Jump to main content or area navigation.

Contact Us

Extramural Research

Grantee Research Project Results

Grantee Research Project Results

The Effects of Overwinter Dewatering on Brown Trout Redds and Egg Survival in a Montana Creek

EPA Grant Number: F6E11087
Title: The Effects of Overwinter Dewatering on Brown Trout Redds and Egg Survival in a Montana Creek
Investigators: Torrens, Christa
Institution: The University of Montana - Missoula
EPA Project Officer: Zambrana, Jose
Project Period: September 1, 2006 through September 1, 2008
Project Amount: $74,344
RFA: STAR Graduate Fellowships (2006)
Research Category: Academic Fellowships , Biology/Life Sciences , Fellowship - Field Ecology



Four years ago, a local industry began a year-round diversion of water from Warm Springs Creek; this diversion is temporarily on hold. The diversion of water noticeably lowers stage and streamflow levels in the spawning areas of the creek during the fall and winter months. These months are critical to brown trout (Salmo trutta) spawning and egg development. This study seeks to determine if the lower level of water in the stream during the wintertime diversion period decreases natural redd building at the site or creates environmental conditions that impact brown trout egg survival. The study will compare data collected last year and this year, when creek levels are at their natural height, with data collected next year, when creek levels are again lowered by the diversion.

To determine if the lowered water levels from an industrial water diversion decreases natural redd building or creates environmental conditions that impact egg survival for brown trout in Warm Springs Creek, Montana.


The primary environmental conditions measured will be temperature, dissolved oxygen (DO) and ammonia at the egg pocket depth; many studies have shown that these are critical to egg development and survival. Percent saturation of oxygen will be determined from temperature and DO measurements. The study will compare data collected last year and this year, when creek levels are at their natural height, and next year, when creek levels are impacted by the overwinter diversion. There is an ongoing 4+-year count of natural redds at the study site; any changes between the diversion and non-diversion years will be examined for statistical significance. The study will also compare historical and current streamflow levels in Warm Springs Creek and other area creeks to provide a basis for comparison and to monitor for any unusual conditions during the study period. Flow data at the study site and other creeks is readily available from USGS stream gauges.

Expected Results:

The results of this applied study will show the effects, if any, of overwinter dewatering on brown trout redd building and egg survival rates in Warm Springs Creek. It will provide the Butte branch of Trout Unlimited with information they need to determine whether they support the practice of overwinter dewatering. In addition, the study site is part of an ongoing monitoring effort by Trout Unlimited. The information gathered here will add to the body of knowledge about this study site as well as to the body of knowledge concerning the effects of wintertime diversions on fall-spawning salmonid egg survival.

Supplemental Keywords:

brown trout, Salmo trutta, egg survival, spawning habitat, dewatering, industrial water diversion, Warm Springs Creek, Montana,, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Habitat, Environmental Monitoring, Ecology and Ecosystems, habitat dynamics, brown trout, fish, ecological consequences, breeding site contamination, conservation biology

Top of Page

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

Jump to main content.