Secondary Site Locations on Large Reservoirs Issue 1 – How to select tributary arms for criteria...

Secondary Site Locations on Large Reservoirs

Issue 1 – How to select tributary arms for criteria monitoringMissouri’s large reservoirs are highly dendritic and monitoring should be limited to the largest of tributary arms.

Issue 2 – Where to locate monitoring site within tributary armsSites need to be located down-lake of transition zone but far enough away from main lake to eliminate influence from main channel.

Issue 3 – How to calculate the predicted total phosphorus valueShould the theoretical dam height be reservoir specific or based on an average relationship between water depth and dam height?

Issue 4 – Will mode of action at secondary sites be dependant on the mode of action at dam site?If the dam site is in Zone A and nutrients are being held to current long-term mean conditions, should secondary sites with phosphorus levels in Zone B be allowed to increase up to regional reference values?

Issue 1 – How to select tributary arms for criteria monitoringIn order to limit secondary sites to only substantial tributaries, the following conditions should be met:

A tributary arm must be connected to the main lake. The main lake is defined as either the major river stem (ex. Osage River in Lake of the Ozarks) or in situations where there is no single dominant river, the open water extending from the dam (ex. Smithville Lake).

A tributary arm should have 1 ½ miles of length for every 10 feet of depth at the mouth of the arm. Length is measured from the mouth of the arm to the point where riverine conditions become obvious.

Depth at the mouth of the tributary arm should be at least ¼ the depth at the dam.

Issue 2 – Where to locate monitoring site within tributary armsIn order to avoid locating the site in the transition zone while reducing the possible influence of the main lake, sites should meet the following conditions:

A site should be located at least ¼ of the arm’s length from the mouth, but no farther than ½ the arms length from the mouth.

Depth at the site should be at least 1/3 the depth of the tributary mouth.

Issue 3 – How to calculate the predicted total phosphorus valueThe ratio of dam height to water depth ranges from a low of 1.40 (Table Rock and Mark Twain) to a high of 7.7 (Clearwater).

Reservoir specific dam height to water depth conversions should be used

Issue 4 – Will mode of action at secondary sites be dependant on the mode of action at dam site?If the dam site is being held at current water quality levels, then secondary sites should not be allowed to become nutrient enriched.

If the dam site is Zone A, then all secondary sites will be held to the highest of the following; the long-term mean or the predicted phosphorus value.

Table Rock Lake James River Arm

Long Creek Arm

Kings River Arm

Upper LowerDepth (feet) 60 100Dam (feet) 84 140TP μg/L 14 10

Conversion = 1.4 Whole SectionDepth (feet) 40Dam (feet) 56TP μg/L 18

Upper LowerDepth (feet) 80 120Dam (feet) 112 168TP μg/L 12 9

Table Rock Lake

Predicted – 18 μg/LMean - 21 μg/L

Predicted – 12 μg/LMean – 13 μg/L

Predicted – 14 μg/LLong-Term Mean - 27 μg/L

Recent Mean – 17 μg/L

Lake of the Ozarks

Grand Glaize Arm

Gravois Arm

Osage River

Niangua Arm

Depth (feet) – 70Dam (feet) – 115Predicted TP (μg/L) - 11Mean (μg/L) - 29

Pomme de Terre Lake

Lindley Creek Arm

Pomme de Terre Arm

Stockton Lake

Big Sac Arm

Little Sac Arm

Truman Reservoir

Osage River

Pomme de Terre Arm

South Grand River Arm

Smithville LakePlatte River Arm

Camp Branch Arm

Mark Twain Lake

Lick CreekSouth Fork

Middle Fork

North Fork

Indian Creek

Lake Wappapello

Asher CreekMost of section is less than 10 feet deep.

Lost Creek

St. Francois River

Thomas Hill Reservoir

Sinking Creek ArmMaximum water depth 10 feet through whole section.

Long Branch Lake

Maximum water depth 10 feet through whole section.

Clearwater LakeBlack River

Logan CreekMaximum depth in most of section is 10 feet.

Lake Taneycomo