand (confined aquifer)

27. Stream has cut through
Confining layer.
Water from confined
sand flows into channel.

28. If stream is dammed, water flows onto plain.

29. Thick organic
deposits form
on plain.
Dismal Swamp

30. Stratified Soil with Confined Aquifer
Where do you place your piezometers?
A-horizon (Loam)
SUGGESTION:
Place wells in surface aquifers down
to confining layer.
Place piezometers
in confined
aquifers.
E-horizon (Loam)
Bt-horizon (CLAY)
C- LOESS (silt)
Btb-PALEOSOL (CLAY)

31. Ideal:
Piezometers
In permeable
layers
Avoid:
Piez. Will
not fill in clays
Well
slots
A-(Loam
E-(Loam)
Bt (CLAY)
C- LOESS
Btb-PALEOSOL (CLAY)

32. Recharge - EpiSATURATED or PERCHED
A-(Loam
E-(Loam)
Bt (CLAY)
Water levels
C- LOESS
Btb-PALEOSOL (CLAY)

33. Discharge - EndoSATURATED
A-(Loam
Water levels
E-(Loam)
Water in loess
Under pressure:
Artesion
Condition
Bt (CLAY)
C- LOESS
Btb-PALEOSOL (CLAY)

34. Soil or bentonite + soil Carefully packed. Check
Loose Cap: use
Pop (soda) can
Basic Piezometer
Installation Method
Drill air hole
In tube if cap
Is tight
Surface Cone
Soil or bentonite + soil
(2:1) mix for sandy soils.
Carefully packed. Check
every visit.
Backfill with
soil, packed
well
Bentonite Seal
3 to 6 inches
Sand Pack
~ 3” above
slots
6” of Well
Screen or slots
3+”

35. Soil or bentonite + soil Carefully packed. Check
Loose Cap: use
Pop (soda) can
Basic Well
Installation Method
Drill air hole
In tube if cap
Is tight
Surface Cone
Soil or bentonite + soil
(2:1) mix for sandy soils.
Carefully packed. Check
every visit.
Backfill with
soil, packed
well
Bentonite Seal
3 to 6 inches
Sand Pack
Well Screen or slots
over depth of interest
3+”

36. Fabric Covers or Socks for Wells
and Piezometers
Cover holes
With porous
fabric.
Tape
Sand and
Soil may fall
into holes in
Wells and
Piezometers.
Can use”
Geotextile,
Drain Sock,
Women’s nylons
Knot at
bottom

37. For Flooded Sites Use a Surface Marker
Along with wells and piezometers
Gauge showing
water height
above surface

38. Stolt, Univ. Rhode Island
High Water Table
Indicator
Stolt, Univ. Rhode Island
Well pipe cut in half
To see inside
Steel rod
Magnet
Cork Float

39. High water mark, Reset after measurement

40. Another Type of Well Recorder This is Circular 1409,
B. J. Boman, and T. A. Obreza,
Cooperative Extension Service,
University of Florida
Gainesville, FL

41. Overview Criteria for picking monitoring sites
Selection of equipment and installation
Data collection & interpretation
Rainfall measurements

42. Time to Make Readings
Collect data weekly during a critical time of year when water levels are “high” (usually winter, spring, and fall).
Monthly readings may be adequate when water levels are low (e.g. in summer).

43. Typical Wetland Hydrograph
Winter Peak
Summer ET
Jan July Dec
ponded
Surface
Saturated < 30cm
Water Table Depth (cm)
-30cm
Spring
Falling Limb
Fall Rising Limb
Time (Months)

44. How often do you make measurements?
Measure at least weekly
Daily measurements are needed for some modeling work
If you use automated systems, set for daily measurements, and visit monthly.

46. Water levels in piezometers
differ with depth in recharge and discharge areas
Recharge
Discharge

47. Piezometer Readings
Data must be plotted separately for each piezometer.
Note when free water present at depth of slotted portion of tube.
Can plot depth of water or plot “saturated”or “not saturated” as a bar over time.

48. Finding the Water Table with Piezometers
Where is the water table in this soil?
2 ft.
Piezometers
6 ft.

49. If you must use a piezometer to identify a water table,then use the water level in the shallowest piezometer for your estimate
Water table
2 ft.
6 ft.

50. Water Table Fluctuations during rain events
In some soils, water tables move up and down quickly during and after a rain.
In other soils, there is much less fluctuation.
The amount the water table rises during a rain is related to the soils drainable porosity.

51. Influence of Drainable Porosity on water table fluctuation
High drainable
porosity (little
fluctuation)
Low drainable
porosity (much
fluctuation)

52. Drainable Porosity Is roughly the Volume of Air-Filled Porosity
When soil is wet to Field Capacity.
It is related to the volume of macropores, or
large cracks, root channels, and pores
between sands and gravels.

53. Low Drainable Porosity
1 inch of
rain raises
water table
by 10 inches
because of low
amount of
Pore Space
Rock with no
internal pores

54. High Drainable Porosity
1 inch of
rain raises
water table
by 2 inches
because of high
amount of
Pore Space

55. Very porous layer of organic soil
1 inch of rain
must fill much
pore space
to saturate
soil
Little water table
Fluctuation in this
zone

56. Soils with Low Drainable Porosity
Water table fluctuation is large:
Water tables may rise 2 ft. or more after a large rain event, and also fall within several days.
Water tables need to be read weekly or more often in these soils.
Unless water tables are read daily, you aren’t recording maximum level.

57. This device is best
for soils with
Low Drainable
Porosity, where weekly
readings are made
Steel rod
Magnet
Cork Float

58. Water Table Fluctuations in Discharge Areas
RECHARGE
FLOWTHROUGH
DISCHARGE
Fig Illustrations of recharge and discharge in a landscape (after Richardson et al. 1992).

59. Oval-shaped depressions oriented
Carolina Bays
1.6 km
(1 mile)
Carolina Bays
Oval-shaped depressions oriented
In a NW-SE direction N

60. This Bay has ridges on western
and eastern sides”
Does Ground
Water flow
Into Bay here?

61. Water Balance for Juniper Bay Today (2002-03)
PET
845 mm
Precip.
1115 mm
Surface
Outflow
707 mm
Storage
6 mm
Wetland
Groundwater
Inflow-Outflow
543 mm

62. Well on East Side of Bay Hourly water table levels
Days
Depth (in.)

63. Sawtooth Pattern Caused by ground water inflow
Days
Depth (in.)
Fall in water table
during day
due to Et

64. Wetland is Discharge Area
Days
Depth (in.)
Rise in water table
at night
due to groundwater
inflow

65. Well at Center of Bay Water Table Depth (in.)
8/1/02
8/2/02
8/3/02
8/4/02
8/5/02
8/6/02
8/7/02
8/8/02
8/9/02
8/10/02
8/11/02
8/12/02
8/13/02
8/14/02
-20
No daily fluctuation: no ground-
water inflow
-25
-30
Water Table Depth (in.)
-35
-40
-45

66. Recharge
Today
Flowthrough
Discharge
Gi=Go
Gi<Go
Gi>Go

67. Overview Criteria for picking monitoring sites
Selection of equipment and installation
Data interpretation
Rainfall measurements

68. Rain gauge
Solar Panel
Net Radiometer

69. Rainfall
Daily rainfall measurements are critical for identifying years or “normal” rainfall
Each site should be instrumented with an automatic recorder
A manual recordering gauge is needed (essential) for backup

70. Rainfall
Locate the gauge on level ground, about 30 in. or more above the surface.
The gauge needs to be in the clear, at a distance of twice the height of the nearest obstruction

71. Rain gauge located in clearing at a distance from the trees that Is equal to twice the height of the trees
Gauge
30 in. above
ground

72. Rainfall cont’d.
Nearest available weather stations usually aren’t “near enough” for daily data
Be sure to protect gauges against bird droppings--install wires that cut feet.

73. Rainfall Variability for a 750 acre Site
How Many Gauges Do You Need?
Gauges not working

74. Points on Rainfall
Rainfall data are just as important as water table data.
One gauge per 750 acres is adequate—if the gauge is working
More rain gauges are fine, but they increase the chance that one or more gauges will fail.
Use only the amount of equipment you can keep in working order.

75. Acceptable Rainfall
Rainfall can be within a range that is either normal (or drier than normal).
Wetter than normal rainfall is not acceptable
Normal rainfall is defined as a range on the WETS Tables.

76. WETS Data Table
Precipitation data
Enlarged next slide

77. WETS Data Table
Growing
Season

78. USDA-NRCS’s WETS TABLE Defines Normal Rainfall
Normal rainfall for August is: 3.65 to 6.45 inches

79. Summary Select sites that represent large areas
Pay attention to microtopography
Use wells for water table measuremens, and piezometers to find saturation depths

80. Summary
Install wells and piezometers so they don’t leak by by-pass flow from surface.
Read instruments weekly, and be sure to visit site monthly if using automated equipment
Measure rainfall whenever possible