Tesis doctoral: Dinámica hidrológica de una cuenca pirenaica de campos abandonados con pinar en expansión (Alt Berguedà, Barcelona)




The Cal Parisa catchrnent is a representative example of agricultural abandoned terraced fields where forest is in clear expansion over these terraces. This process also occurs in other Pyrenean regions and european alpine landscapes. The surface forest of Cal Parisa basin has increased in area fiom 5 % in 1967 to 25 % in 1988. This fact could change the hydrological balance of this kind of region and would involve a discharge decrease in the rivers.

Measurement of soil water content using the TDR method in the Cal Parisa basin during two years shows that the soil water content in forest areas is lower and statisticaily different in relation to gmssland areas. The interception effect and a Ggher evapotranspiration-of forest areas explains this Merent soil water content between grassland areas and forest areas.

The runoff volume generated in fomt areas appears lower than terraced and non forested areas. This fact indicates a possible future decrease of human usable water if forest areas continue increasing as they are at present. At present the real evapotranspiration from the Cal Parsa catchment represents 80 % of the annual precipitation volume whde the runoff volume is about 20% of the annual precipitation volume. On the other hand, the forest areas have an important role in the runoff temporal distribution. The forest involves delayed and lower maxirnum hydrograph discharge in relation to terraced and grassland areas.