Verifiable Water Use Inventory Using ICT …
19
of the pollution impact on water resources and represents the volume of freshwater
needed to dilute the pollution to maintain water quality above regulatory water quality
standards [29]. There is no scientific consensus at present on a suitable method for
quantifying dilution volumes for the assimilation of pollutants, so the estimation of
the graywater footprint is subjective [34]. In addition, the graywater footprint is an
indicator of environmental impact, so its analysis corresponds to the water footprint
impact assessment phase (iii), where the environmental impacts of graywater are
more appropriately addressed in other impact categories such as eutrophication or
toxicity [40]. In any case, it is not a real volume of water used during production,
rather the volume necessary to restore the quality of the water after it has been contaminated throughout the production process, and therefore should not be considered in
the inventory of water use [36].
Crop Water Footprint (WF C ) can then be obtained as the sum of the green and
blue components, and is normally expressed in m
3 /t or in l/kg (Eq. 13):
WF c = WF green + WF blue
(13)
The green component of a crop’s water footprint (WF green ) is calculated as the
green component of crop water use (CWU green , m
3 /ha) divided by the crop yield, (Y)
in t/ha:
WF green =
CWU green
Y
(14)
where CWU green is crop green water use, equivalent to the effective rainfall gathered
over the whole production period, which was calculated daily, ERn, according to
Eq. (9).
In water-scarce regions, greenhouse roofs are frequently used as rain catchment
surfaces. These roofs drain to farm rafts. If a water meter were installed in the
drainpipe in the reservoir, green water storage can be estimated and considered as
a fraction of the total amount of applied irrigation. Otherwise, in greenhouse crops,
CWU green will be considered null.
Unlike other works, the methodology proposed herein uses real-time information
recorded or calculated from on-site or remote sensors by ICTs (actual water content
in the soil, crop evapotranspiration and daily precipitation) as has been explained in
previous sections. For the whole crop season, CWU green is obtained by Eq. (15)
CWU green = 10 ·
lds
n=1
ER n
(15)
where 10 is the conversion factor of water depth (mm) into water volume per unit
surface (m
3 /ha), ER n is the daily calculation of effective precipitation, n = 1 is the
first day of the crop season and lds is the first day of the harvest. For permanent
19
of the pollution impact on water resources and represents the volume of freshwater
needed to dilute the pollution to maintain water quality above regulatory water quality
standards [29]. There is no scientific consensus at present on a suitable method for
quantifying dilution volumes for the assimilation of pollutants, so the estimation of
the graywater footprint is subjective [34]. In addition, the graywater footprint is an
indicator of environmental impact, so its analysis corresponds to the water footprint
impact assessment phase (iii), where the environmental impacts of graywater are
more appropriately addressed in other impact categories such as eutrophication or
toxicity [40]. In any case, it is not a real volume of water used during production,
rather the volume necessary to restore the quality of the water after it has been contaminated throughout the production process, and therefore should not be considered in
the inventory of water use [36].
Crop Water Footprint (WF C ) can then be obtained as the sum of the green and
blue components, and is normally expressed in m
3 /t or in l/kg (Eq. 13):
WF c = WF green + WF blue
(13)
The green component of a crop’s water footprint (WF green ) is calculated as the
green component of crop water use (CWU green , m
3 /ha) divided by the crop yield, (Y)
in t/ha:
WF green =
CWU green
Y
(14)
where CWU green is crop green water use, equivalent to the effective rainfall gathered
over the whole production period, which was calculated daily, ERn, according to
Eq. (9).
In water-scarce regions, greenhouse roofs are frequently used as rain catchment
surfaces. These roofs drain to farm rafts. If a water meter were installed in the
drainpipe in the reservoir, green water storage can be estimated and considered as
a fraction of the total amount of applied irrigation. Otherwise, in greenhouse crops,
CWU green will be considered null.
Unlike other works, the methodology proposed herein uses real-time information
recorded or calculated from on-site or remote sensors by ICTs (actual water content
in the soil, crop evapotranspiration and daily precipitation) as has been explained in
previous sections. For the whole crop season, CWU green is obtained by Eq. (15)
CWU green = 10 ·
lds
n=1
ER n
(15)
where 10 is the conversion factor of water depth (mm) into water volume per unit
surface (m
3 /ha), ER n is the daily calculation of effective precipitation, n = 1 is the
first day of the crop season and lds is the first day of the harvest. For permanent