Trends in low flows in Spain in the period 1949–2009

This study analyses trends in low flows in Spain in the period 1949–2009, based on daily flow data collected at 60 gauging stations located in near-natural catchments. Two low-flow indicators were considered: (i) the seven-day annual minimum streamflow and (ii) the 10th percentile of the yearly flow duration curve. Catchments were clustered into three regions in terms of monthly mean flows. The Mann-Kendall test was used considering four periods between 1949 and 2009. A multi-temporal trend analysis was also applied to the longest series to identify wet and dry periods that could influence the results. Lastly, a field significance test provided a regional assessment of the at-site detected trends at each region. The results for each indicator reveal a clearly decreasing trend in low flows throughout the northern half of Spain that was found to be field-significant over the (Atlantic and Mediterranean) regions.Editor Z.W. Kundzewicz; Associate editor not assigned