AppendixF

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

Indoor and outdoor usage values are calculated using the percent indoor and percent
outdoor uses (percent outdoor is calculated as 100% - percent indoor). Changes in annual
usage due to climate changes are calculated as:
total outuse_annual = total outuse_annual * (climate_adjustYR)
(3-5)
where "YR" is the year number since the start of the simulation (starting with yr = 1).
Conservation impacts, which are considered reductions in usage, are calculated with the
following:
total inuse_annual = total inuse_annual *(1 - conservln_reduct annual) (3-6)
&
total outuse_annual = total outuse_annual *(1 - conservOut reduct annual) (3-7)
Similar to the CU tracking performed on the source water, consumptive use requirements
for the demands must also be calculated. This equation, which calculates the net
consumptive use percentage in the demand, is written as:
percentCU annual = percentCU annual in *(total inuse_annual / total use_annual) +
percentCU annual out *
(total outuse_annual / total use_annual). (3-8)
Reuse is a demand management scheme that effectively reduces the external water
demand of a user (or group of users) for a given total usage. The governing equation is:
demand = total use_annual - reuse
(3 -9)
where all terms can be expressed as acre-feet (AF) of water, and reuse is the total amount
of water that gets reused.
For exchange reuse schemes, the model assumes reuse is carried out to extinction (or at
least close to extinction). In other words it gets reused multiple times, with
losses/consumption at each application, until it is essentially completely consumed. These
additional iterations of reuse (beyond the lst reuse) are simulated with a calculated reuse
multiplier. In other words, the reuse multipliers are used in calculating the amount of
additional reuse water that can be derived in a reuse program after the lst time reuse (i.e.
the return flows from the reuse applications are iteratively captured and reused multiple
times). This parameter is calculated as a function of the user-input return flow associated
with exchange reuse, according to:
reuse _ multiplier _ exch = ~ ~~eturnFlow _ exch)'
,_, returnFlow exch
(3-10)
Note that Equation 3-10 assumes that the incrementally smaller return flows can
realistically be exchanged ten times, thus we use 10 terms in the series (rather than the
7