Navajo Unit Operations

Coordination Meeting

April 20, 2021 1:00 PM

Microsoft Teams Virtual Meeting
• Review of operations to date WY 2021

• Current basin status

• WY 2021 weather – Aldis Strautins, NWS

• WY 2021 flow forecast – Ashley Nielson, CBRFC

• Colorado Dust on Snow – Jeff Derry, CSAS

• WY 2021 proposed operations

• Comments and Reports

Agenda


Reclamation Hydro Data 

https://www.usbr.gov/uc/water/hydrodata/reservoir_data/site_map.html
Reclamation Teacup Diagrams

https://www.usbr.gov/uc/water/basin/index.html
https://waterwatch.usgs.gov/index.php?id=wwdur_cumflow
Weather Outlook

April 2021

Aldis Strautins

National Weather Service

Grand Junction, CO

http://www.weather.gov/gjt
Weather Outlook

April 2021

• Since the first of the water year temperatures over southeastern 

Utah were cooler than normal and over southwestern Colorado 

warmer than normal. For Precipitation well below normal over 

the headwaters since the first of the water year. 

• So far for the beginning of January colder than normal with 

precipitation well below normal for most locations except along 

the Utah and Colorado border north of the Four Corners. 

• Storms in late February and March brought some brief relief to 

portions of the Four Corners Region but the first half of April has 

been very dry.

Discussion / Outline
Weather Outlook

April 2021

• Extreme to Exceptional drought remains entrenched over the 

head waters and Four Corners region. 

• ENSO - Neutral conditions are present and are expected to 

continue this spring into summer and then transition toward a 

weak La Nina next fall. 

• Spring into early summer higher chances of below normal 

precipitation. Higher chances of above normal temperatures 

• Drought is predicted to remain.

Discussion / Outline
The Past

April 2021

Precipitation - % of normal

Water year 2020 Aug – Oct 2020
The Past

April 2021

Water Year 2021

Temperature

Departure from normal

Precipitation

% of normal
The Past

April 2021

Since Jan 1, 2021

Temperature

Departure from normal

Precipitation

% of normal
Snotel

April 2021

SNOTEL - Precipitation

Percent of Normal 

March, 2021 March 11-31, 2021
The Past

April 2021

From April 1, 2021

Temperature

Departure from normal

Precipitation

% of normal
Snotel

April 2021

SNOTEL - Percent of Normal - Colorado

Water Year 2021 (as of Apr 15)

SWE Precipitation
Snow

April 2021

SNOTEL Snow Water Equivalent – NRCS

Southwestern Colorado
Drought

April 2021

April 13, 2021 April 14, 2020

Drought – Monitor
Season La Niña Neutral El Niño

MAM 2021 50% 50% 0%

AMJ 2021 21% 79% 0%

MJJ 2021 15% 81% 4%

JJA 2021 20% 68% 12%

JAS 2021 30% 57% 13%

ASO 2021 37% 50% 13%

SON 2021 41% 46% 13%

OND 2021 46% 41% 13%

NDJ 2022 47% 40% 13%

ENSO

April 2021

CPC/IRI Early-Month Consensus ENSO Forecast 

Probabilities

(using NWS CPC classification system)

ENSO – Outlook

Neutral remaining through spring and summer
Weather Outlook

April 2021

Temperature Precipitation

May – Outlook 
Weather Outlook

April 2021

Temperature Precipitation

May/Jun/Jul – Outlook
Weather Outlook

April 2021

Temperature Precipitation

Jun/Jul/Aug – Outlook
Weather Outlook

April 2021

Temperature Precipitation

Jul/Aug/Sep – Outlook
Weather Outlook

April 2021

Seasonal

Drought– Outlook
Weather Outlook

April 2021

Aldis Strautins

NWS Grand Junction, CO

http://www.weather.gov/gjt
Navajo Reservoir/San Juan Basin

Water Supply Outlook

April 20, 2021

Ashley Nielson

Senior Hydrologist

Colorado Basin River Forecast Center

National Weather Service/NOAA
Outline

● Modeled Soil Moisture Conditions

● Snow Conditions

● April 2021 Water Supply Forecasts

● Forecast Uncertainty

● Summary

● Contact Information
● Soil moisture conditions entering the winter were 

below normal and generally in the bottom 3 of the 

1981-2020 40-year period. 

● Conditions are similar to last year in the eastern 

headwaters but worse over the rest of the basin. 

● A portion of the snowmelt will be absorbed into the 

dry soils. The forecasts are accounting for this loss.

Modeled Fall Soil Moisture Conditions

Fall 2020

April - October 2020 SNOTEL Precipitation Ranking Fall 2020 Modeled Soil Moisture Conditions

● Near to record low historical precipitation from AprilOctober of last year.

● SNOTELs have a 35-40 year period of record.

● Lack of monsoon and a below average 2020 spring runoff 

exacerbated dry conditions.
Snow Conditions: SNOTEL Snow Water Equivalent

April 20, 2021

Snowpack in the San Juan Basin is much below normal. 

Snow did not reach the normal peak SWE and significant 

early melt has occurred.

SWE vs. runoff is not a 1-to-1 relationship; spring weather 

will play a role in the final outcome.

Snow Conditions: SNOTEL Snow Water Equivalent

2021 FCST: 185 KAF / 45%

1988: 296 KAF / 71%

2003: 242 KAF / 58%

2013: 178 KAF / 42%
Snow Conditions: CBRFC Model Snow Water Equivalent

April 19, 2021

*Only areas above 9000 ft that are significant to 

runoff

Model snow includes areas above and below SNOTEL sites.

● SNOTEL locations range from 8,500-11,500’ 

● Some modeled basins extend to over 13,000’

Upper Model SWE Median (11,000’-13,000’+)

Upper 2021 Model SWE (11,000’-13,000’+) 

Middle Model SWE Median (9,500’-11,000’)

Middle 2021 Model SWE (9,500’-11,000’) 

● Modeled snow is below normal above 9500’

● Significant melt has occurred below 11,000’; earlier than 

normal.

● Snow is still accumulating above 11,000’.

● Model indicates normal time of peak for SWE above 11,000’ 

is early May.
April 1st Water Supply Forecasts: San Juan River Basin

April-July Forecasts

Volume in 1000’s acre-feet / Percent of 1981-2010 average

Animas-Durango

4/1: 210 / 51%

4/16: 185 / 45%

● April 1st forecasts range from 35-75% normal with a median forecast of 50%.

● Forecast guidance has decreased by ~5-10% of average since the April 1st 

forecasts.

Main forecast drivers:

• Dry antecedent soil moisture conditions

• Below normal snow conditions

Vallecito

4/1: 103 / 53%

4/16: 92 / 47%

Rio Blanco-Pagosa

4/1: 41 / 76%

4/16: 41 / 76%

Navajo Reservoir

4/1: 395 / 53%

4/16: 370 / 50%

San Juan -Bluff

4/1: 505 / 46%
Forecast Progression: Navajo Reservoir Inflow

Blue shading: Daily Raw Model Guidance 90% - 10% exceedance range

Blue line: Daily Raw Model Guidance 50% exceedance

Pink line: Official forecast 90%, 70%, 50%, 30%, 10% exceedance

Green solid: 1981-2010 average April-July volume

Green dotted: 1981-2010 median April-July volume

Brown dotted: Average observed

Orange dashed: 2021 Observed Streamflow

Navajo Reservoir Inflow Forecast Plot Link

San Juan River Forecast Plots Link

10%

50%

90%

AVERAGE

MEDIAN

Historical Minimum

Jan 

Fcst

Feb 

Fcst Mar 

Fcst

Apr 

Fcst

10% chance volume will be greater 

than 550 KAF/ 75% of average

April 16 50% Forecast: 370 KAF / 50% 

90% chance volume will be greater 

Mid than 270 KAF/ 37% of average -Apr 

Fcst

Observed: 52 KAF (provisional)
Forecast Verification

Mar 1st average error: 22% 

Apr 1st average error: 18% 

May 1st average error: 15% 

Navajo Reservoir Inflow

April 1st Forecast 1991-2020

Over forecast

Under forecast

YEAR

APR 1 FCST 

(KAF)

OBSERVED 

(KAF) Error KAF / %

2003 400 307 93 / 30%: over

2006 395 379 16 / 4%: over

1999 375 755 380 / 50%:under

2013 370 267 103 / 38%: over

Historical Forecast Errors with similar April 1 Forecasts
Summary

• Below normal water year precipitation in the San Juan River Basin

• Below normal snow conditions

• Early melt

• Near/record low antecedent soil moisture conditions entering water year 2021 snow accumulation & runoff season

• Two consecutive years of poor Monsoon 

• Limited groundwater recharge since 2019 runoff

• April water supply forecasts (% of normal):

• April 1st forecasts range between 35-75% of average

• Forecast guidance has decreased by ~5-10% since the April 1st

• Best conditions are located in the eastern headwaters and deteriorate moving west towards the Animas River Basin.

• Dry soils will most likely impact runoff with a portion of the snowmelt being absorbed into the ground.

• Early runoff implications:

• Impacts depend on specific basin characteristics

• Could be less efficient early in the melt due to dry soils

• Could be more efficient due to faster melting snow pack

• Could cause increased evapotranspiration in the later portion of normal the runoff period as bare ground and soils dry out sooner; 

ultimately leading to lower flows.
Contact Info

Contact Information

• Operational Hydrologist: in office

• 801-524-4004

• cbrfc.operations@noaa.gov

• Ashley Nielson - San Juan River Forecaster

• ashley.nielson@noaa.gov

• 801-524-5130 x333 

CBRFC Webpage

https://www.cbrfc.noaa.gov/

CBRFC Water Supply Presentations

https://www.cbrfc.noaa.gov/present/present.php

Colorado Dust on Snow Program (CODOS)

Wolf Creek Pass, Reported April 14th, 2021
CBRFC Water Supply Forecasts

https://www.cbrfc.noaa.gov/

Water Supply 

Forecasts 

(April-July)

As of Jan, 2021
Water Supply 

Forecasts (April-July)

Navajo: 370 kaf (50% avg)

Vallecito: 92 kaf (47% avg)

Lemon: 22 kaf (40% avg)

Animas: 185 kaf (45% avg)

McPhee: 95 kaf (32% avg)

Powell: 2,700 kaf (38% avg) As of April 15, 2021
PRELIMINARY AVAILABLE WATER CALCULATION FOR WY 2021

CBRFC Forecast Date: April 2021

Forecast

Available Water 

over 6050 (kaf)

Available Days 

at Peak (need 

min of 21 for 

SPR)

Proposed 

Release

Proposed 

Release 

Volume (kaf)

Volume over 

6063 ft on 

Sept 30th 

(kaf)

Sept 30 Pool 

Elevation (ft) 

with proposed 

release

MIN -373 0 none 0 0 6013

MOST -149 0 none 0 0 6036

Current Forecast

MAX -33 0 none 0 0 6052

San Juan River Recovery Implementation Program Modified Decision 

Tree (updated 2018)



What does it mean?

Based on current storage levels and the ESP trace forecasts, 

• No spring peak release is planned

• Releases through the summer will likely range from 600 cfs to 1,000 cfs.

• Most probable forecast peak pool elevation is near 6043 ft (Min Prob 6038)

• Most probable forecast Sept 30th pool elevation is near 6035 ft (Min Prob 6021)

• Flows at Four Corners are unlikely to meet SJRIP Flow Targets under these 

forecasts.

• No runs result in a shortage for WY 2021, however, 3% chance of shortage in WY 

2022 (one run out of 35 results in a shortage).
• Extreme to Exceptional drought remains entrenched over the headwaters and Four Corners and is 

predicted to remain.

• Snowpack peak was below-average for the San Juans, and runoff has begun early.

• The April-July runoff most probable forecast for Navajo is 370kaf (50% of average). Other basins 

in the San Juans have similarly low forecasts. 

• Antecedent soil moisture was record low entering this winter, which is another driver of belowaverage forecast runoff.

• Based on current conditions (snowpack and reservoirs), and the range of forecast possibilities 

provided by CBRFC, no spring peak release is planned

• Expect low releases throughout the runoff season (300-500 cfs) as minimum releases to meet the 

target baseflows will be made. Summer releases will likely be higher than normal, between 600 

and 1,000 cfs releases will be likely unless we have a wet summer.

• Currently no shortage is in the forecast for the San Juan River Basin in water years 2021-2022.

Summary Next mtg August 24th – Virtual? In-Person?
Reclamation Contacts:

Marc Miller – Water Management Group Chief

970-385-6541 mbmiller@usbr.gov

Susan Novak Behery – Hydrologic Engineer

970-385-6560 sbehery@usbr.gov

To be added to Navajo Dam notices email list, send an email to 

westcoloareaoffice@usbr.gov 

Useful Links

Reclamation: www.usbr.gov/uc

USGS: water.usgs.gov/nwis

CBRFC: cbrfc.noaa.gov