STATISTICAL ANALYSIS OF THE BEAVER VALLEY WETLANDS

  Nicole Williams and Mark Ecker

   In the summer of 2003 students and faculty at the University of Northern Iowa have been analyzing water quality in a wetlands area dominated by West Lake and Railroad Lake just northwest of campus.  A statistical goal for West Lake and Railroad Lake was to check the two lakes for spatial correlation, i.e., pairs of observation closer in space tend to be more similar then pairs further apart.  We explore spatial correlation for the variables water depth, sediment depth, dissolved oxygen, and phosphorus.  Then phosphorus concentrations can be predicted for any unsampled sites within each lake.  After inspecting empirical variograms we find little evidence of spatial correlation.  Another goal concerning the Iowa wetlands is to run an analysis of covariance to explore what relationship (regression) exists between the dependent variable phosphorus and the independent variables dissolved oxygen, water depth, and sediment depth.  The goal of this analysis is to predict the phosphorus level in either West Lake or Railroad Lake when different levels of an independent variables are used.  We conclude that the slopes for the independent variables are all the same, but the intercepts for West Lake and Railroad are different, i.e., West Lake has a higher phosphorus level.

This research was supported by the Roy J. Carver Charitable Trust and the Iowa Space Grant Consortium.