Contractors working for the U.S. Army Corps of Engineers Pittsburgh District install a 23-foot-tall concrete shaft enclosure weighing approximately 120,000 pounds as part of the guard wall at the Monongahela River Locks and Dam 4 in Charleroi, Pennsylvania, Nov. 16, 2023.

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Beyond snow: How snowpack benefits reservoirs once it melts

Pittsburgh District
Published Jan. 31, 2022
snowy reservoir

Snowpack forms around Shenango River Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Hermitage, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Hannah Smith)

snowy reservoir

Snowpack forms around Tionesta Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Tionesta, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Melody Wilson)

snowy reservoir

Snowpack forms around Tionesta Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Tionesta, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Melody Wilson)

snowy reservoir

Snowpack forms around Kinzua Dam and Allegheny Reservoir operated by the U.S. Army Corps of Engineers Pittsburgh District in Warren, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but it will also benefit the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Douglas Helman)

snowy reservoir

Snowpack forms around Youghiogheny River Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Confluence, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Karen Osler)

snowy reservoir

Snowpack forms around Youghiogheny River Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Confluence, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Karen Osler)

snowy reservoir

Snowpack forms around the dam of Mahoning Creek Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in New Bethlehem, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Grover Pegg)

snowy reservoir

Snowpack forms around Shenango River Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Hermitage, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Hannah Smith)

snowy reservoir

Snowpack forms around Crooked Creek Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Ford City, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Amberlee Bozic)

snowy reservoir
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Snowpack forms around Loyalhanna Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Saltsburg, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Paige Lupyan)

PITTSBURGH – Snowfall turns reservoirs into wintery landscapes throughout the Pittsburgh District, with park rangers inviting visitors to build snow persons and venture into their trails for cross-country ski trips.

The snow offers immediate reservoir-recreational activities for those who love winter, but another benefit of snow extends well beyond the cold season.

snowy reservoir
Reservoir Snowpack
Snowpack forms around Tionesta Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Tionesta, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Melody Wilson)
Photo By: Michel Sauret
VIRIN: 220127-A-XX234-0017

“Snowpack acts as a sort of battery, storing water that eventually raises reservoir levels in the late winter and spring,” said Carl Nim, a biologist who works for the Water Quality section of the U.S. Army Corps of Engineers Pittsburgh District.

The upper Allegheny River area receives a snowpack of 12 to 24 inches each year,  equivalent to one to two inches of rainfall.

snowy reservoir
Reservoir Snowpack
Snowpack forms around Crooked Creek Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Ford City, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Amberlee Bozic)
Photo By: Michel Sauret
VIRIN: 220127-A-XX234-0010

The Pittsburgh District manages the land and water levels of 16 reservoirs. Dam operators lower the pool as winter approaches, and they allow water levels to rise as reservoirs prepare for summer. Releasing water is easy because each reservoir has a gated dam that opens, but filling the reservoirs relies on the weather.

“There is no spicket or a faucet we can turn on to refill our reservoirs. We use the snowmelt and spring rain to build from winter pool to summer pool,” said Megan Gottlieb, the Water Management unit lead for the Pittsburgh District.

snowy reservoir
Reservoir Snowpack
Snowpack forms around Shenango River Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Hermitage, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Hannah Smith)
Photo By: Michel Sauret
VIRIN: 220127-A-XX234-0011

Filling to summer pool is part of the annual plan to store water for later needs. Reservoirs help mitigate flood damage, improve water quality and support river navigation downstream.

Gottlieb estimates half of the water flowing into the reservoirs in the spring comes from snowpack, and the other half comes from rain and runoffs.

“Without a snowpack, it would delay our ability to fill to summer pool by at least a month or two,” Gottlieb said. “Or we run the risk of not reaching summer pool at all if it’s extremely dry.”

snowy reservoir
Reservoir Snowpack
Snowpack forms around Loyalhanna Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Saltsburg, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Paige Lupyan)
Photo By: Michel Sauret
VIRIN: 220127-A-XX234-0009

Nim, a biologist, said snowpack could benefit water quality as well. Cold water also holds more gases than warm water, meaning aquatic life benefits from its abundant dissolved oxygen.

“That’s definitely a water quality benefit since the reservoirs get filled with high dissolved oxygen water,” Nim said.

If snow melts slowly and gradually, it contributes to groundwater recharge without some of the harmful components that come with heavy rain, such as erosion and pollution. From a fishery perspective, snowmelts increase flow, and with warming weather, the change in temperature cues riverine fish for spawning.

snowy reservoir
Reservoir Snowpack
Snowpack forms around Youghiogheny River Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Confluence, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Karen Osler)
Photo By: Michel Sauret
VIRIN: 220127-A-XX234-0015

“It’s a complex relationship between the correct amount of water flow and the correct water temperature that triggers fish spawning,” said Anthony Honick, a biologist with Water Quality.

However, a rapid snowmelt in developed areas could be damaging as well, Nim said. In developed areas, accumulated snow can store contaminants such as salt and metals entering the stream and impacting aquatic life and drinking water. The benefits of snow can vary from case to case based on context.

“Recharging the water table and keeping our streams and reservoirs full is probably the best benefit that snowpack has to offer,” Honick said.

snowy reservoir
Reservoir Snowpack
Snowpack forms around Tionesta Lake operated by the U.S. Army Corps of Engineers Pittsburgh District in Tionesta, Pennsylvania, January 2022. The snow provides not only a wintery landscape, but also a benefit for the upcoming summer. When the snow begins to melt in the spring, it will serve as a critical boost to returning the reservoir's water level to summer pool. (U.S. Army Corps of Engineers Pittsburgh District photo by Melody Wilson)
Photo By: Michel Sauret
VIRIN: 220127-A-XX234-0018


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