Minimum Flows in the Tennessee River Valley
William D. Proctor River Operations Habitat Benefits of In-stream Flow
more wetted channel area improved attraction water for fish spawning runs continuous flushing of deep natural pools reduced thermal shock. water supply, assimilative capacity/water quality, MINIMUM FLOW: SMALL HYDRO UNITS
•Blue Ridge •Nottely •Tims Ford 8000 cfs turbine discharge MINIMUM FLOW: REREG WEIRS 1996 •Chatuge •Norris •South Holston
200 cfs minimum flow
1300 cfs turbine discharge Norris reregulation weir (TVA) 3 km downstream 1996 from hydropower dam Siphons at Tellico Purpose: cold water for downstream fish refuge
Siphons at WF George Purpose: Blend oxygenated water with leakage that is low in oxygen Turbine pulsing could provide minimum flow at 8 of 16 projects
Big turbine, little river: Tims Ford
100 ft target flow 80 cfs pulse interval 5 min / 12 hrs
3900 cfs Big turbine, big river: Douglas
585 cfs 30 min / 4 hrs 600 ft target flow 4000 cfs pulse interval Pulsing for Minimum Flow A Win-Win Below Douglas Dam
Douglas 5000 Dam 4500 max Pulsing vs 4000 Continuous 3500 Minimum Flow
3000 below Douglas
2500 Dam Flow (cfs) 2000 French Broad 1500 River in 1000 600 cfs pulsed (4500 cfs for 0.5 hr every 4 hr) Tennessee mean 500 300 cfs continuous Participants: 0 min 0 5 10 15 20 25 30 River Mile TVA TWRA Methodologies
Project support (Nottely, Little Bear Creek, Cedar Creek, Tims Ford) Statistics (7Q10, 3Q20, etc.) Inflection point (South Holston) Assimilative Capacity downstream (Elk, Watauga, Duck Rivers) Cedar Creek Requested Flows Cedar Creek -- Headwater Elevation Percentile Minimum Flows: Jan-Apr = 240cfs; May-Jun = 71cfs; Jul-Oct = 20cfs; Nov-Dec = 51cfs 590
580
570
560
Elevation in Feet Above MSL 550 Minimum
10%
540 25% Median
Operating Guide
530 1-Jan 31-Jan 1-Mar 31-Mar 30-Apr 30-May 29-Jun 29-Jul 28-Aug 27-Sep 27-Oct 26-Nov 26-Dec Cedar Creek Final Flows
Note 90 instead of 240 cfs
In 2007, flows were 10 cfs Statistics
Percentage of 7Q10, 7 day – 10 year low flow 3Q20, 3 day – 20 year low flow, which ranges from 50 to 90 percent of the 7Q10 IHA, Indicator of Hydrologic Alternation Analysis Inflection Point 900 River Mile 119.6 - 120.1
880
860
840
820
800 Surface Area (1000 sq ft/mile) (1000 sq Area Surface Or diminishing returns 780
760 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 Flow (cfs) TVA Minimum Flows
They were first proposed as something that TVA could do and still meet pool level targets in the spring. Evaluated the habitat (wetted area) improvements associated with the minimum flows (35% to 85% increases in wetted area). In some cases, several flows were tried in the field and photographed with oblique aerial photography. Generally, the selected minimum flows ranged from 50% to 100% of the unregulated 7Q10 For TVA the Net Result
TVA Release Improvements 16 dams 1990-1996 Minimum Flow: 35%-85% wetted area increase in riffles Release DO: was 0-3 mg/L now 4-6 mg/L TVA Minimum Flows Current Leakage Target Minimum Minimum Percentage Flow Natural 7Q10 Flow Flow plus Leakage Flows 7Q10 Dam (cfs) (cfs) (cfs) (cfs) Melton Hill 10b 274 c c Watauga - 115 c c Fontana 40 725 725 c Hiwassee - 350 c c Ocoee 2 - 300 c c Ocoee 3 - 290 c c Douglas 35 1060 585 585 55% Cherokee 50 650 375 375 58% Boone 10b 428 750 800 187% Wilbur 30 119 107 220 185% Ocoee 1 50 320 140 140 44% Apalachia 30b 370 200 200 54% S. Holston 10 154 80 90 / 150 58% / 99% Blue Ridge 20 157 75 140 89% Nottely 15 97 75 50 52% Chatuge 10 86 85 60 70% Norris 60 290 200 200 69% Tims Ford 15 85 100 80 94% LIP Minimum Flow Commitments PROJECT MIN FLOW TECHNOLOGY NOTES Nottely 55 Small unit Continuous Ocoee 1 140 Pulsing 1 hour/ 4 hours Pickwick 15,000 Turbine Jun – Aug Bi-weekly 9,000 Turbine May/Sept Bi-weekly 8,000 Turbine Oct – Apr Daily Avg South Holston 90 150 Weir/Pulse 30 minutes/ 128 hours Tims Ford 80 Small unit Continuous
Wilbur 107 220 Pulsing 1Continuous hours / 4 hours Apalachia+Ocoee 1 600 Turbine Combined Daily Avg Fayetteville 120 Tims Ford Knoxville 2000 Cherokee + Douglas + Local (Daily Avg) Chilhowee Dam 1000 Turbine May – October only Fontana + local + Santeetlah LIP Minimum Flow Commitments
PROJECT MIN FLOW TECHNOLOGY NOTES Apalachia 200 Pulsing 30 minutes / 4 hours Blue Ridge 115 Small unit Continuous Boone 400 Turbine Average Daily Chatuge 60 Weir/Pulse 30 minutes/ 12 hours Cherokee 325 Pulsing 30 minutes/ 6 hours Chickamauga 13,000 Turbine Jun – Aug Bi-weekly 7,000 Turbine May/Sept Bi-weekly 3,000 Turbine Oct – Apr Daily Avg Douglas 585 Pulsing 30 minutes/ 4 hours Fort Patrick Henry 800 Turbine Pattern 3-hour average Kentucky 18,000 Turbine Jun – Aug Bi-weekly 15,000 Turbine May/Sept Bi-weekly 12,000 Turbine Oct – Apr Daily Avg Norris 200 Weir/Pulse 30 minutes/ 12 hours Environmental Sustainability
environmental benefit
max. bang for the buck cost
benefit / cost
Treatment Level Aeration technologies: turbine venting
Air is drawn in or forced into the turbine to aerate the releases 160
140 turbine venting 120
100
80 Fish Mass (g) Mass Fish forebay oxygen 60 no aeration 40 90 120 150 180 210 240 270 300 330 360 Day - 1995 12
10 turbine venting
8 forebay oxygen 6
4
2 no aeration Daily Release DO (mg/L) DO Release Daily 0 90 120 150 180 210 240 270 300 330 360 Day - 1995 Aeration technologies: surface-water pumps
Impeller forces higher DO water at the surface down to the turbine intake, increasing the release DO Aeration technologies: weirs
Weirs are used to create artificial waterfalls downstream of the dam to aerate the reservoir releases Aeration technologies: oxygen injection
Gaseous oxygen is forced to the bottom of the reservoir through pipes to add oxygen to the reservoir releases
Deployment of diffuser lines Environmental Sustainability
environmental benefit IHA Marty Method
Texas ISFP
7Q10 max. bang for the buck cost
benefit / cost
Treatment Level DROUGHT OPERATIONS TO MEET MINIMUM FLOWS PROJECT REQUIRED MINIMUM ACTUAL MINIMUM South Holston 90 1280 Watauga 107 1080 Cherokee 325 2420 Douglas 585 2930 Chilhowee (Fontana) 1000 2720 Norris 200 3690 Chatuge 60 440 Nottely 50 290 Hiwassee (Apalachia) 200 780 Blue Ridge 115 360 (local inflow) 3100 Chickamauga 13,000 17,000 (local inflow) 600 Pickwick 15,000 17,600 (local inflow) 400 Kentucky 18,000 18,000