Rain, Rivers, and Watersheds

Fall rains are here. I am listening to the sound of rain pinging on the roof as I write this. The sound heralds the beginning of winter rains for the coast.

I can expect to hear a lot of rain in the next months. This is when the majority of Victoria's rainfall will happen.

Victoria's average monthly rainfall. Notice the huge difference between the dry summer months, and the wet winter months. Source: https://weatherspark.com/y/466/Average-Weather-in-Victoria-Canada-Year-Round

I have been thinking about the connection between rainfall and rivers. 

Earlier this year, in January, Vancouver Island had an amazing winter storm. This resulted in huge rainfall over large parts of the island. Shortly after, I hiked with friends along Pease Creek, in Gowland Todd Provincial Park. 

The park was alive with water. Motion was everywhere; it felt like the forest was in flow, as water dripped from branches, seeped over the ground, and ran in rivulets towards the valley bottom. Saturated soil was oozing and slumping. The trail was mud, sometimes filled with pools of water.

Pease Creek February 1, 2020, after a big rainfall event (Gowland Todd Provincial Park)

Pease Creek emptying into McKenzie Bight, February 1, 2020

The rivers of Vancouver Island are unique in Canada, because of winter rainfall. Unlike rivers elsewhere in the country, those on the Island have their peak flows in the winter months. Everywhere else the biggest flows are associated with spring runoff from snow melt. 

Here are two "hydrographs" which show the difference:

A hydrograph for the Cowichan River in 2003, showing how it peaks in the winter (Source: Capital Regional District - https://www.crd.bc.ca/education/protection-stewardship/watersheds/watershed-basics/watershed-water-flows)

. 

A hydrograph for the Fraser River, 2003. Data are missing for January and February. The river peaks in the spring due to the watershed of the interior, and spring snow melt. Source: (Source: Capital Regional District - https://www.crd.bc.ca/education/protection-stewardship/watersheds/watershed-basics/watershed-water-flows)

I love to think about the interplay of the gigantic forces of the weather from the sky, and the landscape systems of the earth - the terrain, the flows of water across the terrain, and the intricate connection with plants which grow upon it. 

The following two diagrams show the water cycle, and how it interacts with the landscape.

The circular system of water on earth. Source: US Geological Survey

 

The water cycle, showing the influence of urban development and human use of water. Source: waterbalance.ca

Nature is amazing at responding to the annual variation of water in Victoria. Here is one example - the Garry Oak. These trees grow only in southern Vancouver Island, and are well adapted to the dry summers and rainy winters, with deep tap roots.

Garry Oak trees in late summer. Virtually no rain falls on the landscape in Victoria in the summer months. 

The word "watershed" reflects the interplay of weather forces and terrain; it describes the area of land which drains into a particular creek, or a larger area which all would flow into a river.

Capital Regional District has a very progressive exploration of watersheds on their website. I have been impressed at the work they are doing to raise awareness. I suspect that some of this work can be attributed to Jody Watson, who for many years was the CRD "harbours and watersheds" coordinator, and now is supervisor of environmental planning and initiatives.

Excerpt from the CRD Watersheds map. Each colour represents a different creek watershed, except for orange. The orange areas are described as "drainage areas that flow towards the harbours and marine shorelines without a creek or river".  This would include storm drains, and water that seeps into the soil and naturally percolates towards the ocean.

Urbanization, and the paving of ground, has changed the way water flows. For years the approach to managing rainwater was to "pipe it away". This meant depletion of local groundwater reserves, and it also meant the culverting of creeks. 

Now, we have more understanding of the importance of keeping water in place, and reducing the amount of hardened ground with more porous landscaping.

There is a whole movement to managing rainwater and minimizing runoff to storm drains, through actions such as on-site rain barrels, and landscaping with swales and areas of deep, water absorbing soil. Here are a few examples of what we can do. These are taken from an earlier blog post I did in February 2019 (https://shuswapreflections.blogspot.com/2019/02/pondering-snow-and-rain.html)

 

Stormwater Swale - a feature of Zero Impact Development. Source: The Nature Conservancy

Individual properties can help keep rain in place, by diverting runoff to rain gardens, areas planted with deep soil and water loving plants. Source: http://www.thewalleye.ca/event/rain-garden-tour-2 (Thunder Bay, Ontario)

A local Victoria example of an effort to create a  rain garden

Detail from the rain garden at Fishermen's Wharf Park. 

As I enjoy the rain over the winter months, I will continue to marvel at the remarkable ways of nature. We humans will never be able to replicate nature, but perhaps we'll be able to reduce the size of our footprints as we continue to learn.