Impact of climatic change on river discharge in the driest region of Poland

Discharge in the Warta River in Poland has been analysed based on long series of measurements at the Gorzow Wielkopolski gauge station (covering the whole catchment area) and at Poznan (middle and upper catchment area), and the Notec River is characterized by the gauge station at Nowe Drezdenko. The annual mean discharge of the Warta River for the period 1981-2010 was equal to the average value for the last 163 years (209 m(3) s(-1)), and there was no significant change in comparison with the ratio of runoff in the summer and winter half-years. In the driest region of Poland, the climate has been described on the basis of precipitation and air temperature. The annual mean precipitation for 1981-2010 (544 mm) in the Warta River catchment area was the same as that for the period 1848-2010. The precipitation has been increasing in spring and winter, and decreasing in summer. There is a positive and very significant correlation (r = 0.705) between the annual discharge and annual precipitation totals. The annual mean air temperature has risen by 0.6 degrees C between the periods 1848-1980 and 1981-2010.