Lower Susquehanna River Reservoir System Bathymetry<br />In cooperation with - Pennsylvania Dept. of Environmental Protect...
Problem / Background<br /><ul><li>Reservoirs filling with sediment and associated 	nutrients reducing capacity for sedimen...
   Approximately 55-60% of the sediment and 40% of 	the phosphorus is being trapped
  Revised estimate in 2001 of 25-30 years of 	remaining sediment storage capacity (SSC)
  At capacity sediment and phosphorus loads may 	increase significantly to the upper 	Chesapeake Bay</li></li></ul><li>Pro...
  Provide updated estimates of remaining capacity for 	sediment storage
  Provide information useful to consider appropriate 	management options</li></li></ul><li>v<br />Lower Susquehanna River ...
Courtesy Exelon Corp.<br />
Susquehanna River Sediment Transport<br /><ul><li>Historical and current trends
  Reservoir Transport and Dynamics</li></ul>	- importance<br />	- implications for predicting reservoir capacity<br /><ul>...
Current “trends” in sediment loads<br />Long-term AVG <br />(1980-1999) (3.2 Mt in, 1.2 Mt out, 55% trap w/scour)<br />Fro...
Estimated Sediment Loads to Reservoirs 1900-2008<br />
Streamflow Hydrograph<br />01578310 - Susquehanna  River at Conowingo, 1996-2008<br />Hurricane Ivan<br />390,000 cfs (sco...
Predicted Sediment Scour vs. Flow<br />30<br />Scour estimates<br />95th percentile<br />25<br />tons)<br />95th percentil...
Wendy McPherson  (USGS) - 9/20/04<br />
Hurricane Ivan – September 2004<br />Susquehanna River<br />Bay Bridge<br />
Delta<br />(sand)<br />Density current<br />(Silts)<br />Fine sediments<br />(silts & clays)<br />Idealized Reservoir Sedi...
CurrentBathymetry 2008<br />Safe Harbor Dam<br />(Lake Clarke) <br />
Safe Harbor Dam<br />(Lake Clarke) <br /><ul><li>  1.7 M tons deposited
  Total 92 M tons
  Deepest areas near the     	dam (turbine and 	spill gates) and 	along an old 	canal</li></li></ul><li>CurrentBathymetry ...
Holtwood Dam<br />(Lake Aldred) <br /><ul><li>  1 M tons deposited
  Total 14 M tons
  Deepest areas near 	sides of natural 	narrow channels 	(hydraulic scour 	areas)
  Notice sediment 	depths near dam </li></li></ul><li>QA lines<br />CurrentBathymetry 2008<br />Conowingo Dam<br />(Conowi...
Conowingo Dam <br />(Conowingo Reservoir)<br /><ul><li>  12 M tons deposited, 	all in lower third
  Total 174 M tons
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Conowingo Presentation- USGS

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one of two powerpoints used during the Conowingo Dam presentation

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  • Completed in 1931, design capacity of 150,000 acre ft, newest of the 3 dams, dam height is 80’
  • Completed in 1910, design capacity of 60,000 ac ft, dam height is 60’
  • Most downstream, completed in 1928, design capacity of 300,000 ac ft., dam height is 110’
  • Conowingo Presentation- USGS

    1. 1. Lower Susquehanna River Reservoir System Bathymetry<br />In cooperation with - Pennsylvania Dept. of Environmental Protection - Susquehanna River Basin Commission<br /> - Lower Susquehanna River Keeper <br />
    2. 2. Problem / Background<br /><ul><li>Reservoirs filling with sediment and associated nutrients reducing capacity for sediment storage
    3. 3. Approximately 55-60% of the sediment and 40% of the phosphorus is being trapped
    4. 4. Revised estimate in 2001 of 25-30 years of remaining sediment storage capacity (SSC)
    5. 5. At capacity sediment and phosphorus loads may increase significantly to the upper Chesapeake Bay</li></li></ul><li>Project Objectives<br /><ul><li>Collect bathymetry data to update and map bottom- surface profiles
    6. 6. Provide updated estimates of remaining capacity for sediment storage
    7. 7. Provide information useful to consider appropriate management options</li></li></ul><li>v<br />Lower Susquehanna River Reservoirs<br />Lake Clarke<br />Lake Aldred<br />Conowingo Reservoir<br />
    8. 8.
    9. 9.
    10. 10. Courtesy Exelon Corp.<br />
    11. 11. Susquehanna River Sediment Transport<br /><ul><li>Historical and current trends
    12. 12. Reservoir Transport and Dynamics</li></ul> - importance<br /> - implications for predicting reservoir capacity<br /><ul><li> Reservoir Filling and Remaining Capacity</li></li></ul><li>Estimated Sediment Loads to Reservoirs 1900-1999<br />Significant decrease in sediment loads<br />120<br />Loads to Reservoirs<br />100<br />80<br />60<br />Sediment Load (million tons)<br />40<br />20<br />0<br />1900’s<br />1910’s<br />1920’s<br />1930’s<br />1940’s<br />1950’s<br />1960’s<br />1970’s<br />1980’s<br />1990’s<br />YEAR<br />
    13. 13. Current “trends” in sediment loads<br />Long-term AVG <br />(1980-1999) (3.2 Mt in, 1.2 Mt out, 55% trap w/scour)<br />From 2000-2008<br />(avg 3.1 Mt in, 1.2 Mt out,<br />55% trap w/scour)<br />
    14. 14. Estimated Sediment Loads to Reservoirs 1900-2008<br />
    15. 15. Streamflow Hydrograph<br />01578310 - Susquehanna River at Conowingo, 1996-2008<br />Hurricane Ivan<br />390,000 cfs (scour threshold)<br />
    16. 16. Predicted Sediment Scour vs. Flow<br />30<br />Scour estimates<br />95th percentile<br />25<br />tons)<br />95th percentile<br />Expon. (Scour estimates)<br />1972<br />20<br />15<br />Predicted scour (millions of <br />1996<br />10<br />2004 Ivan<br />5<br />1975<br />0<br />300<br />400<br />600<br />700<br />800<br />900<br />1,000<br />1,100<br />1,200<br />500<br />Instantaneous Flow (times 1,000)<br />
    17. 17. Wendy McPherson (USGS) - 9/20/04<br />
    18. 18. Hurricane Ivan – September 2004<br />Susquehanna River<br />Bay Bridge<br />
    19. 19. Delta<br />(sand)<br />Density current<br />(Silts)<br />Fine sediments<br />(silts & clays)<br />Idealized Reservoir Sediment Dynamics<br />Turbid inflow<br />Floating Debris<br />Water Surface<br />Relatively clear water<br />(clay)<br />Sluiceway<br />
    20. 20. CurrentBathymetry 2008<br />Safe Harbor Dam<br />(Lake Clarke) <br />
    21. 21. Safe Harbor Dam<br />(Lake Clarke) <br /><ul><li> 1.7 M tons deposited
    22. 22. Total 92 M tons
    23. 23. Deepest areas near the dam (turbine and spill gates) and along an old canal</li></li></ul><li>CurrentBathymetry 2008<br />Holtwood Dam<br />(Lake Aldred) <br />
    24. 24. Holtwood Dam<br />(Lake Aldred) <br /><ul><li> 1 M tons deposited
    25. 25. Total 14 M tons
    26. 26. Deepest areas near sides of natural narrow channels (hydraulic scour areas)
    27. 27. Notice sediment depths near dam </li></li></ul><li>QA lines<br />CurrentBathymetry 2008<br />Conowingo Dam<br />(Conowingo Reservoir) <br />
    28. 28. Conowingo Dam <br />(Conowingo Reservoir)<br /><ul><li> 12 M tons deposited, all in lower third
    29. 29. Total 174 M tons
    30. 30. Total storage 204 M tons (SSC)
    31. 31. Approx 30 Mt remain
    32. 32. Deepest areas near the dam (turbine and spill gates) and natural hydraulic scour areas</li></li></ul><li>Change in depth by transect - Conowingo<br />Pa/Md state line<br />
    33. 33. Conowingo 3-D Longitudinal Profile<br />Distancebelow surface, in feet<br />Pa/Md state line<br />0 5 10 15 20 25 30 35 40 <br />Distance upstream (feet times 10,000)<br />
    34. 34. Loss of sediment-storage capacity with time<br />
    35. 35. SSC Predictions<br />From 1996-2008, 14.7M tons deposited<br />Approximately 30M tons remain before SSC<br />Predictions at steady state -- 15-20 years<br />Predictions with future change<br /> - decrease transport (3.2 to 2.5), add 5 years<br /> - statistically expected scour removal, add 5 years<br /> - trapping efficiency of 55%, add 0 years<br />25-30 years with future change<br />
    36. 36. Summary <br /><ul><li> From 1996-2008, sediment loads approximate 20 year average
    37. 37. Less scour producing events resulting in slightly lower sediment transport to upper BAY
    38. 38. Remaining capacity of 30M tons
    39. 39. Under current conditions, 15-20 years to SSC
    40. 40. Could be extended to 25-30 years considering future scenarios
    41. 41. Encourage bathymetry be conducted more frequently</li></li></ul><li>Where Do We Go From Here <br /><ul><li> Work with other Federal and State agencies and other partners considering solutions (USACE, USGS USEPA, PADEP, MDDNR, SRBC)
    42. 42. USACE new study
    43. 43. Reconvene the Sediment Task force (STF)
    44. 44. Some solutions under consideration include (from STF)</li></ul> - reservoir sediment removal<br /> - reduce sediment transport from source areas (BMP’s stream stabilization, wetlands, buffers, etc.)<br /> - use of floodplains to dissipate stream energy and store sediment<br />
    45. 45. The ultimate DESTINY of all reservoirs is to fill with sediment<br />- Linsley and others, 1992<br />Thank You <br />

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