Water - GCAM

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Model Documentation - GCAM

Corresponding documentation
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Model information
Model link
Institution Pacific Northwest National Laboratory, Joint Global Change Research Institute (PNNL, JGCRI), USA, https://www.pnnl.gov/projects/jgcri.
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.

Supply of Water

Three distinct sources of fresh water are modeled, renewable water, non-renewable groundwater, and desalinated water. Renewable water is water that is replenished naturally by surface runoff and subsurface infiltration and release (groundwater recharge). Non-renewable groundwater is water from aquifers whose recharge is sufficiently low as to be depletable on a human time scale and which have replenishment timescales greater than 100 years. Renewable water and non-renewable groundwater are separately modeled for each basin. Desalinated water of brackish groundwater and seawater is available as an additional source of freshwater within each basin and for municipal and industrial end-use demands for water. See Supply of Water for a full description.

Demand for Water

Water demand is calculated for six major sectors: agriculture, electricity generation, industrial manufacturing, primary energy production, livestock, and municipal uses. For each sector, up to four types of water demand are represented. Types of water include

  • water withdrawals: water diverted or withdrawn from a surface water or groundwater source (Vickers 2001).[1]
  • 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).[1]
  • biophysical water consumption: total water required for crop evapo-transpiration; the sum of “blue” and “green” water in Mekonnen and Hoekstra 2011.[2]
  • seawater: water from the oceans, including brackish estuaries, that is withdrawn for cooling thermo-electric power plants, or used in primary energy production.

For more information, see Demand for Water.

Water Module Details

For more information on water in GCAM including on basin-to-region and basin-to-sector mappings and water markets, visit the detailed water page.

  1. 1.0 1.1 Vickers, A. 2001. Handbook of Water Use and Conservation. WaterPlow Press, Amherst, MA, USA.
  2. Mekonnen, M.M., and Hoekstra, A.Y. 2011. The green, blue and grey water footprint of crops and derived crop products. Hydrology and Earth System Sciences 15, pp 1577–1600.