The results of mass pair comparisons of the groundwater flow of small rivers of the southern part of the European territory of the USSR are revealed showing considerable differences in the density of forests covering the basins. The growth
of the normal groundwater flow is shown where the forests are dense in comparison with lesser afforestated lands comprising from 4 to 7 mm annually which is 2540 % higher than the flow where the territories lack forests. The minimum of groundwater flow
for a number of years grows where there are forests from 0.32 to 1.89 mm annually (428 %). Thus although the water preserving role of forests can be traced in a number of cases as a whole it is small. (Ed.).