snowpocalypse - colorado river water conservation district · lessons from snowpocalypse • the...
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2019 Annual SeminarColorado River DistrictGrand Junction, CO – September 18, 2019Jeff Lukas, Western Water AssessmentCIRES, University of Colorado Boulder
SnowpocalypseA 2019 feast after a 2018 famine
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Image: Shaune Goleman
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US Drought Monitor for Upper Colorado River Basin
October 2, 2018
Source: US Drought Monitor;https://droughtmonitor.unl.edu/
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CBRFC modeled antecedent soil moisture – Nov 2018
Source: NOAA CBRFC; https://www.cbrfc.noaa.gov/
• Much below normal almost everywhere in Upper Basin
• Near-record-low in San Juan and Gunnison basins
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CBRFC forecast evolution plot – Lake Powell Apr-Jul inflows
Source: NOAA CBRFC; https://www.cbrfc.noaa.gov/wsup/
4.55 maf
9.20 maf
10.40 maf
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February – persistent trough, favorable flow
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March 1st-15th – persistent trough, favorable flow
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Rank of Feb-Mar 2019 precip at SNOTEL sites
Source: NRCS Interactive Map; https://www.nrcs.usda.gov/wps/portal/wcc/home/quicklinks/imap
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“Historic” avalanche cycle in early March in CO mts
From February 28th
- March 10th:• 10-15 feet of
snow• 6”-12” of SWE• Avalanche
activity not seen since 1950s
Conundrum Creek slide down Highlands Ridge, AspenSource: Colorado Avalanche Information Center, from Telluride Helitrax
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Feb-Mar Upper Basin precip, 1900-2019
2019
Source: NOAA NCEI Climate at a Glance; https://www.ncdc.noaa.gov/cag/
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May – very deep trough, favorable flow
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Rank of May 2019 precip at SNOTEL sites
Source: NRCS Interactive Map; https://www.nrcs.usda.gov/wps/portal/wcc/home/quicklinks/imap
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Oct-May Upper Basin precip: 2019 2nd highest since 1900
2019
Source: NOAA NCEI Climate at a Glance; https://www.ncdc.noaa.gov/cag/
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Oct-May Upper Basin temps: 2019 coolest since 2010
2019
Source: NOAA NCEI Climate at a Glance; https://www.ncdc.noaa.gov/cag/
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WY 2019 SWE plot –Lake Powell 104 Group
Source: NOAA CBRFC; https://www.cbrfc.noaa.gov/station/sweplot/snowgroup.php
130% of median peak SWE
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US Drought Monitor for Upper Colorado River Basin
July 2, 2019October 2, 2018
Source: US Drought Monitor;https://droughtmonitor.unl.edu/
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Schematic of typical winter El Nino effects on U.S.
Source: NOAA; https://www.climate.gov/news-features/
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CPC seasonal outlook for Feb-Apr, issued Jan 17th
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CPC seasonal outlook for Mar-May, issued Feb 21st
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Upper Basin Feb-May precip vs. ENSO state, 1979-2019Pr
ecip
itatio
n, in
ches
El Niño La Niña Neutral
75th
25thMedian
2019
Average of all years
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Jun-Aug Upper Basin precip: 2019 8th driest
2019
Source: NOAA NCEI Climate at a Glance; https://www.ncdc.noaa.gov/cag/
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July-Aug Upper Basin temps: 2019 6th warmest
Source: NOAA NCEI Climate at a Glance; https://www.ncdc.noaa.gov/cag/
2019
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Lees Ferry water-year natural flows: 2019 looking good, but not great
0
5
10
15
20
25
30
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020
2019est.17.5 maf(118% of average)
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UCRB Oct-May precip vs. Lees Ferry flows, 1900-2019
0
5
10
15
20
25
30
0 5 10 15 20
2019est.
UCRB Oct-May precip, in.
Lees
Fer
ry W
Y na
tura
l flo
w, m
af
2018
R2 = 0.67
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UCRB Oct-May precip vs. Lees Ferry flows, 1900-2019
UCRB Oct-May precip, in.
Lees
Fer
ry W
Y na
tura
l flo
w, m
af
0
5
10
15
20
25
30
0 5 10 15 20
2000-2019
1906-1999
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Increasing hydroclimatic variability and volatility?
• Upper Basin interannual precipitation variability has increased ~10% since 1980
• Consistent with expectations from climate models: more warming = more precip variability
• Individual storms will tend to be ”juicier” in a warmer climate
• And: Warmer summer temperatures will dry out land surface faster
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Lessons from Snowpocalypse
• The snowpack and runoff outlook can turn around in a month, given the right weather pattern
• El Niño tilts the odds towards a wet late winter-spring in the Upper Basin, but randomness does the rest
• Extreme seasonal conditions will always be hard to forecast
• There is such a thing as too much snow
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Lessons from Snowpocalypse
• Near-record precipitation and snowpack does not necessarily translate into near-record annual runoff
• We will likely see more frequent feast-after-famine years (and the reverse)
• As well as more within-season volatility
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Colorado River Basin Climate and Hydrology report
Volume I. Background• Introduction• Current understanding of basin
hydroclimate• Primary operations and planning tools
Volume II. Informing all time scales• Observations – Weather and climate • Observations – Hydrology• Hydrologic models
Volume III. Short-term and mid-term• Weather and climate forecasting• Streamflow forecasting
Volume IV. Long-term• Historical hydrology• Paleohydrology• Climate-change-informed hydrology
Scheduled release: December 2019
