{"id":1618,"date":"2026-02-14T04:22:32","date_gmt":"2026-02-14T04:22:32","guid":{"rendered":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/chapter\/ch023-xhtml\/"},"modified":"2026-08-01T08:27:31","modified_gmt":"2026-08-01T08:27:31","slug":"measuring-and-recording-water-levels","status":"publish","type":"chapter","link":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/chapter\/measuring-and-recording-water-levels\/","title":{"raw":"5.1 Measuring and Recording Water Levels","rendered":"5.1 Measuring and Recording Water Levels"},"content":{"raw":"
\r\n
\r\n
\r\n\r\nWater levels are measured to establish pre\u2011 and post\u2011testing water level trends, as well as during both the pumping and recovery phases of pumping tests. Water levels can be measured with several manual and automated devices, some of which are installed in the wells for the entire test (Figure 15<\/a>).\r\n\r\n<\/div>\r\n
\r\n\r\n\"\"\r\n\r\n<\/div>\r\n
\r\n
\r\n
\r\n\r\nFigure 15 -<\/strong> Groundwater level monitoring methods. The diagram shows how each measuring device would be used in a well.<\/span>\r\n\r\n<\/div><\/blockquote>\r\n<\/div>\r\n
    \r\n \t
  1. Steel graduated tape with the measuring end chalked with carpenter\u2019s chalk https:\/\/aces.nmsu.edu\/pubs\/_m\/M118\/welcome.htm).l<\/a>\u2197.<\/li>\r\n \t
  2. An older technology float recorder using a pen and paper chart records water level changes and time. The initial water level below the top of the casing is determined and used to convert water level changes recorded on the chart to changes in head.<\/li>\r\n \t
  3. An electric tape used to measure water levels sends a signal to the tape case once the probe contacts the water. The tape is graduated, and a direct water-level reading is taken at the measuring point (e.g., https:\/\/www.solinst.com\/<\/a>)\u2197.<\/li>\r\n \t
  4. Transducers are submerged below the static water level and record changes in the pressure of the overlying column of water over time (pressure decreases as drawdown occurs). An initial measurement of the static water level is recorded at installation and used to convert pressure changes to water levels. Transducers come either sealed to the atmosphere (absolute pressure) or vented to the atmosphere. Unvented (sealed) transducers require simultaneous collection of barometric pressure (e.g., Solinst barologger) readings. These data are used to make corrections to recorded water levels (measurements include water level changes and barometric changes) (e.g., https:\/\/www.solinst.com\/<\/a>\u2197; www.onsetcomp.com<\/u><\/a>)\u2197.<\/li>\r\n \t
  5. Observation wells where the water level is above the top of the casing can be closed in with a valve outfitted with a pressure gauge or a pressure transducer. The changes in pressure are recorded during pumping and converted to length measurements (although the gauge shown reads feet of water directly) www.Grainger.com\/<\/a>\u2197.<\/li>\r\n \t
  6. A sonic water level meter is used most often for deep wells, wells with partial obstructions and\/or not perfectly straight wells. A sound pulse travel time is used to measure the water level (e.g., https:\/\/enoscientific.com\/well-watch-670\/<\/a>)\u2197.<\/li>\r\n<\/ol>\r\n
    \r\n\r\nManual measuring tapes can be used to monitor water levels (Figure 15<\/a>). Graduated electronic water level meters (or electric tapes) indicate the depth to water below a measuring point (usually the top of casing) when a sensor contacts the water surface, and a circuit is completed resulting in a beep or light. The tape reading at the measuring point is the depth to water. One or more electric tapes are usually on site to periodically measure background water levels in pumping and observation wells during a test. When multiple electronic water level tapes are used, they should be calibrated to a steel tape or reference electronic water level tape that is used as a standard. Each tape used may have its own individual correction factor relative to the standard tape. Some water level data may need to be corrected for instrument error.\r\n\r\n<\/div>\r\n
    \r\n\r\nIf only a steel tape is available, it can be used to determine water levels. A steel graduated tape with the end portion of the dry tape marked with chalk or water-soluble ink is lowered into the well and then held at a designed measuring point (top of casing) at an even measurement mark (e.g., 15 m). The tape is then retrieved, and the amount of wet tape recorded. The depth to water from the top of casing is obtained by subtracting the length of wet tape from the measuring point value. If multiple steel tapes are used during a test, they should be standardized. When using only measuring tapes to record test water level changes, the timing of measurements is dependent on the speed at which the tape can be deployed, the water level read, and the time and level data recorded. Rapid measurement during early periods of pumping and recovery are often difficult to capture using measuring tapes, especially when steel tapes are applied. Thus, other devices such as pressure transducers are recommended.\r\n\r\n<\/div>\r\n
    \r\n\r\nWater level data may need to be corrected for operator error. This is quantified when an operator consecutively measures the background water levels in a single well multiple (at least three) times. Assuming these water level measurements represent a single value, the mean water level and error are computed. The recorded error is the operator error for the field personnel reporting the data. All water level data collected by that operator includes the computed error.\r\n\r\n<\/div>\r\n
    \r\n\r\nOlder float recorders can also be used to record water levels in monitoring wells that are not outfitted with pumps or other piping that would prevent installation of a float and counterweight (Figure 15<\/a>). Typically pens controlled by the float record water level changes over time on paper charts. Clock mechanisms can be mechanical or electrical. A reference initial water level is measured and recorded prior to the initiation of the test and several times during the test. Float recorder water levels are corrected using hand measured water level data when they do not agree. For the most part, float recorders have been replaced with transducers.\r\n\r\n<\/div>\r\n
    \r\n\r\nPressure transducers are suspended with a cable to a depth below the anticipated decline in maximum level of drawdown (Figure 15<\/a>). Transducers measure the pressure exerted by the column of water above the transducer at the start of the test and then the decrease in pressure as drawdown occurs. Pressure transducers have specified submerged operational ranges within which they are designed to operate (e.g., 0 to 5 m, 5 to 10 m, 10 to 25 m, 25 m to 50 m, etc.). Transducers should be selected for test wells to match their published operational range and sensitivity. For example, if the water level in the pumping well is anticipated to change 20 m during a test, a transducer with a range of 5 m to 25 m should be used. However, for the same test an observation well located 100 m from the pumping well that is anticipated to change about 7 m would have a transducer installed with a range of 5 to 10 m. The relationship between the background water level and the water level height over the transducer is established by measuring the water level at the start of the test using a calibrated electronic water level measuring tape. It is recommended that water levels are periodically measured manually during the test and used to collaborate\/correct transducer records as needed.\r\n\r\n<\/div>\r\n
    \r\n\r\nTransducers are often set to record measurements using fixed time intervals (e.g., every second, 1 min, 10 min, etc.) or at variable time intervals following a logarithmic trend. Many transducers and cables include air tubes open to the atmosphere (vented), but some do not (absolute or unvented). If transducers are not open to the atmosphere, they are paired with an on\u2011site micro\u2011barometric sensor. The barometric data are used to correct the water levels as the unvented transducers record the combined barometric change and water level change during operation.\r\n\r\n<\/div>\r\n
    \r\n\r\nA mechanical pressure gauge or pressure transducer can be used to monitor water levels in observation wells where the total head is greater than the elevation of the top of the casing (Figure 15<\/a>). Gauge specifications including ranges, accuracy, and precision are provided by manufacturers.\r\n\r\n<\/div>\r\n
    \r\n\r\nSonic meters work by transmitting a sound wave into the well and measuring the time it takes for the pulse to return after reflecting off the water surface. The distance is calculated using the speed of sound and time. Sonic meters are operated at the top of the well casing and do not physically touch the water surface (Figure 15<\/a>). They are useful in wells with deep water levels (100s of meters), when wells have partial obstructions, and where casings are angled. Some meters are hand operated and others can be programmed to collect water level data over time. It should be noted that accuracy and precision of sonic meters is typically less than that of electronic water level measuring tapes (e.g., 0.03 m versus 0.003 m). Manufacturers specifications should be reviewed, and error bars included with water level data. If conditions allow steel tape or electronic water level measurement tapes to be deployed, sonic measurement records can be calibrated to standard water level values.\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>","rendered":"
    \n
    \n
    \n

    Water levels are measured to establish pre\u2011 and post\u2011testing water level trends, as well as during both the pumping and recovery phases of pumping tests. Water levels can be measured with several manual and automated devices, some of which are installed in the wells for the entire test (Figure 15<\/a>).<\/p>\n<\/div>\n

    \n

    \"\"<\/p>\n<\/div>\n

    \n
    \n
    \n

    Figure 15 –<\/strong> Groundwater level monitoring methods. The diagram shows how each measuring device would be used in a well.<\/span><\/p>\n<\/div>\n<\/blockquote>\n<\/div>\n

      \n
    1. Steel graduated tape with the measuring end chalked with carpenter\u2019s chalk https:\/\/aces.nmsu.edu\/pubs\/_m\/M118\/welcome.htm).l<\/a>\u2197.<\/li>\n
    2. An older technology float recorder using a pen and paper chart records water level changes and time. The initial water level below the top of the casing is determined and used to convert water level changes recorded on the chart to changes in head.<\/li>\n
    3. An electric tape used to measure water levels sends a signal to the tape case once the probe contacts the water. The tape is graduated, and a direct water-level reading is taken at the measuring point (e.g., https:\/\/www.solinst.com\/<\/a>)\u2197.<\/li>\n
    4. Transducers are submerged below the static water level and record changes in the pressure of the overlying column of water over time (pressure decreases as drawdown occurs). An initial measurement of the static water level is recorded at installation and used to convert pressure changes to water levels. Transducers come either sealed to the atmosphere (absolute pressure) or vented to the atmosphere. Unvented (sealed) transducers require simultaneous collection of barometric pressure (e.g., Solinst barologger) readings. These data are used to make corrections to recorded water levels (measurements include water level changes and barometric changes) (e.g., https:\/\/www.solinst.com\/<\/a>\u2197; www.onsetcomp.com<\/u><\/a>)\u2197.<\/li>\n
    5. Observation wells where the water level is above the top of the casing can be closed in with a valve outfitted with a pressure gauge or a pressure transducer. The changes in pressure are recorded during pumping and converted to length measurements (although the gauge shown reads feet of water directly) www.Grainger.com\/<\/a>\u2197.<\/li>\n
    6. A sonic water level meter is used most often for deep wells, wells with partial obstructions and\/or not perfectly straight wells. A sound pulse travel time is used to measure the water level (e.g., https:\/\/enoscientific.com\/well-watch-670\/<\/a>)\u2197.<\/li>\n<\/ol>\n
      \n

      Manual measuring tapes can be used to monitor water levels (Figure 15<\/a>). Graduated electronic water level meters (or electric tapes) indicate the depth to water below a measuring point (usually the top of casing) when a sensor contacts the water surface, and a circuit is completed resulting in a beep or light. The tape reading at the measuring point is the depth to water. One or more electric tapes are usually on site to periodically measure background water levels in pumping and observation wells during a test. When multiple electronic water level tapes are used, they should be calibrated to a steel tape or reference electronic water level tape that is used as a standard. Each tape used may have its own individual correction factor relative to the standard tape. Some water level data may need to be corrected for instrument error.<\/p>\n<\/div>\n

      \n

      If only a steel tape is available, it can be used to determine water levels. A steel graduated tape with the end portion of the dry tape marked with chalk or water-soluble ink is lowered into the well and then held at a designed measuring point (top of casing) at an even measurement mark (e.g., 15 m). The tape is then retrieved, and the amount of wet tape recorded. The depth to water from the top of casing is obtained by subtracting the length of wet tape from the measuring point value. If multiple steel tapes are used during a test, they should be standardized. When using only measuring tapes to record test water level changes, the timing of measurements is dependent on the speed at which the tape can be deployed, the water level read, and the time and level data recorded. Rapid measurement during early periods of pumping and recovery are often difficult to capture using measuring tapes, especially when steel tapes are applied. Thus, other devices such as pressure transducers are recommended.<\/p>\n<\/div>\n

      \n

      Water level data may need to be corrected for operator error. This is quantified when an operator consecutively measures the background water levels in a single well multiple (at least three) times. Assuming these water level measurements represent a single value, the mean water level and error are computed. The recorded error is the operator error for the field personnel reporting the data. All water level data collected by that operator includes the computed error.<\/p>\n<\/div>\n

      \n

      Older float recorders can also be used to record water levels in monitoring wells that are not outfitted with pumps or other piping that would prevent installation of a float and counterweight (Figure 15<\/a>). Typically pens controlled by the float record water level changes over time on paper charts. Clock mechanisms can be mechanical or electrical. A reference initial water level is measured and recorded prior to the initiation of the test and several times during the test. Float recorder water levels are corrected using hand measured water level data when they do not agree. For the most part, float recorders have been replaced with transducers.<\/p>\n<\/div>\n

      \n

      Pressure transducers are suspended with a cable to a depth below the anticipated decline in maximum level of drawdown (Figure 15<\/a>). Transducers measure the pressure exerted by the column of water above the transducer at the start of the test and then the decrease in pressure as drawdown occurs. Pressure transducers have specified submerged operational ranges within which they are designed to operate (e.g., 0 to 5 m, 5 to 10 m, 10 to 25 m, 25 m to 50 m, etc.). Transducers should be selected for test wells to match their published operational range and sensitivity. For example, if the water level in the pumping well is anticipated to change 20 m during a test, a transducer with a range of 5 m to 25 m should be used. However, for the same test an observation well located 100 m from the pumping well that is anticipated to change about 7 m would have a transducer installed with a range of 5 to 10 m. The relationship between the background water level and the water level height over the transducer is established by measuring the water level at the start of the test using a calibrated electronic water level measuring tape. It is recommended that water levels are periodically measured manually during the test and used to collaborate\/correct transducer records as needed.<\/p>\n<\/div>\n

      \n

      Transducers are often set to record measurements using fixed time intervals (e.g., every second, 1 min, 10 min, etc.) or at variable time intervals following a logarithmic trend. Many transducers and cables include air tubes open to the atmosphere (vented), but some do not (absolute or unvented). If transducers are not open to the atmosphere, they are paired with an on\u2011site micro\u2011barometric sensor. The barometric data are used to correct the water levels as the unvented transducers record the combined barometric change and water level change during operation.<\/p>\n<\/div>\n

      \n

      A mechanical pressure gauge or pressure transducer can be used to monitor water levels in observation wells where the total head is greater than the elevation of the top of the casing (Figure 15<\/a>). Gauge specifications including ranges, accuracy, and precision are provided by manufacturers.<\/p>\n<\/div>\n

      \n

      Sonic meters work by transmitting a sound wave into the well and measuring the time it takes for the pulse to return after reflecting off the water surface. The distance is calculated using the speed of sound and time. Sonic meters are operated at the top of the well casing and do not physically touch the water surface (Figure 15<\/a>). They are useful in wells with deep water levels (100s of meters), when wells have partial obstructions, and where casings are angled. Some meters are hand operated and others can be programmed to collect water level data over time. It should be noted that accuracy and precision of sonic meters is typically less than that of electronic water level measuring tapes (e.g., 0.03 m versus 0.003 m). Manufacturers specifications should be reviewed, and error bars included with water level data. If conditions allow steel tape or electronic water level measurement tapes to be deployed, sonic measurement records can be calibrated to standard water level values.<\/p>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"author":8,"menu_order":16,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-1618","chapter","type-chapter","status-publish","hentry"],"part":517,"_links":{"self":[{"href":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/wp-json\/pressbooks\/v2\/chapters\/1618","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/wp-json\/wp\/v2\/users\/8"}],"version-history":[{"count":3,"href":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/wp-json\/pressbooks\/v2\/chapters\/1618\/revisions"}],"predecessor-version":[{"id":2555,"href":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/wp-json\/pressbooks\/v2\/chapters\/1618\/revisions\/2555"}],"part":[{"href":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/wp-json\/pressbooks\/v2\/parts\/517"}],"metadata":[{"href":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/wp-json\/pressbooks\/v2\/chapters\/1618\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/wp-json\/wp\/v2\/media?parent=1618"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/wp-json\/pressbooks\/v2\/chapter-type?post=1618"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/wp-json\/wp\/v2\/contributor?post=1618"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/books.gw-project.org\/an-introduction-to-hydraulic-testing-in-hydrogeology\/wp-json\/wp\/v2\/license?post=1618"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}