8 páginas, 4 figures.An analysis of the phosphorus increase in the watersheds of Andorra as a result of
the increase of human population in the river banks is made. The greater concentrations in
phosphorus are found in relation to the increase of population and also in some sampling
stations in the highlands of this country. In high altitude the phosphorus concentrations
are related to hotel and sport facilities. Also the influence of water catchements to power
works are analized. In August the major stream, the Valira river, is dried in this catchement
process in station 22 and until the time of return of water (station 14) the main
river receives only wastewaters of two villages and water of minor tributaires. This means
a great increase in the phosphorus concentration in waters in stations 15 and 16 (figs. 1
and 2).
A modification in the composition of animal communities can be stated examining
the macrofauna, especially insects, of river stones. There is a relationship between phosphorus
concentration and the modification of communities. As a result of human population
increase the lower part of Andorra is higly enriched in nutrients in August, especially
in phosporus. A great quantity of phosphorus, estimated between 4 and 8 MT/month, leaves
the Valira river in the sampling station 1.Peer reviewe