Evolution of water discharge in a mountain catchment of the Central System: the headwater of the Tormes river (1941-2004)

Abstract

The present work analyses the temporal trend of water discharge in the headwater of the Tormes catchment related with the temporal behaviour of main climatic variables (temperature and precipitation) and the changes that have occurred in the forest cover. The results show how water discharge decreases with a significant correlation with precipitation (r2= 0,708; p-value < 0,001). Although the forest cover has increased about 30 % in the last 45 years, the analysis of hydro-climatic normalized variables does not suggest that the forest expansion has influenced in the discharge decreasing trend. An interesting result has been the monthly variation in discharge due to rainfall decreasing in February and March, and a significant increase in temperature during March. This fact has triggered losses of the snow contribution within the fluvial regime of the catchment in the last decades.