Hydrological drought response to meteorological drought in the Iberian Peninsula

In this study we assessed the impact of meteorological droughts on streamflow droughts in 187 river basins of the Iberian Peninsula. For each basin we correlated the 1 mo to 48 mo standardized precipitation index (SPI) with the standardized streamflow index to assess the response time of streamflow droughts to the SPI, and to determine the best climatic time scale over which to monitor hydrological droughts. In addition, we analyzed the effects of dam construction and reservoir use on changes in the response of hydrological droughts. The analysis revealed 2 main types of hydrological drought response to meteorological drought: (1) a peak response pattern involving enhanced hydrological sensitivity at short SPI time scales, which largely characterized basins in the northern sector of the Iberian Peninsula, and (2) a sustained response pattern involving greater sensitivity to meteorological droughts at much longer time scales, which primarily characterized the central and southern basins of the Iberian Peninsula. Water management has significantly altered the natural hydrological response to meteorological droughts, delaying the impacts of precipitation deficits over long time scales, especially downstream of reservoirs used for irrigation purposes.