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Thermal artifacts in measurements of fine‐scale water level variation
Author(s) -
McLaughlin Daniel L.,
Cohen Matthew J.
Publication year - 2011
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 - 10.1029/2010wr010288
Subject(s) - evapotranspiration , environmental science , diurnal temperature variation , infiltration (hvac) , wellhead , atmospheric pressure , surface water , soil science , hydrology (agriculture) , atmospheric sciences , materials science , meteorology , geology , ecology , environmental engineering , physics , geotechnical engineering , petroleum engineering , composite material , biology
The estimation of evapotranspiration (ET) from observed diurnal surface water level fluctuations may be highly sensitive to measurement errors. Available total pressure transducers (TPT) can provide requisite accuracy and precision but require atmospheric pressure compensation with equally accurate and precise barometric pressure transducers (BPTs). The BPT installation location determines the thermal setting, and sensor sensitivity to temperature could affect compensated water levels and any analyses requiring fine‐scale data. We investigated the effects of BPT installation location on compensated surface water levels and estimates of ET and net infiltration using the White method in four isolated forested wetlands in northern Florida. Water levels compensated with two differently positioned BPTs, one in buffered thermal conditions (BPT buf ; dry well at the TPT depth) and one in ambient temperatures (BPT amb ; screened wellhead space), resulted in markedly different diurnal signatures. Both displayed the expected diurnal pattern, but compensation with BPT amb amplified diurnal variation by as much as 1.5 cm, greatly overestimated ET, and suggested net exfiltration, while BPT buf compensation resulted in ET estimates similar to potential ET and suggested net infiltration. BPT temperature sensitivity followed diurnal temperature variation and generated systematic water level bias with the same signature as the expected trend, making these errors difficult to detect and underscoring the importance of proper BPT positioning.