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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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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
Let’s start with a quick introduction to the original version of WEAP, and most other water resource management simulation models for the matter.
What are we assuming? • That we know how much water is flowing at the top of each river. • That we know how much water is flowing into or out of the river as it moves downstream. • That we know what the water demands are with certainty.
What are we assuming? • That we know how much water is flowing at the top of each river. • That we know how much water is flowing into or out of the river as it moves downstream. • That we know what the water demands are with certainty. • Basicly, that this system has been removed from it HYDROLOGIC context.
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?
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?
WEAP, with its integrated Hydrology Molude, provides a framework for answering both set of questions.
The WEAP 2-Bucket Hydrology Module Surface Runoff = f(Pe,z1,1/LAI)
This last point leads to a stylized groundwater representation
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
Reservoir Storage SHASTA
Phenologies of reproductive events in freshwater phase of Chinook salmon life-cycle in the SV watershed.□ = adult immigration; ∆ = spawning and hatching; ◊ = juvenile emigration
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.
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 Schwarzenegger’s Executive Order S-3-05.
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.
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 Schwarzenegger’s Executive Order S-3-05.
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.
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 Schwarzenegger’s Executive Order S-3-05.
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
Spatial Disaggregation Sacramento Valley WEAP Model
Spatial Disaggregation Before After Stone Corral HUC
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.
Future Work • Disaggregate and calibrate Lower Butte HUC • Run climate change scenarios • Modify Assumptions (e.g. add dynamic cropping patterns) • Perform economic assessment
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.