Lower Colorado Water Supply Outlook, March 1, 2019

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.

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

	Forecast Period	90% Exceedance Volume	70% Exceedance Volume	50% Exceedance Volume	Percent Median	30% Exceedance Volume	10% Exceedance Volume
Salt
Roosevelt, Nr	January-May	395	465	530	171	630	710
	March-May	225	295	360	150	460	540
Tonto Ck
Roosevelt, Nr, Gun Ck, Abv	January-May	84	96	114	271	144	185
	March-May	37	49	67	305	97	138
Verde
Tangle Ck, Blo, Horseshoe Dam, Abv	January-May	370	415	480	306	565	660
	March-May	163	210	275	257	360	455

	Forecast Period	90% Exceedance Volume	70% Exceedance Volume	50% Exceedance Volume	Percent Median	30% Exceedance Volume	10% Exceedance Volume
Gila
Gila, Nr	January-May	47	53	61	109	77	101
	March-May	23	29	37	109	53	77
Virden, Nr, Blue Ck, Blo	January-May	56	65	72	95	89	112
	March-May	27	36	43	100	60	83
Solomon, Nr, Head Of Safford Vly	January-May	86	104	117	85	150	187
	March-May	47	65	78	88	111	148
San Carlos Res, Coolidge Dam, At	January-May	77	91	104	109	138	184
	March-May	27	41	54	102	88	134
San Francisco
Glenwood, Nr	January-May	10.7	12.9	14.6	70	19.8	26
	March-May	5.1	7.3	9	59	14.2	20
Clifton	January-May	31	37	45	74	58	79
	March-May	14.1	20	28	74	41	62

	Forecast Period	90% Exceedance Volume	70% Exceedance Volume	50% Exceedance Volume	Percent Median	30% Exceedance Volume	10% Exceedance Volume
Little Colorado
Lyman Lk, Abv, St. Johns, Nr	January-June	2.9	3.4	3.9	55	5.3	7
	March-June	2.4	2.9	3.4	57	4.8	6.5
Zuni
Black Rock Res, Abv	January-May	0.25	0.3	0.36	77	0.65	1.1
	March-May	0.19	0.24	0.3	130	0.59	1
Chevelon Ck
Winslow, Nr, Wildcat Cyn, Blo	January-May	29	34	38	273	46	62
	March-May	10.9	16.2	20	144	28	44

	EOM Contents	Percent EOM Average	Percent Usable Capacity	Last Year EOM	Last Year %Average	EOM Average	Usable Capacity
Salt
Roosevelt	832.9	87	50	946.0	99	953.2	1653.0
Horse Mesa	237.8	103	97	231.1	100	231.1	245.1
Mormon Flat	53.6	99	93	55.5	102	54.3	57.9
Stewart Mountain	65.6	104	94	64.4	102	63.0	69.8
Horseshoe	99.6	208	91	12.4	26	47.8	109.2
Bartlett	147.1	122	83	85.5	71	120.3	178.2
untitled
TOTAL	1436.8	98	62	1395.0	95	1469.7	2313.2


Bill Williams
Alamo	120.8	76	12	108.9	69	158.3	1045.0
Agua Fria
Lake Pleasant	779.0	106	90	722.0	98	734.3	869.9
Gila
San Carlos	71.7	18	8	68.7	17	404.1	875.0
Colorado
Lake Powell	9277.9	54	38	13345.8	78	17054.6	24322.0
Lake Mead	10670.5	52	41	10707.3	52	20575.4	26120.0
untitled
TOTAL	20919.8	54	39	24952.7	64	38926.8	53231.9

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

Lower Colorado Water Supply Outlook, March 1, 2019

Lower Colorado Summary

Salt Basin Conditions

Gila Basin Conditions

Little Colorado Basin Conditions

Salt Specific Site Forecasts (kaf)

Gila Specific Site Forecasts (kaf)

Little Colorado Specific Site Forecasts (kaf)

Lower Colorado End of Month Reservoir Contents (kaf)

Precipitation Maps

Definitions

Additional Information