Great Basin Water Supply Outlook, June 1, 2015

Note: This publication is scheduled for revision. If you have feedback on content, format, or publication frequency, please contact us.

Prepared by W. P. Miller
NOAA, National Weather Service
Colorado Basin River Forecast Center
Salt Lake City, Utah
www.cbrfc.noaa.gov

Contents

Water Supply Forecast Discussion
Bear Basin Conditions
Weber Basin Conditions
Six Creeks Basin Conditions
Utah Lake Basin Conditions
Bear Specific Site Forecasts
Weber Specific Site Forecasts
Six Creeks Specific Site Forecasts
Utah Lake Specific Site Forecasts
Reservoir Contents
Precipitation Maps
Definitions
Additional Information
Questions or Comments

Great Basin Summary

*Median of forecasts within each basin.

Bear Basin Conditions

Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Weber Basin Conditions

Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Six Creeks Basin Conditions

Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Utah Lake Basin Conditions

Snow Water Equivalent in Percent of Median.
* Percent usable capacity, not percent average contents.
Click for multi-month Graph.

Bear Specific Site Forecasts (kaf)

Click site name for graph.

	Forecast Period	90% Exceedance Volume	50% Exceedance Volume	Percent Average	10% Exceedance Volume
Bear
Utah	April-July	71	74	66	81
	June-July	38	41	62	48
Woodruff Narrows Rsvr, Abv	April-July	54	56	46	63
	June-July	23	25	44	32
Montpelier, Nr, Stewart Dam, Blo *	April-July	63	67	37	78
	June-July	37	41	45	52
Smiths Fork
Border, Nr	April-July	82	84	94	88
	June-July	37	39	78	43
Logan
Logan, Nr, State Dam, Abv	April-July	70	72	65	75
	June-July	35	37	61	40
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv	April-July	17.6	17.6	41	17.7
	June-July	8.4	8.4	52	8.5
Little Bear
Paradise	April-July	10.2	10.2	22	10.4
	June-July	3.6	3.6	31	3.8

*Regulated Forecast, i.e. Observed flow uncorrected for upstream diversion.

Weber Specific Site Forecasts (kaf)

Click site name for graph.

	Forecast Period	90% Exceedance Volume	50% Exceedance Volume	Percent Average	10% Exceedance Volume
Weber
Oakley, Nr	April-July	71	72	61	80
	June-July	34	35	55	43
Rockport Res, Wanship, Nr	April-July	54	58	44	65
	June-July	24	28	44	35
Coalville, Nr	April-July	56	62	46	67
	June-July	21	27	43	32
Chalk Ck
Coalville	April-July	13.4	13.7	33	17
	June-July	4.1	4.4	28	7.7
Weber
Echo Res, Echo, At	April-July	66	73	43	81
	June-July	23	30	40	38
Lost Ck
Lost Ck Res, Croydon, Nr	April-July	3.8	3.8	28	3.8
	June-July	0.83	0.83	29	0.84
East Canyon Ck
East Canyon Res, Morgan, Nr	April-July	8	8.1	30	8.3
	June-July	2.5	2.6	31	2.8
Weber
Gateway	April-July	117	119	37	133
	June-July	34	36	33	50
Sf Ogden
Huntsville, Nr	April-July	21	21	38	22
	June-July	7.1	7.1	51	7.9
Ogden
Pineview Res, Ogden, Nr	April-July	35	35	31	41
	June-July	9.4	9.6	42	15.3

Six Creeks Specific Site Forecasts (kaf)

Click site name for graph.

	Forecast Period	90% Exceedance Volume	50% Exceedance Volume	Percent Average	10% Exceedance Volume
Little Cottonwood Ck
Salt Lake City, Nr	April-July	19.2	21	55	22
	June-July	11.6	12.2	51	14.7
Big Cottonwood Ck
Salt Lake City, Nr	April-July	14.5	16.4	46	16.4
	June-July	7	7.8	41	8.9
Mill Ck
Salt Lake City, Nr	April-July	1.7	1.8	28	1.8
	June-July	0.76	0.76	23	0.89
Dell Fk
Little Dell Res	April-July	2.3	2.3	42	2.4
	June-July	0.64	0.64	48	0.69
Parleys Ck
Salt Lake City, Nr	April-July	3.9	4.2	30	4
	June-July	1.3	1.3	27	1.4
Emigration Ck
Salt Lake City, Nr	April-July	0.88	0.96	24	0.93
	June-July	0.45	0.45	39	0.5
City Ck
Salt Lake City, Nr	April-July	3.3	3.6	47	3.5
	June-July	1.4	1.4	39	1.6
S Willow Ck
Grantsville, Nr	April-July	1.7	1.8	57	2
	June-July	0.78	0.83	49	1

Utah Lake Specific Site Forecasts (kaf)

Click site name for graph.

	Forecast Period	90% Exceedance Volume	50% Exceedance Volume	Percent Average	10% Exceedance Volume
Spanish Fork
Castilla, Nr	April-July	18.2	18.2	26	19.2
	June-July	11.3	11.3	47	12.3
Provo
Woodland, Nr	April-July	70	72	72	76
	June-July	27	29	62	33
Hailstone, Nr	April-July	79	80	73	85
	June-July	31	32	62	37
Deer Ck Res	April-July	69	71	56	76
	June-July	23	25	45	30
American Fork
American Fork, Nr, Up Pwrplnt, Abv	April-July	9.7	10.1	33	12.1
	June-July	4.7	5.1	28	7.1
West Canyon Ck
Cedar Fort, Nr	April-July	0.14	0.14	8	0.16
	June-July	0.09	0.09	11	0.11
Jordan
Utah Lake, Provo, Nr	April-July	138	141	43	150
	June-July	37	40	31	49

Differences between the full period forecasts and the residual forecasts may not exactly equal the actual observed volumes due to rounding conventions (see Definitions section).

Great Basin End of Month Reservoir Contents (kaf)

	EOM Contents	Percent EOM Average	Percent Usable Capacity	Last Year EOM	Last Year %Average	EOM Average	Usable Capacity
untitled Bear
Woodruff Narrows Res, Woodruff, Nr	55.7	118	100	48.5	103	47.1	55.8
untitled Bear River
Bear Lake, Nr Lifton	759.3	92	58	760.0	92	829.8	1302.0
untitled Little Bear
Hyrum Reservoir	14.7	101	96	14.5	99	14.6	15.3
untitled Weber
Rockport Res, Wanship, Nr	48.0	95	87	43.5	86	50.8	55.2
Echo Res, Echo, At	61.9	92	84	51.1	76	67.0	73.9
untitled Lost Ck
Lost Ck Res, Croydon, Nr	15.9	91	70	18.5	106	17.4	22.5
untitled East Canyon Ck
East Canyon Res, Morgan, Nr	35.0	76	71	34.4	75	45.8	49.5
untitled Sf Ogden
Causey Res	7.1	101	100	7.1	102	7.0	7.1
untitled Ogden
Pineview Res, Ogden, Nr	91.5	93	83	103.8	106	97.9	110.1
untitled Jordanelle Dam
	248.2	85	77	239.4	82	290.9	320.3
untitled Provo
Deer Ck Res	144.0	108	96	117.4	88	133.8	149.7
untitled Dell Fk
Little Dell Res	14.1	-99	69	14.2	-99	-9999.0	20.5
untitled Jordan
Utah Lake, Provo, Nr	576.8	68	66	643.2	76	844.2	870.9
untitled
TOTAL	2058.2	84	68	2081.4	85	2446.2	3052.8

Precipitation Maps

Definitions

10% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 10% chance of being exceeded. Previously referred to as "Reasonable Maximum Forecast".

50% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 50% chance of being exceeded. Previously referred to as "Most Probable Forecast".

90% exceedance forecast: Given the current hydrometeorological conditions, i.e current snowpack, soil moisture and streamflow, the volume that has a 90% chance of being exceeded. Previously referred to as "Reasonable Minimum Forecast".

Acre-Foot (af): The volume equal to one acre covered one foot deep (43,560 cubic feet). See kaf below.

Average: The arithmetic mean. The sum of the values divided by the number of values. Values from 1981-2010 are used for this publication.

Categories: Much Above Average=Greater than 130%, Above Average=111-130%, Near Average=90-110%, Below Average=70-89%, Much Below Average=Less than 70%.

CBRFC: Colorado Basin River Forecast Center.

Forecast Period: The period from April 1 through July 31, unless otherwise noted.

kaf: Thousand Acre-Feet. See Acre-Foot above.

Inflow: The volume of water that flows into a reservoir or lake.

Median: The middle value of an ordered set of values. Half of the values are higher and half of the values are lower. When the set contains an even number of values the median is the average of the two middle numbers.

NOAA: National Oceanic and Atomospheric Administration.

NWS: National Weather Service.

Rounding Conventions:

Range		Round to
0-1.99		0.01
2.0-19.9		0.1
20-199		1.0
200-999		5.0
1000+		3 significant digits

Streamflow: The volume of water that flows past a specific stream site.

Water Year: The 12-month period, October 1 through September 30. The water year is designated by the calendar year in which it ends. Thus, the year ending September 30, 2008, is called the "2008 water year."

Additional Information

Water supply forecasts take into consideration present hydrometeorological conditions and use average basin temperatures and precipitation for the forecast period. As the forecast season progresses, a greater portion of the future hydrologic and climatic uncertainty becomes known and monthly forecasts become more accurate. For more information on the tools we use, consult Water Supply Forecasting Tools.

Volume forecasts represent adjusted flows; that is, observed flows with upstream water use taken into account. Adjusted flows will closely approximate natural or unimpaired flows. However, not all upstream diversions or impoundments are measured or quantifiable. For specific adjustments used with each forecast point, consult the Guide to Water Supply Forecasting.

The Water Supply Outlook is issued monthly January through May by the Colorado Basin River Forecast Center. It represents a coordinated effort between the National Weather Service, Natural Resources Conservation Service, Bureau of Reclamation, U.S. Geological Survey and local water district managers.

Note: Data used in this report are provisional and are subject to revision.

For more information, or to be included on the mailing list, please contact:

Colorado Basin River Forecast Center
2242 W North Temple
Salt Lake City, UT 84116
(801) 524-5130
www.cbrfc.noaa.gov

Hydrologist: W. P. Miller