I would like to post the following questions and request for
information to the group.
One of the key limitations to the quantification of sediment effects
on fish and aquatic habitats is the characterization of sediment
release events (i.e. the concentration and duration of the sediment
episode). With respect to in-stream construction operations, the
elevated sediment loads associated with activities in and about a
watercourse are highly variable with several peaks of high sediment
concentrations and then respites of clear water. As a result, it is
difficult to describe the event simply as a concentration of sediment
for a specific duration of time.
Due to the variable nature of sediment loads associated with in-stream
construction I have two questions to ask;
1. I am aware of turbidity probes which are available which would
allow for the continuous or quasi-continuous logging of nephlometric
turbidities. However, the costs of such probes tend to restrict their
use ($3,000 Can). There has been some literature on the design of
low-cost probes (e.g. Lawler and Brown 1992). My question is, has
anyone out there used these designs to construct and use turbidity
probes and what are their limitations. Alternately, are there low
cost alternatives to the probes which are commercially available which
would allow for the continuous monitoring of high levels of turbidity
(2000-3000 NTU) at locations through out a watershed.
2. Once the continuous turbidity information has been collected and
converted to suspended sediment concentrations (using site-specific
relationships), what would be the best approach to describing the
sediment episode (other than a weighted average and duration of
In order to reduce unwanted noise, please send replies to me directly
and I will post results to the list in the new year.
Thanks for your interest, All the best in 1997!
Paul G. Anderson, M.Sc. P.Biol.
email - [log in to unmask]
Golder Associates Ltd.
1011 Sixth Ave S.W.
Calgary, Alberta. T2P 0W1