Water - IFs
|Model Documentation - IFs|
|Institution||Frederick S. Pardee Center for International Futures, University of Denver https://pardee.du.edu/ (Pardee Center), Colorado, USA, .|
|Solution method||Dynamic recursive with annual time steps through 2100.|
IFs represents water demand as the sum of the demand of three sectors—municipal, industrial (differentiating energy-related from other industrial demand), and agriculture. The data from AQUASTAT differentiates between these three sectors and many other water models represent these same sectors. AQUASTAT refers to these data series as “water withdrawal.” IFs treats water withdrawal as equivalent to water demand.
Water supply is defined as the sum of five components: surface water withdrawal, renewable groundwater withdrawal, non-renewable (fossil) water withdrawal, desalinated water, and direct use of treated wastewater.
The size of a country’s urban population and water use per capita for the urban population drive municipal water demand. Water use per capita for the urban population is driven by GDP per capita (at purchasing power parity), the portion of the population with access to piped water, and the portion of the population that lives in urban areas. Non-renewable electricity generation capacity and the overall size of a country’s manufacturing sector drive industrial water demand. The area of land under irrigation drives agricultural water demand. The shadow price index impacts all three water demand sectors.
Surface and (renewable) groundwater withdrawals are driven by the shadow price index and constrained by their country-specific exploitable limits. Estimated stocks constrain fossil water withdrawals. The price index and an initial growth rate (which can be altered by user) drive change in desalinated water. Direct use of treated wastewater is driven by the price index and the volume of wastewater which is treated. Total water demand and total water supply are used to adjust the price index. The water price index then impacts each sector of demand and most sources of supply the following year. This algorithmic logic keeps water demand and water supply in approximate equilibrium over time, even though it does not require exact equality in any time step.
Water available for agriculture in this equilibrating process affects both the efficiency of water use and the extent of irrigated land. The latter affects yield in the agricultural model.