Nutrient levels and biostimulation in the lower Colorado River/reservoir system

Abstract

The lower Colorado River is a very important resource for the southwestern U.S. Previously, biostimulation and the problems associated with it had not been studied from a basin wide approach. This research had three goals in mind while investigating biostimulation on the lower Colorado. First, a data base was assembled containing 843 cases, each of which included from 1 to 7 limnological parameters. Second, a simple model was formulated, for managing biostimulation, which predicts total phosphorus and chlorophyll a concentrations. Third, statistical analyses of the data base provided an indication of the present state of the river. N:P ratios inferred that the system was phosphorus limited. Trophic states were generally in the oligo-mesotrophic range, except around Imperial Reservoir, where they were meso-eutrophic. The results of this study suggest that the lower Colorado River/Reservoir system is not currently threatened with biostimulation problems.