Electronic Data Collection and Analysis System
Yin Foo, Des; Foley, Margaret
E-Publications; PublicationNT; E-Books; Report ; 39/1992
Made available via the Publications (Legal Deposit) Act 2004 (NT).
Power and Water Authority
Report ; 39/1992
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Technical Report WRD92039 Viewed at 15:07:17 on 29/07/2010 Page 170 of 192. D2. l~\KING BAROMETRIC CORRECTIONS TO WATER LEVELS LOGGED WITH AN UNVENTED PROBE Any water level data logged using unvented transducers must be correc'ted for the changes which have occured in the atmosDheric pt'essure either since the transducer was calibrated or the transducer was at a set depth. In some situations (e.g. the analysis of a pump test), only the data subsequent to a particular time (TO) needs to be correc'ted. In dny case, a time TO at which the head (HO) or drawdowll (DDO) is known must be selected, and the changes in barometric pressure compared to the value at that time (BO) I must be applied to the data to be analysed. I f the change in barometric pressure (B) compared to its' value at a reference time (BO) is at any time BC, then BC = B - BO (2) i.e. the chanqe in barometric pressure at any time is the barometric pnlssure minus the barometric pressure at the reference time, head must Since an increase in barometric pressure J:ead by the transducer, the heads logged be decreased by that amount. If the corrected head data is BCH then : BCH- H - BC increases the by the system barometrically (3) Conversely f since an increase in head is associated with a decrease in drawdown : BCDD - DD + BC (4) \,her., BCDD is the barometrically corrected drawdown, and BC the change in barometric pressure from that at the reference time ~ro. 'Phe procedure for applying barometric corrections to a set of logged head data is :