To detect possible changes in the habitat quality of the Gran Paradiso
rivers from 2005 to 2020, we applied the RHS method to evaluate their
hydro-morphological status and we measured the main chemical water
parameters. In Figure 2 we reported the boxplots of the three indices
derived from the RHS application on the 12 river stretches.
FIG2
For all three indices the difference between the two years is not
significant (Wilcoxon Signed Test p>0.05). The median value
of HQA is slightly lower in 2020, whereas HMS remains almost the same
and the LRD highlights an even more lotic character in 2020. Overall,
from 2005 to 2020 the hydro-morphology of the examined stretches did not
highlight any evident change. Analyzing the individual sites, Leviona
has suffered some deterioration in the HQA, while Valnontey is the site
that has improved the most. In terms of HMS, Forzo, Roc and Nampio
indicate the most marked increases in morphological alterations while
Entrelor, Vaudaletta and Noaschetta are the most improved.
Concerning the physical and chemical water parameters, Table 1 reports
the summary for the two years.
TAB1
The only significant differences concern nitrate, which increased in the
2020 survey, and pH, which showed a decrease (Wilcoxon Signed Test
p<0.05 for both parameters). A slight yet not significant
increase regards also SRP and conductivity.