Thursday, 11 April 2013 14:31

Lower water level in Cypress Lake East Dam

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The water level in the Cypress Lake East Dam is currently kept below the full supply level until engineers have completed a survey of the dam’s foundation and embankment.

 

Cypress Lake is located about 20 kilometres north of the village of Consul in southwest Saskatchewan. The East Dam is operated and maintained by Agriculture and Agri-Food Canada (AAFC).

AAFC Acting Director of Water Infrastructure Scott Roy said the water level in the reservoir is currently maintained at about two feet or 600 millimetres below the full supply level, which will keep the dam at around 90 per cent full.

“About two years ago the reservoir filled after it had been dry for quite some time,” he mentioned. “Once it had filled we noticed that there were some settlements along the top of the dam.”

Settlement of a dam will sometimes occur, but it is not entirely clear why it happened in this case. It might be related to the dam’s location in a semi-arid area with dry and wet cycles.

According to Roy the dam had been through a prolonged dry cycle of about 15 years when the runoff in the Battle Creek and Frenchman River was low.

“There would be some runoff, but not enough to fill it,” he explained. “So what happened in 2010 and 2011 is that we entered into a bit of a wet cycle and there was more water available, so we stored more water.”

It is therefore suspected that the sudden refilling of the reservoir after years of a dried-out embankment might have resulted in the settlement of this earthfill dam.

“We think the settlements that had been occurring over the past had maybe increased a little bit because the reservoir had been dry for so long and then was filled very quickly,” he said. “What happens is that either the foundation of the dam might settle a little bit or the embankment itself might settle and move.”

As a result of the settlement the top of the dam wall is slightly lower in some areas. Roy emphasized this is not an emergency situation and the investigation of the dam structure will be done as a precautionary measure.

This dam, as in the case of all 33 reservoirs operated and maintained by AAFC in Saskatchewan, is monitored and inspected throughout the year. A more formal and rigorous inspection by a group of specialists takes place every five years.

“So the inspection part is routine and the fact that we find certain things to follow up on is routine,” he said. “We’ve experienced settlement at this dam in the past and we’ve basically dealt with that and made whatever improvements throughout its history.”

AAFC officials have been meeting with stakeholders in the area, including the town of Eastend, the R.M. of White Valley and irrigation districts, to inform them about the current situation.

The dam’s lower water level during the assessment period will not have an impact on the short-term water supply for irrigation, which is sufficient for two to three years.

This is an off-stream storage dam, which means it is situated to the side of the stream. It is therefore easy to control the water level in the reservoir.

“We have a diversion canal into the reservoir and then a canal that releases it back into the creek so that it makes its way down to the various irrigation projects,” he said.

AAFC is using consulting engineers to conduct the assessment of the dam embankment and foundation. These studies may include some geotechnical drilling of the foundation and soils testing on the embankment and foundation.

“We anticipate that the studies will probably take two to four months and then once we have the results of those studies we would basically take action,” he said. “We would try to complete whatever modifications are required this year and if we’re not able to complete them this year then plan for them for next year.”

The dam is owned by the Canadian government, which means the inspection and any repair costs will be carried by the federal government.

“As the owner of the dam it’s our intent and our responsibility to make sure that it stays safe and that it’s able to store as much water as possible,” Roy said.

 
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Matthew Liebenberg

Reporter/Photographer

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