The occurrence of a hydraulic connection between piezometers is identified based on similar changes in water levels. Some piezometers react to changing upper or lower water levels, some may also react to atmospheric precipitation. If the reaction to variable upper water levels is significant, then leakage of seepage control devices is identified and the dam is subjected to repair works. The aim of this research paper is to present and analyse the dynamics of variability of water lev-els in open piezometers of the Chańcza dam, located at the 36 km of the Czarna Staszowska River in the town of Korytnica in Świętokrzyskie province (Poland). Before the analysis of the piezometric data was commenced, the Grubbs statistical test was used to identify and reject the outliers. The scope of the research includes the data captured between January 14, 2014 and January 13, 2017. A hypothesis was formulated that the change in the trend occurred after the spring of 2015 when the water level in the reservoir was reduced by approx. 1.5 m. Two trend lines were adapted for the water levels of each pie-zometer using the least squares method – the first one for the period from January 2014 to May 2015, and the second one from June 2015 to January 2017. In this way, two slopes of the linear function were obtained together with an estimation of their errors. These slopes were compared using a statistical parallelism test.

The intensification of agricultural production is one of the factors determining economic development. Increasing mechanisation and use of fertilisers in agriculture lead to higher yields, but at the same time they can pose a threat to the environment. The overuse of chemical fertilisers contributes to increased concentration of nutrients in agricultural runoff. One of such areas is the Szreniawa River catchment, the study area located in the southern part of Poland. In this catchment, intensive mostly mechanical ploughing is applied in, for instance, vegetable production. The area has loess soils, which with intensive ploughing are susceptible to erosion. The study aims to determine changes in the quality of flowing waters against the background of agricultural production and land-use characteristics. Surface waters were classified as class II and occurred at all analysed points. The highest concentrations of N-NO3, N-NH4 and P-PO4 were found at a point in the middle of the catchment (lower part of research area). There, the lowest concentrations were recorded in 2018, which was related to the amount of precipitation during the growing season. On the other hand, the volume of plant and animal production closely correlated with the quality of surface water in the area. This was also confirmed by the land use structure. In conclusion, intensive agricultural production, mainly in terms of plough tillage causes significant hazards associated with soil erosion especially on agriculturally sensitive soils, although it provides good yields.