Water Quality Stream Water Temperature Temperature Water temperature data, collected through use of continuous loggers, was analyzed for the six study streams using methods described above. Each temperature logger was assigned a score by dividing the Summer Average Temperature by Percent Growth. These scores ranged from 60 to greater than 90. Scores of greater than 90 are considered harmful to trout. Reaches with scores ranging from 60 to 70 are suitable for brook trout and had few temperature readings considered stressful to brook trout (the indicator species). About half of the sites had healthy scores between 60 and 70. Conversely, a few sites scored poorly including lower Chester Creek, middle Tischer Creek and upper Amity Creek (Figure 9). The healthiest score was assigned to a site in the headwaters of Tischer Creek. Figure 9. Map of all computed temperature scores for continuous temperature records in the six Duluth streams. Sub-watershed Temperature Rating The size of each individual temperature monitoring drainage area varied widely, from over four square to 0.04 square miles. In order to normalize the temperature changes that were taking place within these streams the temperature change for each sub-watershed was divided by that sub-watershed’s area in square miles. The results were used to identify which areas and land-uses within Duluth are disproportionately warming or cooling stream temperatures (Figure 10). Figure 10. Map showing the temperature rating for each temperature monitoring sub-watershed in Duluth. Dark green symbolizes stream temperatures are decreasing rapidly per square mile of drainage area. Red indicates the opposite – temperatures are increasing rapidly. No color indicates that stream temperatures are changing very little within that particular sub-watershed. The results show several specific Duluth sub-watersheds in which it would be appropriate to pursue restoration or protection strategies to address water temperatures. The following is a short list of the highest priority areas where water temperatures are warming disproportionately and where restoration efforts should be focused. Potential sources of warming are identified, as well as implementation concepts aimed at decreasing stream temperatures. Chester Creek between stream mile 1.4 and 1.6 The Chester Creek sub-watershed between stream miles 1.4 and 1.6 (Reach 6) contains the dams and ponded water in Chester Park, and is well known to cause increased stream temperatures. The water
Water Quality Stream Water Temperature Temperature Water temperature data, collected through use of continuous loggers, was analyzed for the six study streams using methods described above. Each temperature logger was assigned a score by dividing the Summer Average Temperature by Percent Growth. These scores ranged from 60 to greater than 90. Scores of greater than 90 are considered harmful to trout. Reaches with scores ranging from 60 to 70 are suitable for brook trout and had few temperature readings considered stressful to brook trout (the indicator species). About half of the sites had healthy scores between 60 and 70. Conversely, a few sites scored poorly including lower Chester Creek, middle Tischer Creek and upper Amity Creek (Figure 9). The healthiest score was assigned to a site in the headwaters of Tischer Creek. Figure 9. Map of all computed temperature scores for continuous temperature records in the six Duluth streams. Sub-watershed Temperature Rating The size of each individual temperature monitoring drainage area varied widely, from over four square to 0.04 square miles. In order to normalize the temperature changes that were taking place within these streams the temperature change for each sub-watershed was divided by that sub-watershed’s area in square miles. The results were used to identify which areas and land-uses within Duluth are disproportionately warming or cooling stream temperatures (Figure 10). Figure 10. Map showing the temperature rating for each temperature monitoring sub-watershed in Duluth. Dark green symbolizes stream temperatures are decreasing rapidly per square mile of drainage area. Red indicates the opposite – temperatures are increasing rapidly. No color indicates that stream temperatures are changing very little within that particular sub-watershed. The results show several specific Duluth sub-watersheds in which it would be appropriate to pursue restoration or protection strategies to address water temperatures. The following is a short list of the highest priority areas where water temperatures are warming disproportionately and where restoration efforts should be focused. Potential sources of warming are identified, as well as implementation concepts aimed at decreasing stream temperatures. Chester Creek between stream mile 1.4 and 1.6 The Chester Creek sub-watershed between stream miles 1.4 and 1.6 (Reach 6) contains the dams and ponded water in Chester Park, and is well known to cause increased stream temperatures. The water
Duluth%20Urban%20Streams.docx