Changes in the hydrologic periodicity of the Mississippi River, USA

Abstract

The Mississippi River Basin is the largest in North America. Throughout much of its recent hlstory, it has experienced channel modification from management schemes that have relied on engineered solutions. To determine how some of the hydrologic processes have changed the present study examines the temporal variability in data from hlstoric river stage records. The temporal autocorrelation at nine gages along the mainstem of the Mississippi River were examined using semivariance analysis for pre- and post-regulation timeperiods. Significant changes in the temporal dependence were identified from the pre- to post-regulation periods. There were also distinct differences in temporal variability along the Mississippi River. Variance along the Upper Mississippi River (UMR) declined from the pre- to post-regulation period. The average range of the temporal autocorrelation on the UMR doubled between the two time-periods. The Middle Mississippi River (MMR) exhibited a large increase in variance and the range. There was a sigmficant decline in the variance along the Lower Mississippi River (LMR), but the range remained relatively constant from the pre- to post-regulation periods. The findings supply baseline data for process-oriented management schemes and show the need for the development of management techniques that account for intra-basin variability.