How the cycle of water and nature has changed in the Cowichan Valley
I am going to show how the plants and animals that we find here in the valley have changed over the years – salmon are a keystone element of life and this depends on the water cycle in the valley.
Can we head back 25,000 years to the end of the ice age – the glaciers that covered our island are melting and the land emerging from under the ice is barren – devoid of life. Over the next few thousand years life slowly moves in – first plants – gradually as soils build up, trees will move in along with many of the animals we still find on the island – birds, bears, elk, deer, cougars, racoons… Salmon will move into our rivers and some 5,000 years ago the First Nations people were here – exactly when they arrived is not known.
Before the first Europeans discovered Vancouver Island it was covered by forest and inhabited by First Nations peoples. The Europeans brought with them two things – iron and diseases. The First Nations had only stone tools (argillite (volcanic glass) made really sharp blades) and were quick to see how much better metal knives were and traded extensively for it. The diseases (measles, smallpox, etc.) killed off large numbers of the natives who had no resistance to such diseases.
The forests covered much of the Cowichan Valley – old-growth – large trees – all connected together by fungal fibres in the soil through which nutrients were absorbed. Older trees would die and woodpeckers would make holes in them and perhaps nest there too – in places near water any nests vacated by the woodpeckers might be used by swallows & purple martins, and other cavity nesting birds. When it rained the water would slowly move through the forest some being taken up the trees and other vegetation. Much of the rest will soak into the soil and thus become groundwater. Some will, especially when there is heavy rain, get into the streams and rivers directly. Thus river flows will reast slowly to rain.
In the forests wildlife, cougars, bears, elk, deer roamed. On the west coast sea otters were abundant and eventually hunted until none remained for their fur. River otters were abundant on the east side of the Island. However much of the life of the forest depended on the salmon. Each fall adult salmon came to the many river estuaries waiting for the rains to swell river flows so they could head upstream to spawn. Seals and sea lions would head to these estuaries to feed on the waiting salmon.
Once on the spawning beds each female salmon would, in batches, release over 1,000 eggs – a really large Chinook might have 10,000 eggs. Males would join the females on the red and fertilize the eggs. The dead salmon would now drift down the river where bears and bald eagles would feast on them. The dead bodies would usually be taken into the forest to be eaten and any pieces not eaten would fall to the forest floor and fertilize the trees.
The eggs spend the next 100 days in the gravel beds slowly developing into a bay salmon. These emerge from the gravel and swim downstream, usually swimming close to the river bank under overhanging vegetation. In addition to feeding on insects and other critters in the water they would feed on any terrestrial insects falling into the water from overhanging branches. Ducks, such as mergansers and herons would also be on the river looking to feed on the baby salmon. Hopefully most of the baby salmon would read the estuary and would find eelgrass beds there where they could hide from larger fish while they prepare to head out into salt water and life in the ocean for a number of years before returning.
Before the settlers arrived salmon would be abundant in part due to the way in which the natives treated them. They would make fish traps in the estuaries and make sure that a good number of adults made it upstream to spawn before taking others for food. Each river has its own population of salmon and by only catching the returning fish the natives would ensure that should returns be low one year sufficient adults would be allowed to spawn.
What happened when the settlers arrived?
1. Trees were felled – in the lowlands for farms – dairy farms. In the upper parts of the valley logs were pushed into the river in the fond hope that heavy rains would wash them down to the estuary where they would be made into lumber. However only a small proportion made it – most got jammed in bends in the river and attempts to move them using explosives damaged the river banks releasing silt into the river which could smother spawning beds.
2. Roads were built, houses, factories, etc. Railways made to move the logs since the river way was not successful. Towns were made, usually next to the river and streams diverted and dike made to stop flooding.
The immediate result of this is that when it rains there is less forest through which the water will flow being absorbed into the soil – it is flowing quickly into the river. So when it rains the rivers and streams will quickly rise send the water downstream. Soon after the rain stops the river levels will begin to fall. These sudden changes in water flow may have great effects on the organisms living there – they may get washed downstream out of their normal habitat. The heavy rain may also bring soil into the river covering spawning gravel beds.
Climate change is resulting in us having wetter winters and drier summers. These dry summers and clearly having an effect – Just recently pumps were installed so that water could be pumped over the weir at Cowichan Lake in order to keep water flowing in the river. Normally flows over the weir are controlled to try to maintain flows during the summer months – this year it could not be done. In the Koksilah watershed regulations were made to restrict water removal from the river and its aquifer that would be used to irrigate hay and corn crops in order to keep more water flowing in the river.
How are our salmon being affected by these changes – when there are good flows of water in the Cowichan 80% of the baby salmon leaving the spawning beds near the lake will make it to the estuary. When river flows are low only 20% will make it. I’m sure you can see that herons and mergansers can more easily find the salmon to eat when there is only a few inches of water slowly moving downstream as opposed to a foot or so of water moving more quickly.
In 2009 only 500 Chinook salmon returned to the Cowichan – each fall a fish fence goes in just below the Allenby Road bridge where returning salmon are counted. Last year 7,500 or more returned. Steps have been taken by various groups to clean up the river removing tons of trash. River banks have been stabilized by planting trees and bushes. Sources of silt have been stabilized. Chinook are the fish that our endangered resident killer whales feed on.
When the railway line was built in Cowichan Bay it went down the centre of the Bay effectively cutting off the south part of the Bay from fish coming down the Cowichan River which mostly flows into the north side. A road was built adjacent to the rail line and two breaches have now been made in this causeway. Since the WFP mill usually has log booms in the estuary on the north side bark from these have killed off the eelgrass beds on this side. On the south side eelgrass beds are growing well since the log sort there closed over 20 years ago. Volunteers have prepared eelgrass for transplanting – a few years ago Genoa Bay, which had a mill many years ago was cleaned up and eelgrass successfully planted there. This year we are waiting to see how successful our transplants were.
A week or so ago I spent and fee hours transplanting saltmarsh plants on to the bare areas around the second breach in the causeway. Next month some plants will be placed along areas over river bank currently lacking vegetation – salmon usually swim close to the banks so this vegetation will provide some cover for them.
One solution to maintaining a good river flow in the Cowichan in the summer is to build a new higher weir at the outflow of the Lake. Funds have been received for design work to be done and hopefully funding will be found to make a new weir which can hold back more of the winter rainfall which can then be slowly released during the dry summer months.