Eutrofització dels rius d'Andorra

Resum

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.