Hydrology and Hydraulics

Reservoir Configuration

AlternativeCurrent ConditionsFlood StorageMulti-Purpose (Hydropower) Total storage capacity (AF)080,000145,000 Reservoir surface area (ac)NA1,0001,450 Bottom elevation (ft)NA Spillway elevation (ft)NA Dam crest elevation (ft)NA Dam crest length (ft)NA1,4501,800 Outlet capacity (cfs)NA 2,000 Spillway length (ft)NA500 Spillway weir coefficient 1 NA Spillway maximum capacity (cfs)NA49,640 Power plant minimum operating elevation (ft) NA Power plant capacity (cfs)NA 732 Power plant tailwater elevation (ft)NA Table 3 Dam and Outlet Configuration for Alternatives. Notes: 1 The spillway weir coefficient was calculated from the given spillway length and a spillway capacity requirement of 50,000 cfs

DatesPower Release (cfs) October 1-November November 24-March April 1-September Table 7 Multi-Purpose Reservoir Power Release Schedule

Reservoir Pool Elevation (NGVD + 1,000 ft) Description of Release to cfs bypass release No power release to Ramp to 140 cfs bypass release (10 cfs per foot elevation) No power release to No bypass release 140 cfs low power release 592 cfs high power release to Ramp to 1,268 cfs bypass release (50 cfs per foot elevation) 140 cfs low power release 592 cfs high power release to ,268 cfs bypass release 140 cfs low power release 592 cfs high power release Table 8 Multi-Purpose Reservoir Overall Release Schedule (November 24 to March 31)

Reservoir Pool Elevation (NGVD ft) Description of Release to cfs bypass release No power release to Ramp to 140 cfs bypass release (10 cfs per foot elevation) No power release to No bypass release 140 cfs low power release to Ramp to 592 cfs bypass release (50 cfs per foot elevation) 140 cfs low power release No bypass release 140 cfs low power release 592 cfs high power release to Ramp to 1,268 cfs bypass release (50 cfs per foot elevation) 140 cfs low power release 592 cfs high power release to ,268 cfs bypass release 140 cfs low power release 592 cfs high power release Table 9 Multi-Purpose Reservoir Overall Release Schedule (April 1 to November 23)

Flood Modeling

Figure 3 Reservoir Water Surface Elevation and Outflow – 100-year Event, Flood Storage Alternative

Figure 2 Comparison of Flood Storage Alternative to Current Conditions – 100-year Event, USGS Gage at Doty

EventEmptying Time (days) 100 year24 50 year21 10 year flood50 Table 6 Flood Storage Reservoir Emptying Time after Flood Events Notes: Time is calculated starting from the time when the reservoir begins storing water (reservoir inflow > 2000 cfs) and ending at the time when reservoir outflow is equal to reservoir inflow.

Event Peak Flow (cfs) 1-Day Average Flow (cfs) 3-Day Average Flow (cfs) 7-Day Average Flow (cfs) CurrentFloodDiffCurrentFloodDiffCurrentFloodDiffCurrentFloodDiff 100-yr 39,35317, %24,33110, %13,6647, %8,1924, % 50-yr 32,56214, %20,3989, %11,8746, %7,3444, % 10-yr 19,8579, %12,9376, %8,2335, %5,4723, % Dec07 63,10025, %41,39017, %20,3109, %11,3935, % Table 5 Comparison of Flood Storage and Current Conditions Modeling Results at the USGS Gage at Doty Notes: Current = current conditions alternative Flood = flood storage alternative

Figure Flood Hydrograph at Mellen Street

Figure Flood Water Surface Elevation Profile, Existing and Proposed

Figure year Hydrograph at Mellen Street

Figure year Flood Profile, Existing and Proposed

Figure year Water Surface Elevation Profile, Existing and Proposed

Figure year Water Surface Elevation Profile, Existing and Proposed

Figure 18 2-year Water Surface Elevation Profile, Existing and Proposed

Flow Exceedance Analysis

Figure 7 Exceedance Curves for the Flood Storage and Current Conditions Alternatives – USGS Gage at Doty

Month Average MaximumMinimum 90% 50%10% Flood Current Flood Current Flood Current Flood Current Flood Current FloodCurrent Oct ,9825, Nov1,0081,0287,10213, ,7312,411 Dec1,3391,36717,22640, ,0933,103 Jan1,3931,3708,24616, , ,9562,933 Feb1,0331,0209,12819, ,5182,029 Mar ,3819, ,8361,658 Apr585 6,23611, ,1241,076 May273 2, Jun161 2,6022, Jul Aug Sept60 2, Table 10 Comparison of Flood Control and Current Conditions Alternatives Monthly Flow Statistics at the USGS Gage at Doty Notes: Flood = flood storage alternative Current = current conditions alternative

Month Average MaximumMinimum 90% 50%10% Flood Current Flood Current Flood Current Flood Current Flood Current FloodCurrent Oct ,60516, ,694 Nov3,9393,96032,66138, ,325 10,20310,200 Dec6,1266,15738,79461, ,380 4,1654,03514,09914,400 Jan6,6456,61750,33358,5001,010 1,843 5,2074,99513,20112,990 Feb5,2455,23554,16664, ,482 3,570 10,48610,300 Mar4,2604,24619,90821, ,361 3,235 8,6848,593 Apr3,0043,00734,21538, ,260 2,225 5,313 May1,5331,5317, ,220 2,809 Jun969 5, ,641 Jul400 1, Aug267 2, Sept344 3, Table 13 Comparison of Flood Control and Current Conditions Alternatives Monthly Flow Statistics at the USGS Gage at Grand Mound Notes: Flood = flood storage alternative Current = current conditions alternative

Month Average MaximumMinimum 90% 50%10% Flood Current Flood Current Flood Current Flood Current Flood Current FloodCurrent Oct 1,055 15, ,259 Nov 5,2715,29432,91638, ,250 13,84213,800 Dec 8,6328,66045,69367, ,131 6,1005,93519,60420,170 Jan 9,5179,48154,57860,3001,580 2,900 7,6707,37019,27019,190 Feb 7,764 52,37555,0001,180 2,246 5,7905,78016,36016,180 Mar 6,2336,22028,81529,6001,090 2,200 4,945 11,800 Apr 4,3364,34132,01535,8001,120 1,960 3,350 7,270 May 2,2142,2099, ,030 1,860 3,919 Jun 1,393 7, ,110 2,401 Jul 625 1, Aug 427 2, Sept 487 5, Table 14 Comparison of Flood Control and Current Conditions Alternatives Monthly Flow Statistics at the USGS Gage at Porter Notes: Flood = flood storage alternative Current = current conditions alternative

Figure 5 Comparison of Multi-purpose Alternative to Gage Records – USGS Gage at Doty – Water Years 2001 to 2003

Figure 6 Reservoir Results for Multi-purpose Alternative – Water Years 2001 to 2003

Figure 8 Exceedance Curves for the Multi-purpose and Current Conditions Alternatives – USGS Gage at Doty

Month Average MaximumMinimum 90% 50%10% Multi Current Multi Current Multi Current Multi Current Multi Current MultiCurrent Oct ,662 5, Nov 756 1,028 6,303 13, ,939 2,411 Dec 1,392 1,367 16,393 40, , ,585 3,103 Jan 1,349 1,370 7,092 16, , ,404 2,933 Feb 1,129 1,020 8,795 19, ,967 2,029 Mar ,478 9, ,429 1,658 Apr ,479 11, ,076 May ,045 2, Jun ,161 2, Jul Aug Sept , Table 11 Comparison of Multi-Purpose and Current Conditions Alternatives Monthly Flow Statistics at the USGS Gage at Doty Notes: Multi = multi-purpose alternative Current = current conditions alternative

Month Average MaximumMinimum 90% 50%10% Multi Current Multi Current Multi Current Multi Current Multi Current MultiCurrent Oct ,28516, ,5291,694 Nov 3,6773,96032,50438, ,1122,3259,44410,200 Dec 6,1826,15737,96161, ,6051,3804,4054,03513,32614,400 Jan 6,6026,61749,17958,5001,0361,0101,9101,8435,1684,99512,74012,990 Feb 5,3335,23553,83364, ,4881,4823,9063,57010,19310,300 Mar 4,3154,24619,43121, ,3821,3613,5253,2358,2948,593 Apr 2,8423,00732,35638, ,2591,2602,1782,2254,7705,313 May 1,5531,5316,2227, ,2681,2202,8302,809 Jun 1, ,3955, ,6481,641 Jul ,2661, Aug ,7402, Sept ,6023, Table 15 Comparison of Multi-Purpose and Current Conditions Alternatives Monthly Flow Statistics at the USGS Gage at Grand Mound Notes: Multi = multi-purpose alternative Current = current conditions alternative

Month Average MaximumMinimum 90% 50%10% Multi Current Multi Current Multi Current Multi Current Multi Current MultiCurrent Oct 1,0261,05514,59515, ,1332,259 Nov 5,0035,29432,35438, ,1073,25012,68613,800 Dec 8,6888,66045,50167, ,4412,1316,3395,93519,01620,170 Jan 9,4749,48153,34360,3001,5791,5802,9122,9007,5507,37018,69819,190 Feb 7,8457,76451,40655,0001,2251,1802,2522,2465,9845,78015,70316,180 Mar 6,2926,22028,81529,6001,1421,0902,1822,2005,2274,94511,59111,800 Apr 4,1794,34130,15635,8001,1701,1201,9531,9603,3173,3506,8487,270 May 2,2302,2098,4329, ,0881,0301,8981,8603,8493,919 Jun 1,4401,3937,6807, ,1631,1102,3992,401 Jul ,8311, Aug ,3202, Sept ,1225, Table 16 Comparison of Multi-Purpose and Current Conditions Alternatives Monthly Flow Statistics at the USGS Gage at Porter Notes: Multi = multi-purpose alternative Current = current conditions alternative

Water Quality/Temperature Modeling

Figure 20 Inflow Hydrographs Used at the Upstream Boundary (Doty Gage) for Temperature Modeling

Locations of Temperature Probes/Water Quality Data

Figure 25 Riverwide flows simulated on July 15, 2010 for the baseline and multi-purpose reservoir scenarios

Figure 26 Riverwide flows simulated on August 22, 2010 for the baseline and multi-purpose reservoir scenarios

Example of Reservoir Output – CE QUAL 2 Model

Calibration of Water Quality Model

Number of days Average Water Column Temperature Exceeds 18°C For Various Reaches