From Field to Bottle: Water Footprint Estimation …
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for C nat : the first assumes that the observed background water quality in the receiver
provides a reasonable estimate of C nat [48]; the second assumes C nat is equal to zero
[28]. The grey WF is overestimated by the first approach, and underestimated by the
second.
The proximity and known impacts of human activity on background water quality,
as well as the magnitude of background concentrations as they compare to C max ,
should be considered when selecting an appropriate value for C nat . In addition,
there may be spatial variations in the characteristics of a receiver that affect background concentrations (such as confluences with other water bodies or discharges of
other effluent streams) or maximum allowable concentrations (such as presence of
species at risk or drinking water intake zones). Therefore, careful evaluation of the
actual discharge location and site-specific characteristics of the receiver should be
incorporated into a grey WF assessment, as these factors can significantly affect the
magnitude of the calculated footprint [34, 60].
Finally, two approaches have been used to estimate the grey WF related to the
discharge of WWW effluents to the environment, with significant variability in the
magnitude of the calculated footprint associated with each. The first approach, which
results in a grey WF less than the volume of the effluent discharged, assumes that
the effluent meets all regulatory limits applicable to the receiver, or that the effluent
concentrations for all parameters are less than the corresponding value of C max [10,
21, 27]. The second approach recognizes that wastewater treatment facilities are
often designed to meet effluent target concentrates in higher than the receiver water
quality target concentrations (C max ), resulting in a grey WF that is larger than the
volume of effluent discharged despite treatment performance meeting or exceeding
treatment targets [26, 34, 48].
5.5 Considerations and Limitations
Selecting the overall scope of the assessment is the first critical step of the WF process.
Questions to consider include: Will the WF be developed for a single winery? Will the
impacts of only some of the process(es) be considered? Will a regional approach be
used that considers all wineries in a geographic area? Limiting the system boundary
to a single winery or a subset of the processes in use at a single winery can provide
better resolution and more accurate WF estimates. Conversely, a regional assessment
is better suited to quantify overall impacts of wine-making activities on local water
resources.
Once the facilities and/or processes have been selected, the system boundary can
then be defined. While factors affecting the direct WF should be included, the decision to include or exclude factors affecting the indirect WF must also be made. If
the purpose of the WF assessment is to reduce the ecological impacts of winery
operations on water resources, choosing to exclude the indirect WF associated with
the production of bottles, labels, glues, chemicals, etc., may be preferred since the
125
for C nat : the first assumes that the observed background water quality in the receiver
provides a reasonable estimate of C nat [48]; the second assumes C nat is equal to zero
[28]. The grey WF is overestimated by the first approach, and underestimated by the
second.
The proximity and known impacts of human activity on background water quality,
as well as the magnitude of background concentrations as they compare to C max ,
should be considered when selecting an appropriate value for C nat . In addition,
there may be spatial variations in the characteristics of a receiver that affect background concentrations (such as confluences with other water bodies or discharges of
other effluent streams) or maximum allowable concentrations (such as presence of
species at risk or drinking water intake zones). Therefore, careful evaluation of the
actual discharge location and site-specific characteristics of the receiver should be
incorporated into a grey WF assessment, as these factors can significantly affect the
magnitude of the calculated footprint [34, 60].
Finally, two approaches have been used to estimate the grey WF related to the
discharge of WWW effluents to the environment, with significant variability in the
magnitude of the calculated footprint associated with each. The first approach, which
results in a grey WF less than the volume of the effluent discharged, assumes that
the effluent meets all regulatory limits applicable to the receiver, or that the effluent
concentrations for all parameters are less than the corresponding value of C max [10,
21, 27]. The second approach recognizes that wastewater treatment facilities are
often designed to meet effluent target concentrates in higher than the receiver water
quality target concentrations (C max ), resulting in a grey WF that is larger than the
volume of effluent discharged despite treatment performance meeting or exceeding
treatment targets [26, 34, 48].
5.5 Considerations and Limitations
Selecting the overall scope of the assessment is the first critical step of the WF process.
Questions to consider include: Will the WF be developed for a single winery? Will the
impacts of only some of the process(es) be considered? Will a regional approach be
used that considers all wineries in a geographic area? Limiting the system boundary
to a single winery or a subset of the processes in use at a single winery can provide
better resolution and more accurate WF estimates. Conversely, a regional assessment
is better suited to quantify overall impacts of wine-making activities on local water
resources.
Once the facilities and/or processes have been selected, the system boundary can
then be defined. While factors affecting the direct WF should be included, the decision to include or exclude factors affecting the indirect WF must also be made. If
the purpose of the WF assessment is to reduce the ecological impacts of winery
operations on water resources, choosing to exclude the indirect WF associated with
the production of bottles, labels, glues, chemicals, etc., may be preferred since the