Cheakamus River Water License Requirements ... - BC Hydro

Cheakamus River Benthic Community Monitoring, Progress Report 1
1 0BINTRODUCTION
A project was started May 12, 2008 to monitor periphyton, benthic invertebrates,
and associated habitat attributes in the Cheakamus River during each of 4 seasons in
2008 - 2010. Objectives are to increase sample size for a range of biological
assemblages and habitat attributes for which measurements were started in past
projects. The updated data will contribute to a model used to examine effects of variation
in flow on various indices of river condition. These objectives meet the Terms of
Reference for water monitoring that is required as part of the water license issued to BC
Hydro for power production on the Cheakamus River (BC Hydro 2007). The area of
interest includes the main channel of the Cheakamus River extending from the Daisy
Dam downstream to the confluence with the Squamish River. Methods follow those used
in development of the Cheakamus Benthos Model (CBM), a decision support tool for
water use planning that was developed in 2001 (Perrin 2001). CBM consists of
regression equations that can be used to predict benthic invertebrate biomass as a
function of several habitat and biological attributes and show the most important habitat
attributes that determine the invertebrate biomass. Data supporting CBM is from
monitoring over all seasons in 1996 (Perrin 1998) and 1999-2000 (Perrin 2001). The
model is not easy to use because it involves feedback loops between a periphyton
biomass model and an invertebrate biomass model. The two models must be run
together over a time series to look for equilibration of the feedbacks. No interface has
been written for the model so it is awkward to use. New data from monitoring in 2008-
2010 will be used to restructure and simplify the analysis and modeling. It will involve not
just one endpoint as in the present CBM (invertebrate or periphyton biomass) but the
complete assemblage of invertebrates. The approach will use multivariate techniques to
show what habitat attributes are most important in determining assemblages of benthic
invertebrates. The techniques will also identify taxa that are indicators of temporal and
spatial variation in assemblages and thereby river health. A second step will use
regression techniques to examine change in the biomass or abundance of indicator taxa
as a function of habitat variables found to be important in discriminating between
assemblages in the multivariate analyses. This two step process will show the
importance of flow (as one of the habitat variables) in determining the assemblage of
invertebrates that are indicators of river condition. If flow or flow metrics (e.g. coefficient
of variation of flow, maximum or minimum flow during a sampling series, mean flow, etc.)
are important, the model can be used to predict change in key biological indicators with
variation in values of those flow metrics. There are five project objectives:
1. Update CBM with additional data to increase sample size and simplify modeling
approaches to link biological and habitat attributes, including flow. The modeling will
be used to interpret changes in the health of the Cheakamus River that may result
from different flows released from the Daisy Dam.
Limnotek/InStream
November 2009