The Tagliamento river plain is very rich in water thanks to the underground aquifers which, precisely in the passage between the high and low plains, emerge on the surface. There are therefore many resurgences that create lakes (olle) and rivers (for example, Varmo and Stella). These resurgence streams have great naturalistic, landscape, historical and cultural value.
The resurgences were once present in much of the transition zone, giving rise to large wetlands, as can be seen in this map taken from the Von Zach Map (late 1798-1805).
However, the wetlands have gradually been reclaimed, becoming cultivable areas. This brought immediate benefits for the populations but, years later, it greatly improved the ecosystem of the Friulian plain.
The groundwater and resurgence water system is closely linked to the Tagliamento river and, like the river, threatened from increasingly greater water withdrawals, reduction of the now rare wooded areas and excessive land consumption.