TRAYLS Monitors Stream Temperatures in Spasski Watershed

What is stream temperature monitoring?

Stream temperature monitoring is collecting a long-term dataset of stream temperatures. The goal of the program is to have a minimum of 5 years of continuous data from a single spot. HIA has installed stream temperature monitors called “HOBO loggers” that collect water temperature data so we can find out what the average water temperature is per stream. There are five streams with loggers and two loggers per stream just in case one fails to work. We put the loggers in the pools because that’s where the fish spawn and because the pools won’t dry out during years with less rains. The loggers have been in the rivers now for around a year and can stay in the river for around 5 years collecting data before the battery needs to be changed. It is important that the loggers are durable. They are inside a small food cage for birds with a brick and the logger. The cage is there to protect the logger from being destroyed, and the brick is to keep the logger and cage at the bottom of the river so it won’t float up.

A HOBO temperature monitor tethered to a brick in its cage

What the data shows

The average water temperatures of the main Spasski River taken from August, 2019 until August, 2020. Last year during the drought thet water was 52°F compared to just 50°F this year. A 2° difference may not seem like a lot to you, but it’s a lot for the fish!

How did we collect the data?

We (Ian Johnson, Dylan Johnson, Ted Elliott, and Arianna Lapke) drove out to the tributaries and hiked to the loggers and collected the data by bluetooth, pairing the hobo logger with a tablet to transfer the results. When we went to collect the data we had to wade through the water, some of it being a calm stream barely reaching our ankles and some of it a swift stream up to our waists. There were certain spots that were calmer than others because of fallen trees in the stream, which help slow down the stream and create pools. We couldn’t collect the data from one stream site due to road conditions. Then we analyzed the data later by creating some graphs in the office.

Why are we doing this?

Ted and Dylan pull up the HOBO monitor to retrieve the data

We are monitoring water temperatures in the Spasski watershed to check how climate change is affecting rivers and streams. We expect water temperatures to rise in the future and we want to see the impacts of warmer waters on fish populations and habitat. By collecting data now we are creating a baseline data set that we can use to compare future temperature data with. The data we are collecting is going to our partner the Southeast Alaska Watershed Coalition (SAWC) who is looking at water temperature data around the state, that way other people and communities can see how Alaska’s water temperatures fluctuate. Hoonah can also benefit from this project because we’ll have a better understanding of where to find more fish. Not only that, but we can identify streams that are too warm and do projects to make those areas more suitable for fish. This is the beginning of a long-term project that will help our community and others by identifying suitable fish habitat as well as streams that can be restored in the future.

Written by the TRAYLS Crew: Ted Elliott and Dylan Johnson
August, 2020

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