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A. Landscape Irrigation Audit
In the event the
fails to meet the percent
in a reporting year required in the approved
Harvesting Plan, Tucson Water may request that additional information or documentation be submitted to assist in determining the cause of the violation. A
visit and a landscape irrigation audit may be required to verify the
Harvesting Plan is being adhered to and all components are properly functioning.
B. Non-Compliance
determined to be in non-compliance may be required to submit monitoring reports monthly and may be required to provide Owner’s annual certification of continued maintenance and proper operation of
systems and the irrigation system and associated controls.
Designing
systems at a commercial
requires coordination between
developers,
engineers and landscape architects from the inception of the
design process. The information below is provided to inform
designers and engineers of the assumptions and methods the city recommends for use in designing and engineering water harvesting for a commercial
. This approach can be used both in preparation of the two components of the
Harvesting Plan: the
Water Budget and the Water Harvesting Implementation Plan.
Preparing a
Water Budget that meets the requirements of Commercial
Harvesting Ordinance and Technical Standard 4-01 requires projecting yearly plant water demand for the
landscape then determining how much harvested water supply is needed to meet at least 50% of this demand.
may choose to use
(earthworks),
(tanks), or a combination of both methods to accomplish this goal. Because most
will be able to accomplish the 50% goals with
alone, the
design calculations provided at the end of this exhibit focus on data for
sites. An example
Water Budget is shown in Table A-1. This example is provided to serve as a model for
undertaking
design. An excel spreadsheet of this water budget is available from <http://www.tucsonaz.gov/PDSD/What_s_New/what_s_new.html> for use by
designers in preparing their
Water Budget. This information in turn should be used to prepare the
Implementation Plan. Calculations
1.0 WATER DEMAND ASSUMPTIONS
Multiple techniques can be used to determine how much water is needed to support plants at a
. For purposes of complying with city requirements, the methods and assumptions described below are recommended.
1.1 Reference
To determine how much water plants need, a measurement of how much water plants consume through
is needed.
is the transfer of water from land surface to the atmosphere through the combination of evaporation and plant transpiration. In the Reference
Method (ETo Method), water use by plants is estimated for a high-water-use grass cover crop (such as alfalfa) for which
can be directly measured. Monthly Reference ETo values for a high-water-use grass crop in Tucson have been tabulated in Table A-2.
MONTHLY REFERENCE
(Inches) | |||||||||||
Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
3.0 | 3.72 | 6.0 | 8.04 | 9.96 | 10.56 | 9.36 | 7.92 | 7.20 | 5.76 | 3.60 | 2.64 |
Line | DESCRIPTIONS OF WATER BUDGET COMPONENT | SOURCES FOR EACH
(WHIAs) | EXAMPLE WHIA |
PLANT WATER DEMAND
|
Line | DESCRIPTIONS OF WATER BUDGET COMPONENT | SOURCES FOR EACH
(WHIAs) | EXAMPLE WHIA |
PLANT WATER DEMAND
| |||
1 | Individual WHIA identifier | APPLICANT PROVIDES | WHIA - 1 |
2 | Plant water demand category for this WHIA | APPLICANT PROVIDE USING ADWR PLANT LIST | low |
3 | (square feet) for this WHIA. Add the canopies of understory, midstory and overstory plant areas to get total canopy for each WHIA. Assume 60% of mature plant size | APPLICANT PROVIDE. CAN BE BASED ON LANDSCAPE PLAN OR PLANT LIST | 1250 |
4 | Plant water demand per year (vertical feet of water per year per square foot of canopy) for this WHIA | APPLICANT USES APPROPRIATE NUMBER BASED ON PLANT WATER DEMAND CATEGORY FOR THIS WHIA | 1.7 |
5 | CALCULATE: Annual plant water demand for this WHIA based on (gallons) | = line 3 times line 4 times 7.48 gallons/cubic foot of water | 15,895 |
6 | OVERALL SUPPLY | ||
7 | WHIA area (square feet) | APPLICANT PROVIDE | 1000 |
8 | WHIA average depth (feet) | APPLICANT PROVIDES | 0.5 |
9 | CALCULATE: WHIA capacity (gallons) | line 7 times line 8 times 7.48 gallons/cubic foot of water | 3,740 |
10 | If is used: | ||
11 | Subwatershed identifier | APPLICANT | S-1 |
12 | Ratio of subwatershed area to needed to meet plant water demand in this WHIA in July through March (use March plant water demand as the indicator month) (no units) | APPLICANT USES APPROPRIATE NUMBER BASED ON PLANT WATER DEMAND CATEGORY FOR EACH WHIA | 3.85 |
13 | CALCULATE: Total ideally needed to meet plant water demand in March (square feet) | = line 3 x line 12 | 4,813 |
14 | Actual total designed for this WHIA including the WHIA area itself (square feet) | APPLICANT PROVIDE | 1500 |
15 | CALCULATE: Actual for this WHIA | = line 14 divided by line 3 | 1.20 |
16 | CALCULATE: Actual percent of plant water demand that will be met for this WHIA | = 64% times line 15 divided by line 12 | 20% |
17 | If is used: | ||
18 | Tank identifier | APPLICANT PROVIDES | T-1 |
19 | above or below ground? | APPLICANT PROVIDES | above |
20 | tank height (feet) | APPLICANT PROVIDES | 8 |
21 | tank diameter (feet) | APPLICANT PROVIDES | 6 |
22 | tank capacity (gallons) | APPLICANT PROVIDES | 1619 |
23 | tank location | APPLICANT PROVIDES | East corner |
24 | CALCULATE: Percent of plant water demand for this WHIA met by this tank | (Assume tank will be filled and emptied 4 times per year). Total water provided = 4 times line 22 divided by line 5 | 41% |
25 | CALCULATE: Percent of plant water demand for this WHIA met using harvested from passive systems and active systems (as applicable) | = line 16 + line 24 | 61% |
26 | TOTAL INFORMATION | ||
27 | Percent to total annual landscape demand met using harvested water | Prorate percent of supply based on area of each WHIA | 61% |
28 | capacity offsetting retention basin size capacity | APPLICANT PROVIDES | |
1.2 Plant Coefficients
Four categories of plant types are typically used in Tucson. These categories are established based on their water use characteristics (Table A-3). Plant coefficients are an estimate of the water needed by each plant type expressed as a fraction of the water needed for the reference high-water-use grass crop. Plant types and corresponding plant coefficients are shown in Table A-3.
PLANT TYPE | PLANT COEFFICIENT |
Very low water use | 0.13 times monthly Reference ETo |
Low water use | 0.26 times monthly Reference ETo |
Moderate water use | 0.45 times monthly Reference ETo |
High water use | 0.65 times monthly Reference ETo |
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