An inseparable element of rural areas and farms are built-up areas organized in the form of a farmstead. Under almost all conditions, the presence of such facilities is linked with the appearance of sources, usually spot-like of water contamination. The aim of this study was to analyse the factors that affect changes in the water level and quality in a dug well at a farmstead situated in the catchment area of Lake Wydmińskie. The research was conducted in the years 2016-2018 in the farm in the village of Sucholaski (Warmian-Masurian Voivodeship, Poland). Changes in the water level and quality were examined in a 3.75 m deep dug wall. In the past, it was used as a drinking water intake; now it is only an extra water source, used for the farm’s needs (watering plants and cattle). The study showed that changes in the well water level and physicochemical parameters were affected to the greatest extent by the weather conditions at the moment (precipitation and air temperature). The quality of water in the well was affected by the amount and distribution of rainfall as well as by the farm buildings, especially by the cow shed and its surroundings. The amount and distribution of rainfall did not always have a direct impact on the water level in the well and the intensity of impurity migration within the soil profile, which was associated with a temporal shifting of groundwater resource replenishment relative to the time of rainfall. High concentration, mainly of nitrate nitrogen (NO3-N) and potassium ions in the well water, indicate that it is poorly protected against impurity influx from the immediate surroundings, with the cow shed being their main source.