With spring’s arrival, flood concerns rise

Opinion

Hey there, time traveller!
This article was published 16/03/2022 (1308 days ago), so information in it may no longer be current.

I’M staring out my window into a snow drift almost to the eaves. Near-record accumulation and continued freezing temperatures are raising fears of widespread spring flooding, something we haven’t experienced in several years. Rather, we’ve lately become more familiar with the unpredictable flooding caused by extreme rain events.

That’s the bad news. But last summer’s widespread drought severely depleted soil moisture, which means there’s a very large capacity to absorb excess runoff; and another dry spring could have spelled disaster for farmers. The good news is, with a gradual thaw and not much spring rain, our farmers could be in good shape heading into the growing season.

The U.S. National Weather Service has already forecast a two-thirds probability of flooding at the international boundary, while our own provincial forecasters — we have no national flood forecasting system in Canada — have issued an early alert of a “risk” of flooding in most southern Manitoba watersheds.

In other words, it’s too early to tell. What we can say is that most record snow seasons have not resulted in historic floods; that temperature and rain/snowfall during the pivotal mid-March to mid-April period are still critical determinants that can turn a huge snowpack into a gradual runoff or a modest one into severe flooding.

Although there are some benefits to be had with a national forecasting network — and this may be one of the deliverables of the long-promised and yet to be seen Canada Water Agency — we are well served by our local flood forecasting team. Stay tuned; they will keep us and the province’s flood response machinery well informed as spring unfolds.

We are talking about the next two months, the short term. We can, in preparing for the worst, take measures to protect property. We can utilize existing works, such as the Winnipeg floodway, the Portage Diversion, the Shellmouth dam and reservoir and community ring dikes, to minimize damage to community, residential and commercial property.

These works are somewhat flexible. We can control the timing of water movement; we can raise the height of dikes; we can even in extreme circumstances divert water onto agricultural land.

On the agricultural landscape, however, we are pretty much reliant on a fixed and largely inflexible water-management system, designed piecemeal to meet the conditions of the stable hydrologic regime of the first half of the last century. Climate change has rendered that regime unstable. Extreme events are becoming more intense and more frequent. Instability is accelerating as we continue on an almost-certain trajectory toward a global temperature increase of at least three degrees C.

We tend to think of agriculture as just another sector of our economy. Surely world events, climate-related and geopolitical, ought to be shaking that complacency. Prairie agriculture is a national treasure; in an uncertain world, Canada should be striving to render its food supply as self-sufficient as possible.

Of the four environmental inputs to agriculture — water, temperature, soil and nutrients — temperature and water will be dramatically impacted as climate changes. At least at the local level — we may be forced into planetary engineering schemes — we can do nothing about ambient temperature; but there’s a great deal we can do about water.

We can construct and manage works to move water off the landscape, or retain it there; move water from where it’s abundant to where it’s scarce; and apply it in a controlled manner to crops. To one degree or another, we do these things now. We have a water-management system in agro-Manitoba. Were this, say, 1970, we would probably be content to leave it pretty much as is.

But it’s not 1970. Late spring and early summer rain-induced flooding over the last couple of decades has revealed just how vulnerable is our drainage network to extreme events. Last summer’s drought demonstrated the need for water storage and enhanced infrastructure to apply water to crops.

But we’ve also seen the perils of simply dumping water downstream, as demonstrated by the devastation visited on several First Nations communities. We now know that without wetland storage we have little chance of arresting the deterioration of Lake Winnipeg.

The transformation of Manitoba’s agricultural water-management system to meet these challenges will take careful planning and design, time and money. It can be done without environmental carnage, but not without impact. But we are talking about managing an already managed environment.

Only two of Manitoba’s eight major watersheds — both in the remote North — are without hydrologic controls. All of agro-Manitoba is a created environment, but still natural in that it is governed by the laws of nature.

At any rate, none of this will happen without taking a first step. It seems certain, whatever the pace of melt, that there will be much water on the landscape. Let’s seize the opportunity to take that first step, and measure and document the performance of the water-management network as one major (and ongoing) input to system redesign, because in order to change the system, you need to know what’s there now and how it is performing.

Norman Brandson was deputy minister of the former Manitoba departments of environment, water stewardship and conservation from 1990 to 2006.