Monitoring lake level to prevent flood

[mag-lite]

The snowpack is 150% of normal and cool temperatures delayed melting in March. With more rain coming in April and sudden high temperatures expected in May, it's a perfect storm for serious flooding again this year. Common sense and past experience tell us the best prevention is to bring the lake down as quickly and as low as possible. What are the chances that will happen?

[vegas1500]

The snowpack is 150% of normal and cool temperatures delayed melting in March. With more rain coming in April and sudden high temperatures expected in May, it's a perfect storm for serious flooding again this year. Common sense and past experience tell us the best prevention is to bring the lake down as quickly and as low as possible. What are the chances that will happen?

Have you seen the lake? They have been bringing it down for quite some time now.... everyone is a expert.

[the truth]

ya except the one's in charge, last year proved that

[dirtybiker]

Have fun walking out to the buoys in loon "sediment" to get to the puddle.

[andrea-lake]

Research shows that 80 years of operating experience tells us the lake needs to be drawn down 1 foot (or 30 cm) more from the current level as of March 29th, 2018. Refer to the extract below taken from the detailed flood review report in 1998.

You can see that we are currently at 1.3 on the left axis of the graph below (or elevation of 340.55 meters). To be reasonably certain that we won’t have another flood, the lake managers should draw it down to at a minimum 1.0 on the graph (or elevation of 341.25 meters).

Over the past 5 to 7 years the lake managers have typically drawn it down to only 1.5 (or elevation of 341.75 meters) due to more of a focus on possible drought and desire to rebuild the fishery. As a result, they have tended to hedge on leaving the lake higher than the historic guidelines suggest are prudent to avoid flood damage from high lake levels.

Okanagan residents can help by discussing this publicly because this level of drawdown will be controversial among some political interests that lobby for a high lake level.

[andrea-lake]

My previous post states that the lake should be drawn down by about 1 more foot (30 cm) from the current level on March 29th. The following information shows that this can reasonably be achieved based on historical experience.

The dotted line circle on the first chart below shows the outflow pattern just before the spring freshet in 1997. You can see that the lake level was drawn down from 1.3 on the left axis in early March to 1.2 within just 1 month. (Reference the 1997 lake level picture in my first post on March 18th). However, in 1997, even at this lower level there was still some flood damage, (although nothing like in 2017), because they didn’t follow the 1974 rules stating that it should have been drawn down to 1.0 given the conditions at that time.

Now refer to the second chart below to compare this years’ outflow pattern with the 1997 outflow pattern. You can see that even with 150% current snowpack, the lake managers are not drawing down the lake as quickly as in 1997. In addition, we currently have saturated ground water and a forecast for more rain and cool temperatures in April, which could create an even higher snowpack. http://www.obwb.ca/weather-report-april/

All this suggests they should be discharging the lake faster now than they did in 1997. It might take 65 cubic meters per second (m3/s) outflow from early next week until the freshet starts and then an increase to 75 or 85 m3/s during full freshet.

Although the original target in my March 18th post was 1.2 the target has changed to 1.0 now because of further research that revealed the 1974 rules for prudent lake management and a study of the 1997 flood review showed there was some flood damage even though they drew the lake down to 1.2 that spring. (Image of 1998 report below). Since March 18th we have also had updated reports on weather, snowpack and ground water. If anyone can add additional information or insights it would be much appreciated.

[andrea-lake]

Below are graphs of the current lake conditions as of April 7th and projections of where the lake would be after the freshet if it’s drawn down to the level recommended by the 1974 Rules. You can see that officials need to increase the outflow from 58 cubic meters per second (m3s) to 70 m3s right away if we are going to have any chance of avoiding another flood. At the rate they are going they will only be able to lower the lake another 18 cm by the end of April when it needs to be lowered by a further 28 cm (a total of 46 cm from today). If they make that adjustment to achieve the lower level, then the expected large freshet will quickly raise the lake back up by 1.7 meters to an elevation of 342.72 meters, which is 25 cm above full pool. That elevation would not create a problem. However, if they don’t increase the outflow as suggested, the lake will rise to 343 meters. That elevation is only 24 cm below last year’s flood level, which would be a big problem.

Lake level Mar 31 - Apr 7, 2018

Lake level Mar 31 - Apr 7, 2018

Outflow at Penticton Nov 1, 2016 - Apr 7, 2018

Outflow Nov 1, 2016 - Apr 7, 2018

Lake level Nov 1, 2016 - Apr 7, 2018

Lake level Nov 1, 2016 - Apr 7, 2018

Referring to above graphs, the lake is currently at an elevation of 1.24 meters on the left axis or 341.48 meters’ elevation. This is a drop of only 5 cm total since March 31st or roughly a 0.71 cm per day drop. At this same rate over the next 25 days the lake will drop approximately 18 cm to a level of 1.06 meters on the left axis or 341.2 meters’ elevation. At that level it will be almost 60 cm below where it was at the same time last year, but if you add the expected rise in the lake level of 1.7 meters you get a predicted level for late June of 342.9 meters (2.7 on the left axis) which is well above the full pool level of 342.48 meters. That would still be at flood level but 30 cm below last year’s peak of 343.24 meters (3.0 on the left axis).

It should be noted that the 1974 Rules for prudent lake management recommend that in an expected flood year the lake should be about 0.78 on the left axis or 341.02 meters’ elevation. Remember that after the freshet comes down the lake will rise at a minimum 1.5 meters from the low to 342.52 meters’ elevation (2.28 on the left axis) which is above the full pool level of 342.48 meters and 52 cm below the 343.24 meters flood level that was reached in 2017.

Remember that both the snowpack and a very wet spring caused the total rise of 1.5 meters in 2017. This year the snowpack alone will likely cause that much rise even if we get a dry May and June. The result after an extra drawdown to the level of the 1974 Rules will still be full pool. The projected rise of 1.7 meters allows for some further increase in the snowplak and unexpected rain this spring.

[Glacier]

While we have a lot of snow this year, it's nowhere near as high as 1974 or 1999. Therefore, not a good idea to draw down more than is currently being done.

[andrea-lake]

Glacier, your graph posted on April 3rd shows that we are close to the same snowpack level as in 1998/99. Based on the snowpack that year, the officials drew down the lake to 15 cm below where it is today (April 7th). That same graph also shows that we are currently above the level of the 1973/74 snowpack. In that year, they drew the lake down to 26 cm below where it is today. Considering this, it seems that the lake should continue to be drawn down at a higher rate to achieve at least the 1974 drawdown level. However, remember there was a flood in 1974 so clearly, they should have drawn it down more.

There is some additional information that you might be able to provide to help with ongoing discussion and overall perspective. 1997 was a flood year, so it would be helpful if you could post the snowpack graph for 1996/97. Another flood year was 1948, so if it’s possible to get the snowpack graph for 1947/48 that would be very useful as well. Thanks.

Comments in my posts are simply to remind people what the experts stated in the “Okanagan Water Level Management Review of Past Trends with Recommendations” written for the Ministry of Environment, Lands and Parks by two Ph.D. engineers, Ward and Yassien. (Interim report in 1998 and final report in 2000). This report included the 1974 Rules, which I posted on March 31st in this forum. In addition to the rules and recommendations, a general observation in the above-noted report was: “… the lake is operated most of the time at levels higher than necessary…”

[brentville]

Comments in my posts are simply to remind people what the experts stated in the “Okanagan Water Level Management Review of Past Trends with Recommendations” written for the Ministry of Environment, Lands and Parks by two Ph.D. engineers, Ward and Yassien. (Interim report in 1998 and final report in 2000).

"Water Level Management"? What a joke. They may as well put the Marx Bros. in charge!

Kim Hyatt of DFO co-wrote the program used to predict inflows in to Okanagan Lake. Here is what he said a year ago...



10-day forecasts are certainly NOT RELIABLE !!!!!. They start screwing with the flood gates in NOVEMBER to set levels in FEBRUARY. They knew the data that predicted a drought was suspect yet these bozos acted as if what the program spat out was written in stone.

https://globalnews.ca/news/3517301/okanagan-lake-wasnt-lowered-sooner-to-protect-fish-stock/
Reimer told Global News that DFO told him to hold back the water...LIES!
Quote from Global ...."The federal Department of Fisheries and Oceans said it asked Reimer to hold back the lake water to maintain compliance with the Okanagan Basin Agreement." I took Reimer to task on this and eventually he admitted DFO made no such request!

"Management my azz...I do better than these morons at the craps tables!

REMOVED THE DAM FLOODGATES and there will be no more Okanagan Lake floods !!!!!

[andrea-lake]

Of immediate concern is the need to draw down the lake NOW at a faster rate to reach the level prescribed by the rules and thereby prevent the flood that the City of Kelowna and the Regional District are already warning us to prepare for. That's the focus of "Monitoring lake level..."

[seewood]

Of immediate concern is the need to draw down the lake NOW at a faster rate to reach the level prescribed by the rules and thereby prevent the flood that the City of Kelowna and the Regional District are already warning us to prepare for. That's the focus of "Monitoring lake level..."

I hear ya. Thinking there is more to it than just opening up the gates in Penticton. Dams downstream and the flows in the channel also have to be taken into account. Be stupid not to..

[Fancy]

The Okanagan and Similkameen both registered snowpacks 152 of normal on April 1, with the Boundary not far behind at 149 per cent.

The April survey is considered the most valuable for predicting spring flooding. Last year, the April snowpack in the Okanagan was 105 per cent and 95 per cent in the Similkameen

https://www.castanet.net/edition/news-s ... htm#223232

That doesn't sound good.

[Glacier]

[Frisk]

The Okanagan and Similkameen both registered snowpacks 152 of normal on April 1, with the Boundary not far behind at 149 per cent.

The April survey is considered the most valuable for predicting spring flooding. Last year, the April snowpack in the Okanagan was 105 per cent and 95 per cent in the Similkameen

https://www.castanet.net/edition/news-s ... htm#223232

That doesn't sound good.

We've got the snow so I guess it depends on how quickly it melts now.