# Optimization and Linear Programing

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Objective
The objective of this exercise is to provide examples to estimate:
a) Current water use,
b) Future urban water demands,
c) Agriculture water demands,
d) Irrigation and urban water efficiency, and
e) Water savings.
This exercise will use the population estimation and the Water Use Per Capita (WUPC) knowledge
acquired in the previous exercise (Exercise 1). The concepts in this exercise are very simple, but
they are very illustrative of the complexities involved when estimating future water demand. This
exercise uses the same case of study, the city of Watsonville, now also including the irrigation area
denominated “Pajaro Valley” (Figure 1).
Figure 1 – Watsonville City and Pajaro Valley
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Urban Water Demand
Urban water use has been divided into two sections, indoor and outdoor water use. Within indoor
water use there is current water use and projected urban water demand. Open the file
Ex_2_Data.xls. In this section we will work on the blue tabs, which are related to urban water
demand. Go to the “Population” tab. Notice that in column D (D17:D25) the population for
Watsonville is already calculated from Exercise 1 (Figure 2)
Figure 2.- Population Tab
Now, let’s move to the “Urban Water Demand” tab. This is the same tab seen in the previous
exercise called “Water Use Per capita” (Figure 3). Just a reminder, in 2010 the Water Use Per
Capita in Watsonville was 120 gpd/person (gallons per day per person), and we will assume that
2012 has the same water use per capita. We will come back later for this number to verify some
of our calculations.
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Figure 3.- Urban Water Demand Tab
Indoor Water Use
Baseline Scenario
Let’s estimate the indoor water use1 for the Baseline scenario, which represents the current water
use in Watsonville. Indoor water use includes the following uses:
1) Laundry – water used to clean clothes, fabrics and related
2) Dishwashers – water used to wash dishes
3) Faucets – water used in faucets, from washing hands to washing dishes
4) Shower – water used to take a shower
5) Toilet
1
Cahill, R.J. (2011). Household Water Use and Conservation Models using Monte Carlo techniques for the East Bay
Municipal Utilities District. Master Thesis. University of California, Davis. p. 31-32
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For laundry water use, Figure 4 shows the water consumption for different types of laundry
machines (vertical and horizontal axis) and models. For the Baseline scenario we are going to
consider a traditional vertical axis machine, 16.1 gpd/person.
Figure 4
For dishwasher use, Figure 5 shows the water consumption for different types of dishwashers (high
efficiency, average dishwasher and hand washing). For the Baseline scenario we are going to
consider an average dishwasher, 4.7 gpd/person.
Figure 5
So, let’s start calculating the indoor water use in Watsonville. Define the Standard consumption
for Laundry as 16.1 gpd/person and the daily use as 1 per day (Figure 6). The Indoor water use for
the laundry concept is 16.1 gpd/person (Column B * Column D) (Figure 7).
Figure 6
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Figure 7
Similarly, define that the Standard consumption for a Dishwasher is 4.7 gpd/person and that the
daily use is 1 per day (Figure 8). The Indoor water use for the dishwasher concept is 4.7 gpd/person
(cell B10 times cell D10) (Figure 9).
Figure 8
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Figure 9
Now, for the faucets (water consumption used to brush your teeth, wash your hands and face, and
rinse the dishes), let’s define the standard flow rate of the faucet as 2.2 gallons per minute (gpm)
and that on average the faucet is open for 6 minutes per day (Figure 10). The indoor water use for
faucets is 13.2 gpd/person (cell B11 times cell D11) (Figure 11).
Figure 10
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Figure 11
For the shower water consumption, define the standard flow rate of the shower as 2.5 gallons per
minute (gpm) and the average shower length is 10 minutes per day (Figure 12). The indoor water
use for faucets is 25 gpd/person (cell B12 times cell D12) (Figure 13).
Figure 12
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Figure 13
Finally, for the toilet water consumption define the gallons per flush for the standard toilet
considered as 2.2 gallons per flush (gpf) and that the average flushes per day are 4 (Figure 14).
The indoor water use for toilets 8.8 gpd/person (cell B13 times cell D13) (Figure 15).
Figure 14
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Figure 15
Let’s estimate the indoor daily water user per person by summing all the indoor water use (Figure
16), which is 67.8 gpd/person
Figure 16
Finally let’s estimate the percentage that each of the concepts represents for the indoor water use
(Figure 17). Notice that shower consumes about one third of the indoor water use (~37%), laundry
a quarter of the use, dishwashers and faucets combined use another quarter (7%+19%=26% ~
25%) and toilets use about one eighth of the indoor water use (~13%).
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Figure 17
To be turned in: a) a table of the indoor water use, b) Did you have an idea of your indoor water
use before this exercise? Do you think this value is too high? Too low? How does it compare with
other sources?

c) Can you compare it to indoor water uses in other countries?

Scenario I –Indoor Conservation
Now, let’s propose that we start conserving water by:
a) Implementing some incentives, such as rebates and component replacements (toilets,
shower nozzles and faucets)
b) Educations campaigns
c) Enforcing new house builders to include water conservation components in their new home
designs
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Let’s preserve the daily use quantities and propose the following modifications to the standard
consumptions (Figure 18):
● Laundry: People are encouraged to switch from vertical axis traditional washers (16.1
gpd/day) to typical horizontal axis washer (6.4 gpd/day),
● Dishwashers: People are encouraged to get rid of average dishwashers (4.7 gpd/day) and
start buying high efficiency dishwashers (2.6 gpd/day),
● Faucets: Faucet nozzles are switched from 2.2 gpm nozzles to 1.8 gpm nozzles
● Showers: Showerheads are swtiched from 2.5 gpm nozzles to 2.0 gpm nozzles.
● Toilets: Toilets are switched from 2.2 gpf to 1.8 gpf.
Figure 18
Similarly, that in the previous section, let’s estimate the indoor water use of each category by
multiplying the Standard consumption and the daily use (Figure 19). Let’s calculate the total indoor
water use which is 47 gpd/person (Figure 20) and the percentage that each category represents
(Figure 21).
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Figure 19
Figure 20
Figure 21
Finally, let’s create a summary table for the calculations we have done (Figure 22), with the current
(Baseline scenario) for indoor water use as 67.8 gpd/person and a conservation scenario (Scenario
1) for expected water use as 47 gpd/person.
Figure 22
To be turned in: a) the summary table comparing the baseline and scenario I, b) What is the
reduction in indoor water use (in volume and percentage) of moving from the baseline
consumption to the Scenario I consumption? c) There is a lot of discussion about water
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conservation and water use efficiency; this discussion is centered in the concept of consumptive
use of water. Consumptive water use is the water effectively used or consumed for a particular
purpose. Water conservation refers to reducing the consumptive water use, or in other words,
because the need for water is reduced (consumptive use is reduced), water is saved (conserved).
Water efficiency refers to reduce the losses of water in its use. This means that the consumptive
use is the same but, because inefficiencies are fixed (leakages, better irrigation methods, reduction
in evaporation losses, etc.), less water is used. Question: Can Scenario I be catalogued as a water
conservation or water efficiency policy?
Outdoor Water Use
Evapotranspiration and Water Consumption of Crops and Plants
In this section we will analyze the outdoor water use; using the approach of WUCOLS (2000)2
which depends on different factors:
● Geographical location: The mean reference evapotranspiration (ET0) will be used to
account for this.
● Mean landscaping area
● The type of landscaping: A crop coefficient factor (Kc) will be used to estimate the water
consumption for different types of landscaping
● Irrigation efficiency: This factor considers how much of the applied water is beneficial to
the plant
The usual way to estimate the water needs of a plant, crop or, in this case, landscape area
(ETLandscape), is by estimating the Evapotranspiration of that area (ETLandscape, or Evapotranspiration
2 Water Use Classifications of Landscapes Species (WUCOLS) 2000. “A guide to Estimating Irrigation Water Needs
of Landscape Planting in California” University of California Cooperative Extension, Agriculture and Natural
Resources.
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of the Landscape) (Equation 1). Every crop needs a different amount of water, so here is how
ETLandscape is estimated. First, you need to know the Reference Evapotranspiration (ET0) of the
region. ET0 is the evapotranspiration of a cool-season grass that is used as a reference value. This
value varies depending on the geographic conditions (latitude, longitude, altitude), and climate
conditions (wind speed, relative humidity/vapor pressure, air temperature solar radiation), so this
value accounts for the geographic position of our study. The crop coefficient (Kc) is a scaling
factor, which is used if the crop in question has a water consumption larger than the reference
evapotranspiration (Kc>1) or smaller than the reference crop (Kc<1). ET0 and ETL are expressed
in units of length (usually inches, feet or centimeters), so, if a Landscape has a evapotranspiration
(ETLandscape) of 36 inches, it means that this crop needs a water depth of 36 inches for every square
foot of crop during the whole crop season to be successfully produced.
𝐸𝐸𝑇𝑇𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 = 𝐸𝐸𝑇𝑇0 ∗ 𝐾𝐾𝑐𝑐 
With equation 1, we just have the height of water needed. The volume is obtained by multiplying
the height of water needed by the area covered by the crop (Equation 2), which gives us the volume
of water that the crop needs and not a drop more!
𝑊𝑊𝑊𝑊𝑊𝑊𝑊𝑊𝑊𝑊𝐸𝐸𝐸𝐸 = 𝐸𝐸𝑇𝑇𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 ∗ 𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴 ∗ 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 
In reality, not all the water that is provided to the plant is used in the evapotranspiration process.
Some of it is lost into the ground or to the atmosphere due to evaporation. This depends on a lot
of things (irrigation method such as drip irrigation, sprinklers, drip irrigation; human behavior such
as leaving the irrigation system turned on).The point is, the applied water depends on the irrigation
efficiency as shown in equation 3:
𝐴𝐴𝑊𝑊𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿𝐿 = 𝑊𝑊𝑊𝑊𝑊𝑊𝑊𝑊𝑊𝑊𝐸𝐸𝐸𝐸
𝐼𝐼𝐼𝐼𝐼𝐼.𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸𝐸 
Baseline Scenario
Let’s apply the previous equations to our case of study, the outdoor water use in the city of
Watsonville. Let’s start with the equation for the evapotranspiration of the landscape (ETLandscape)
(Eq. 1). There is Reference Evapotranspiration (ET0) data already available for the whole state of
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California (http://www.cimis.water.ca.gov/). Figure 23 shows the ET0 values for the climate
station of Watsonville (Station 95). The annual average reference evapotranspiration (ET0) is 38.67
inches, which we will approximate as 39 inches for practical purposes. Then the plant factor for
the landscape (crop coefficients Kc) is obtained from a specialized publication for landscape water
irrigation needs3
. The grass that we are selecting is a cool season turfgrass (regular grass) that has
a Kc value of 0.8. With these values we can estimate the landscape evapotranspiration using
Equation 1 (ETLanscape=ET0*Kc), which is 31.2 inches/year, as shown in figure 24.
Figure 23 – ET0 values for the Station of Watsonville (95)
3 Water Use Classifications of Landscapes Species (WUCOLS) 2000. “A guide to Estimating Irrigation Water Needs
of Landscape Planting in California” University of California Cooperative Extension, Agriculture and Natural
Resources.
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Figure 24 – Evapotranspiration of the Landscape (ETLandscape), Baseline Scenario
To estimate the Landscape’s water requirements, we will use Equation 2
(WaterET=ETLandscape*Area*Conversion factors). The average yard area in Watsonville is around
3,000 square feet, and the conversion factor to obtain gallons per year is 0.62. The Landscape’s
water requirement (WaterET) is 58,032 gallons/year (Figure 25).
Figure 25 – Landscape’s Water Requirements (WaterET), Baseline Scenario
Then we can obtain the Applied Water by using equation 3 (AWLandscape=WaterET/Irr.Efficiency),
the irrigation efficiency is estimated to be 0.75 (sprinklers). The applied water is 77,376
gallons/year (Figure 26), which represents 212 gallons/day (figure 27).
Figure 26 – Applied Water (AWLandscape), Baseline Scenario
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Figure 27
If we consider that the numbers of persons living on a house is 4 persons per house, the Outdoor
water use per capita is 53.0 gpd/person (Figure 28).
Figure 28 – Per Capita Landscape’s Water Requirements, Baseline Scenario
Scenario I –Outdoor Conservation
Now, let’s propose that we start conserving water outdoors by implementing some financial
incentives (paying people to change their lawn) to change the type of landscape from a highly
water consumptive (regular grass) to a less consumptive type of grass (native grass).
Let’s preserve the rest of the parameters (quantities) and just modify the crop coefficients (Kc)
from 0.8 (regular grass) to 0.4 (native grass). The landscape evapotranspiration (Eq. 1) is 15.6
inches/year (Figure 29). The landscape’s water requirement (Eq. 2) is 29,016 gallons/year (Figure
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30). The applied water (Eq. 3) is 38,688 gallons/year (Figure 31) or 106 gallons/day (Figure 32).
The Outdoor water use per capita for Scenario I is 26.5 gpd/person (Figure 33).
Figure 29. Evapotranspiration of the Landscape (ETLandscape), Scenario I
Figure 30 – Landscape’s Water Requirements (WaterET), Scenario I
Figure 31 – Applied Water (AWLandscape), Scenario I
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Figure 32
Figure 33 – Per Capita Landscape’s Water Requirements, Scenario I
Finally, let’s create a summary table of the Outdoor water use calculations that we’ve done (Figure
34), with the current (Baseline scenario) indoor water use of 53.0 gpd/person and the conservation
scenario (Scenaio 1) of 26.5 gpd/person.
Figure 34 – Summary Table Outdoors Water Use, Baseline and Scenario I
To be turned in: a) the summary table of the outdoor water uses (such as Fig 34), b) What is the
reduction in outdoor water use (in volume and percentage) of moving from the baseline
consumption to the Scenario I consumption? c) Similar to the indoor analysis, can Scenario I be
catalogued as a water conservation or water efficiency policy? (See the discussion of water
conservation and efficiency on page 13) and d) If we DID NOT change the plant factor “Kc” (from
0.8 to 0.4) and we proposed to improve the irrigation efficiency by changing the irrigation method
from sprinklers (0.75 efficiency) to drip irrigation (0.95 efficiency), would this new Scenario II be
catalogued as a water conservation or water efficiency policy? Did the Evapotranspiration of the
Landscape (ETLandscape) change or the Landscape’s Water Requirements (WaterET) change compared
to the Baseline Scenario?
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Future Urban Water Demand
Move to the “Projected Water Demand” tab. Create a summary table for the Baseline and Scenario
I (Figure 35) by copying the values of water use per capita (WUPC) for the indoor and outdoor
categories. Sum both categories for each scenario. For the Baseline scenario, the WUPC is 120.8
gpd/person, and for the Scenario I (Water Conservation) it is 73.5 gpd/person (Figure 36). Scenario
1 reduces the WUPC by 47.3 gpd/person, which is 40% of the baseline scenario!!!
Figure 35
Figure 36
Estimate the share of indoor and outdoor water use for each scenario (Figure 37). Notice that in
the baseline scenario the outdoor water use (44%) is about half of the WUPC, this means that half
of the water is not directly used by the person, it is used to “keep the lawn green.” From the
Baseline to Scenario I, outdoor water use is reduced by half (from 53 gpd/person in the Baseline
Scenario to 26.5 gpd/person in the Scenario I) to about a third (36%) of the WUPC.
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Figure 37
To be turned in: a) How much water could be saved indoors (Baseline minus Scenario I)? b) How
much water could be saved outdoors (Baseline minus Scenario I)? c) Where can more water be
saved, indoors or outdoors? d) Before this class, did you realize about the large consumption of
water outdoors compared with indoors? e) Have you noticed that the WUPC for the Baseline
Scenario (120.8 gpd/person) is very similar to the results obtained in Exercise 1 (120 gpd/person)!?
This is not a coincidence; data was selected carefully to represent the urban water demand in
Watsonville. How do these two calculations support each other? Do you think having these two
calculations makes a stronger argument about their validity and help support one another?
There are three columns to estimate the future water use for the Baseline Scenario (light orange
color, Figure 38). The first column (Column C) is the water use per capita (WUPC), the second
and third (Column D and E) are the water demand in gallons per year and acre-feet per year,
respectively. The water demand will be calculated until 2030.
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Figure 38
First, let’s estimate the water demand in gallons, which can be obtained by multiplying the
population by the WUPC times 365 days/yr (Figure 39). We had to multiply by 365 days/yr
because the WUPC is in gallons per day per person (gpd/person). Copy the same formula for the
rest of column C (Figure 40).
Figure 39
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Figure 40
Let’s convert this demand from gallons per year to acre-feet per year, which is the standard unit
for mid-sized water management. Divide the water demand in gallons per year by 325851 gallons
per acre-foot (Figure 41). Apply the same formula for the rest of column E (Figure 42).
Figure 41
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Figure 42
Notice how the chart on the right, it shows the estimated future water demand: If the current
conditions are preserved until 2030 (Baseline scenario), the urban water demand will increase from
~7,200 AF/year in 2012 to ~9,500 AF/year in 2030, and the city of Watsonville will need 2,300
AF/year more of water which is 32% of the current demand!!! Wwwooww!!!
Now, let’s do a similar procedure to estimate the future water demand for Scenario I (light blue
cell color). In Scenario I, we will consider that every year 5% of the population will move from
the Baseline scenario WUPC (120.8 gpd/person) to a more conservative Scenario I WUPC (73.5
gpd/person). This is represented in columns F and G where it shows the percentage of the
population that is still consuming the WUPC of the Baseline scenario (Column F) and Scenario I
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(Column G). In reality, even though as a planner we plan for a smaller water demand, this does
not happen in a blink of an eye. A policy needs time to start working, to develop. This method of
planning also allows us to define goals for the future; e.g. “for 2020, 40% of the population in
Watsonville should be using 73.5 gpd/person or less” or “for 2030, 90% of the population in
Watsonville should be using 73.5 gpd/person or less.” In this way, not only we are proposing
policies, but we are also defining thresholds to be used for monitoring the advancement of the
policy.
To calculate a global WUPC in Watsonville (column H), we will multiply the percentage that is
still using the Baseline WUPC times the Baseline WUPC plus the percentage using Scenario I
WUPC times the Scenario I WUPC (Figure 43), e.g. for 2013 this will be 95%*120.8+5%*73.5
(=F39*\$C\$10+G39*\$E\$10). The dollar signs fix the WUPC cells (keep them in place) (C10 and
E10) when copying the formula. We can calculate this global WUPC for the rest of the years
(Figure 44). Notice that, as Scenario I gains popularity, the global WUPC becomes more similar
to Scenario I’s WUPC (73.5 gpd/person).
Figure 43
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Figure 44
Now let’s do the same procedure as in the previous scenario to calculate the water demand in
gallons per year by multiplying the population (column B) times the global WUPC (Column H)
times 365 days (Figure 45). Copy the same formula for the rest of column I (Figure 46).
Figure 45
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Figure 46
To estimate the water demand in acre-feet/year, it is necessary to divide the water demand in
gallons/year by 325,851 (Figure 47). Repeat this calculation for the rest of column J (Figure 48).
Figure 48
Figure 49
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Notice that once again the chart on the right has been modified (Figure 50). While using the
Baseline scenario increases water demand, in Scenario I, when the water conservation is gaining
popularity, the water demand starts decreasing. In fact, by conserving water it is possible to go
back to 1990s water demand in 2030!!!
Figure 50
To be turned in: a) Figure 50 (chart) with both water demands: Baseline and Scenario I, b) In
which year will the water demand start to go down? 2014? 2015? 2016?
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Agriculture Water Demand
Most of the water is used for agriculture, you’ll see. In addition, agricultural water is a hot-hotvery hot topic in California. People are using water for agriculture, but farmers will rarely say how
much water they are using, or let the authorities put in meters to learn how much water they’ve
been using. This does not mean that farmers are wasting water (remember “everyone is innocent
until proven guilty”). In fact, recent trends show that they have been doing better than a decade
ago. What this means is that the job of being a planner is tough but more interesting. Please go to
the Ag Water Demand Tab (Green Tab) and let’s start with the big picture (Figure 51). According
to our calculations for the Baseline scenario, the City of Watsonville is currently using ~7,209
AF/year (~13%), the rural domestic demand is using 2,508 AF/year (4.5%) and the agriculture and
industrial are using 46,370 AF/Year. Around 82.5% of the water in this region is being used for
Agriculture related purposes!!!!
Figure 51.- Water Uses and Water Demands in Pajaro Valley
Figure 52 and 53 shows the distribution of crops grown in this region; the main crops are
strawberries, vegetable row crops (several types of lettuce, celery, zucchini) and
Raspberries/Blackberries. These three categories add up to 70% of the irrigated area. In fact, a lot
of these commodities in the grocery store come from this area. If we add the 10% of acreage that
is fallowed (nothing is grown here), well, pretty soon we are accounting for 80% of the total
irrigated area in this region, so now we can identify which crops are the big players in this region.
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Figure 52.- Crops Acreage
Figure 53 Crop distribution
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The first step is to calculate the water use for these crops. It is important to clarify that the acreages
that are reported in column 1 are the property acreages and not the production acreages. In other
words, the values in column 1 are the acreage of the properties, but the production area, which is
where the water is applied, is about 80% of the property acreages; take a look at the calculation
shown in Figure 54.
Figure 54
The .8 Acreage Factor has been applied to all the crops (column 4) except to the Nurseries category
which in this case is 0.13 (13%) of the property acreage (Figure 55).
Figure 55
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How much water is used per acre (Column 5)? Uffff!! This is the million-dollar question!!! The
values in column 5 were derived by analyzing the well production and the land use data. The idea
was to match a production well with a specific property that grows a specific commodity. For
instance, Figure 56 shows the case of using 35AF of water over 11.2 acres of production area, in
which case the water use per acre was 3.1 AF/acre (= 35AF / 11.2 acres)
Figure 56
Several properties (polygons) were analyzed and evaluated. Figure 57 shows the distribution of
the water use per acre for each crop- tons of good data!!!. What figure 57 says is that the value that
we are using in column 5 is the average water use per acre for each crop. Notice that in each crop
the water use per acre varied. For instance, for vegetables “veggies” (mostly lettuce), there were
farmers that used 1.65 AF/acre; 50% of the growers used between 2.19 and 3.08 AF/acre, the
average use was 2.67 AF/acre, and some growers used 4.13 AF/acre- as you can see, they were all
over the place!!!!
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Figure 57 Distribution of water use for different crops
As you can see, there was a lot of work done to determine the values that you will use in column
5 (Figure 58), which represent the average (actually the weighted average) water use for each crop.
If you remember the main crops are strawberries, vegetables and raspberries/blackberries, so, more
attention was paid to those crops.
Figure 58
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The applied water for each crop (column 6) was estimated by multiplying the Acres (column 2)
times the acreage factor (column 4) times the water use per acre (column 5). The formula is written
in the header of column 6 Figure 59.
Figure 59
Copying this formula for each crop in Column 6 will help us calculate the agriculture water use
for each crop in Pajaro valley (Figure 60). The total agriculture water use is 46,370 AF/year (Figure
61) and the water use for strawberries, vegetables and raspberries/blackberries is 83% of the total
agriculture water use [0.83=(15,441+15,442+7,796)/46,730]!!!!!
Figure 60
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Figure 61
Column 7 shows the prospective water savings that can be achieved if all the water used in Pajaro
Valley were 100% efficient, or in other words, if every drop applied in the basin were used by the
crops. These numbers were obtained by a statistic analysis of how water is used by each crop. The
Irrigation Efficiency expresses how efficiently water is used in the valley, which is “1 – percentage
of water not used efficiently = 1 – Water Savings/Water Applied = 1 – (column 7 / column 6)”, as
shown in Figure 62. Water use efficiency can also be estimated as follows: Crop
Evapotranspiration / Water Applied
Figure 62
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The irrigation efficiency can be estimated for every crop that has a water savings estimate, which
excludes vines/grapes, artichokes and other, as shown in Figure 63. If we apply the same formula
for the whole system, we will find out that the efficiency for the agriculture water use is 89% as
shown in Figure 63 and 64. Notice that the total water use is 46,370 AF/year and the total water
savings are 5,095 AF/year. Thus, a rough estimation of the evapotranspiration of the crops is
41,275 AF/year (46,370 AF/year – 5095 AF-year).
Figure 63
Figure 64
Now, let’s estimate a future water demand for agriculture water use. In the baseline scenario, let’s
consider that on average, the same amount of water will be used, around 46,370 AF/year (Figure
65), so let’s repeat that value until 2030 in column C.
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Figure 65
Now, for the “Scenario I Ag. Water Demand Reduction”, we are going to consider that on average
every year there will be a 5% increase in water savings in the system, so the water demand is going
to be: 46370 – %Savings * 5095, as shown in Figure 66. Remember, 5095 AF/yr is the total water
savings. These water savings will come from implementing irrigation methods that reduce the loss
of water through drip irrigation, on-farm soil moisture monitoring system, etc.
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Figure 66
Applying the same formula for the whole column E, we have the projected water demand for
Scenario I that considers that each year, 5% of the total water saving will be achieved. (Figure 67).
Figure 67
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Figure 68 shows the chart of both water demand scenarios, Baseline and Scenario I. As can be
seen, achieving water savings can reduce the future water demand for Pajaro Valley.
Figure 68
To be Turned in: a) A figure of the future water demand as shown in figure 68, b) given the
discussion of the indoor scenario about water efficiency and water conservation, is “Scenario I Ag.
Water Demand Reduction” a water conservation or a water efficiency policy? In this case the
Consumptive use is the Evapotranspiration (41,275 AF/year). Water conservation refers to
reducing the consumptive water use (Evapotranspiration), or in other words, because the need for
water is reduced (consumptive use is reduced) water is saved (conserved). Water efficiency refers
to reducing the losses of water in its use, which means that the consumptive use is the same but
because inefficiencies are fixed (leakages, better irrigation methods, reduction in evaporation
losses, and so on) less water is used. Question: Can Scenario I be catalogued as a water
conservation or water efficiency policy?
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Pajaro Valley Projected Water Demand
Let’s integrate the calculation of urban and agriculture water demands. Let’s move to the tab
“Water Demand Pajaro Valley” (purple tab). There are two set of columns, one for the Baseline
Scenario (orange) and one for Scenario I (light blue) as shown in figure 69.
Figure 69
Actually, we have almost all the data available for every column. Rows 7 and 8 show where the
Column 1 “Municipal” has already been calculated in the “Projected Urban Water Demand” tab
in Column “E”, as it indicates in rows 7 and 8. Let’s get that information by linking cell “C10” in
the current worksheet with cell “E16” in the “Projected Urban Water Demand” worksheet (as
shown in Figure 70). Then let’s copy that same formula for the whole column (Figure 71)
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Figure 70
Figure 71
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Now for Column 2, the baseline calculation for “Rural,” we will consider that the Rural Water
Demand is 35% of the Municipal water demand. That is, multiply Column 1 by a factor of 0.35,
as shown in Figure 72. Figure 73 show the water demand estimation until 2030 for the Rural sector.
Figure 72
Figure 73
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For Column 3, the baseline calculation for “Agriculture,” we need to link with the data from the
worksheet “Ag Water Demand” Column “C”. For instance, for year 1990 (Cell “E10”) we need to
recall the data from the worksheet “Ag Water Demand” cell “C34”, as shown in Figure 74. Figure
75 shows the calculation until 2030.
Figure 74
Figure 75
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Finally, Column 4 “Total” is the sum of Municipal (column 1), Rural (column 2) and Agriculture
(column 3) as shown in Figure 76. Copy that formula for the whole column. Figure 77 shows the
calculation of the Total baseline water demand until 2030!
Figure 76
Figure 77
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Now let’s do the same for Scenario I. First, let’s recall the water demand already calculated for the
“Municipal” sector in column 5 of Scenario I from column J of the worksheet “Projected Urban
Water Demand,” as shown in figure 78. Let’s copy that formula for the whole column 5 to bring
the water demand for the Municipal sector of Scenario 1, as shown in Figure 79.
Figure 78
Figure 79
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Similarly, we will consider that the “Rural” water demand represents 35% of the “Municipal”
water demand as shown in Figure 80. Copy the same formula for all of column 6 of “Rural” water
demand, as shown in figure 81.
Figure 80
Figure 81
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Data for the “Agriculture” sector, column 7, has to be recalled from the worksheet “Ag Water
Demand” column E, as shown in figure 82. Let’s copy that formula for the whole column 7 to
bring the water demand for the Agriculture sector of Scenario I, as shown in Figure 83.
Figure 82
Figure 83
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Finally, column 8 “Total” is the sum of Municipal (column 5), Rural (column 6) and Agriculture
(column 7) as shown in Figure 84. Copy the formula for the whole column. Figure 85 shows the
calculation of the Total Scenario I water demand until 2030!
Figure 84
Figure 85
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Let’s take a look at the chart with the water demand under the Baseline scenario and Scenario I
(Figure 86). As can be seen, some of the water efficiency measures proposed in Scenario I can
help save a significant amount of water. The water demand for 2030 for the Baseline and Scenario
I are 59,253 AF/year and 50,128 AF/year, respectively. Even though there was an increase in
population and the value for consumptive water use (evapotranspiration) was conserved, Scenario
I shows that improving the efficiency of the system can help to save water today and in the future.
This type of analysis also helps to define targets to evaluate during the future implementation of
Scenario I.
Figure 86 – Comparison of Water Demands, Baseline Vs. Scenario I
To be turned in: a) A chart similar to Figure 86, b) Is it possible to keep reducing the water demand
in the future? If so, which kind of policies will you apply? Water conservation? Recycling water?
Water harvesting?

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