Falls River Project Water Use Plan Falls River Fish ... - BC Hydro

Falls River WUP Monitoring 2008/2009
2.3.2 Data Analysis
To analyze the effect of total discharge rate on water levels, tidal influence was detached from the
water depth data in the study area. Hourly tide chart readings (Appendix II) were cross referenced
with actual water levels (hourly data obtained from the pressure transducer) and tidal peaks
(considered ‘noise’) were manually identified. Data points which were exaggerated by tidal influence
were excluded from the data-set to reduce noise and augment the underlying data analysis.
Pearson’s product-moment correlation analyses were then applied to the discharge/water level data
to determine if a linear relation exists between total discharge levels and water depth in the tailpond.
2.4 Substrate Composition (Wolman Pebble Counts)
The particle size characteristics and potential temporal changes of particle size at each sample site
were assessed using modified Wolman pebble counts (Wolman 1954). The Wolman pebble count
involves a surveyor following a transect across a river stream width with heel/toe steps, picking up
the first particle touched by a pointed index finger at the tip of the boot. This is performed until 100
particles are measured. Since our study areas and sample sites were relatively small, we used a grab
technique where the observer sampled as much substrate at each sample site (n=9), that could be
held in both hands. The sample was then taken to the shoreline, where the intermediate diameter of
each selected particle was measured with a gravelometer (a piece of aluminum metal with 14 square
holes of common sieve sizes (1/2-phi unit classes) ranging from 2 mm to 180 mm). This was
performed until 100 particles were measured. The Wolman pebble counts were conducted 3 times
during the study: at the eyed stage (September 23 rd –October 27 th , 2008), February 19 th , 2009,
and at the emergence stage (early May 12 th , 15 th , 2009).The crew member completing this task
differed between the three sampling periods; however, on a survey date the same observer was used
at all 9 sites to sample the substrate. See Figure 8 (e and f) for photos of substrate sampling, as well
as an overhead view of the surface substrate at incubation area 2 (photo d).
Data from the Wolman pebble count were arranged and analyzed according to size (13 size classes,
ranging from 2.8 to 180 mm). The percent frequency and cumulative percent finer for each size
class were then calculated and plotted (cumulative frequency curve and particle size histogram).
Cambria Gordon and Metlakata Fisheries 14