Despite its inhospitable appearance and lack of any ... - Udine Cultura

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Literature defines this environment in myriad ways, each a nuance of the
other, the only differences being the thickness attributed by each expert to
the hyporheic layer. Aquatic ecotones are areas in which large-scale hydraulic
exchanges occur and where biogeochemical activity - more intense than in
adjacent habitats - affects the quality of water flowing through the interface.
Hyporheic environments thus regulate water flow, and temporarily or
permanently store organic, mineral and sometimes polluting matter. The
microbial and animal components in them actively modify the timing and
volume of nutrient and pollutant flows. From the structural viewpoint, the
hyporheic zone is a matrix of permanently dark interstices saturated with
water flowing slowly, with slight daily temperature variations and great
bedrock stability. The hyporheic zone is an aphotic (without light), mechanical
and biogeochemical filter between surface and underground water systems,
ensuring their purification and maintenance.
From this viewpoint, an important contribution came in 1993 from the
American researchers Stanford and Ward with their concept of hyporheic
corridor, which describes the connections and interactions between the
hyporheic zone and the catchment basin. The role played by the hyporheic
corridor in a catchment basin is essential for many ecological processes
associated with nearby water sources: 1) the primary productivity in the
Three-dimensional (longitudinal, transversal, vertical) nature of a river system
stream above the hyporheic zone is strongly influenced by the distribution
and frequency on the vertical scale of zones of upwelling (where the watertable
supplies the stream), outwelling (areas where subsurface water supplies
the stream laterally) and downwelling (areas where surface water supplies the
water-table) of the stream, because the last two are usually richer in algal
nutrients like nitrates and phosphates than surface water; 2) the temporal and
spatial variability of processes of hydric exchange cause biodiversity in the
hyporheic zone to increase more than in the adjacent water-table and surface
habitats.
Although Italian rivers are relatively well-known from the hydrological,
biological and ecological viewpoints, an integrated overview of the Italian
river ecosystem is still missing. Research emphasises a lateral dimension,
i.e., the relationships between stream beds and surrounding floodplain and
river areas in particular; a longitudinal dimension, i.e., the variations occurring
along the length of rivers, from spring to outlet, although little is known about
the vertical dimension, i.e., the relationships of rivers with their underlying
aquifers. And the spatial scale is even less well-known in its temporal
evolution. This three-dimensional spatial view, with the addition of a fourth
temporal dimension, is the so-called four-dimensional nature of a river
ecosystem (as defined by Ward).
Spring at the base of a deposit of glacial origin (Pederù, South Tyrol)
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