Analysis and quality control of weighing lysimeter water storage data

Abstract

A tool was developed to analyze 5-minute weighing lysimeter apparent relative water storage data and reduce it to values of the water balance components, including evapotranspiration (ET), dew and frost accumulation, precipitation, irrigation, and drainage while applying quality control measures. Algorithms automatically identify precipitation, and dew and frost accumulations in the 5-minute data, and place flags appropriately (“P” or “DW”) in a column that is referenced by formulae that separately calculate values for these. Noise can, however, cause false identification of precipitation or frost and dew accumulations, so another column is made available in which the user can enter flags to either nullify (“NO”) false automatic identification, or conversely, identify precipitation or dew and frost accumulations (“P” or “DW”) not automatically identified. This column also serves for entry of specific flags identifying, amongst others, apparent relative water storage changes due to irrigation, drainage tank emptying, and counterweight adjustments. Other algorithms act upon these flags to correct and adjust the original raw relative storage values so that the adjusted relative storage reflects only ET. Two different methods of ET calculation provide for error checking and data validation. The spreadsheet was applied to 30 + years of 5-minute lysimeter data. Example data from 2018 illustrate the processing and quality control procedures.