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Shuswap Runoff 2013 - Forecast as of April 24, 2022

  2013 Runoff Forecast: Content and Index
   
The 2012 Flood Year     Chart Index:
What Can We Expect From the 2013 Runoff?   The Snowpack
  1. Mid-range / Upper-range Snowpack   Lake Level Comparison
  2. Current Lake and River Levels   2010 Weather / Lake Level Relationship
  3. Weather, Rain, and Temperatures   2011 Weather / Lake Level Relationship
Summary / Final Remarks   2012 Weather / Lake Level Relationship
Lake Levels, Flooding, Tourism   2013 Weather / Lake Level Relationship


During the past few years weather has been a major factor for lake levels and peak during the main runoff. This year's runoff will certainly not be an exception. Previously, cooler temperatures and rain periods have reached well into May, followed by a quick switch to warm summer temperatures. This has caused a rapid snow melt in mid and upper range mountains during the beginning of the main runoff, leading to a quick raise of the Shuswap Lake water levels. Usually, most of the snowpack has been melted away before the summer heat, ensuring a modest lake peak in the final stages.

  The 2012 Flood Year

Last year's runoff was different. Cooler temperatures lasted well into April, where periods of heavy rain caused a rapid raise in lake levels. After the rain period a normal runoff led to a steady but moderate increase of the lake levels. The snowpack, at this time well within the normals for this region, continued to melt away until early June, when the watershed was hit by another rain period. The combination of a mushy snowpack and continued rain showers has accelerated the water flow in creeks and rivers, bringing the Shuswap Lake peak to near 1972 flood levels.
The 2012 flood was a direct result of the unfortunate timing of snowmelt and weather. There hasn't been more snow in the mountains than in previous years. Rain has simply pushed the lake levels to a higher starting point for the main runoff. And rain provided the volume of water to maintain a rapid level raise during the end of the snow melt period.


  What Can We Expect From the 2013 Runoff?

At the given time it is still too early to make definite predictions about the 2013 runoff. However, there are some indications pointing towards another high peak level for this year, at least matching that of the 2011 Shuswap Lake peak. This does not necessarily mean that we will have some flooding again this year. We don't know that. But once again the weather during the coming few weeks can quickly steer the 2013 runoff in either direction. This is what we know so far:

1. Mid-range / Upper-range Snowpack:

The following chart illustrates the current snowpack on Park Mountain at an elevation of 1,857 m. Park Mountain is located between Mabel Lake and Sugar Lake. This area of the watershed accounts for over 40% of water during the main runoff. Snow water drains into the Shuswap River and is discharged into Mara Lake and, through the Sicamous Channel, is feeding the Shuswap Lake and subsequently the South Thompson River as the only outlet of the lake.

The chart shows a current snowpack water equivalent of 1,150 mm, compared to last year's 900 mm (which is close to the average normal). This calculates to a water equivalent of 28% above last year.

That is a lot of water being locked into the snowpack - and it all has to come down into Sugar Lake, Mabel Lake, Shuswap River, and Shuswap Lake. The critical factor is the weather, how fast the snowpack will melt. This volume of water certainly carries a potential for high water levels and flow rates in the Shuswap River, foremost in the area between Mabel Lake and Mara Lake. Additional rain showers during the height of the runoff may cause spill-overs and flooding along the Shuswap River and Mara Lake.

For more information about the current snowpack, water equivalent, and snow bulletin reports, please visit the Ministry of Environment (River Forecast Centre) web site at http://bcrfc.env.gov.bc.ca/data/asp/realtime/asp_pages/asp_1f03p.html


2. Current Lake and River Levels:

All lakes in the Shuswap watershed have a distinct water storage capacity before spilling over into floodplains and residential areas. High flow rates, foremost for the Shuswap River and Eagle River, also have a direct effect on river levels, wash out embankments, weaken levees and dikes, and flood large areas of (mostly) farmland.

The river flow is regulated by:
* the volume of melt water
* the elevation difference
* the level of the lake near the inflow
* the height of levees and embankments.

A high lake level will slow the water flow, cause a backwash, and raises the river level near the river mouth.

Snow water above the Sugar Lake is regulated by the Sugar Lake dam, operated by BC Hydro to feed their power generators. However, the main water supply during the runoff originates from the mid- and upper-range mountains between Sugar Lake and Mabel Lake, which includes the Park Mountain as noted above. This section of the Shuswap River has the largest elevation difference with a high flow rate before getting discharged into the Mabel Lake. Like the Shuswap Lake, Mabel Lake is acting as a water storage reservoir during the initial phase of the runoff. Once the maximum spill point is reached, the outflow (discharge) will accelerate along the significant elevation drop towards Enderby.
The river section between Enderby and Mara Lake carries the highest potential for flooding and spill-overs. The elevation drop is minimal and with the backwash from Mara Lake slowing the discharge, rapid upstream water flow is pushing the river levels up significantly.

Now, what does this all mean?

Shuswap Lake, Mara Lake, Mabel Lake, and the Shuswap River all currently show higher water levels than usual, clearly exceeding the levels of 2012 for this time of year. In fact, lake levels on Mara Lake during the last 2 weeks are continuously above record levels since 2002. On April 1st, the level difference between 2012 and 2013 has been 0.338m (1 ft.), rapidly growing to a difference maximum on April 9 to 0.846 m (2 ft. 9 1/2 in.). As of April 24 the level difference has decreased to 0.493 m (1 ft. 8 in.), which is based on the up to 3 in. daily level raise for this time last year (see the chart above). The full chart can be viewed here.

The 2013 runoff will proceed on top of this elevated start level, adding a minimum of another 3.0 m to 3.5 m (9-10 ft.) raise to this level. Following this calculation, the 2013 lake level peak can be estimated to reach the lower 349 m range, not taking any potential rainfall into account. This clearly indicates that the weather of the coming few weeks will be an important factor.


3. Weather, Rain, and Temperatures:

The charts below illustrate the relationship between lake levels and air temperatures for the period of 2010 to today. The yellow line represents the lake levels, the colored area the daily low and high temperatures. Please note that rain periods have not yet been added to the charts.

All temperatures have been recorded in Sicamous at an elevation of 352 m (1,155 ft.). Air temperatures vary with the altitude at a rate of 1.94444°C for each 1,000 ft. For example, a temperature of 20°C at lake level calculates to a temperature of 10.4°C on Park Mountain (1,857 m). As we will explain later, this fact becomes important for predicting the runoff and lake level changes. True temperatures for any given altitude can be calculated using the following formula:

Tc - ((Ax - Am) * (1.944444444 / 304.8))
where
  • Tc = current temperature (in °Celsius)
  • Ax = altitude for the temperature to be calculated (in metres)
  • Am = altitude where the temperature was measured (in metres)

More details about temperatures and snow melt in general can be found at http://www.shuswaplakewatch.com/research/snowmelt.html.

The Shuswap Lake reacts to temperature changes and snow melt in upper elevations with a delay of 2.5 days.

For the snowpack to melt in the upper mountains a temperature of min. 10°C to 12°C at lake level is needed. Especially during the initial runoff stages snow is melting during daytime but often will slow or stop during the cooler nighttime temperatures. The charts below clearly illustrate that, once the nighttime temperatures are above 10°C, the runoff will accelerate and the lake will raise more rapidly. The chart for the 2011 runoff is a good example for that.
However, last year has been different. Temperatures remained cooler during nighttime until well into May, making rainfall the main driver for the the rapid level raise. The rain softened the snowpack and allowed it to melt more quickly during the following warmer and dry weather through late May and June. Combined with more heavy rain showers in early June, this has over-saturated the sloped soil, causing a continued rapid sub-surface and surface flow, and finally led to the rapid level raise and flooding during the final runoff stages. The (moderate) height of the snowpack itself hasn't been as much of a critical factor as during the 2010 and 2011 runoff.

Now, looking at the 2013 weather pattern so far, the variables have changed again. Compared to 2012 there has been an early wave of warmer daytime temperatures at the beginning of April. However, nighttime temperatures have been consistently cooler than last year, even as recent as of today. Some moderate rain at lake elevations has mostly happened during the cooler nighttime, turning rain into snow in the mountainous regions and increasing the overall snowpack. Today there are still solid snow patches visible as low as at 2,500 ft. which are now slowly beginning to melt away. Daytime temperatures at this point are now lower than last year, pushing the main runoff even further into May and may expose the full above normal snowpack to the summer temperatures in June. This may translate into a potential rapid and prolonged raise of the lake in June with some regional flooding as a consequence, most likely along the Shuswap River and Mara Lake. Rain periods during this time can easily amplify the flood risks significantly, even pushing the lake near last year's peak level.

Even more than during the past years, the 2013 runoff and subsequent lake peak will largely depend on the weather during the coming weeks. The above normal snowpack, the elevated lake level as starting point for the runoff, and the prolonged cooler temperatures are the ammunition; the weather during the next 2-3 weeks will certainly be the ignitor - either way...


  Summary / Final Remarks

As of this day all indications point to another high Shuswap Lake peak for the 2013 runoff. An above normal snowpack, lower spring temperatures, and a higher than normal lake level as starting point for the runoff have once again created an environment in which a high level peak becomes a strong possibility.
Each of those conditions on its own can become a driver for an above average level peak during the runoff:

  • The snowpack is the main source for the total water supply flowing through the Shuswap Lake. The higher the snowpack, the more water has to flow through the lake. As illustrated above, more water is stored in the snowpack at the southern mountains of the watershed which, by accounting for over 40% of the total Lake inflow, is the primary driver for the main runoff and the Shuswap Lake levels.
  • Lower day and night temperatures can delay the start of the runoff well into a time of summer-like weather pattern, therefore causing a consistent rapid snow melt and level raise by shortening the overall times pan for the runoff. It is a simple equation: the shorter the times pan for the snow melt, the higher the water flow in the watershed, and the faster the discharge into rivers and lakes with a given limited outflow potential.
    The significance of the times pan is best described by the bathtub effect. The open drain has a fixed maximum outflow capacity (= South Thompson River). A fixed volume of water (= snowpack) is allowed to flow into the bathtub. If you open the tap just a little, all water will instantly disappear; but it will take a very long time for the water tap to be open (= times pan). Opening the tap a bit more to allow more water to flow into the bathtub than the drain is able to discharge, the water level in your bathtub will slowly raise (= lake level); it will take less time for the water tap to remain open. Opening the water tap all the way will take the least amount of time to discharge the given volume of water into the bath tub. However, the water in the tub will more quickly raise to a much higher level before slowly flowing out the drain.
    The water tap in this example represents the air temperature in the watershed. The tap opens more during the day and closes a bit during night, therefore regulating the water level in the bath tub. If you now pour additional buckets of water into the bath tub while the water tap is still open, it would simulate the rain effect on the lake level during the runoff.
    Of course, the reality is a bit more complex, as we have to take flood plains, river and creek spill-over points, and the water storage capacity of Mabel Lake and Sugar Lake into account.
  • The height of the snowpack in the watershed defines the total volume of water during runoff to be added to the initial lake level, less the the outflow during the same time period. The average yearly lake level increase during the runoff calculates to about 3 - 3.5 metres (9-10 ft). A low lake level at the beginning of the runoff leads to a lower peak. Therefore, the higher the initial level, the higher the peak.

All that does not necessarily mean that we will have another flood year similar to 2012. However, the potential for flooding does exist, more so than last year. Weather will again become a critical factor, and the next 2 or 3 weeks will set the stage as to what we can expect for this year's runoff. Long-term weather models do not project excessive rain periods similar to last year. But this remain to be seen how accurate those weather models are in reality. A hot early summer can also quickly become a game changer. On the other hand, preferable conditions can marginalize the flood risk, as we have seen many times before.

It is certainly not the objective of this report to predict a new flood year or to cause worries in this regard. It is simply too early to tell with certainty as to what degree the currently given circumstances may translate into lake level raise and peak levels. What we can say with certainty is that there is a definite potential for another above average peak level for 2013, even more so than existed in 2012. The 2012 flooding came unexpected, even to shuswaplakewatch.com. This year is much different; we already see the indicators and can prepare for a worst-case scenario, regardless if it may happen or not. The final chapter of this report will provide some details in this regard.

The purpose of this report is to create awareness, nothing more. Awareness provides a platform for preparedness which in turn can make a difference towards avoiding or minimizing the consequences of flooding. If your property is located within the floodplains or close to the shoreline, this is the time to review or upgrade your flood emergency plans. It is always a good idea to have precautionary measures in place. Prepare a phone list where you can get the supplies needed to protect your property. Create a to-do checklist list of all tasks you need to complete, like cutting the power to the basement, moving valuables into a safe place, how many sandbags you might need and where to get them, a phone list of helpers, things like that. If you don't need your emergency plan, that is great. But if you do, you are prepared and ready. That is what preparedness is all about.
Sometimes this year shuswaplakewatch.com will create an online version of such an emergency plan, allowing you to fill in the blanks and to store it at our secure data server, ready to download whenever it may be needed.


  Lake Levels, Flooding, Tourism

The real disaster of the 2012 flood year was the near collapse of the Shuswap tourism and the subsequent economic consequences of that. Many tourism-dependent businesses struggled through last year's season and many are still continue to do so. The weak tourism season has created an economic ripple effect through the whole region, negatively affecting many other local businesses as well as the job market. It certainly will take years to bring the Shuswap tourism back to its previous levels, considering a possibility that the lessons and failures of the 2012 event have been learned.

A high lake level and/or flooding does not necessarily equal a loss of recreational value for the lake visitor. There are always lots of things to do and places to go without being impacted by high water or flooding. Boating on the lake remains a great and safe activity. Some beaches might be smaller and increased debris flow may require more of your attention, but in general high water or flooding doesn't make this much of a difference.

Of course, it is common knowledge that flooding always requires a basic amount of precautionary measures, especially when septic fields are washed out, manure-soaked fields being flooded, and debris from years of untouched beaches being washed into the lake. There is a lot of good general information available on the Internet to this regard. Being aware of the risk factors will help you to avoid them and ensures a trouble-free and safe vacation. The lake water quality is constantly tested and beaches which carry a potential health risk are always identified as such on the Interior Health web site. Free bottled water is provided where drinking water quality has been affected. During the summer shuswaplakewatch.com will always publish important warnings and information on this site and try to address and answer all your inquiries and concerns. Our reporting is always independent, open, honest, and unbiased; we do not beautify the facts, nor do we offer selective reporting. If we do not know the answer we will follow up or get you in touch with agencies to help you further. If there are places we feel you should not visit, we will tell you "Do not go there", plain and simple. And we also inform you about facilities taking extraordinary steps to ensure a safe and pleasant stay on the Shuswap. Like the Brother's Pub in Sicamous during last year's water crisis, for example. They have quickly adjusted the menu, used only bottled water for cooking, and served dinner on disposable plates and cutlery. How do we know? We went there.

If you have concerns regarding your visit to the Shuswap, ask the facility where you booked your vacation about the specific steps and precautions taken to ensure your safety and the recreational options available to you. And come to the Shuswap to enjoy a wonderful and relaxing vacation, regardless of high water levels, flooding, or not. And keep this web site address handy for checking our daily comments, warnings, and suggestions.

Bernhard Kramer
Founder / Owner of
www.shuswaplakewatch.com
Sicamous, BC
webmaster@shuswaplakewatch.com


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