Impact of changing rainfall conditions on surface and groundwater resources in an experimental watershed in Greece

The present study concerns the impact of a change in the rainfall regime on surface and
groundwater resources in an experimental watershed. The research is conducted in a gauged
mountainous watershed (15.18 km2) that is located on the eastern side of Penteli Mountain, in the
prefecture of Attica, Greece and the study period concerns the years from 2003 to 2008. The
decrease in the annual rainfall depth during the last two hydrological years 2006-2007, 2007-2008 is
10% and 35%, respectively, in relation to the average of the previous years. In addition, the monthly
distribution of rainfall is characterized by a distinct decrease in winter rainfall volume. The field
measurements show that this change in rainfall conditions has a direct impact on the surface runoff
of the watershed, as well as on the groundwater reserves. The mean annual runoff in the last two
hydrological years has decreased by 56% and 75% in relation to the average of the previous years.
Moreover, the groundwater level follows a declining trend and has dropped significantly in the last
two years.