Water - GCAM

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Model Documentation - GCAM

Corresponding documentation
Previous versions
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Model information
Model link
Institution Pacific Northwest National Laboratory, Joint Global Change Research Institute (PNNL, JGCRI), USA, http://www.globalchange.umd.edu.
Solution concept General equilibrium (closed economy)GCAM solves all energy, water, and land markets simultaneously
Solution method Recursive dynamic solution method
Anticipation GCAM is a dynamic recursive model, meaning that decision-makers do not know the future when making a decision today. After it solves each period, the model then uses the resulting state of the world, including the consequences of decisions made in that period - such as resource depletion, capital stock retirements and installations, and changes to the landscape - and then moves to the next time step and performs the same exercise. For long-lived investments, decision-makers may account for future profit streams, but those estimates would be based on current prices. For some parts of the model, economic agents use prior experience to form expectations based on multi-period experiences.

The types of water flows represented in GCAM include the following:

  • water withdrawals: water diverted or withdrawn from a surface water or groundwater source (Vickers 2001).
  • water consumption: water use that permanently withdraws water from its source; water that is no longer available because it has evaporated, been transpired by plants, incorporated into products or crops, consumed by people or livestock, or otherwise removed from the immediate water environment (Vickers 2001).
  • biophysical water consumption: total water required for crop evapo-transpiration; the sum of “blue” and “green” water in Mekonnen and Hoekstra 2011
  • seawater: water from the oceans, including brackish estuaries, that is withdrawn for cooling thermo-electric power plants, or used in primary energy production.

Water demand representations have been constructed for six major sectors: agriculture, electricity generation, industrial manufacturing, primary energy production, livestock, and municipal uses. Municipal water demands are represented in a specific “municipal water” sector, but all other water demands are modeled as inputs to otherwise existing technologies in the energy and AgLU systems. The sectors relevant for water demands are described in the documentation.