Great Basin Water Supply Outlook, May 1, 2014

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 B.Bernard
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	94	107	96	121
	May-July	85	98	94	112
Woodruff Narrows Rsvr, Abv	April-July	83	95	79	111
	May-July	68	80	76	96
Montpelier, Nr, Stewart Dam, Blo *	April-July	92	107	59	119
	May-July	77	92	63	104
Smiths Fork
Border, Nr	April-July	94	106	119	114
	May-July	85	97	121	105
Logan
Logan, Nr, State Dam, Abv	April-July	100	110	99	118
	May-July	88	98	102	106
Blacksmith Fork
Hyrum, Nr, Upnl Dam, Abv	April-July	36	38	88	45
	May-July	27	29	94	36
Little Bear
Paradise	April-July	18.1	20	43	27
	May-July	13.8	15.7	49	23

*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	81	92	78	110
	May-July	72	83	78	101
Rockport Res, Wanship, Nr	April-July	77	89	67	111
	May-July	65	77	68	99
Coalville, Nr	April-July	75	90	67	110
	May-July	61	76	67	96
Chalk Ck
Coalville	April-July	17.1	22	54	28
	May-July	12.9	17.5	51	24
Weber
Echo Res, Echo, At	April-July	90	110	64	137
	May-July	72	92	64	119
Lost Ck
Lost Ck Res, Croydon, Nr	April-July	7.2	7.8	58	9.9
	May-July	4.2	4.8	50	6.9
East Canyon Ck
East Canyon Res, Morgan, Nr	April-July	11.3	12.6	47	15.3
	May-July	7.4	8.7	46	11.4
Weber
Gateway	April-July	125	153	47	205
	May-July	111	139	57	192
Sf Ogden
Huntsville, Nr	April-July	34	39	70	52
	May-July	22	27	68	40
Ogden
Pineview Res, Ogden, Nr	April-July	65	80	71	98
	May-July	38	53	73	71

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	24	27	71	30
	May-July	22	25	71	28
Big Cottonwood Ck
Salt Lake City, Nr	April-July	22	23	64	28
	May-July	19.1	20	63	25
Mill Ck
Salt Lake City, Nr	April-July	2.4	2.7	42	3.7
	May-July	2	2.3	43	3.3
Dell Fk
Little Dell Res	April-July	2.5	2.7	49	3.7
	May-July	1.6	1.8	47	2.8
Parleys Ck
Salt Lake City, Nr	April-July	4.5	5.1	36	7.5
	May-July	3.2	3.8	36	6.2
Emigration Ck
Salt Lake City, Nr	April-July	1	1.3	31	1.6
	May-July	0.86	1.1	41	1.5
City Ck
Salt Lake City, Nr	April-July	2.5	3	39	3.8
	May-July	2	2.4	37	3.2
S Willow Ck
Grantsville, Nr	April-July	1.5	1.7	55	2.1
	May-July	1.2	1.3	49	1.8

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	24	26	38	30
	May-July	19.4	21	39	25
Provo
Woodland, Nr	April-July	78	86	86	99
	May-July	65	73	82	86
Hailstone, Nr	April-July	86	95	86	108
	May-July	71	80	82	93
Deer Ck Res	April-July	88	102	80	113
	May-July	68	82	79	93
American Fork
American Fork, Nr, Up Pwrplnt, Abv	April-July	11.1	12.4	40	16.6
	May-July	9.4	10.7	38	14.9
West Canyon Ck
Cedar Fort, Nr	April-July	0.31	0.62	35	1.3
	May-July	0.3	0.61	40	1.3
Jordan
Utah Lake, Provo, Nr	April-July	155	172	53	205
	May-July	107	124	50	158

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	38.1	85	68	17.5	39	45.0	55.8
untitled Bear River
Bear Lake, Nr Lifton	728.7	95	56	961.1	125	770.8	1302.0
untitled Little Bear
Hyrum Reservoir	14.5	102	95	14.8	104	14.2	15.3
untitled Weber
Rockport Res, Wanship, Nr	36.1	90	65	37.7	94	40.1	55.2
Echo Res, Echo, At	43.0	79	58	34.1	63	54.3	73.9
untitled Lost Ck
Lost Ck Res, Croydon, Nr	14.7	110	65	17.2	129	13.3	22.5
untitled East Canyon Ck
East Canyon Res, Morgan, Nr	3.4	9	7	33.9	86	39.5	49.5
untitled Sf Ogden
Causey Res	5.9	117	83	6.9	136	5.0	7.1
untitled Ogden
Pineview Res, Ogden, Nr	83.0	104	75	69.9	88	79.7	110.1
untitled Jordanelle Dam
	173.1	69	54	183.8	73	251.3	320.3
untitled Provo
Deer Ck Res	133.6	108	89	141.4	114	123.5	149.7
untitled Dell Fk
Little Dell Res	13.3	-99	65	12.1	-99	-9999.0	20.5
untitled Jordan
Utah Lake, Provo, Nr	-9999.0	-99	-99	771.7	93	827.8	870.9
untitled
TOTAL	1274.1	89	59	2289.9	101	1436.7	2181.9

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 B.Bernard