Changes of springs' yield of Lublin Upland and Roztocze Region in 1998-2008

Lublin Upland and Roztocze region are known for the occurrence of a large number of springs of high yield. These springs are fed mainly from Cretaceous or Tertiary water-bearing horizon. In order to determine variability of springs' yield, 61 selected springs were analysed in spring periods of the years 1998-2008. Collected hydrometric materials allowed for comparing average and extreme yield values of springs in various physiographic regions within the period of 11 years. Average value was 76.1 dm 3 ·s −1 , while the mean of the minimal yields was 44.7 dm 3 ·s −1 and of the maximal - 132.7 dm 3 ·s −1 . Coefficient of irregularity of the springs' yield ranged from 1.5 to 5.0, which may lead to the conclusion that the springs' yield is constant or varies slightly. In some cases the irregularity was higher but it was determined by hydrogeological, meteorological and local factors.