Straight from the Tap

Freezing Weather Doesn't Always Mean a Frozen Lake Erie

01/08/2018

We constantly monitor the temperature of the 250 million gallons of raw water we draw from Lake Erie into our treatment plants. In fact, Cleveland’s official water temperature, the one meteorologists report on the news, comes from the gauges inside the intake at Cleveland Water’s Garrett A. Morgan Treatment Plant near Whiskey Island.

For the first week in January 2018, water temperatures in Lake Erie hovered around 32°F. Yet the water running through our treatment plants has little chance of freezing. The reasons why start with the location of our water intakes.

Each Cleveland Water intake crib is located about 3 to 5 miles offshore. The cribs protect the top portion of the 7- to 9-foot diameter pipes which go down into the lakebed then towards the shore through giant tunnels. The tunnels are about 50-feet below the bed of Lake Erie, which makes them about 100 feet below the surface of the water. Water is drawn into the intake pipes from the middle and bottom of the lake – not the surface where water is more likely to freeze and pieces of ice float.

Their location far offshore is important because when a winter is cold enough very shallow areas along the lake can freeze solid. Even a few hundred feet offshore needle-shaped ice crystals called frazil ice can develop and clog intake pipes. Our intakes are located in 50-foot deep water where the water cannot freeze solid. Additionally, the temperature 50-feet below the bed of the Lake Erie where our intake tunnels are located is actually warmer than the lake water.

Water at the bottom of Lake Erie is also in motion. Flowing water can have enough internal energy to resist crystallization. While most people will never experience underwater currents, people who scuba dive in Lake Erie will attest to the fact that water at the bottom of the lake moves. The National Oceanic and Atmospheric Administration’s (NOAA) Great Lakes Environmental Research Lab has a real-time map that shows currents. Once water is in our intake pipes, pumps constantly move water into and through the plants and distribution system. This continual movement help prevents freezing. This is also why it’s a good idea to let a small stream of water flow from your faucet to prevent your pipes from freezing during extremely cold temperatures.

Additionally, water under pressure has a lower freezing point. Lake water drawn into our plants is under pressure from the many feet of water above it. When water is in our intake pipes and distribution mains, the pressure comes from the pumps that push water from place to place. Pressure’s impact on the freezing point effects packaged drinks, too. If you’ve left a sealed beverage outside over the last few weeks, it may still look liquid. If you crack the lid and some of the liquid instantly freezes, it’s because opening the bottle released the pressure and increased the freezing point.

Finally, when water has stuff in it temperatures must be colder than 32°F for water to freeze. The stuff can be dissolved oxygen, minerals, or the ingredients in your favorite drink. Raw water in Lake Erie has extra stuff in it, including more oxygen. The impact of minerals on water’s freezing point is why spreading salt on sidewalks melts ice. Salt lowers the freezing point. This is also why temperatures need to drop to around 28.4°F for seawater to freeze.

All of these reasons are why, even when much of Lake Erie looks frozen, we're still able to provide our customers with quality drinking water.

 

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