Acquisition and interpretation of water level data
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Acquisition and Interpretation of Water-Level Data. Travis von Dessonneck. Importance of Water-Level Data. The acquisition and interpretation of ground-water data are essential for environmental site assesment Can be used to determine hydraulic head in formations Used to make 3D flow patterns.

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Importance of water level data
Importance of Water-Level Data

  • The acquisition and interpretation of ground-water data are essential for environmental site assesment

  • Can be used to determine hydraulic head in formations

  • Used to make 3D flow patterns


Water level and hydraulic head relationships
Water level and Hydraulic-head relationships

  • Hydraulic head varies spatially and temporally

  • Piezometer

    • Monitoring device for measuring water levels

    • Hollow vertical pipe with a screen

  • Elevation head

    • The elevation of the bottom of the well/piezometer


Water level and hydraulic head relationships1
Water level and Hydraulic-head relationships

  • Pressure head

    • The height of the water above the bottom of the well

  • Total hydraulic head

    • Elevation head + Pressure head


Hydraulic media and aquifer systems
Hydraulic Media and aquifer systems

  • Aquifer is not “a water-bearinglayer of geologic material, which will yield water in a usable quantity to a well or spring” in this instance

  • Aquifer is where water lies with respect to the top of a geologic unit


Design features for water level monitoring systems
Design features for water-level monitoring systems

  • Takes into account water-level monitoring and sampling

  • 2 phases

    • Site data collection

    • Monitoring for changes and proper placement of wells

      • Can also be used to determine if monitoring system is not set up correctly

  • Site geology must be known

    • Heterogeneous sites require more monitoring than homogeneous sites


Piezometers or wells
Piezometers or wells

  • Piezometers are generally not used to gather water samples

    • Small diameter pipe

    • Can accommodate pressure transducers

  • Wells are designed for sampling

    • Larger diameter


Approach to system designs
Approach to system designs

  • What to consider

    • Boring and well logs

    • Surficial geology

    • Topographic maps

    • Drainage features

    • Cultural features (well fields, irrigation, pipes)

    • Rainfall

    • Recharge


Approach to system designs1
Approach to system designs

  • Review the data to get

    • Depth and characteristics of high and low K areas

    • Depth to water, intermittent or perched zones

    • Flow direction

    • Vertical hydraulic gradients

    • Possible causes and frequency of fluctuation

    • Existing wells that may be incorporated


Number and placement of wells
Number and placement of wells

  • Dependant on size and complexity of site

  • Minimum to establish direction and rate of flow

  • Larger sites usually have a grid of six to nine wells to get direction

  • Take into account screen depth and length


Water level measurement precision and intervals
Water-level measurement precision and intervals

  • Need to accurately located wells vertically and horizontally

    • Survey/GPS

    • Accuracy to 0.1 and 0.01 ft

  • Need to know what you are looking for

    • Seasonal changes

    • Diurnal changes


Reporting of data
Reporting of data

  • Monitoring installations

    • Geologic sequence

    • Well construction features

    • Depth and elevation of well casing

  • Water-level data

    • Date and time of measurement

    • Method used

    • Other conditions that might affect the well level


Manual measurements in nonflowing wells
Manual measurements in nonflowing wells

  • Wetted chalked tape method

    • Weight attached to bottom of tape

    • Coat bottom 2-3ft of tape with carpenter’s chalk

    • Accurate to 0.01ft (USGS 1980)

    • Disadvantages

      • Stretching of the tape

      • Need to know approximate depth to water


Manual measurements in nonflowing wells1
Manual measurements in nonflowing wells

  • Air-line submergence method

    • Insert a small diameter tube below the water surface

    • Pump the water out the bottom by hand or electric pump

    • Ending psi * 2.31 gives feet

      • Subtract the calculated distance from length of tube


Manual measurements in nonflowing wells2
Manual measurements in nonflowing wells

  • Electrical methods

    • Whistler

      • Open circuit is completed when it comes in contact with the water and beeps at you

      • Wires are at the end of a measuring tape

      • Read the tape to determine depth


Manual measurements in nonflowing wells3
Manual measurements in nonflowing wells

  • Pressure transducer methods

    • Measures the pressure in the well at the sensor

    • Open to the atmosphere by a small capillary tube

    • Usually have a sealed data logger

    • Sensor is lowered a known distance into the water when installed


Manual measurements in nonflowing wells4
Manual measurements in nonflowing wells

  • Float method

    • A float is attached to the end of a steel tape

    • Read the depth off of the steel tape


Manual measurements in nonflowing wells5
Manual measurements in nonflowing wells

  • Sonic or audible methods

    • The classic “drop the pebble in the well approach” only with a tape attached to the pebble

    • Drop a battery powered probe down the beeps when it is in the water (whistler)


Manual measurements in nonflowing wells6
Manual measurements in nonflowing wells

  • Ultrasonic/radar/laser methods

    • A sonar type device

    • Calculates the reflection time

    • Can get depth to water and total depth of the well


Manual measurements in flowing wells
Manual measurements in flowing wells

  • Manometers and pressure gauges

    • Well is sealed and a pressure gauge is installed in the top

    • Mercury can be accurate to 0.005ft

    • Pressure gauges can be accurate to 0.2 ft


Methods of continuous measurement
Methods of Continuous measurement

  • Mechanical: float recorder systems

    • A float attached to a seismometer type drum

  • Electromechanical: Iterative Conductance Probes (dippers)

    • Probe is lowered to the water surface by a stepping motor

    • Sensor like on a whistler tells the motor to stop

    • Motor reverses and repeats at set intervals

  • Data loggers


Analysis interpretation and presentation of water level data
Analysis, Interpretation, and Presentation of Water-level data

  • Water-level can be effected by recharge and discharge conditions

    • Water flows down during recharge and up during discharge


Approach to interpreting water level data
Approach to Interpreting Water-level data data

  • Conduct a thorough site analysis

  • Review monitoring wells features

  • Establish groundwater flow direction and magnitude

    • Monitor for several days to see long term fluctuations


Transient effects
Transient Effects data

  • Water level can change due to many things

    • Seasonal precipitation

    • Irrigation

    • Well pumping

    • River stage

    • Tidal fluctuations

  • These can reverse flow direction


Contouring water level elevation data
Contouring water level elevation data data

  • Made like a topo map, only of the water table and not the surface elevation

  • May require cross sections in areas with high vertical flow