Flowing with Changes

Anderson Creek
Upstream, Anderson Creek

Natural streams are living systems, and like all living things they change. Indeed, a stream remains what it is only by changing.

One of WaterWealth’s watershed monitoring sites has been a story of change, large to small.

The stream has no name in the Ministry of Environment stream report. We started out calling it “Unnamed Stream 31300” from its watershed code 100-065700-09700-31300. A sign refers to the pond downstream as "Anderson Pond." The name “Anderson” also appears next to a structure, likely a homestead, near what is presumably this stream on a map drawn by Chief William Sepass in 19181 (the stream itself is unlabelled). We're not aware of a Halq'eméylem name for this stream.

Large Change

When we were scouting locations for temperature loggers, the lower part of Anderson Creek was flowing through a tall wooden box structure near Chilliwack Lake Road, then away from the road for a bit before spilling out into the pond.

Anderson Pond

The wooden box was a bit of a puzzle, but screwing the temperature logger to the inside of it seemed like a good way to secure a logger here.

To our surprise, when we returned to place the logger, the stream was dry!

wood structure with Anderson Creek no longer flowing through, September 2020

Walking up what had been the stream we found where it had gone. Tumbling down the slope from the south, it flowed straight under Chilliwack River Road through a square cement culvert that looked big enough to drive a small car through!

Anderson Creek flowing through large culvert under Chilliwack Lake Road

With a culvert that large, how had the stream ever flowed to and through the wooden box thing where we’d first seen it? Leaving that puzzle unanswered, we went a little way upstream and found a suitable spot. The logger was placed inside a landscaping brick, secured to shore with a rope.

By November most of our loggers had been in streams for at least a little while, and one of our former high school streamkeepers, now a UFV student, had called looking for data for a GIS class project. So our next visit to Anderson Creek was November 13, 2020 to retrieve what data it had. That trip was a bit cold and wet, but uneventful.

Our plan is to retrieve data from the loggers roughly every three months. The arctic outflow weather in February 2021 put things a little behind schedule, so it was on March 7 we were there next. As we approached the stream I was explaining to April, who hadn’t been there in September or November, why the location had had to be changed and how surprised I had been to find the stream completely dry where we'd seen it flowing when we were planning our sites.

I was cut off mid-explanation by the sight of the stream again flowing abundantly out of the wooden structure and then away from the road for a bit before spilling out into the pond!

wood structure with Anderson Creek flowing through again

“Sure Ian, wasn’t flowing at all,” April joked.

Heading over to the culvert we found that someone had arranged boulders in the stream to divert about half of the flow to go along the channel through the wooden box and down to the pond. The realization also set in that fresh gravel we'd seen by the road was most likely excavated from the channel leading to the wooden structure. DFO restoring flows, presumably.

Medium Change

Carrying on upstream to the logger site, we found our brick out of the water. This was a little disappointing, but not really surprising. It’s a fast little stream in that part. Sometime when flows were high it popped the brick out of the pool we’d put it in and carried it to the end of its rope. Then when water levels dropped, the brick was left just out of the water.

Anderson Creek logger out of the water, 7 March 2021

The first logger we’d bought to try them out had wound up out of the water once too. (A bit of that logger's story on our blog post "Lost, found, and looking forward") Looking at the data from that first logger it had been easy to tell when the logger was no longer in the water. The magnitude of temperature variations became markedly greater from February 25. (Click on any of these graphs for a larger version, and then your browser 'back' button to return.)

Temperature data from Hope River showing greater temperature fluctuations after it was left on shore by falling flows

About every ten kilometres up the watershed we have an air temperature logger placed in the vicinity of the water temperature logger. Data from those sites illustrates how the water temperatures and air temperatures follow the same longer term trends but the air temperature is much more variable from day to night and on occasional particularly warm or cold days.

Graph of water and air temperatures at Chilliwack River by the Chilliwack Hatchery

Small Change

We expected the differences between water temperatures and air temperatures at Anderson Creek would be no more difficult to discern than had been the case elsewhere. We would just separate the data from when it was in the water or out of the water.

At Anderson however, the change from water temperatures to air temperatures was not always so obvious! And it might have been out of the water more than once.

Temperature data from Anderson Creek, 7 March 2021

Comparing the Anderson Creek data to Chilliwack River water and air temperature data we got:

Comparison of Anderson Creek temperatures to Chilliwack River water and air temperatures

Our first logger had been in a brick in Hope River and when the waters receded it was left on shore exposed to the sun. Sites where we have intentional air loggers they are placed some metres from the water. At Anderson Creek when the logger was out of the water it was only just out of the water, and Anderson Creek is fast there and generates a lot of spray. It’s also coming down a north facing slope in a narrow channel well shaded by forest. These characteristics of the Anderson Creek site contribute to the air temperatures the logger saw being most of the time not so different from the water temperatures, and our job of separating out the two sets not quite as certain.

One take on how it went:

Anderson Creek data compared to Chilliwack River water and air, marked up with where the logger may have been out of water

You can click on that image to get a larger version to zoom in and see what you think. It's not so much that the Anderson Creek temperature, like the Chilliwack River air temperature, is sometimes lower than the Chilliwack River water temperature. It's more a matter of looking at the magnitude of temperature fluctuations to try to determine what times it was recording water temperature and what times air temperature. We would have liked for those changes in fluctuations to be larger!

The clearly deliberate change to flows of Anderson Creek prompted a bit of online searching that was rewarded with an article by Matt Foy and Gary Logan in a Spring 1997 copy of ‘Streamline’ Stream Restoration Technical Bulletin. The stream is referred to as Anderson Creek in the article. It explains that the wooden box thing is a flow control structure. According to the article, pre-construction trapping indicated no use of the side channel there by salmonids. Post-construction trapping in April 1996 found good numbers of coho and steelhead, some cutthroat and one Dolly Varden. June 1996 they found newly emerged chum and coho fry.

Perspective Change

Much as we love all the streams in this watershed, large and small, we're glad to have had our perspective on this particular stream and associated habitat elevated by learning more about its history and value. We are grateful again for the habitat work that was done in years past to try to recover from damage done by colonization and development that didn't care for such things. And we're glad to have seen that the loss of flows in the constructed channel was fairly quickly corrected.

The 1997 Streamline article said that they expected 5,000 to 7,000 smolts to migrate from the site that year. Perhaps WaterWealth streamkeepers could do some follow up fish surveys and see how the numbers compare all these years after the original work. What we've learned there will be passed on, and our temperature logger site will help ensure that there are more appreciative eyes on this waterway in future. Like the Luke Wallace song says, "Little Rivers Matter Too"!

1 Chief William Sepass 1918 map seen in A Stó:lō Coast Salish Historical Atlas, (first edition) plate 43, page 127


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published this page in Blog 2021-03-09 18:43:11 -0800