Mark Twain Lake Water Control Operations December 16th, 2015 US Army Corps of Engineers BUILDING STRONG® Overview . District and Watershed Overview . Project Purposes . Water Control Plan . Minimum Discharge/Water Quality Issues . Sedimentation Surveys BUILDING STRONG® St. Louis District Mark Twain Lake Lake Shelbyville Illinois River Illinois Carlyle Lake Rend Lake Wappapello BUILDING STRONG® Lake Lake Shelbyville Reservoirs Mark Twain Lake Illinois River Illinois Carlyle Lake Wappapello Lake Rend Lake BUILDING STRONG® Salt River Watershed BUILDING STRONG® BUILDING STRONG® Project Purposes . Flood Control . Hydroelectric Power . Recreation . Water Supply . Fish and Wildlife BUILDING STRONG® Project Purposes . Flood Control ►Flood Control provides flood damage reduction along both the Salt and the Mississippi Rivers. ►Releases maybe restricted because of flooding on the Lower Salt River or on the Mississippi River at Louisiana and/or St. Louis. BUILDING STRONG® Project Purposes . Hydropower ► Objective is to obtain the maximum amount of hydroelectric power generation revenue the project is capable of producing in conjunction with other project purposes. ► Normal lake drawdown within the joint use pool as a result of hydroelectric power generation will be limited • 2 foot per calendar week or 4 foot per month during May – October. • Remainder of the year limited to 2 foot per week with no monthly maximum. BUILDING STRONG® Project Purposes . Recreation ►Objective is to provide the best possible water conditions to support recreational activities such as boating, swimming, fishing, hunting, camping, etc. in coordination with other project purposes. BUILDING STRONG® Project Purposes . Water Supply ►The State of Missouri and the Federal Government have negotiated the water supply contracts. BUILDING STRONG® Project Purposes . Fish and Wildlife ►Objective is to enhance fish and wildlife to as great an extent as possible without conflicting with the achievement of other project purposes. ►Coordination is necessary between the Water Control Office, MDC, SWPA and Mark Twain Lake Project Office. BUILDING STRONG® Project Purposes . Fish and Wildlife . Fish Spawn: The pool elevation of Mark Twain Lake will be regulated from April 23rd to June 15th whenever possible so as to minimize the amount of fluctuation during spawn. This effort is in coordination with SWPA, COE and Missouri Department of Conservation. The Chief of Water Control Operations, taking into account all project purposes, hydrologic conditions and weather forecasts may attempt to moderate pool fluctuations during critical fish spawn when the pool elevation is 610.0 feet NGVD or below coordinated with Missouri Department of Conservation and Mark Twain Lake personnel. BUILDING STRONG® BUILDING STRONG® Water Control Plan BUILDING STRONG® Water Control Plan . Conservation Pool (<606.0) ►Minimum flow: 50 cfs ►Maximum flow (crop season): 10,000 cfs • Max releases based upon downstream conditions ►Maximum flow (dormant season): 12,000 cfs ►Drawdown limits (recreation season): • 2 feet/week, 4 feet/month ►Drawdown limits (non-recreation season): • 2 feet/week BUILDING STRONG® Water Control Plan . Flood Control Pool (606.0 – 638.0) ►Minimum flow: 50 cfs ►Maximum flow (dormant season): 12,000 cfs ►Maximum flow (crop/recreation season) • Pool < 615, No Mississippi River flood: 10,000 cfs Releases are based upon downstream conditions • Pool < 615, Mississippi River flood: 6,000 cfs Cut back to 2,000 24 hr prior to crest and releases increased on recession side Releases are based upon downstream conditions • Pool >615 & < 638.0: 12,000 cfs Releases are based upon downstream conditions BUILDING STRONG® Water Control Plan . Surcharge Pool (638.0 – 648.0) ►Minimum flow: 12,000 cfs ►Maximum flow: • Determined from surcharge regulation curve Based upon Pool Elevation and Inflow • If pool elevation is forecasted to reach surcharge (water on the ground), the max discharge may be preempted increased to discharge called for on the surcharge curve for that given elevation and inflow. ►Recession side of Surcharge - Target 1 to 2 foot fall per day not to exceed previous max event release until pool elevation 620.0 BUILDING STRONG® BUILDING STRONG® Minimum Releases BUILDING STRONG® Sedimentation Report BUILDING STRONG® Sedimentation Report . Purpose ►Determine if the reservoir is filling as designed ►Update Reservoir Area and Capacity Curves BUILDING STRONG® Sedimentation Report Clarence . Sediment Ranges Cannon are Surveyed Dam . The survey lines are used to grossly estimate the reservoir volume BUILDING STRONG® Sedimentation Report . Sedimentation does not necessarily occur at the bottom of the reservoir ►Sedimentation tends to occur at the mouth of the tributaries (i.e. the upper end of the reservoir) Reservoir Dam Sedimentation BUILDING STRONG® Sedimentation Report . Survey Ranges are compared to the original 1982 survey and other past surveys BUILDING STRONG® Sedimentation Report . 2010 Findings ►The sedimentation rate is as expected Amount of Rate of Percent of Sediment Deposition Storage Deposition (ac-ft/yr) Lost (ac-ft) Total Reservoir 56,850 2,060 4.0% BUILDING STRONG® Questions BUILDING STRONG®.