Jan. 2003: Watershed assessment could spark sediment reduction
By John Deppe, coordinator of Lower James RC&D (SD)
Lewis and Clark Lake is filling up with sediment and its life has been estimated at between 75 and 135 years by the Corps of Engineers. The Corps of Engineers estimates that an annual average of 4,235,000 cubic yards of sediment enters the Lake which is equivalent to a pile of sediment 2300 feet tall the size of a football field.
Local efforts to address the sedimentation issue have been ongoing for the past 30 years with few positive actions resulting. A partnership of area citizens, local organizations, river communities, and local, state, tribal, and federal units of government currently feel the solution to the sedimentation problem will involve three activities:
1. Reducing sediment entering the river and lake through land management activities in the watershed.
2. Removing a portion of the sediment likely through dredging.
3. Managing the sediment through methods that deposit sediment where it is least damaging.
On January 6th, 2003, in Wagner, the local partnership of citizens and organizations met with representatives of both the South Dakota and Nebraska to address the issue of sediment reduction by working to develop a watershed assessment. The watershed area of concern is all drainage into the Missouri River and Lewis & Clark Lake from Ft. Randall Dam to Gavins Point Dam. The purpose of the watershed assessment is to identify, quantify and locate sources of water pollution with a focus on sources of sediment.
Those attending the meeting agreed to move forward in putting a watershed assessment plan together. The proposed plan at the meeting was a cooperative plan for South Dakota and Nebraska covering a three-year period. Due to uncertain funding the initial effort will be for one year and include water sampling and watershed modeling in watersheds in both states. The Randall Resource Conservation and Development Council, (RC&D), Lake Andes was tentatively selected to lead and administer this effort. The proposed plan will be further developed and finalized by February 1, 2003, and if approved by participating organizations implemented in 2003.
It is expected that the watershed assessment findings will help landowners and conservationists understand how much sedimentation can be reduced through application of best management practices within the watersheds. If sediment delivery from the watersheds was reduced by 30% and the life of Lewis and Clark Lake is 75 years then this 30% reduction should extend the lakes life another 20-25 years.
Representatives attending the Wagner meeting or providing a letter of support for this effort include: 10 SD Conservation Districts; Spring-Bull Creek Watershed District; South Central Water Development District; Lewis & Clark SD-NE Preservation Association; Missouri Sediment Action Coalition; City of Springfield; City of Yankton;; SD Department of Environment and Natural Resources; South Central RC&D; Randall RC&D; and Lower James RC&D - all in South Dakota. From Nebraska: Middle Niobrara River Natural Resource District (NRD); Lower Niobrara River NRD; Lewis & Clark NRD; Northeast Nebraska RC&D; North Central Nebraska RC&D; Village of Niobrara, Knox County; and Nebraska Department of Environmental Quality. Also attending the meeting were representatives of USDA Natural Resources Conservation Service and US Army Corps of Engineers will also be on hand.