Climate Drought, Snow, and Water II
Remote Sensing Based Actual Evapotranspiration Mapping for Drought Monitoring and Water Budget Analysis - Gabriel Senay
Products to calculate ET:
– Satellite-based ET is being estimated operationally using Land Surface Temperature (LST)\
– MODIS – 1km data thermal – Watershed analysis
– Landsat based ET – 100m thermal
ET = transpiration + evaporation
– It is a RESPONSE variable as opposed to precipitation (driver)
– Two components:
o Potential: Energy + Wind/RH
o Limitations: Soil Moisture, Vegetation, Environmental Stress
Operational Simplified Surface Energy Balance Modeling Approach (SSEBop)
– Land Surface Temperature (ET) combine with Weather Data (Air Temp)
o LST measured by satellite 2 times per day by MODIS satellite
o Weather data – TopoWx, Daymet, PRISM
– Solve Penman-Monteith equation
– When LST close to Air Temp, higher ET
Model Performance Evaluation
– Evaluate with EC Flux Towers data
– Spatial distribution of ET is well represented
– Daymet and TopoWx perform similarly
– Daymet and PRISM perform differently (up to 6’C)
– Must parameterize model with the same or similar to data used to run model
Water Budget Analysis
Precipitation minus ET
– Irrigated areas will have negative water balance
– EC Flux Towers
Conclusions:
– We can monitor landscape response anomalies every 1 Km every decade globally – for early warning for drought events
– We can map and quantity crop water use volumes – for planning and designing irrigation systems
– Careful ground-truthing of remote sensing ET is necessary to remove bias before use in volumetric calculators
Questions:
Can use to reproduce historic consumptive use in water budget?
– Yes, this is the plan!
Is your ET model able to capture accumulated affects of multi-year stress?
– Question of analysis – our model is a snap-shot, but it should show in soil moisture
There are lots of uncertainties in the datasets you are using in calculations and validation. Do you feel confident in your results?
– Confident within 20% error and I think that is good enough, it depends on the project.
Where did you get the wind data?
– NOAA
Can you explain why you did 8-day windows?
– We solve ET every 8-days using satellite 8-day average
– We start from April as the beginning of the growing season
Do you have change maps showing the trends over time?
– We have a historical map showing all the years at the end of the season
– If there are other ways of the displaying the data, please let me know
How long has this product been available?
– 5 years, but we are not actively promoting it so not widely used
Did you do a comparison with weather based ET using Penman-Monteith estimate that requires crop coefficient?
– We did not use that method, we don’t use NDVI. We assume static stomatal conductance and uniform grass cover.
– EC flux tower directly measured ET for comparison
To what degree to does the data foretell actual impacts on the ground?
– We know by mid-season, we know what will happen once crops are in the ground
– Every week we publish results and talk with partners to check if the projections are reliable
Determining Climate Change Impacts on Future Basin-Scale Flows in Colorado for Water Resource Planning – Taryn Finnessey
Objectives:
– Importance for Actionable Science – two-way connection between science creators and users
– Consistency with Colorado’s Water Plan
Projected depleted flows:
Under future hot & dry conditions and between 20th century observed and hot & dry
– Significantly drier conditions “dry river conditions” - quantified
– No big response yet, likely because calls on the river during moderate years date back to 1860s
Can use information for:
– Basin Planning
– Utility Planning
– State Planning
Lessons Learned
– Water providers are now feeling the need to consider climate impact projects in planning – people want utilities to use this information!
– The single biggest challenge is planning under a great deal of uncertainty
– New “adaptive management” approaches are being developed
Question:
What are your thoughts about the impact of population increase and tension between urban and rural water demands?
– Yes those are important issues that will become more demanding in the future. This is why we included many drivers of water demand in our projections, including population increases.
Decision-centric adaptation appraisal for water management across Colorado’s Continental Divide – Kathleen Miller
Research Questions:
– How will climate change and water governance arrangements interact to affect CO transbasin water diversions?
– How well will drought response options work in different future conditions?
Decision-centric approach:
Collaborative dialogue > System evaluation Performance metrics Option(s) appraisal
Transbasin diversions: Roughly 25% of in-state consumptive use of Colorado river
Relaxation Agreement:
– March – May when flows between 1408 and 704 cfs
– Worked with senior calls to reduce their call during low flow conditions
– Also allow “paper filling” for junior calls:
o End of season, if senior calls get their fill, then fine. If not, junior releases fill to supply senior call downstream (“pay-back”).
Water Evaluation and Planning (WEAP) System
– Modeled flows with and without relaxation
– Denver’s storage softens the impact of declining stream flow except in the second severe year of drought
– Benefit from Relaxation Agreement is relatively small for Denver!
– More impactful for other reservoirs
Questions:
What if this power-plant doesn’t want to follow relaxation agreement?
– They have incentives to agree. They get pay-back for reduced energy production and get additional cooling water.
Section Discussion
I see a spectrum of approaches – starting a larger scale using climate scenarios, perhaps at local level it’s better to start with the decision.
Benefit of back and forth dialogue to get to the middle ground with both decision based and climate scenarios.
I’m concerned that the more complicated the GCM models become and with the great uncertainty they become less useful. It seems better to be focused on scenario planning with all the other factors and a more generalized consideration of climate change projections.
Depends on location! Some places GCMs converge.