Long-term trends for water circulation in the lowland basin

The basin of the River Utrata (a tributary of the Bzura included in the Vistula River basin) is one example of the lowland regions in Poland that is particularly threatened by water deficits in different seasons and years. This is the result of relatively low annual precipitation totals, as well as of human activity including deforestation, drainage. the intensive abstraction of groundwater and the intensive development of agriculture and urban agglomerations. Water deficits can be confirmed hydrologically in long-term negative trends for flow in the Utrata at the Krubice profile and for freatic groundwater at several observation points (piezometers and wells). An analysis was made of annual trends for elements of the climate, namely precipitation and air temperature, at the Brwinow station representing the lowland basin of the Utrata. In estimating future changes in elements of water circulation (percolation and flow), use was made of the GFDL and GISS scenarios for global climate change (Global Circulations Models). Negative trends were noted for percolation (vertical feeding of groundwaters) in the cases of both the pessimistic GFDL scenario and the moderately pessimistic GISS scenario. The anticipated unfavourable conditions for the supply and renewability. of groundwaters coincide with significant changes (reductions) already noted in subsurface storage and the flow of the Utrata.