Citizen-based monitoring characterizes water quality and benthic macroinvertebrates throughout a western Sierra stream

Background/Question/Methods

Deer Creek, a perennial stream running through the western foothills of the Sierra Nevada, is impacted by a century and a half of gold mining, development, agriculture, and water management.  Concerns about the health of this watershed led to the formation in 1995 of a citizen-based monitoring group, Friends of Deer Creek, based in Nevada City, California. In 2010, Friends of Deer Creek reorganized as Sierra Streams Institute (SSI), reflecting an increasingly regional focus. SSI has been collecting water quality and benthic macroinvertebrate (BMI) data for 10.5 years in an effort to address the hypotheses that water quality and BMI composition will change over time and will differ in less impacted upstream reaches compared to highly-impacted downstream reaches. 

Results/Conclusions

We have found statistically significant patterns with respect to 6 water quality variables and 4 BMI metrics.  Although total BMI abundance increased over time (χ²= 76.8646, p< 0.0001), other differences in water quality and BMI composition with respect to time need further investigation to determine the nature of these patterns. Between sites, there is variation in conductivity (p< 0.0001), pH (p< 0.0001), O₂ saturation (p= 0.0075), water temperature (p< 0.001), phosphate (PO₄; p< 0.0001), and nitrate (NO₃; p< 0.0001), with the top of the watershed generally containing better quality water, with lower nutrient levels (PO₄ and NO₃), higher dissolved oxygen, and lower water temperatures than those sites near the bottom of the watershed.  Three BMI metrics support these findings, showing greater macroinvertebrate richness, as well as an intolerant taxa index and a sensitive EPT (Ephemeroptera, Plecoptera, and Trichoptera) index 8 and 10 times higher, respectively, in the upper watershed than in lower stretches of the creek (p< 0.0001 for all 3 metrics).  Preliminary analyses of this long-term data set show the Deer Creek watershed decreasing in overall water quality and ability to support diverse and sensitive BMI communities as it travels from the relatively pristine headwaters to areas more heavily impacted by human activities.   Future work will more extensively investigate the impact of known point-source pollution, the success of restoration projects, and the correlations between water quality variables and BMI metrics.  These data will be used to inform future restoration and conservation planning in Deer Creek and other imperiled watersheds.