Analysis of Changes in the Trends Recorded in Piezometers of the Solina Dam in the Study Period 2010–2015

This paper aims to analyze the changes in the trends of water levels in closed piezometers installed in the largest dam in Poland, i.e. Solina Dam located in the Podkarpackie province. The scope of the research includes the analysis of water levels in piezometers in the study period between 2010 and 2015. Statistical tests for identifying and rejecting outliers were performed before carrying out the analysis of the data acquired from the Automatic Technical Dam Monitoring System including: two variants of the Q-Dixon’s test (denoted as N9 and N13), as well as Grubbs’ test and Hampel’s test. A hypothesis was formulated that a change in the trend occurred after the floodin 2010. Using the least squares method , for each piezometer, two trend lines were matched to their water levels – the firstone for the year 2010 and the second one for the period of 2011–2015. In this way, two slope coefficientof the linear function were obtained, together with the estimation of their errors. These slopes were compared using a statistical parallelism test.