The name conjures up sailboats, spinnakers, and a stiff breeze. But the BC Conservation Foundation’s annual Flow Regatta had none of that. There wasn’t a boat in sight. There was, however, a lot of talk about flow, in the hydrological sense, and a lot of standing around in the creek at Rosewall Park.
Three of us from BWS joined representatives from the Province, BC Conservation Foundation, sponsors of the event, and watershed groups from all over Vancouver Island and other islands as well, for a day devoted almost entirely to measuring how fast water moves in creeks. It was exactly our kind of party. It was also, as these events always are, a great chance to catch up with friends from other stewardship groups who we don’t see often enough.
We split into two groups: beginners and advanced. The beginners spent their morning brushing up on the use of a FlowTracker II, the handheld instrument that measures water velocity at a chosen spot. It’s deployed at different points across a stream to build a model of total flow. Much of the lesson focused not on the happy path but on the messy one: what to do when the instrument reports an error or a warning. The beginners split into two sub-groups and each took a set of measurements at the same site. They came back with numbers that didn’t quite match. After some discussion, the consensus was that both readings fell within the bounds of measured uncertainty which is a fancy way of saying: close enough for hydrology.
Meanwhile, the advanced group spent the day walking up and down their section of the creek, discussing the pros and cons of various measurement sites. They engaged in deep debates over such philosophical questions as why the BC Hydrometric Standards call for 80/20 measurements at points over 0.5 metres of depth rather than 0.75 and when you might deviate from the 60% depth placement standard. By the end of the day, this group of experienced samplers had thoroughly examined the questions from every angle and, as far as we can tell, never actually put a probe in the water. We’re choosing to see this as a triumph of theory over practice.
After lunch, everyone reconvened for sessions on benchmark surveys and rating curves. Benchmark surveys are simply a procedure to confirm that a sensor hasn’t moved during the yearly rising and falling of the creeks. Rating curves are more complicated. But they are what allow us to determine how much water flowed over a given period of time which is the whole point of a flow monitoring program. The key to creating these magic curves is the flow measurements we take in the field.
This is why we have entire regattas to learn the all the nuances and pitfalls of the process. Thank you to BCCF for providing this opportunity for us to hone our craft.