Water Levels and Flooding

When rain falls or snow melts, the water flows downward. Some water percolates into the ground and becomes ground water that may then flow through the ground into a water body. Some water flows overland or through drain pipes and enters a nearby water body from the surface, like Grays Lake. The area of land around Grays Lake that drains into Grays Lake is called the Grays Lake watershed. There are no streams or rivers that flow into Grays Lake, instead there are storm drains and local water run-off. There are approximately 230 acres (three times the size of Grays Lake) of land around the lake that drain into the lake. Any pesticides, week killers, motor oil, or animal droppings deposited in this area will eventually wash into the lake if they are not cleaned up or naturally break down. Ground water or springs are not believed to contribute significantly to the lake's water because the lake bed is believed to be underlain by 230 feet of clay.

Today, lake level is controlled by a weir in a spillway along the north east end of the lake.It is visible in the picture below in the center of the picture. This spillway drains overflow water into a pipe that flows into the Avon-Fremont drainage ditch which flows past the south side of the Grayslake Shell station on Route 83 and eventually into Mill Creek. Mill Creek in turn flows north to Third Lake and then east into the Des Plaines. The Des Plaines flows to the Illinois River, then the Mississippi River, and eventually into the Gulf of Mexico and the Atlantic Ocean.

The photo below shows this structure with the lake at a low level during the drought in August 2005.

Compare the structure to this photo taken in June 2004 with the lake just about as full as it can get before pouring over the large opening at the top of the structure.

.

When the lake is this full, it nears the banks around the perimeter of the lake. Note the lake level here also in June 2004.

After the drought of 2012 the lake returned to a low stage. This photos is from September 23, 2012.

Things become exposed that are typically under water. Like this are at the end of George Street in September, 2012.

Or the typically sunken sea wall on Jones Island in a picture taken January 12, 2013.

This flood map from Lake County shows the flood prone areas in purple. Note that area around Hawley Court. This was probably the overflow point for this lake in the distant past.

Countour maps of the Hawley Court area show the low elevation of the land that contributed to flooding in the past.

The past is recorded in the land contours that remain today. . This area has been home to a sandy beach for as long as anyone can remember . This end of the lake is still very sandy and also contains gravel. Perhaps as the glacier that formed this lake melted, the water breached the lake rim through this area shown below, today.

More recently we know that the lake overflowed at this point. The flow of water from here most likely eroded the land scape and allowed sand and gravel to be deposited where escaping water velocities slowed and allowed the sand to settle. Gray's Lake is at the top of the watershed. That means that there are no streams or rivers that flow into it. Instead, a small area of land that surrounds the lake drains into it, primarily through a series of drain pipes and run off. Many of these drain tiles are small and not readily visible. A few are easily observed.

This drain pipe is located at the south end of the lake and passes under Route 120.

This drain pipe passes under Allegany and into the west channel near Jones Island.

A major drain into the lake also passes into the west channel at the northwest end. It is visible here emerging from the grass at the very upper left corner of the channel. The building at right is a Grayslake Park District building on the corner of Allegany and Harvey at the entrance of Jones Island.

Often times during the winter months, Jones Island floods over. On January 1, 2009 the island was so completely flooded and still that it became the ideal ice rink. The islands grass and sand was visible beneath the crystal clear ice. Soon after we discovered these conditions, word spread and dozens of folks were gliding effortlessly across the island.

Here is the same general area of Jones Island in the seven months later.

Jones island flooding is controlled by a series of drains connected to a common pipe that leads to a pump. This is the middle drain on the island. The white PVC drain pipe is visible leading to the pump. Often times the island floods as lake level rises above its elevation.

This structure houses the pump used to drain the island when it is flooded. The pump's discharge is into the south channel. In the winter, this area is often unfrozen. The discharge is marked by a metal pole in the channel.

The problem is that Jones Island is slowly sinking back into the wet lands it was built upon. Here a concrete block attached to the sheet pile that wraps the island like a belt, is exposed as the soil is sinking around it.

In 2008 the southeast corner of the island was repaired. The seawall had heaved out of the ground and was hazardous. It was replaced.However, the area behind the wall is lacking fill and flooded in August 2009.