Tuesday 15 November 2016

Challenge 2

Although I love learning from people around me and exploring my surroundings I am at heart a science person.  I like to understand the why and how of what is going on around me and because of that I chose to go with option 2 for this challenge.  However I have incorporated important landmarks such as the Weir on the Lesser Slave River and the anecdotes and responses from lake users and long term citizens of the area.


Water Levels have frequently been an issue of concern for the people residing on or around Lesser Slave Lake.  So much so that in 1983 a weir was installed over the outflow to the Lesser Slave River on the East Basin of the Lake.  The intent of the weir instillation was to help mitigate the effects of flooding and decrease the amount of fluctuation in lake water levels.


The instillation of the weir had the unintended consequences of disrupting and changing downstream flows of the Lesser Slave River.  This is most noticeably in the winter months when on occasion the river froze solid preventing downstream flow, causing a host of problems including low water levels and low levels of dissolved oxygen in the remaining water.



For a number of years siphons were installed in the fall it keep water flowing over the winter.  However this installation was costly and dangerous so this year the Government of Alberta installed a flow gate which can be raised to allow 6 cubes of water per second to flow downstream.  6 cubes was determined to be the amount required to maintain a healthy dissolved oxygen content downstream.   The hope is that the gate will only have to be used during extraordinarily dry years.


Information on the Lesser Slave River and weir from: LSWC http://lesserslavewatershedcouncil.ca/watershed-planning/lesser-slave-river-wmp/

Photos credit: Lesser Slave Watershed Council archives



Lake Levels are also a large issue of concern when it comes to public recreation.  Lesser Slave Lake is a very popular fishing destination and there is a large tourism industry built around getting visitors and there boats out onto the lake.   Because of where our watershed is located we don't have glacial headwaters and because of this are dependent on snow melt and precipitation to replenish lake and stream levels.  Last winter was a very mild winter leading to almost no snow melt so lake levels have been a hot topic over the last year.


There are multiple Harbors and Marianas around the lake which generally allow for lots of access points for recreational users   After talking with several people though I heard story upon story of how no one was able to get there boats into the water until mid June due to extremely low water levels.  Thankfully in June a large rain came to the area raising the water level dramatically and allowing boats to be launched with ease.

A common thread I found when speaking with people about lake levels was that residents who had lived in the area less then 10 years saw spring of 2016's low water levels as a terrifying and new situation.  Where as residence who had grown up in the area and had family who had settled or been living here for generations were much less surprised at the low levels.  In many cases stated that this was nothing and that in the early 90s the lake was so low you could practically drive across  The Narrows (a channel that connects the East and West Basins of the  lake together)  

                                                                                                 Map created by the Government of Alberta

When it comes down to it, it seams that due to our geographical location and the unpredictable nature of our weather and climate the lake will always be prone to fluctuating water levels, even if that fluctuation has been slightly evened out due to the construction on the weir.


1 comment:

  1. This was really interesting. I initially expected that the weir was constructed with the sole purpose of controlling the River water levels, for flood protection benefits. Was flooding an issue in the past on the River, or did the lake effectively dampen the effect of big storms or large melt events?

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