Use Mendenhall Lake to buffer the flood

The Mendenhall Lake begins to freeze on Wednesday, Nov. 26, 2025. (Jasz Garrett / Juneau Independent)

By Theresa Svancara

From what I have read in the news, the 2026 glacial lake outburst flood (GLOF) may have been less severe for several reasons, including:

– The release from Suicide Basin was slower;

– The release under the glacier may have happened differently from previous years;

– The level of Mendenhall Lake was lower than in 2025 (due to less precipitation in the summer of 2026).  

So, that got me thinking. A lower level of Mendenhall Lake may have acted as a buffer, absorbing some of the floodwaters before they roared down the river. Perhaps we could drop the lake level even further to provide more of a buffer. Let's say we move water from Mendenhall Lake and send it down the Mendenhall River prior to the GLOF. Hydrologists with knowledge of Mendenhall Lake volumes could calculate how much water would need to be removed to create enough of a buffer to prevent damaging floodwaters from entering the Mendenhall River. 

Water from Mendenhall Lake could be moved into the river by gravity-powered siphon pipes, mechanical water pumps, or a combination of various methods. The Alaska Department of Fish and Game would need to be consulted to ensure the safety of the salmon run in Steep Creek. Impacts to commercial users of Mendenhall Lake would need to be considered. Canoe and kayak tours may need a modified access point to accommodate a lower lake level, and raft tours may need to access the river from a different location when the lake is lowered. 

The advantages of using Mendenhall Lake as a buffer include:

– It's fast and could be done before the 2027 GLOF;

– It's relatively inexpensive, especially compared to draining Suicide Basin by drilling a tap;

– It does not require extensive infrastructure;

– It's flexible and when or if these GLOF's from Suicide Basin stop, you simply stop lowering the lake level annually. 

• Theresa Svancara is a 35-year resident of Juneau. She is an environmental specialist, and has worked with the oil industry on the North Slope and for several departments for the State of Alaska.