With the US Army Corps of Engineers technical assistance, MSAC & stakeholders are developing a sediment management plan for Lewis and Clark Lake. A sediment management plan provides a framework to prevent sediment from reducing water storage capacity at a reservoir and increasing water storage capacity through sediment removal at a reservoir. Lewis and Clark Lake has already lost nearly 35% of its water storage capacity to sediment.
Sustaining our nation’s reservoirs for future generations takes a shift in thinking. MSAC wants to join stakeholders & river managers in building a broad, holistic plan that looks upstream & downstream taking into account a truer picture of actual costs & benefits.
Learn more about ideas discussed at a Solutions Workshop in June of 2021, focused on producing a plan for sediment management at Lewis and Clark Lake.
Volumes of information exist regarding the sediment conditions at Lewis and Clark Lake and the delta. A sediment management plan (SMP) is more than another study. The goal for a SMP is to bring past research together with new information building an action plan.
One challenge is the economic model federal planners use to determine how a project’s benefits compare to its costs. The current model nearly makes maintaining water storage capacity at L&C Lake impossible. Stakeholders hope to illustrate this early on in planning. This could benefit planning at other Missouri River reservoirs and elsewhere.
Damages due to lack of sediment management at Lewis & Clark Lake account for 70 percent of the actual construction costs and would likely exceed construction costs if damage information was available. (Source: Reservoir Sustainability & Sediment Management/Journal of Water Resources and Planning Management – M. George, R. Hotchkiss & R. Huffaker)
If nothing changes, Lewis and Clark Lake will be half full of sediment by the year 2045. More than 75,000 acre feet of sediment enter the six Missouri River main stem projects annually. Gavins Point Dam traps 2,700 acre feet annually in the system’s smallest reservoir. Sedimentation problems in the Missouri River reservoirs may not be visible to the naked eye in all locations, but they are occurring in all the reservoirs, including near tributary confluences. As sediment continues to accumulate it can, and will, result in the loss of hydropower production, negatively affect recreation, including fishing and boating, cause a reduction in flood control capability, and negatively impact public drinking water and agricultural water intakes, plus have many other negative impacts.
