Comparative Study of a Long‐Established Large Weighing Lysimeter and a State‐of‐the‐Art Mini‐lysimeter

Abstract

The resulting water‐balance estimates were then compared with those of the lower resolution large lysimeter, whose processing has remained unchanged since its installation. A number of additional, retrospectively applicable processing steps for the large lysimeter were then tested to mitigate the main sources of error for this instrument. Those found to be most beneficial were the application of a 10‐min moving average to the mass measurements and the setting of ET and condensation to zero in hours with liquid precipitation. In spite of the differences in design, a generally close agreement between the two lysimeters was observed, which was further improved with the optimized large‐lysimeter processing. A comparison of the lysimeter mass increases associated with liquid precipitation further revealed, however, that the large lysimeter experiences a previously unknown under‐catch of about 11.5%, which could also be important for other lysimeter facilities. This under‐catch led to a reduction in large‐lysimeter seepage during the analyzed period, although the ET flux was not found to be affected.