The types and abundance of organisms found in a stream reach are a function of the water quality and physical habitat within the reach. Our objective was to examine the relationship among physical, chemical, and biological characteristics of stream reaches in the South Platte River Basin and the natural and anthropogenic factors affecting this relationship. This study is a part of the U.S. Geological Survey's National Water Quality Assessment (NAWQA) program.
As a first step in this assessment, we conducted a synoptic survey of 23 stream reaches within the South Platte River Basin.
We made qualitative habitat measurements of riparian vegetation, bank stability and composition, presence and number of floodplain terraces, geomorphic channel units, and substrate composition. Also, we made quantitative habitat measurements of width, depth, discharge, bedform and substrate distributions, bank height, and bank angle using transects across the channel.
The relative abundance of algae and macrophytes were recorded along the transects. A qualitative assessment of invertebrates was made to select the sites for quantitative sampling. Invertebrates were collected quantitatively at the most "faunistically rich" channel unit.
Dissolved oxygen, pH, temperature, and specific conductance were measured in situ. Water samples also were collected and analyzed for nitrogen and phosphorus.
We found a positive relationship between physical, chemical and biological characteristics. But, chemical characteristics exhibited the least influence. Those reaches with greater physical diversity showed greater numbers of different types of biota.
1 U.S. Geological Survey, Box 25046, MS 415, Denver Federal Center, Lakewood, CO 80225