An analysis of the dynamics of changes to water levels in the open piezometers of the Pieczyska dam in the study period between January 2016 and April 2017

Abstract

The construction This paper aims to analyze the changes in trends of water levels in open piezometers installed at the dam in Pieczyska, which is the only seepage dam in Poland constructed via the silting technique. The scope of the research includes the analysis of piezometric data for each of the 82 active piezometers installed on the dam from January 2016 to April 2017 and taking into consideration the accident which occurred in February 2016, during which at the downstream of the dam there was hydraulic piping, following which ca. 150 m3 of soil was eroded. A Statistical Rosner’s test for identifying and rejecting outliers was performed before carrying out the analysis of the piezometric data. A hypothesis was formulated that change in the trend occurred after the accident in February 2016. Using the method of least squares, for each open piezometer, two trend lines were matched to its water levels - the first one for the period January 2016-February 2016 and the second one for the period March 2016-April 2017. In this way, two slope coefficients for the linear function were obtained, together with the estimation of their errors. These slopes were compared using a statistical parallelism test.