The role of a groundwater exchange index in a multiregressive model for water resources regionalization

The report describes a multivariate regressive model for the regionalization of surface water resources which takes interactions with groundwater circulation into account by using a suitable Broundwater Exchange Index (B.E.I.). The B.E.I. provides an estimate of the ratio between the rainfall for those areas which are drained, either superficially or underground, and the rainfall which only regards the natural basin boundaries. Two applications of the model are described for some cross sections of several rivers in Liguria (Northwestern Italy), which flow in non carbonatic areas; and for two rivers in Abruzzo (central Italy) which flow in highly permeable areas. The first application shows the effectiveness of the model for non carbonati areas; the second one shows how the model can be improved and good results be obteined by the introduction in the model of the B.E.I. as an independent variable for carbonatic areas.