Before The Nature Conservancy established the Silver Creek Preserve, the watershed had been degraded by years of livestock grazing and overfishing. Preserve managers have been concerned about sedimentation, increasing stream temperatures, and invasive species.
In 1974, we established streamgage station 13150430 (Silver Creek at Sportsman Access near Picabo) to monitor stream discharge, stage, and temperature. The streamgage, funded in cooperation with The Nature Conservancy and the Idaho Department of Water Resources, collects data every 15 minutes and disseminates that data every hour to the USGS National Water Information System Web Interface (NWIS Web).
Since 1997, our biologists have visited Silver Creek every three years to collect water-quality data at this streamgage and at another site upstream of the streamgage on the preserve itself. We measure pH, dissolved oxygen, conductivity, and temperature. These data are also available on NWIS Web after they have been reviewed and approved.
Our biologists also collect, identify, examine, and count macroinvertebrate and fish species to evaluate long-term trends in biological communities. At riffles where macroinvertebrates are collected, we measure habitat variables that include velocity and depth; riverbed substrates (percent fines and embeddedness); and riparian growth (percent canopy cover).Data are available from the USGS BioData database.
At our trend sites, we found fish communities composed predominately of coldwater species. Brown trout—an introduced species—are common at these sites, too. The fathead minnow another introduced species, has recently been found at both sites, but in very low numbers. This species is commonly sold as baitfish in most midwest and eastern states.
We also found New Zealand mud snails—an invasive species—though the population doesn’t appear to be affecting other aquatic organisms.
Recorded water temperatures are warmer at the downstream site than at the upstream site. Coldwater-adapted macroinvertebrates such as stoneflies are more common at the upstream site on the Preserve.