o_19f3m1n7k170b14e9u0oqipgu4a.pdf

tuations, which can affect system reliability. However,
the general methodologies described in this section can
also be applied to other uses of reclaimed water and other
locations as long as the appropriate parameters are defined.
3.5.1 Identifying the Operating Parameters
In many cases, a water reuse system will provide reclaimed
water to a diverse customer base. Urban reuse
customers typically include golf courses and parks and
may also include commercial and industrial customers.
Such is the case in both the City of St. Petersburg,
Florida, and Irvine Ranch Water District, California, reuse
programs. These programs provide water for cooling,
washdown, and toilet flushing as well as for irrigation.
Each water use has a distinctive seasonal demand
pattern and, thereby, impacts the need for storage.
Reuse systems have significant differences with traditional
land application systems starting with the fundamental
objectives of each. Land application systems
seek to maximize hydraulic loadings while reuse systems
provide nonpotable waters for uses where a higher
quality of water is not required. Historical water use patterns
should be used where available. Methodologies
developed for land application systems are generally
poorly suited to define expected demands of an irrigation-based
reuse system and should be replaced with
methodologies expressly developed to estimate irrigation
needs. This point was illustrated well by calculations
of storage required to prevent a discharge based
on: (1) actual golf course irrigation use over a 5-year
period and (2) use of traditional land application water
balance methods using site-specific hydrogeological information
and temperature and rainfall corresponding to
the 5-year record of actual use. Use of historical records
estimated a required storage volume of 89 days of flow,
while traditional land application methods estimated a
required storage volume of 196 days (Ammerman et al.,
1997). It should also be noted that, like potable water,
the use of reclaimed water is subject to the customer’s
perceived need for water.
The primary factors controlling the need for supplemental
irrigation are evapotranspiration and rainfall. Evapotranspiration
is strongly influenced by temperature and
will be lowest in the winter months and highest in midsummer.
Water use for irrigation will also be strongly
affected by the end user and their attention to the need
for supplemental water. Where uses other than irrigation
are being investigated, other factors will be the driving
force for demand. For example, demand for reclaimed
water for industrial reuse will depend on the needs of the
specific industrial facility. These demands could be estimated
based on past water use records, if data are available,
or a review of the water use practices of a given
industry. When considering the demand for water in a
manmade wetland, the system must receive water at the
necessary time and rate to ensure that the appropriate
hydroperiod is simulated. If multiple uses of reclaimed
water are planned from a single source, the factors affecting
the demand of each should be identified and integrated
into a composite system demand.
Figure 3-12 presents the average monthly potential
evaporation and average monthly rainfall in southwest
Florida and Davis, California (Pettygrove and Asano,
Figure 3-12.
Average Monthly Rainfall and Pan Evaporation
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