16.14.070 Water-efficient landscape worksheet.
(A) The applicant shall complete the water efficient landscape worksheet which contains two sections:
(1) A hydrozone information table for the landscape project; and
(2) A water budget calculation for the landscape project. For the calculation of the maximum applied water allowance and estimated total water use, a project applicant shall use the ETo values from the table below:
| NAPA County | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual ETo |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Carneros | 0.8 | 1.5 | 3.1 | 4.6 | 5.5 | 6.6 | 6.9 | 6.2 | 4.7 | 3.5 | 1.4 | 1.0 | 45.8 |
* The values in this table were derived from:
1. California Irrigation Management Information System (CIMIS);
2. Reference Evapotranspiration Zones Map, University of California, Davis - Dept. of Land, Air & Water Resources and California Dept. of Water Resources 1999;
3. Reference Evapotranspiration for California, University of California, Davis - Department of Agriculture and Natural Resources (1987) Bulletin 1922;
4. Determining Daily Reference Evapotranspiration, Cooperative Extension University of California, Davis - Division of Agriculture and Natural Resources (1987), Publication Leaflet 21426.
(B) Water budget calculations shall adhere to the following requirements:
(1) The plant factor used shall be from WUCOLS. The plant factor ranges from 0 to 0.3 for low water use plants, from 0.4 to 0.6 for moderate water use plants, and from 0.7 to 1.0 for high water use plants.
(2) All water features shall be included in the high water use hydrozone and temporarily irrigated areas shall be included in the low water use hydrozone.
(3) All special landscape areas shall be identified and their water use calculated as described below.
(4) ETAF for special landscape areas shall not exceed 1.0.
(C) Maximum Applied Water Allowance. The maximum applied water allowance shall be calculated using the equation:
MAWA = (ETo) (0.62)[(0.7 x LA) + (0.3 x SLA)]
(D) Estimated Total Water Use. The estimated total water use shall be calculated using the equation below. The sum of the estimated total water use calculated for all hydrozones shall not exceed MAWA.
Where:
ETWU = Estimated Total Water Use per year (gallons)
ETo = Reference Evapotranspiration (inches)
PF = Plant Factor from WUCOLS (see Section 491)
HA = Hydrozone Area [high, medium, and low water use areas] (square feet)
SLA = Special Landscape Area (square feet)
0.62 = Conversion Factor
IE = Irrigation Efficiency (minimum 0.71)
(1) Example ETWU calculation: landscape area is fifty thousand square feet; plant water use type, plant factor, and hydrozone area are shown in the table below. The ETo value is 51.1 inches per year. There are no special landscape areas (recreational area, area permanently and solely dedicated to edible plants, and area irrigated with recycled water) in this example.
| Hydrozone | Plant Water Use Type(s) | Plant Factor (PF)* | Hydrozone Area (HA) (square feet) | PF x HA (square feet) |
|---|---|---|---|---|
| 1 | High | 0.8 | 7,000 | 5,600 |
| 2 | High | 0.7 | 10,000 | 7,000 |
| 3 | Medium | 0.5 | 16,000 | 8,000 |
| 4 | Low | 0.3 | 7,000 | 2,100 |
| 5 | Low | 0.2 | 10,000 | 2,000 |
| Sum | 24,700 |
* Plant Factor from WUCOLS
ETWU = (51.1)(0.62)(24,700/0.71 + 0)
= 1,102,116 gallons per year
Compare ETWU with MAWA: For this example MAWA = (51.1) (0.62) [(0.7 x 50,000) + (0.3 x 0)] = 1,108,870 gallons per year. The ETWU (1,102,116 gallons per year) is less than MAWA (1,108,870 gallons per year). In this example, the water budget complies with the MAWA.
(2) Example ETWU calculation: total landscape area is fifty thousand square feet, two thousand square feet of which is planted with edible plants. The edible plant area is considered a special landscape area (SLA). The reference evapotranspiration value is 51.1 inches per year. The plant type, plant factor, and hydrozone area are shown in the table below.
| Hydrozone | Plant Water Use Type(s) | Plant Factor (PF)* | Hydrozone Area (HA) (square feet) | PF x HA (square feet) |
|---|---|---|---|---|
| 1 | High | 0.8 | 7,000 | 5,600 |
| 2 | High | 0.7 | 9,000 | 6,300 |
| 3 | Medium | 0.5 | 15,000 | 7,500 |
| 4 | Low | 0.3 | 7,000 | 2,100 |
| 5 | Low | 0.2 | 10,000 | 2,000 |
| Sum | 23,500 | |||
| 6 | SLA | 1.0 | 2,000 | 2,000 |
* Plant Factor from WUCOLS
ETWU = (51.1)(0.62)(23,500/0.71 + 2,000)
= (31.68) (33,099 + 2,000)
= 1,111,936 gallons per year
Compare ETWU with MAWA. For this example:
MAWA = (51.1) (0.62) [(0.7 x 50,000) + (0.3 x 2,000)]
= 31.68 x [35,000 + 600]
= 31.68 x 35,600
=1,127,808 gallons per year
The ETWU (1,111,936 gallons per year) is less than MAWA (1,127,808 gallons per year). For this example, the water budget complies with the MAWA.