Water resources and environmental change in a Mediterranean environment:: The south-west sector of the Duero river basin (Spain)

In the present work we analyse the temporal trend of water supplies to a network of basins, representative of the Mediterranean climate and plant cover, and its relationship with the evolution of temperatures, precipitation, and the changes that have occurred in the plant cover with time. The results point to an important decrease in water supply, with a high degree of dependence on precipitation (r = 0.85; p-value < 0.001). Important changes are also seen in the monthly distribution of water discharges due to modifications that have occurred in the intra-annual distribution of precipitation and an increase in temperatures in spring and summer. The rivers studied are losing their snow regime, with very important reductions in the winter and spring discharges. The results show that to date the changes detected in the forest have not affected the water discharges of the rivers. This absence of effect is probably because the changes observed in the plant cover are currently below the threshold after which it is possible to detect the effect of the forest on water discharges and because the interannual variability in rainfall and discharge in Mediterranean environments is so high that it masks other time-dependent changes. The planning and management of water resources should take these changes into consideration with respect to the functioning of hydroclimatic systems. (C) 2007 Elsevier B.V. All rights reserved.