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					U.S. Army Corps of Engineers Wilmington District

US Army Corps of Engineers Falls Lake Project

U.S. Army Corps of Engineers
Wilmington District

Original Neuse River Plans

• Original plan was for six reservoirs with a mix of hydropower and flood control: Falls, Milburnie, Wilson Mills, Smithfield, Bakers Mill, and Wiggins Mill • Only flood control as economically justified • Later plan was for 13 reservoirs including Falls Dam. • Ground breaking on 23 June 1978 • Falls Lake full for operation on 13 January 1983 • Falls Dam has a total $585 million to date on flood damages prevented.

U.S. Army Corps of Engineers
Wilmington District

Falls Lake Level in Previous Droughts

Operating Levels In Falls Lake

Falls Lake Water Supply

Falls Lake Water Supply
• Storage accounting is used to track percent remaining. • Raw water supply is removed from Falls Lake upstream of Falls Dam, a debit. • 42.3% of net inflow is credited to water supply storage account each day, a deposit. • Net inflow is defined as inflow to Falls Dam minus evaporation and any other losses. • Treated waste water is returned to the Neuse River downstream of Falls Dam.

Falls Lake Water Quality

Falls Lake Water Quality
Two normal downstream water quality flow targets Immediately Downstream of Dam ------------------------------Nov - Mar 40-65 cfs, 26-42 mgd Apr - Oct 100 cfs, 65 mgd Average Daily Flow Target at Clayton ---------------------------184 cfs, 119 mgd 254 cfs, 164 mgd

• Storage accounting is used to track percent remaining. • Amount released from Falls Dam to meet downstream target flows is debited from water quality storage account each day • 57.7% of net inflow is credited to water quality storage account each day, a deposit.

Stakeholders with focus on Neuse River Basin. Many defined operating parameters for water quality conditions downstream of Falls Dam: • US Fish and Wildlife • NC Division of Water Quality • NC Division of Water Resources • NC Wildlife Resources Commission • Counties including Wake, Johnston, Wayne, Lenoir • Cities including Durham, Raleigh, Smithfield, Goldsboro • Industry including Weyerhaeuser and Progress Energy • Upper Neuse River Keeper

U.S. Army Corps of Engineers
Wilmington District

Water Management Actions

Planned Dates of Stakeholder Face to Face Meetings. Frequency may change in response to watershed conditions:
Tuesday, 4 March 2008, Tuesday, 22 April 2008, Tuesday, 3 June 2008, Tuesday, 1 April 2008, Tuesday, 13 May 2008, Tuesday, 24 June 2008

Conference calls are made each Tuesday when there is not a stakeholder meeting.

U.S. Army Corps of Engineers
Wilmington District

Neuse River Basin Falls Dam Watershed

Lake Lake Michie Little River

Level 18 Feb. 2008 337.5 334.9

Feet Below Normal -3.5’ -20.1’

Normal Level Ft-msl 341 355

Reservoirs upstream of Falls Dam which control about one-third of drainage area are in serious drought status.

Lake Michie got down to near 320 and Little River near 328.5 at end of December.

U.S. Army Corps of Engineers
Wilmington District

Recent and Current Reservoir Statistics
Avg. Percent Inflow of cfs MGD Normal 1082 699 108 586 379 44 1023 661 82 1060 685 121 137 89 38 47 30 19 -25 -16 -12 -46 -30 -22 -44 -28 -44 86 56 58 1 1 0 186 120 35 101 65 10 254 164 19 Rank in 80 Years 44 23 33 49 9 8 3 2 3 34 3 14 7 4 Falls Lake Level ft-msl 251.62 251.79 251.81 251.86 251.16 250.24 248.78 246.61 244.50 243.54 242.21 242.97 242.77 243.59 Percent Remain WQ WS 100 100 100 100 100 100 100 100 96 96 85 86 70 72 50 56 35 42 28 37 21 29 27 32 27 29 33 33

End of Month Jan. 07 Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Jan. 08 *Feb.

U.S. Army Corps of Engineers
Wilmington District

Inflows to Falls Dam

U.S. Army Corps of Engineers
Wilmington District

Current and Forecast Inflows to Falls Dam

U.S. Army Corps of Engineers
Wilmington District

Proposed Operational Deviation Courses of Action

COA 3: Maintain normal flow targets Immediately Downstream of Dam ------------------------------Nov - Mar 40-65 cfs, 26-42 mgd Apr - Oct 100 cfs, 65 mgd Average Daily Flow Target at Clayton ---------------------------184 cfs, 119 mgd 254 cfs, 164 mgd

COA 1-2: Drop flow target downstream of Falls Dam to 50 cfs (32 mgd) Drop flow target at Clayton to: April, May: 184 cfs, 119 mgd June: 194 cfs, 125 mgd July-October: 204 cfs, 132 mgd

U.S. Army Corps of Engineers
Wilmington District

Clayton Flows

U.S. Army Corps of Engineers
Wilmington District

Clayton Natural and Regulated Flows

For Period of Record from 1927-1982, min flow was 44 cfs on 15 Sep.1932 Other POR avg. low flows: 7 day= 52.1 cfs (1934), 1 month=67.2 cfs (1933)

U.S. Army Corps of Engineers
Wilmington District

Courses of Action
|------------COA 1-2--------------| |---Reduction in Releases---|
Falls Dm Outflow cfs 50 50 50 50 113 112 mgd 32 32 32 32 73 72 End of Month Elev 244.2 244.9 244.7 244.0 242.6 240.2 Percent Remain WQ 37 43 43 40 34 19 WS 36 38 35 28 19 9

|-----------COA 3--------------| |-----Normal Actions-------|
Percent Normal Inflow Feb Mar Apr May Jun Jul 20% 15 10 10 -10 -10 Falls Dm Outflow cfs 56 57 57 115 112 160 mgd 36 36 36 74 72 103 End of Month Elev 244.2 244.8 244.5 243.2 240.9 237.7 Percent Remain WQ 37 42 41 32 19 2 WS 36 38 35 28 19 9

• Need to focus on end of July for possible conservation storage being depleted. • Highly dependent upon what nature provides, water quality, fishery, other issues.

U.S. Army Corps of Engineers
Wilmington District

Neuse River Basin Falls Lake Level

U.S. Army Corps of Engineers
Wilmington District

Falls Lake Water Supply, Water Quality

Sediment Storage in Falls Lake

For 20,000 acre-feet of sedimentation storage, possible uses: Duration in days: Demand (cfs): Demand (mgd): 30 336 217 60 168 109 90 112 72 120 84 54 150 67 43

Demand will include a TOTAL of what is needed for Raleigh water supply, for releases downstream and any gains/losses by net precipitation/evaporation. Evaporation losses last year were high as 80 cfs (52 mgd)