US Army Corps of EngineersBUILDING STRONG®

Mark Twain LakeWater Control Operations

December 16th, 2015

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Overview

District and Watershed Overview Project Purposes Water Control Plan Minimum Discharge/Water Quality Issues Sedimentation Surveys

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Lake Shelbyville

Rend Lake

Carlyle Lake

Wappapello Lake

Mark Twain Lake

Illin

ois

Riv

er

St. Louis District

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Illin

ois

Riv

er

Reservoirs

Mark Twain Lake

Lake Shelbyville

Carlyle Lake

Rend LakeWappapello Lake

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Salt River Watershed

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Project Purposes

Flood Control Hydroelectric Power Recreation Water Supply Fish and Wildlife

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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.

Project Purposes

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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.

Project Purposes

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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.

Project Purposes

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Water Supply

►The State of Missouri and the Federal Government have negotiated the water supply contracts.

Project Purposes

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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.

Project Purposes

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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.

Project Purposes

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Water Control Plan

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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

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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

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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

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Minimum Releases

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Sedimentation Report

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Sedimentation ReportPurpose

►Determine if the reservoir is filling as designed

►Update Reservoir Area and Capacity Curves

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Sedimentation Report Sediment Ranges

are Surveyed The survey lines

are used to grossly estimate the reservoir volume

Clarence Cannon

Dam

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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

Sedimentation

Dam

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Sedimentation Report Survey Ranges are compared to the

original 1982 survey and other past surveys

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Sedimentation Report

2010 Findings►The sedimentation rate is as expected

Amount of Sediment

Deposition (ac-ft)

Rate of Deposition

(ac-ft/yr)

Percent of Storage

Lost

Total Reservoir 56,850 2,060 4.0%

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Questions