Methodology and site selection
Selecting a good site for water chemistry sampling in the field with a community group requires carefully planning to ensure safety, quality sampling free of errors, and a representative sample for the water body.
Safety and having a positive experience is the primary goal for the entire event. No one should risk personal safety in order to collect data. Never enter the stream unless the streamflow is well below the knee height of any person wading to collect a water sample. Safe passage from the bank elevation to the streambed also needs to be assured before entering the stream.
Locating the chemistry sampling upstream from any areas where people are wading in the water is critical for avoiding “dirty data,” because the boot activity in the stream stirs up sediment that WILL impact readings of turbidity or even the nutrients measurements with the colorimeter.
River Source has worked with large student groups doing sampling for over 20 years and find on occasion that the turbidity sample values increase during the ~ 30 minutes that chemistry sampling is occurring.
Getting a representative sample of the water body in running rivers and streams means collecting dissolved oxygen sampling in the right place (usually below a riffle if present) and making sure water temperature gets measured in a shaded portion of the stream (if possible; if not then use your body as shade from the sun).
Why do you think we would find turbidity reasons rising even though the stream itself is not getting more turbid (from a storm upstream or someone driving in the river upstream, for example)? River Source provides study design and sampling training during intensive workshops to guide community scientists to collect fisheries health data for more information on this topic.
What kind of sampling access and water quality issues might you find in the creek at the bottom of the black and white photo on this page?