Suggestions for monitoring current at a kelp farm
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Hi All,
I am putting a farm in this winter and looking at doing some basic monitoring of the environmental conditions. I will use Hobo loggers for temperature, but am wondering if anyone has suggestions for a relatively cheap way to monitor current. Looking for something I can deploy for a day or two at a time.
Best,
Zach
@zachary_gordon Hi Zach! Great question. We actually wrote a document on this topic a while back, but haven't yet incorporated it into guidance on the Hub. I'm attaching it here if you want to take a deep dive. The short answer is, the cheapest method might be to calculate current based on a drifting time of an object:
Another good option is a tilt meter:
You can read more about these methods and others in the pdf attached.
Measuring Water Current Velocity
@lindsay_olsen Thanks for the very informative document. I am considering a TCM-1. In the doc it says that farmers have attached it to growlines to measure current at the depth the crop is grown. Would the swaying of the line in waves be a concern for getting correct measurements? Do you have recommendations on how to securely attach and correctly deploy the meter on the growline?
@zachary_gordon I'm in the process of installing a farm in the Pacific NW (USA) in an area that has big tidal swings (13' to -3') and strong currents. It was important to me to have current data (speed/direction) in order to design my anchoring system correctly. Initially, I tried to do this in an inexpensive manner by renting an ADCP and deploying it myself (suspended 8' below the surface and anchored/buoyed in place). I was worried about theft so I checked on it regularly and removed it when I wasn't able to be attentive to it. I got 10 days worth of data which was good but my marine engineer wanted a full lunar cycle (30 days) worth of data. In the end, I hired a company that was able to deploy the ADCP on the substrate for 30 days with a device that captured data in the entire water column. It was more expensive but gave me the confidence as to the conditions that the farm would face. For me, this was money well spent. Ideally, you'll also have data for historical wind/wave conditions.
I put a little video together that shows my situation... skip to the 2:30 mark if you want to go directly to the ADCP deployment section.
@mike_spranger Thank you very much for putting this video together. It is very informative and also fun to watch! Good luck with your endeavours!
@mike_spranger Thank you very much for putting this video together. It is very informative and also fun to watch! Good luck with your endeavours!
@zachary_gordon
There is also a free version of an app called saildrone, they have a lot of info about currents ect. i think if you want to see solid numbers of how fast the water is moving, you'd need to pay whatever their yearly fee is.
also, a good read really for everyone here is a book called "oceans and beaches", they talk a lot about ocean conditions and how to measure them.
@lindsay_olsen Thanks for the very informative document. I am considering a TCM-1. In the doc it says that farmers have attached it to growlines to measure current at the depth the crop is grown. Would the swaying of the line in waves be a concern for getting correct measurements? Do you have recommendations on how to securely attach and correctly deploy the meter on the growline?
@zachary_gordon I also recommend checking with your county. Mine has much of that data in some of their technical reports for flood monitoring and coastal waters rising. I have also used the floating method to establish current, but only helps in short time spans. Also check historical nautical charts for historical currents and fetches. Best of Luck! Jackie