By: Hannah Logue
Amidst the record-setting droughts plaguing the Midwest throughout summer 2023, visitors and staff at Copan Lake, managed by the US Army Corps of Engineers, Tulsa District, witnessed Copan Lake’s declining water level. As of early November 2023, Copan Lake’s water level is the lowest recorded since completion of the dam in 1983. According to the National Weather Service, Osage County, where Copan Lake is located, received over two inches of rain between October 23, 2023 and October 30, 2023. After all that rain, why didn’t Copan Lake rise very much?
The answer has to do with drainage basins and soil conditions. Watershed refers to the area that drains water into a common body, commonly a river or lake. Most precipitation that falls in a watershed eventually funnels into a body of water, but when the soil is dry or groundwater levels are already low, the ground absorbs the water. Drier conditions result in greater absorption. Rain that falls outside of the watershed in question travels to another reservoir. Copan is in the Verdigris Watershed, and while plenty of rain fell in late October 2023, most of it landed outside of the watershed. “Runoff from any point in the watershed can contribute to increasing the lake level, but because of the dry conditions that Copan has had to deal with they have been experiencing heavy environmental losses,” said Brian Johnson, water manager, Copan Lake, Tulsa District, USACE.
Copan Lake Manager Brandon Moehrle explained, “The watershed that feeds Copan Lake is predominantly North and West of [the lake]. Although Copan Lake is in Oklahoma, the bulk of the watershed is in Kansas. This means that substantial rainfall needs to occur northwest of the lake to see a substantial rise in lake levels.”
The rain that fell within the watershed was not nearly enough to bring the lake back up the seven and a half feet it’s dropped throughout the drought, particularly given how much was immediately soaked up by the soil. As the lake retreated, it revealed large swathes of land that now sit cracked dry land. When the rain did come, the soil drank it up greedily.
Receding lake levels have negatively affected the recreation mission at Copan Lake. “As the lake dropped to four feet low,” said Moehrle, “our staff started observing a significant decline in recreational activities. It was at this point we decided to close the swim beach and eliminate the designated area for swimming.” The lake office closed Osage Plaines Campground, October 31, 2023, due to safety concerns related to low lake levels.