An Assessment of Hydroclimatic Trends and Mid-Range Streamflow Predictive Capacity in Four Lower Colorado River Sub-Basins

Abstract

Historical changes in hydroclimatic characteristics in four Lower Colorado River sub-basins are examined using the Mann-Kendall test for trends and Kendall's tau-b test for statistical association to better understand the processes taking place in these arid watersheds. During the historical record of 1906-2007, in general, temperatures have increased and streamflows have decreased while there has been no change in precipitation. Streamflow was found to have statistical association with annual maximum temperatures, El Nino/Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). Using this knowledge, two-year and five-year streamflow predictions are made using climate data to force a statistical model. We find no predictive skill at the two-year range but significant (alpha =.05) predictive skill in two of the basins at the five-year range. The dominant climate predictor for the Paria River Basin is ENSO and for the Little Colorado River Basin it is temperature.