ABSTRACT
The last thirty years in Poland were characterized by a noticeable intensification of extreme natural phenomena such as sudden or prolonged precipitation. Their most common effects include floods resulting in significant economic and social losses. The abovementioned negative effects are most noticeable in settlements and industrial plants. This also applies to large opencast lignite excavations, while disruption to the mining process due to extreme rain events results in consequences that go well beyond mining destabilizing the supply of coal to final customers, that is power stations. The abovementioned disruptions are related to the increased frequency of occurrence of water hazards resulting from extreme rainfall events, which should be minimized by properly selected and well-functioning surface drainage systems at opencast mines.
The authors of the present article attempt to perform a statistical analysis of the variability of precipitation in the area one of the largest lignite mines, namely the "Bełchatów" lignite mine. The analysis included an evaluation of annual (seasonal) precipitation taking into account the trend changes. Parametric analysis was expanded to include a detailed analysis of the variability of daily precipitation taking into account the following factors:
 The annual average daily precipitation,
 The annual average efficiency of precipitation totals,
 The annual frequency of daily precipitation totals,
 Long-term variability of the maximum daily precipitation and,
 The annual maximum daily precipitation totals.
The mentioned analyzes were performed for the selected but representative precipitation station in Dobryszyce and are focused on the period from 1961 to 2015.
The analysis of precipitation in the area of Bełchatów, where mining and energy activities were carried out over the last 55 years, has shown an increase in the amount of rainfall (the annual totals, summer totals). By determining the pluviometric characteristics of the climate on the basis of an analysis of the average and maximum daily precipitation, significant changes that are likely related to the anthropogenic impact on the local environment, including the precipitation field, have been shown.