Water Stewardship Information Sources
| Citation | Page, N and Lilley, P. 2010. Analysis of streamflow, water quality and benthic community changes in North Creek (1999-2009). Prepared for City of Surrey. |
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| Organization | City of Surrey |
| URL | http://www.raincoastappliedecology.ca/wp-content/uploads/2010/09/2010-North-Creek-Data-Analysis-Report.pdf |
| Abstract/Description or Keywords | Purpose. The purpose of this report is to measure changes in streamflow, water quality, and the benthic invertebrate community in North Creek between 1999 and 2009. North Creek is an intensively monitored small stream draining from the East Clayton Neighbourhood in the east‐ central portion of the City of Surrey. East Clayton was developed using a variety of innovative stormwater management strategies since 2001. Analyses examined statistical trends in time‐ series data, as well as indicators of streamflow, water quality, and the benthic inverterbrate community. Results. The analyses found that streamflow, water quality, and the benthic invertebrate community changed substantially in North Creek downstream of the rapidly urbanizing East Clayton Neighbourhood between 1999–2009. Some were negative changes to stream condition associated with increasing urbanization, while others were positive changes linked to the use of low impact development measures in the developing catchment. Key results include: • Streamflow as a proportion of precipitation has increased significantly over the study period, even though mean annual discharge has not increased significantly. This suggests that exfiltration galleries and other strategies to infiltration precipitation into the shallow subsurface drainage system has been effective. • Maximum annual stormflow has decreased. This is contrary to the established pattern in urban watersheds where increased imperviousness and catch‐basin and pipe systems increase peak stormflows. The innovative stormwater source controls appear to infiltrate precipitation that would typically contribute to stormflow. • Water temperature has increased significantly during the study period. The large stormwater detention pond upstream of the water quality monitoring station is a likely cause of the elevated water temperature. • Turbidity increased during the initial clearing and development phase (2002–2004), although the overall change was not statistically significant. The number of minor turbidity events has remained consistent during the study period, while more turbidity events classified as moderate occurred in 2003 and 2004 than in all other years combined. This suggests that moderate and minor turbidity events may have different causes. • Specific conductivity has increased significantly and indicates that urbanization has substantial effects on chemical processes in small catchments. While conductivity is a broad measure of ionic concentration, it is likely a useful surrogate for contaminants of concern in urban streams including metals and nutrients. The benthic invertebrate community became more similar to other urban streams in the region because of the loss of sensitive taxa, and the establishment of taxa tolerant of environmental conditions in urban streams. The data indicate that the benthic invertebrate community is in transition as it responds to changing stream conditions accompanying urbanization of the East Clayton catchment. Taxa richness was lower before 2001, peaked between 2002–2004, and then declined. • B‐IBI, a composite measure of the benthic invertebrate community, increased significantly between 1999–2001. The significant increase in B‐IBI was driven by changes in only four the ten component metrics, and specifically by the increase abundance of a single predator taxa – Turbellarian flatworms. Flatworms were not present until 2007 but account for up to 35% of the organisms collected in samples at Station N1. Overall, the results of the analysis suggest that mitigation strategies to avoid or mitigate reduced summer baseflow and increased stormflows have been effective, but that the stormwater system has reduced but not eliminated the effects of urban development on water quality. Changes in the benthic invertebrate community were more variable and reflect the cumulative effects of changing streamflow, water quality, and other factors in North Creek. |
| Information Type | report |
| Regional Watershed | Lower Fraser |
| Sub-watershed if known | North Creek |
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| Project status | complete |
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