AppendixF

• Basin: Statewide
• Title: SWSI Phase 1 Report - Appendix F
• Date: 11/15/2004
• Author: CWCB
• SWSI - Doc Type: Final Report

3.) Model Equations:
The following calculations are performed at each timestep for the simulation duration.
For simplicity, example equations given here assume an annual timestep (but the same
calculations are performed for monthly timestep simulations).
Supply:
The first thing calculated in the model is the incoming available water for the given
timestep, both consumptive use water and total:
infZow_CU = basefZow_annual * basefZow_CU + ag CU * ag lands
+ nonAg transfer (3 -1)
&
infZow_tot = basefZow_annual + nonAg transfer + ag CU * ag lands /ag effic. (3-2)
Note that the consumptive use credits associated with a non-ag water acquisition are
assumed to be 100%.
The inflow CU credits are then mixed with the existing storage CU credits (for reservoir
option) to get the percent CU associated with the direct water supply source, according
to:
percentCU source = infZow_CU/ infZow_tot *(infZow_tot /(infZow_tot + res vol~rev))
+ res~revVol CU * (res vol~rev/(infZow_tot + resyol~rev)), (3-3)
where res vol~rev = the reservoir storage at the beginning of the timestep and
res~revVol_CU = the percent CU associated with this existing reservoir storage. The
calculation in Equation 3-3 is required for properly tracking the CU credits in the water
supply.
For the reach option, the equation is simply:
percentCU source = infZow_CU.
tlsage & Demand:
(3-4)
The next set of calculations in the model evaluate the impacts of conservation and reuse
on the M&I usage and demand. In this model, usage is considered the actual amount of
water used or applied during a given timestep, while demand is considered to be the net
external water requirement (i.e. how much water actually needs to be brought into the
system to meet that usage).
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