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Feasibility of soil moisture monitoring with heated fiber optics
Author(s) -
Sayde Chadi,
Gregory Christopher,
GilRodriguez Maria,
Tufillaro Nick,
Tyler Scott,
van de Giesen Nick,
English Marshall,
Cuenca Richard,
Selker John S.
Publication year - 2010
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2009wr007846
Subject(s) - water content , optical fiber , materials science , environmental science , standard deviation , fiber , temperature measurement , soil science , backscatter (email) , remote sensing , optics , geotechnical engineering , composite material , geology , telecommunications , statistics , physics , mathematics , quantum mechanics , computer science , wireless
Accurate methods are needed to measure changing soil water content from meter to kilometer scales. Laboratory results demonstrate the feasibility of the heat pulse method implemented with fiber optic temperature sensing to obtain accurate distributed measurements of soil water content. A fiber optic cable with an electrically conductive armoring was buried in variably saturated sand and heated via electrical resistance to create thermal pulses monitored by observing the distributed Raman backscatter. A new and simple interpretation of heat data that takes advantage of the characteristics of fiber optic temperature measurements is presented. The accuracy of the soil water content measurements varied approximately linearly with water content. At volumetric moisture content of 0.05 m 3 /m 3 the standard deviation of the readings was 0.001 m 3 /m 3 , and at 0.41 m 3 /m 3 volumetric moisture content the standard deviation was 0.046 m 3 /m 3 . This uncertainty could be further reduced by averaging several heat pulse interrogations and through use of a higher‐performance fiber optic sensing system.