Trend analysis of streamflows in relation to precipitation. A case study in central Italy

The monitoring of water resources is becoming increasingly important for humid temperate climates in light of climate change, which shows a generalised increase in temperatures and a decrease in precipitation, which is not generalised but relative to the area of interest. In this context, it is interesting to understand what the climatic changes have been, in terms of precipitation and how they have affected streamflows, by analysing them on a monthly basis. At the basin scale, interpolations were carried out with geostatistical methods using GIS software, spatialising the areal distribution of precipitation and obtaining an average value that can be correlated with water flows. As a pilot project, this research analysed the Upper Potenza basin in relation to the flow rates of the Potenza River over two reference periods, from 1964 to 1979 and from 2005 to 2020. The results show a decreasing trend in streamflows within the studied basin, while the precipitation trend decreases for the period 1964–1979 and increases for the period 2005–2020. Effective precipitation, in turn, shows a rather pronounced decrease in the more recent 2005–2020 period, due to climate change influencing the increase in temperature and consequently, the increase in evapotranspiration. In this context, it is significant to note that the Pearson correlation coefficient of streamflow to effective rainfall for both periods is about 0.8, suggesting that the net of anthropogenic disturbances, streamflow and actual precipitation maintain a high correlation. This model could be exported to other territories, in order to gain a global view for a better understanding and subsequent adaptation to ongoing climate change.