Observations on land cover changes and water resources in the headwaters of the Ebro catchment, Iberian Peninsula

Large areas in the Southern Pyrenees and other mountain areas in Spain suffered in the last decades considerable increase in forest cover due to both land abandonment and afforestation works. An analysis of the relationships between temporal changes in forest cover and water resources was performed in a sample of the tributaries to the Ebro river, with little changes in water abstractions. The historical records of annual stream water discharge of the sample showed diverse temporal trends weakly related to changes in precipitation and potential evapotranspiration. Several of the discharge decreasing trends were statistically significant, whereas none of the observed discharge increasing trends was significant. The temporal trends of discharge residuals, after annual water balance modelling using precipitation and potential evapotranspiration, have been analysed in relationship to changes in forest cover in the catchments. The results gave support to the expectable decrease in water yield determined by an increase in forest cover, confirming that water resources cannot be assumed as stationary in time where land cover changes are known or foreseen. (C) 2004 Elsevier Ltd. All rights reserved.