Error in hydraulic head and gradient time-series measurements: a quantitative appraisal
<p>Hydraulic head and gradient measurements underpin practically all investigations in hydrogeology. There is sufficient information in the literature to suggest that head measurement errors can impede the reliable detection of flow directions and significantly increase the uncertainty of grou...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-09-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/23/3603/2019/hess-23-3603-2019.pdf |
| _version_ | 1819045897288286208 |
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| author | G. C. Rau G. C. Rau V. E. A. Post M. Shanafield T. Krekeler E. W. Banks P. Blum |
| author_facet | G. C. Rau G. C. Rau V. E. A. Post M. Shanafield T. Krekeler E. W. Banks P. Blum |
| author_sort | G. C. Rau |
| collection | DOAJ |
| description | <p>Hydraulic head and gradient measurements underpin practically all investigations in hydrogeology. There is sufficient information in the literature to suggest that head measurement errors can impede the reliable detection of flow directions and significantly increase the uncertainty of groundwater flow rate calculations. Yet educational textbooks contain limited content regarding measurement techniques, and studies rarely report on measurement errors. The objective of our study is to review currently accepted standard operating procedures in hydrological research and to determine the smallest head gradients that can be resolved. To this aim, we first systematically investigate the systematic and random measurement errors involved in collecting time-series information on hydraulic head at a given location: (1) geospatial position, (2) point of head, (3) depth to water, and (4) water level time series. Then, by propagating the random errors, we find that with current standard practice, horizontal head gradients <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo><</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">4</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="35pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="f11cb695995b68e64d8031662f2334f2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="hess-23-3603-2019-ie00001.svg" width="35pt" height="13pt" src="hess-23-3603-2019-ie00001.png"/></svg:svg></span></span> are resolvable at
distances <span class="inline-formula"><i>⪆</i>170</span> m. Further, it takes extraordinary effort to measure hydraulic head gradients <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo><</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">3</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="35pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="715b0476aca53918edbdf641c0281be8"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="hess-23-3603-2019-ie00002.svg" width="35pt" height="13pt" src="hess-23-3603-2019-ie00002.png"/></svg:svg></span></span> over distances <span class="inline-formula"><10</span> m. In reality, accuracy will be worse than our theoretical estimates because of the many possible systematic errors. Regional flow on a scale of kilometres or more can be inferred with current best-practice methods, but processes such as vertical flow within an aquifer cannot be determined until more accurate and precise measurement methods are developed. Finally, we offer a concise set of recommendations for water level, hydraulic head and gradient time-series measurements. We anticipate that our work contributes to progressing the quality of head time-series data in the hydrogeological sciences and provides a starting point for the development of universal measurement protocols for water level data collection.</p> |
| first_indexed | 2024-12-21T10:35:52Z |
| format | Article |
| id | doaj.art-2f217cb3a03641d2bf007cd128dbb935 |
| institution | Directory Open Access Journal |
| issn | 1027-5606 1607-7938 |
| language | English |
| last_indexed | 2024-12-21T10:35:52Z |
| publishDate | 2019-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Hydrology and Earth System Sciences |
| spelling | doaj.art-2f217cb3a03641d2bf007cd128dbb9352022-12-21T19:07:05ZengCopernicus PublicationsHydrology and Earth System Sciences1027-56061607-79382019-09-01233603362910.5194/hess-23-3603-2019Error in hydraulic head and gradient time-series measurements: a quantitative appraisalG. C. Rau0G. C. Rau1V. E. A. Post2M. Shanafield3T. Krekeler4E. W. Banks5P. Blum6Karlsruhe Institute of Technology (KIT), Institute of Applied Geosciences (AGW), Karlsruhe, GermanyConnected Waters Initiative Research Centre (CWI), the University of New South Wales (UNSW), Sydney, AustraliaFederal Institute for Geosciences and Natural Resources (BGR), Hanover, GermanyNational Centre for Groundwater Research and Training (NCGRT), College of Science and Engineering, Flinders University, Adelaide, AustraliaFederal Institute for Geosciences and Natural Resources (BGR), Hanover, GermanyNational Centre for Groundwater Research and Training (NCGRT), College of Science and Engineering, Flinders University, Adelaide, AustraliaKarlsruhe Institute of Technology (KIT), Institute of Applied Geosciences (AGW), Karlsruhe, Germany<p>Hydraulic head and gradient measurements underpin practically all investigations in hydrogeology. There is sufficient information in the literature to suggest that head measurement errors can impede the reliable detection of flow directions and significantly increase the uncertainty of groundwater flow rate calculations. Yet educational textbooks contain limited content regarding measurement techniques, and studies rarely report on measurement errors. The objective of our study is to review currently accepted standard operating procedures in hydrological research and to determine the smallest head gradients that can be resolved. To this aim, we first systematically investigate the systematic and random measurement errors involved in collecting time-series information on hydraulic head at a given location: (1) geospatial position, (2) point of head, (3) depth to water, and (4) water level time series. Then, by propagating the random errors, we find that with current standard practice, horizontal head gradients <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo><</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">4</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="35pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="f11cb695995b68e64d8031662f2334f2"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="hess-23-3603-2019-ie00001.svg" width="35pt" height="13pt" src="hess-23-3603-2019-ie00001.png"/></svg:svg></span></span> are resolvable at distances <span class="inline-formula"><i>⪆</i>170</span> m. Further, it takes extraordinary effort to measure hydraulic head gradients <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo><</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">3</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="35pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="715b0476aca53918edbdf641c0281be8"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="hess-23-3603-2019-ie00002.svg" width="35pt" height="13pt" src="hess-23-3603-2019-ie00002.png"/></svg:svg></span></span> over distances <span class="inline-formula"><10</span> m. In reality, accuracy will be worse than our theoretical estimates because of the many possible systematic errors. Regional flow on a scale of kilometres or more can be inferred with current best-practice methods, but processes such as vertical flow within an aquifer cannot be determined until more accurate and precise measurement methods are developed. Finally, we offer a concise set of recommendations for water level, hydraulic head and gradient time-series measurements. We anticipate that our work contributes to progressing the quality of head time-series data in the hydrogeological sciences and provides a starting point for the development of universal measurement protocols for water level data collection.</p>https://www.hydrol-earth-syst-sci.net/23/3603/2019/hess-23-3603-2019.pdf |
| spellingShingle | G. C. Rau G. C. Rau V. E. A. Post M. Shanafield T. Krekeler E. W. Banks P. Blum Error in hydraulic head and gradient time-series measurements: a quantitative appraisal Hydrology and Earth System Sciences |
| title | Error in hydraulic head and gradient time-series measurements: a quantitative appraisal |
| title_full | Error in hydraulic head and gradient time-series measurements: a quantitative appraisal |
| title_fullStr | Error in hydraulic head and gradient time-series measurements: a quantitative appraisal |
| title_full_unstemmed | Error in hydraulic head and gradient time-series measurements: a quantitative appraisal |
| title_short | Error in hydraulic head and gradient time-series measurements: a quantitative appraisal |
| title_sort | error in hydraulic head and gradient time series measurements a quantitative appraisal |
| url | https://www.hydrol-earth-syst-sci.net/23/3603/2019/hess-23-3603-2019.pdf |
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