This past summer, I worked for Watershed Watch Salmon Society, visiting pump stations and floodgates along the lower Fraser River to collect data on water quality and fish species.
Did you know that over 1500 kilometres of valuable salmon habitat in the Fraser Valley are blocked by outdated flood infrastructure? Watershed Watch Salmon Society has mapped over 150 sites along the Fraser River where floodgates and pumps prevent fish from accessing side channels and streams they once used for rearing and overwintering. I collected data at over 70 of these sites to help make the case for opening up these blocked habitats for salmon.
Floodgates and pump stations?
I have lived in the lower mainland my entire life, and have passed many of these structures countless times without questioning their purpose or their impacts.
Along the lower Fraser River, pump stations and floodgates work in tandem with dikes to prevent flooding of land. They are often relatively small structures placed at the mouth of side channels (small streams, rivers, creeks, and sloughs) to help control the level of water in these channels from influences such as spring freshet, high tides, or runoff from heavy rainfall. Controlling the depth of the water in these side channels allows municipalities to keep water deep enough that it can be drawn upon for irrigation, but low enough that it doesn’t flood surrounding land.
Flood boxes or floodgates are opened to allow for the passive drainage of water from side channels into the Fraser River, when the Fraser River is low. They can also be opened to allow water to enter into the side channels from the Fraser, though this is not often the case. When the Fraser River is high, the gates are closed to limit flood risk. Closed floodgates are a physical barrier to fish passage.
Pump stations are used to force water out of side channels, so they can be operated around the clock, no matter the depth of the Fraser. Pump stations can force water out of the side channels rapidly, to reduce flood risk during periods of heavy rainfall, for example. Pump stations are not only physical barriers to fish and other aquatic wildlife, but many fish that enter the pumps are ground up and killed. The rapid drainage of water out of the channel can also result in fish stranding and death.
Flood control and salmon
Juvenile salmon require freshwater habitats to rear and some species, such as Chinook, can spend several years in freshwater before heading out to sea. Side channels provide areas of refuge, with slower flows than the Fraser, and an abundance of food. Without access to these habitats, fish may not grow as large before migrating out to sea, making them more prone to predation or disease.
Floodgates and pump stations also alter the hydrology of streams, negatively affecting the quality of the habitat in these side channels. Altered flow can lead to increased sediment accumulation, stagnant water that is low in dissolved oxygen, increased water temperatures, and increased concentrations of pollutants.
This can create conditions unsupportive to native fish, and often invasive fish and plant species proliferate once introduced.
Over the summer, I visited 70 small streams in municipalities from Richmond to Chilliwack. I documented species of fish present, if any, and measured the pH, dissolved oxygen, temperature and salinity of the water, both internal and external to flood control structures. The fish sampling and water quality testing I performed this summer will provide baseline data to help us identify sites to focus on for future initiatives.
On top of the data I collected, I learned a lot about these small tributaries of the Fraser and our relationship to them. Here are a few of my takeaways.
Many of these smaller streams have been heavily altered and have been thought of as drainage systems rather than habitat for fish and wildlife. Many waterways didn’t even have names or watershed codes, which made locating them a bit tricky!
Most of the streams I visited had been channelized and some look like man-made ditches. Many had garbage strewn on their banks or in the water. Sometimes there would be an oily sheen on the water’s surface, or an unpleasant odour, or dead sticklebacks floating on the surface.
But this was not the case at all the waterways I visited. Some have only been moderately impacted by human action. Others have active streamkeeper groups, municipal staff or others working to protect and restore the waterway for fish and wildlife. It would be amazing to see more of these waterways receive the attention of a devoted streamkeeper group. The efforts of local citizens can make a huge difference.
Sticklebacks are hardy fish
Some sites looked so uninhabitable, I almost felt it was a wasted effort to set and place a trap and return to check it the next day. Yet more often than not, I would pull up the trap and find two to over 100 stickleback.
Stickleback are tough little fish, and they were the most common species we observed in these waterways for a reason! They can handle the low dissolved oxygen conditions that are common in many of these waterways in the summer months.
Juvenile salmon: scarce
We would get so excited when we pulled up a trap and it had something other than stickleback and sculpins in it (unless it was invasive, of course). Out of roughly 70 waterways we visited this summer, we found salmon at only five sites. Unsurprisingly, the waterways where we found salmon either had an active streamkeeper group or a hatchery, or were in waterways that flow through protected areas, such as a nature reserve.
Explore! (But watch out for bears!)
Many of the sites I visited this summer are on dikes that also serve as public walking trails. I really recommend going out and walking the dikes along the Fraser, Pitt, and Alouette Rivers, when you get the chance. It’s truly beautiful and you might just get to see something new. Over the summer, I saw many species that I have not seen before, including a lamprey, green heron, a bittern, and a wandering garter snake.
I had almost completed my fieldwork this summer when I headed out to Pitt Meadows to do some water quality testing. I was surprised that thus far, I had not seen a bear while sampling. The site I was visiting on this day was surrounded by tall grasses and blackberry bushes. I rode my bike to reach the site as it was a bit of a way down the trail. After sampling on one side of the dike, I proceeded to head back up and over to the other side to stick the probe in the water when I heard a splash. Out from behind a blackberry bush that was hanging over the waterway, I saw a black bear’s big head move slowly through the water (right next to where I was going to sample) and then move into the middle of the channel.
I was on a popular walking trail and the bear had zero interest in me, but I was probably less than 30 feet away, which is too close. So I hopped on my bike and headed off without finishing my sampling. The next day while sampling near DeBoville Slough in Port Coquitlam, I was lucky enough to spot a mother bear with her two cubs, this time from a much more comfortable distance.
Who would be real winners here?
When visiting these little waterways, I would picture what they would look like if efforts were made to improve them for salmon, by replacing outdated flood control infrastructure with fish-friendly alternatives and by improving water quality and wildlife habitat with restoration efforts.
Making these changes would not just benefit salmon. They would also improve habitat for other species, increasing opportunities for wildlife viewing, fishing, and Indigenous cultural practices. Some waterways could provide urban locations to go kayaking or canoeing if invasive aquatic vegetation is removed. Restoration activities can also increase the ability of the land to absorb water, reducing flood risk and improving water quality. So to me, it sounds like the ones who have the most to benefit from improving these waterways, is us.
Meghan Rooney has worked for Watershed Watch Salmon Society as their fieldwork coordinator since completing her Masters in Ecological Restoration in 2018. She mainly works on riparian restoration and water quality monitoring projects, in addition to hosting events and coordinating volunteers.
This article appears in our April-May issue.