Our New Zealand beaver friend, William Hughes-Games, is getting ready for his presentation to the council about the Hurunui dam project, and is doing a lot of thinking about how beavers raise the water table with their dams. I thought his writing was an easily understood overview of this seemingly magical process, and I wanted to pass it along. If you’d like to read it in novel form, go check out the book he introduced me to “Three against the Wilderness” by Eric Collier. It describes in lively detail what happens to the habitat when beavers are reintroduced to the Canadian Wilderness around the turn of the century.
First, how does the beaver increase the amount of effective water?
Beavers make a series of low dams across streams. If unimpeded, water falling in a catchment flows down the stream and river as fast as the slope and stream characteristics allow. All that fresh water goes straight down to the sea. With a beaver dam, there is a pond which is wider than the original steam bed and a water surface which is higher. The pond itself is a store of water. However this is only a minor part of the water storing capacity created by beavers. With the greater surface area of water in contact with the land and the higher water level, water flows into the surrounding water table. Once underground,the water is protected from evaporation. It seeps seaward at a much slower rate than water in the stream and seeps back into the stream further down stream. Instead of a short sharp flood peak, the water is slowed down and spread out over time. .
A fast running stream provides a certain number of ecological niches for a limited number of plants and animals. Beaver ponds and the eventually produced wetlands provide far more niches. As mentioned, beaver dams settle out suspended mineral material and provide clear water. All sorts of plants can take root on the bottoms of these ponds as well as bull rushes around the edges and water lilies somewhat deeper. All these provide habitat for fish, water insects, ducks etc. and watering places for terrestrial animals. The native people of western Canada called the beaver the Sacred Centre of the earth because they understood the tremendous benefits brought by beavers.
I’ll confess, I’m boning up on my beaver facts to get ready for Saturday’s interview. In addition to Williams fantastic analysis, I reread my section on beavers and the environment from the subcommittee report. Not to toot my own instrument here, but dam(n)! that was some nicely referenced writing. I’ve added it to the reports section of the blog, in case someone needs a quick reference for why beavers matter to the habitat.
