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Interactions with Colorado Municipal Water Managers Elevate the Use of Climate
Information
Jessica Lowrey and Andrea Ray
NOAA and Univ. of Colorado
Western Water Assessment
Overview
Study group
Methods
Uses of climate information and forecasts
Factors affecting the use of climate information and forecasts
Interactions with WWA affect this use
Recommendations
Dillon Reservoir-Denver Water supply
Study Group
Six Front Range water providers: Northern Colorado Water Conservancy District, Boulder, Westminster, Denver, Colorado Springs, and Aurora
Serve about 60% of Colorado’s population
Context:
Interactions with WWA and other climate information providers since 1998
Drought in 2002
NorthernBoulder
DenverWestminster
Colorado Springs
Aurora
Methods: Interactive Model
Researched decision processes and institutional capacity
Interdisciplinary team at WWA and NOAA communicating with water managers
Interviews
Workshops and meetings
Results:Use of climate information & forecasts
Data used in annual and long-term decisions Instrumental record of hydrologyCurrent snowpack and streamflowsStreamflow/reservoir inflow forecasts
Graph from NRCS
Use of climate information & forecasts
Probabilistic streamflow forecasts in the form of exceedence probabilities for precise locations.
GUNNISON RIVER BASIN Streamflow Forecasts - April 1, 2007
<==== Drier === Future Conditions === Wetter ====> Forecast Pt (Forecast Period) 90% 70% 50% (Most Prob) 30% 10% (1000AF) (1000AF) (1000AF)(%AVG.) (1000AF) (1000AF) Taylor Park blw Taylor Park Res (APR-JUL) 54 63 70 68 77 88
Use of climate information & forecasts
Seasonal climate forecasts are used qualitatively…Water managers look at and discuss climate forecastsThey use them in mental models, when they are “on the fence” about drought restrictions
…But they are not in a form that can be incorporated into models.Climate forecasts do not provide data on river basin scaleWater managers can’t use temperature and precipitation in models, only streamflowsSkill/verification information is hard to locate and interpret Climate forecasts are most often “EC” for precipitation in this region
Factors affecting use of climate information & forecasts
Quality of information and forecasts
Institutional capacity
Sensitivity of water supply to climate variability
Perception of risk
Climate literacy
Institutional capacity
Definition: the ability of a decision-making entity to incorporate new information into decision processes.
Higher capacity More staff, diverse areas of expertiseMore time for learningUse of sophisticated operational or planning models
Cities with higher institutional capacity are more likely to try to use new climate information and forecasts.
Sensitivity of water supply
to climate variability Definition: impact of natural climate variability on
water supply.This region is sensitive due to snowmelt dominated water supply, population growth, fully appropriated rivers
Higher sensitivity Ratio of average storage : annual demand = 1:1
Water rights have junior priority
Water supply comes from only one basin
Anticipating high growth
While these cities had different levels of sensitivity, they were all impacted by the drought of 2002 (e.g. water use restrictions).
That experience made them realize that their system may not be reliable if they only plan for droughts in the historic record.
[Undepleted] Annual Flow, South Platte R. at South Platte, CO, 1916-2002
0100200300400500600700800
1915 1930 1945 1960 1975 1990 2005Annual Flow (1000 acre-feet)
Data source: Denver Water
2002
1950’s
Perception of risk
Drought of 2002 made water managers realize that their systems were vulnerable to drought.
Single year with lower snowpack and streamflows than anything water managers had experienced or seen in the hydrologic record.
This led to a change in perception of risk to climate variability…
…And a desire to learn more.After 2002, WWA started to get more information requests (paleo reconstructions, climate forecasts, natural variability, climate change)
Climate literacy
As perception of risk increased…WWA provided education about climate variability, climate system and climate prediction
…Climate literacy increased.Water managers are now asking more specific questions and are considering using additional climate information.
…this lead to increased use of climate information and forecasts.
Paleo reconstructions of streamflows in long-term models.
Downscaled GCM projections in hydrology models.
Climate variables in annual reservoir projections
Putting it all together:
Perception of higher risk, coupled with higher sensitivity of water supply to climate variability increases the desire to use climate information and forecasts.
A severe drought led to perception of higher risk, and water managers sought out climate knowledge from WWA and others.
Climate literacy, plus perception of higher risk, and institutional capacity enabled these water managers to seek out and use new climate information and forecasts.
Use of climate information and forecasts
Perception of risk
Sensitivity of water supply
Climate literacy
Institutional capacity
Interactions with WWA
Drought of 2002-2006
Recommendation 1: Education on climate system and natural variability
Effect of climate patterns (e.g. ENSO) on regional weatherRegional trends in temperature, precipitation, and streamflows; compare anomalous years to natural variabilityRe-occurance interval of single- and multi-year droughts and other extremesRegional variability in historic streamflows among river basins (exceedence probabilities); reliability of current or future water rights
Recommendation 2: Education on forecast methodology and skill
Underlying assumptions and uncertainties of forecast modelsSources of forecast and data errorVerification methods, including hind castingTypes of verification (resolution/sharpness vs. reliability)Skill vs. accuracyRegional patterns of skill
Recommendation 3: Information presentation
Tercile precipitation (inches)
Location (climate division) lower middle upper
W Colorado
precip range less than 3.38 3.38-4.59 greater than 4.59
% chance 33.3% 33.3% 33.3%
SW Arizona
precip range less than 1.46 1.46-2.80 greater than 2.80
% chance 42.9% 35.3% 21.8%
GUNNISON RIVER BASIN Streamflow Forecasts - April 1, 2007
<==== Drier === Future Conditions === Wetter ====> Forecast Pt (Forecast Period) 90% 70% 50% (Most Prob) 30% 10% (1000AF) (1000AF) (1000AF)(%AVG.) (1000AF) (1000AF) Taylor Park blw Taylor Park Res (APR-JUL) 54 63 70 68 77 88
Example of streamflow forecast that water managers use:
Example of climate forecasts presented in a similar manner:
precipitation (inches) in each exceedence
category
95% (min) 75% 50% (most prob)
% of average 25% 5% (max)
different from average?
W Colorado
1.98 3.07 3.96 100% 4.96 6.6 no
SW Arizona
0.4 0.99 1.66 81% 2.62 4.61 below average
