30th September 2023
...continued from Part 1
What can happen is, without a lot of rain, eventually the water levels will start to drop because at some point, unless you start putting more water into the whole system, then they will continue to drop. But because of human water use, that drop can be accelerated to the point where a river can go dry.
It doesnít mean to say that the aquifer is exhausted, it just may be that the groundwater level has dropped below the level of the river valley so no water flows. This was the situation on the Koksilah River, south of Duncan. Their water levels got critical to the point where it was almost running dry back in August, so the province put in water restrictions. That is then used as a measure to lower the human water and allow the environmental flows to still exist.
Thereís another part to the story. For example, the Jump Lake dam that is the City of Nanaimoís water supply and Arrowsmith Lake, which is the partial water supply for the Regional District of Nanaimo and the Parksville Area, thatís a surface water reservoir predominantly used to service communities for their piped water.
Thereís a requirement on those authorities that they have to release a certain amount of water so the river doesnít go dry, to release water to maintain ecological flows. Itís part of the water license that they sign with the province. So theyíre allowed to store water, but they also have to help maintain it to help those ecological flow conditions.
Thatís a kind of a positive spin, because some of those rivers might be going dry if it wasnít for the work that the water managers are doing with the province to maintain those flows.
JC: Youíre kind of building a bit of a case around the risks of groundwater use.
AG: If you do a little bit of digging around and look at other jurisdictions around the world, this is a very common problem with water resource management in general. In many ways, the system in B.C. on the whole works fairly well. But there are some cracks in the system, and there are some areas where we can do a better job.
The legislation has developed over many, many years. And obviously, we now know a lot more of the science behind this. Hindsight is 20/20. If we made some decisions years ago, it would have really helped, but the reality is, that didnít happen. Maybe we didnít have the scientific know-how, maybe there were political reasons. But given the situation weíre in, how are we doing?
I think the interview you did with Bill Sims shows that in many ways, weíre not doing too badly. But other areas, particularly where groundwater is the main driver, are naturally not quite as resilient. So we have to work on ways to make those areas more resilient.
People at the Regional District of Nanaimo are working on that and have a whole bunch of official community plans. Moving forward, development, the new subdivision of land for new housing, is now being done in a very water-centric way, with a view that we now know this can create some problems and to minimize that from the get-go.
We now know thereís a few places regionally where there are definitely water supply or water-related issues (like in Parksville, Lantzville and Cowichan), so what Iím trying to do is to work proactively so that this doesnít become a systemic issue throughout the whole area.
JC: What effect do you think the years of cumulative drought is having on things like tree species?
AG: Thereís a bunch of work being done out of the University of British Columbia and the University of Alberta that looks at the bio-geoclimatic zones, which maps the dominant vegetation within a region. It changes all around the province, because the climate varies around the province and vegetation is adapted to the climate within which it lives.
If you have a seasonally dry climate like we do, with a cool, wet winter and a warm, dry summer, then the vegetation that will naturally grow here really well are species that [are adapted to that].
Now, what youíll find is on the east coast of the Island, generally speaking, the dominant tree vegetation is Douglas fir. But in wet sites, youíll get cedar, it tends to have shallow roots and prefers areas where thereís a lot of surface moisture in the soil.
Because of climate change and these droughts, that is likely becoming less common. I think what weíre seeing is things like cedar being more and more stressed. Although Douglas fir generally can cope with a reasonable amount of drought, in very long droughts theyíll also start to get stressed.
What the predictions are with global climate change is that basically, these biogeoclimatic zones are going to change. Generally speaking, what weíll see is that zones currently dominant down in the southern part of the province will probably slowly migrate north as the area gets hotter.
For example, people are talking about doing agriculture or starting wineries further north because the climate is changing, itís becoming better for certain types of vegetation, so itís the same thing with the natural vegetation. I think that thatís already being seen, and people are already starting to map that.
JC: Whatís the future for snow on Vancouver Island?
AG: Intuitively, if we have a warming climate, particularly if the winters get warmer, then itís likely weíre going to get less snow. The work that Iíve done in developing this water balance model basically reinforces that. If a model is to be believed, it puts some sort of idea on the sorts of changes that we can expect, and how quickly.
It has important implications. What tends to happen on Vancouver Island is that we get most of the rain during the fall and winter and into the spring months, which translates into relatively high water levels in our streams and rivers.
In summer, we get long periods with no rain, or almost no rain, and then the water levels really drop. The exception to that is areas that are fed by rivers that come from high terrain places like Mount Arrowsmith, Strathcona Park, inland of Courtenay, Campbell River. In those areas they accumulate a significant amount of snow.
What my work shows is that currently, we can expect several meters of what we term ďsnow water equivalent.Ē There is a lot of air in snow, if you actually melt it all into a column of water, then thatís directly comparable with liquid water in a stream, river or lake. So we compare those two, thatís called SWI ó snow water equivalent.
No one can predict exactly what the future is going to look like but what the model shows is that with global warming, we will see less snow accumulation in the mountains to the point where ó under some of the worst-case scenarios of business as usual and we donít do anything about global climate change ó there will be very limited snow accumulation at all by the end of the century.
Currently, there are meters of snow up in the mountains in the summer. And it could get to the point where there is very little.
So the snow accumulates here in the winter and acts as a temporary store, and then in the spring when the temperatures rise that snow starts to melt. Rivers that are fed by mountain snow have a very different hydrology. In the summer, they actually start off with relatively high water levels because of all of this melting snow, which tends to sustain water levels much longer, through into the summer before all the snow melts.
When you look at whatís known as the hydrograph, which is the level of water in a river, they tend to have two peaks ó one during the winter when it rains a lot and a second one during the snowmelt in the spring. Thatís whatís known as a hybrid river system.
Now whatís going to happen is that in the future, those hybrid river systems will convert into being just purely rain during the winter. The hydrology of them will change quite a bit.
If the snow doesnít accumulate, it doesnít melt. And that has implications for water management, because in a lot of water systems, including the City of Nanaimo, snow is a big part of the storage picture.
The [city] managers are taking advantage of that snow so they donít have to build dams that are quite as large. If that snow doesnít accumulate, then storing the same amount of water will require a bigger dam or a bigger reservoir, because the waterís still going to come, itís just going to come in the form of rain rather than in the form of snow.
But there also isnít that effect of the snowmelt in the spring, which helps the reservoir to fill so that itís nice and full for the start of the summer period.
Snow sits on the mountains, and then slowly melts during the spring, whereas rain moves much more quickly down through the watershed, so the chance of flooding is also much greater.
JC: So these are some of the weak points with surface water systems because weíre counting on it just sitting there and being stable in the form of snow.
AG: Yeah. For example, Nanaimo has a relatively large watershed, but the Arrowsmith dam that is part of the Parksville area water supply is a much smaller watershed, itís only a couple of square kilometres. A major part of that is the fact that itís way up in the mountains and gets a lot of snow. If that snow doesnít come, then that would make a big difference, and because itís a small watershed, it would have a bigger impact. There isnít as big an area to collect water that would come down as rain.
As those changes start to take place, then water managers are going to have to start thinking more creatively about other things they can potentially do to maintain these water supplies.
JC: What are some of the standout realizations or conclusions that youíre coming to as a result of your current research?
AG: I think weíre getting a better understanding, in particular, about surface water and how it works. Groundwater is less well-constrained. I think it makes sense to move to a system whereby we actually start recording the water weíre using a lot more. Itís very hard to manage something when we have no idea how much of it weíre using. Thatís one takeaway from this.
If you look at the Water Sustainability Act, it definitely is an improvement over the legislation that was around before. But the other thing is, I think we need to take into account things like water when we plan communities, that there is a limit to the amount of development that is available in any region due to a particular resource. Water is a really key one, keeping in mind that there are different ways you manage water. This has to be factored in.
For example, Nanaimo doesnít get its water from the geographic extent of the City of Nanaimo. The South Nanaimo watershed is remote from that. So what goes on up there is different from what happens in the city.
But for groundwater, itís different, because if I go out and buy a rural lot and Iím not on a water service, then Iím reliant on digging a well on my property, that is the only place I can get water from, thereís fewer options. And nobody likely knows how many people we can have in this area before we start having problems with the amount of water that is available.
I think being more proactive and understanding the capability of the land to support people is also very important. We do know something about that but our knowledge is somewhat limited.
At some point, there is a natural limit on what we should allow in terms of water usage in total. But it all depends on what the land is used for, is it domestic use, is it industrial use, is it agriculture? Because there are some very big water users out there, astonishingly so.
Continued in Part 3