Aspinall Operations Meeting

April 27, 2017
SPRING RUNOFF 

FORECASTS AND TARGETS
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 110% 120% 130% 140% 150%

Percent of 1981-2010 Average

Forecasted April-July Runoff

As of April 1st

Gunnison River - near Grand Jct 1,870,000

Ridgway Reservoir Inflow 107,000

North Fork Gunnison River - near Somerset 315,000

Paonia Reservoir Inflow (Mar-Jun) 90,000

Lake Fork Gunnison River - at Gateview 145,000

Tomichi Creek - at Gunnison 110,000

Blue Mesa Reservoir Inflow 850,000

Gunnison River - near Gunnison 500,000

East River - at Almont 245,000

Taylor Park Reservoir Inflow 109,000

Site name and 

runoff volume

in acre-feet

Year Type

Blue Mesa Forecasted Desired Peak at 

Whitewater

Duration of Half Bank 

(8,070 cfs)

Duration of Peak Flow 

(up to 14,350 cfs)

April-July Inflow

Af cfs Days Days

DRY < 381,000 900 0 0

MOD DRY 381,000 to 516,000 2,600 to 8,070 0 0

AVG DRY 516,001 to 709,000 8,070 10 0

AVG WET 709,001 to 831,000 8,070 to 14,350 20 2

MOD WET 831,001 to 1,123,000 14,350 40 10

WET >1,123,000 14,350 60 15

Spring Peak & Duration Targets

Based on Hydrologic Year Type

Mid-Apr

850,000
0

2000

4000

6000

8000

10000

12000

14000

16000

200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

Peak Q (cfs)

Forecast BM Apr-Jul Inflow (thousand af)

Peak Flow and Duration Day Targets at Whitewater

DRY

MOD WET

WET

AVG

WET

AVG

DRY

MOD

DRY

Apr-July Forecast Half bank Duration Peak Flow Duration

(1000 AF) (days @ 8,070 cfs) (days @ up to 14,350 cfs)

<381 0 0 

381-516 0 0 

516-709 10 0

709-831 20 2 

831-1123 40 10

>1123 60 15

14350 cfs
6427 cfs

Apr 15 Forecast

850 KAF

Projected Black Canyon Flows

of > 9000 cfs

to meet ROD targets
300000

350000

400000

450000

500000

550000

600000

650000

700000

0

1000

2000

3000

4000

5000

6000

7000

8000

3/1 3/6 3/11 3/16 3/21 3/26 3/31 4/5 4/10 4/15 4/20 4/25 4/30

Blue Mesa Content (AF)

Flow (cfs)

Reservoir and River Conditions

Gunn R - Black Canyon North Fork Gunn R - Whitewater Blue Mesa Content

Reservoir Elevation

above Spillway Crest

7488 ft

Current Elevation

7498 ft
PROJECTED 

SPRING OPERATIONS
0

1000

2000

3000

4000

5000

6000

7000

8000

50000 100000 150000 200000 250000 300000 350000 400000 450000 500000 550000

Peak (cfs)

Apr-July Volume (ac-ft)

North Fork of the Gunnison River @ Somerset

Forecasted Peak Flow

2500 cfs

April Forecast Runoff Volume

280,000 acre-feet
0

1

2

3

4

5

6

7

4/16 4/21 4/26 5/1 5/6 5/11 5/16 5/21 5/26 5/31 6/5 6/10 6/15

North Fork of the Gunnison River

Peak Flow Timing at Somerset (1934-2016)
0

500

1000

1500

2000

2500

3000

3500

4000

Apr-01 Apr-08 Apr-15 Apr-22 Apr-29 May-06 May-13 May-20 May-27 Jun-03 Jun-10 Jun-17 Jun-24 Jul-01 Jul-08 Jul-15 Jul-22 Jul-29

North Fork @ Somerset

April-July Runoff

1936 1942 1961 1965 1970 1971 1975 1982 1989 1978

10 Days

40 Days

+ 500-1000 cfs

during peak flows
0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

5/1 5/8 5/15 5/22 5/29 6/5 6/12 6/19 6/26 7/3 7/10 7/17 7/24 7/3

Mod Wet Year Tributary Flows

25% Avg Med 75%

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5/1 5/8 5/15 5/22 5/29 6/5 6/12 6/19 6/26 7/3 7/10 7/17 7/24 7/3

Mod Wet Year Tributary Flows

25% Avg Med 75%

Tributary Flows between

Black Canyon and Delta

Tributary Flows between

Delta and Whitewater

10 Days 40 Days 

10 Days 40 Days 
North Fork of the Gunnison River

Forecasted Streamflows

Peak Flow

Forecast

2500 cfs

1080 cfs
0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

14000

15000

16000

0 5 10 15 20 25 30 35 40 45 50

River Flow (cfs)

Days from Start of Spring Operation

Gunnison River Flows

from Start Day of Spring Operation

Gunnison R - Black Canyon North Fork Gunnison R Gunnison R @ Delta Gunnison R @ Whitewater

BC peak = 9700

Delta peak = 12800

WW peak = 14700

Days > 14350 = 10

Days > 8070 = 40

Projection of Flows in the Gunnison River

while meeting the Aspinall ROD Flow Targets

Ramp up = 9 days

Ramp down = 9 days
Outlet 

Capacities (cfs)

Blue Mesa Morrow Point Crystal 

Powerplant 3380 cfs 4900 cfs 1950 cfs

Powerplant + 

Bypass

6030 cfs 6400 cfs 4100 cfs

Spillway 

Elevation 7488 ft 7129.5 ft 6756 ft

Release Capability at the Aspinall Unit
440000

460000

480000

500000

520000

540000

560000

580000

600000

620000

640000

660000

680000

700000

720000

740000

760000

780000

800000

820000

840000

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

Release (cfs)

Content (AF)

Aspinall Unit Operations

Blue Mesa Morrow Pt Crystal BM Inflow CR Side Blue Mesa content
0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

5/1 5/6 5/11 5/16 5/21 5/26 5/31 6/5 6/10 6/15 6/20 6/25 6/30

Flow (cfs)

Colorado River - Grand Junction

2008 2011 2014 2017
OPERATIONS – REMAINDER OF YEAR
100

200

300

400

500

600

700

800

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

1000 Acre

-feet

Blue Mesa Content

End of Month

Apr 1 Forecast = 930,000 AF Apr 15 Forecast = 850,000 AF

Fill to 710 Kaf

Current = 644 Kaf

Maximum Capacity = 829.5 Kaf
0

1000

2000

3000

4000

5000

6000

Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Flow (cfs)

Gunnison River - Black Canyon

Monthly Average Flow
Baseflow Targets