Decision Relevant Climate Change Impact Assessments using WEAP21

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Decision Relevant Climate Change Impact
Assessments using WEAP21

• Stockholm Environment Institute-Boston Center
• National Center for Atmospheric Research
• Natural Heritage Institute
• with support from
• U.S. EPA, Office of Research and Development

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Lets start with a quick introduction to the
original version of WEAP, and most other water
resource management simulation models for the
matter.
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A Simple System
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What are we assuming?

1. That we know how much water is flowing at the top
   of each river.
2. That we know how much water is flowing into or
   out of the river as it moves downstream.
3. That we know what the water demands are with
   certainty.

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What are we assuming?

1. That we know how much water is flowing at the top
   of each river.
2. That we know how much water is flowing into or
   out of the river as it moves downstream.
3. That we know what the water demands are with
   certainty.
4. Basicly, that this system has been removed from
   it HYDROLOGIC context.

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What do we do now?
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ADD HYDROLOGY!
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Hydrology Model
Critical question How does rainfall on a
catchment translate into flow in a river?
Critical question What pathways does water
follow as it moves through a catchment? Runoff?
Infiltration? ET? Seepage?
Critical question How does movement along these
pathways impact the magnitude, timing, duration
and frequency of river flows?
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Planning Model
Critical question How should water be allocated
to various uses in time of shortage?
Critical question How can these operations be
constrained to protect the services provided by
the river?
Critical question How should infrastructure in
the system (e.g. dams, diversion works, etc) be
operated to achieve maximum benefit?
Critical question How will allocation,
operations and operating constraints change if
new management strategies are introduced into the
system?
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WEAP, with its integrated Hydrology Molude,
provides a framework for answering both set of
questions.
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WEAP Hydrology
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The WEAP 2-Bucket Hydrology Module
Surface Runoff f(Pe,z1,1/LAI)
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One 2-Bucket Model Per Land Class
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This last point leads to a stylized groundwater
representation
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An Example from California
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WEAP Schematic of Sacramento Watershed Based Model
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Calibration and Validation

• Model Evaluation (1961-1999)
• Flows Along Mainstem and Tributaries
• Reservoir Storage and Release
• Trinity Diversion
• Agricultural Water Demand
• Groundwater Storage Trends
• Yolo Bypass Flood Inundation
• Sacramento River Water Temperature

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Reservoir Storage
SHASTA
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Stylized Sacramento Climate Scenarios
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Phenologies of reproductive events in freshwater
phase of Chinook salmon life-cycle in the SV
watershed.? adult immigration ? spawning and
hatching ? juvenile emigration
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River Temperature Model

• First-order DO and temperature patterned after
  Chapra (1997)
• Water quality simulated for select rivers, where
  tributaries, discharges, and return flows
  prescribed.
• Mass balance equations for each stream segment
• Hydrologic inflows from rivers and groundwater
  sources simulate the water balance and mixing of
  concentrations and temperature along each reach.
• Same River network for the water resources and
  the water quality simulation, and assumes
  complete mixing.

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Temp. Profile Kms Downriver of Shasta Dam
June July Aug Sep
Historic 100 55 65 220
WmDry 55 14.5 14.9 50
WmWet 65 40 35 110
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Current Decision-Relevant Activity

• Collaborating with PCWA and EID on the
  development of a WEAP21 model of the American
  River Watershed for exploration of potential
  climate change impacts.
• Collaborating with DWR to see if the WEAP21
  Framework can contribute to the quantitative
  climate change assessment envisioned for
  B160-2010.
• Working with the California Climate Center on a
  case study for the Sacramento Valley as part of a
  climate change assessment report called for under
  Governor Schwarzeneggers Executive Order S-3-05.

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Approach

• Develop refined WEAP model of the American River
  watershed.
• Apply the model to understand hydropower
  potential of PCWA system.
• Apply the model to understand the drought
  vulnerability of the EID water supply system.
• Potentially integrated with a model of the Yuba
  River watershed which is managed by Nevada
  Irrigation District and has substantial transfers
  into the American River watershed.

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The American River Watershed in WEAP21
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North Fork American
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Preliminary Calibration 1990 - 1999
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Warmer and Drier Climate Scenario
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Current Decision-Relevant Activity

• Collaborating with PCWA and EID on the
  development of a WEAP21 model of the American
  River Watershed for exploration of potential
  climate change impacts.
• Collaborating with DWR to see if the WEAP21
  Framework can contribute to the quantitative
  climate change assessment envisioned for
  B160-2010.
• Working with the California Climate Center on a
  case study for the Sacramento Valley as part of a
  climate change assessment report called for under
  Governor Schwarzeneggers Executive Order S-3-05.

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Approach

• Train DWR staff on the use of WEAP.
• Develop a link between Sacramento Valley
  application and a Delta Water Quality Model.
• Develop a link with a future demand scenario
  generator developed by RAND.
• Embed the Sacramento Valley application in a more
  stylized system-wide model.
• Run a series of climate change scenarios.
• Evaluate with DWR if the WEAP framework can be
  used for quantitative climate change analysis in
  Bulletin 160-2010.

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Current Decision-Relevant Activity

• Collaborating with PCWA and EID on the
  development of a WEAP21 model of the American
  River Watershed for exploration of potential
  climate change impacts.
• Collaborating with DWR to see if the WEAP21
  Framework can contribute to the quantitative
  climate change assessment envisioned for
  B160-2010.
• Working with the California Climate Center on a
  case study for the Sacramento Valley as part of a
  climate change assessment report called for under
  Governor Schwarzeneggers Executive Order S-3-05.

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Approach

• Disaggregate HUCs to ID level
• Calibrate model
• Run climate change scenarios
• Modify assumptions (e.g. changing irrigation
  technology/efficiency, varying cropping patterns,
  conversion of farmland to urban use, etc.)
• Re-run scenarios
• Perform economic assessment

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Spatial Disaggregation
Sacramento Valley WEAP Model
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Spatial Disaggregation
Before
After
Stone Corral HUC
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Model Calibrated for Stone Corral

• Regional water consumption and delivery within
  Sacramento-Stone Corral HUC corresponds to
  historic data.
• Irrigation district level water consumption and
  delivery reflects historic observations.
• Groundwater levels follow historic trend.

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Future Work

• Disaggregate and calibrate Lower Butte HUC
• Run climate change scenarios
• Modify Assumptions (e.g. add dynamic cropping
  patterns)
• Perform economic assessment

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Conclusions

• The hydrology module is a powerful tool for
  considering changing catchment dynamics.
• Hydrology is essential for conducting rigorous
  analysis of climate change impacts.
• Hydrology could be very interesting for sectoral
  economic analysis because it considers several
  resources in a catchment, rainfed and irrigated
  agriculture, forest and range management, fish
  appropriate flows.
• Increasing activity is taking place with the
  WEAP21 Framework in California, with the real
  potential to influence decision-making processes.