The goal of the paper was to determine surface water resources of an agricultural watershed representative for the areas of intensive crop production in the Kujawy region. This area is characterised by the lowest average annual precipitation in Poland and high water demands related to the intensive crop production.
Hydrological studies were carried out in 2007–2011 in the upper Zgłowiączka River watershed located in the eastern part of the analysed region. Over 90% of the study area is used as an arable land.
Water velocity in the river bed and water level were measured at the outlet of the watershed in the river cross-section Samszyce.
The upper Zgłowiączka River has a snow-rainfall hydrological regime, strongly modified by anthropogenic activities related to the intensive crop production and installation of subsurface drainage system. The study period was characterised by very large temporal variability of hydrological conditions. The mean annual outflow coefficient amounted to 18% and varied highly in time: from 3% in the average years to 62% in the abnormally wet 2011. Average discharge (SSQ) in the Samszyce river cross-section was equal to 0.25 m3·s−1, and the mean unit outflow – to 3.2 dm3·s−1·km−2. The results of the study show that disposable surface water resources of the Kujawy region are very small, especially in the summer half-year. Thus, their utilization as a potential source of water for crop irrigation can be taken into account only, if water excesses will be retained within the watershed and used in conjunction with groundwater resources.