Chemical and biological indicators of nutrient enrichment in the Yellowstone River basin, Montana and Wyoming, August 2000: Study design and preliminary results

A water-quality investigation of the Yellowstone River was conducted during low-flow conditions in August 2000, under the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) program. Samples for analysis of water chemistry (nutrients, field measurements, and other constituents) and biological communities (periphyton, phytoplankton, and macroinvertebrates) were collected at 11 sites on the main stem of the Yellowstone River between Corwin Springs and Sidney, Montana, as well as from tributaries including the Clarks Fork of the Yellowstone River, the Bighorn River, and the Tongue River.

Preliminary results of the investigation indicate concentrations of total nitrogen varied little throughout the length of the main stem of the Yellowstone River; total phosphorus concentrations increased slightly in the downstream direction. In contrast, periphyton chlorophyll a and ash-free dry mass concentrations, and algal productivity rates, were highest in the middle sections of the Yellowstone River.