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Westlands Water District | ||||||||||||||||||||||
| Water for Crop Year from this Water Year, March 1 - February 28 | ||||||||||||||||||||||
| Water Applied from Previous Water Year, 10/1 - 2/28 |
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This farm water budget spreadsheet page is intended to
assist the water user in planning his cropping, within the bounds of the available
water supply. A tentative cropping plan is entered into yellow shaded
columns of the top portion of this page. A total water requirement is
calculated in the bottom line of this section. Since it is not uncommon
for the crop year to extend over two water years, the bottom portion of
this page allows for the incorporation of water applied in the previous year
to be integrated with the upcoming water year to supply the water needs
of your crop. Specific details for each of the columns on this page are
presented below. Click on the column heading to see the descriptive details.
Typical evapotranspiration (ET), effective precipitation (EP),
germination(Germ), salinity control (Leach), other, and irrigation
efficiency(IE) values are supplied as a starting point in tables
below.
Top of
Page
This web page can be used as a standalone worksheet. You do not need to be connected to the internet to use this page. Save this page by using the "File|Save As" menu item onto the desktop or into another directory. Later you can double click on it and the browser will be automatically loaded to view it and the page will have the same recalculation features. Changes can be made to the data entered and the spreadsheet can be recalculated by clicking on one of the two "Compute" buttons on the page.
The general concept for using this spreadsheet is to first deal with the amount of water that must be in or put into the soil profile for use by the crop (CWR) or other beneficial uses, not the amount of irrigation water that must be applied to put that amount of water into the soil. Once the amount water needed in the soil is known, the amount of applied water required can be calculated using an irrigation efficiency value (FWR). The total amount of irrigation water required is calculated by multiplying the FWR for each crop by the number of acres to be grown (FDR). It is assumed that the Farm Delivery Requirement (FDR ) is water that will need to be delivered, beginning March 1. Crops such as Cotton generally have the pre-irrigation applied from the previous water year's water supply, and so that amount of water will need to be entered in the bottom section. The values entered into the lower section will show up in the "Other" category in the upper section as negative numbers because water applied from the previous water year will not need to be applied in the current water year. Again, as in the top section, the values entered will be net results of water stored in the profile. Top of Page
The "RZ In" and "RZ Out" columns will have values that represent the amount of water stored in the profile at the beginning and end of the crop season, respectively. If "RZ In" is larger than "RX Out", some of the water stored in the soil profile at the beginning of the season was used by the crop during the season , say, Cotton after Onions. If "RZ In" is smaller than "RX Out", some of the water applied will not be used by the current crop, say, Onions after Cotton. Unless the water user can anticipate these situations, values should not be entered into these columns.
The section in the lower right corner displays the total water supply situation. If rescheduled water is available it should be entered in the first location. The expected surface water allocation can be calculated from the allocation depth and total allocation acreage, the next two boxes. Expected groundwater supplies are entered in the next box. The total water supply is calculated and the FDR is subtracted to get the remaining supply. The remaining supply is the amount of water still available at the end of this growing season that might be used in the establishment or pre-irrigation of subsequent crops, such as would be accounted for in the lower left section of this page coming into this season.
Column Heading Information:
Crop: The crop name to be grown is entered in the upper section and it will be automatically entered down in in the lower left section. Top of Page
ET: Evapotranspiration is the seasonal crop use of water from the soil profile and is not the amount of water applied, since irrigation systems cannot apply water with 100% uniformity. See the table below for typical values.
Germ: Stands for germination water. This again is a net number taking into account the distribution uniformity. The column in the upper table is for germination water coming from the coming water year, and the lower is for water that was applied from the previous year's water supply. Top of Page
Leach: Stands for leaching, the net amount of water moving below the root zone moving salts to maintain the salinity level of the soil profile.
Other: Other water is used for things like harvest preparation and frost protection. The column in the upper table comes from the values entered into the lower left table. The lower left table is for water that was applied in the previous water year. Top of Page
Total: This is the algebraic total of the previous four columns, which might include negative values.
EP: Stands for Effective Precipitation. Effecive precipitation is the actual amount of rain that is stored in the soil profile for later use by the crop. In Westlands this value is commonly about 35% (25% to 66%) of the rain guage amount, and depends on the crop and the time of year that the rain falls. See the table below for typical values.
CWR: Stands for Crop Water Requirement. The CWR is the amount of water in the root zone that must be supplied by irrigation water. Top of Page
IE: Stands for Irrigation Efficiency. Since irrigation systems cannot apply water with 100% uniformity, in some parts of the field the rootzone an irrigation will store more or less than the average amount applied. In general, the irrigation efficiency is a number that relates the average amount of water applied to the average amount of water stored in the 25% of the field receiving the least amount of water. If you needed of 4 inches of water to refill the active root zone of a crop and the system applied irrigation water with an 80% irrigation efficiency, you would need to deliver an average of 5 inches out of a delivery.
FWR: Stands for Field Water Requirement. The FWR is calculated from the CWR by dividing the IE into it. The FDR is always larger than the CWR because the IE is always less than 100%. Top of Page
Acres: Is the total number of acres to be planted of the crop.
FDR: Stands for Farm Delivery Requirement. The FDR is the total number of acre-feet needed to grow all the acreage of this crop on the farm. Top of Page
Pre.: Stands for Pre-irrigation. This column is used to enter a pre-irrigation that was applied from the previous water year's water supply.
Typical values for various crops are provided as a starting point for using this Farm Water Budget. You should use values specific to your farming operations when available. Three ET values are listed for the Northern, Central, and Southern zones of the District. Leaching requirement uses EC of irrigation water of 0.4 dS/m. A typical range for irrigation efficiency is also presented, the higher part of the range is generally assumed to be microirrigation.
| Crop | ET, In., N / C / S |
Effective Precip, In., N / C / S |
Germ- ination, In. |
Leaching, In. Yield Loss 0% / 10% |
Other, In. | Irrigation Effciciency, % |
| Alfalfa Hay | 43.6/45.2/40.6 | 4.5 /4.3 /4.1 | 1.8 / 0.8 | 80-90 | ||
| Alfalfa Seed | 31.6/33.7/32.2 | 4.5 /4.3 /4.1 | 1.8 / 0.8 | 75-90 | ||
| Almond | 32.6/31.2/27.7 | 2.8 /2.7 /2.6 | 1.7 / 1.4 | 75-85 | ||
| Almond, Drip | 34.6/35.3/31.1 | 2.8 /2.7 /2.6 | 1.7 / 1.4 | 80-90 | ||
| Apples | 37.9/38.2/33.0 | 2.8 /2.7 /2.6 | 2.0 / 1.5 | 80-90 | ||
| Barley | 11.3/11.4/10.9 | 4.0 /3.8 /3.6 | 0.2 / 0.1 | 70-85 | ||
| Beans, Dry | 21.4/21.6/18.7 | 2.5 /2.4 /2.3 | 1.9 / 1.2 | 70-80 | ||
| Corn | 25.7/26.0/22.8 | 2.5 /2.4 /2.3 | 1.4 / 0.9 | 70-80 | ||
| Cotton | 24.7/25.3/22.2 | 2.5 /2.4 /2.3 | 0.3 / 0.2 | 85-90 | ||
| Garbanzo Beans | 7.4/8.2/7.4 | 4.0 /3.8 /3.6 | 70-85 | |||
| Garlic | 11.3/11.2/10.3 | 3.7 /3.5 /3.3 | 1.5 | 60-75 | ||
| Grape | 22.0/22.4/19.3 | 2.6 /2.5 /2.4 | 1.3 / 0.8 | 70-80 | ||
| Grape, Drip | 22.9/23.5/21.0 | 2.6 /2.5 /2.4 | 1.3 / 0.8 | 80-90 | ||
| Lettuce, Fall | 5.1 /5.2 /4.4 | 2.5 /2.4 /2.3 | 3.0 | 0.4 / 0.2 | 50-90 | |
| Lettuce, Spring | 3.8/3.9/3.7 | 0.3 /0.2 /0.1 | 3.0 | 0.4 / 0.2 | 50-90 | |
| Melon | 10.4/10.6/9.2 | 2.6 /2.5 /2.4 | 0.4 / 0.3 | 55-75 | ||
| Olive | 32.6/34.4/30.6 | 4.5 /4.3 /4.1 | 1.1 / 0.8 |
75-85 | ||
| Onions, Dehy | 20.3/20.4/18.4 | 3.0 /2.9 /2.8 | 1.6 / 1.1 | 50-90 | ||
| Onions, Fresh | 13.9/14.0/12.5 | 3.0 /2.9 /2.8 | 1.2 / 0.8 | 50-90 | ||
| Orange | 33.1/35.0/31.1 | 4.5 /4.3 /4.1 | 1.8 / 1.3 | 3.0 | 75-85 | |
| Pistachio | 32.5/32.7/27.3 | 2.5 /2.4 /2.3 | 75-85 | |||
| Pomagranates | 31.9 /-- /-- | 2.5 /--/-- | 1.5 / 1.1 | 70-80 | ||
| Safflower | 23.2/23.4/21.3 | 3.2 /3.1 /3.0 | 0.4 / 0.3 | 80-90 | ||
| Sugar Beets | 32.1/33.4/28.4 | 4.2 /4.0 /3.8 | 0.4 / 0.3 | 65-80 | ||
| Tomato | 19.0/20.0/17.1 | 2.7 /2.6 /2.5 | 2.5 | 0.7 / 0.5 | 75-85 | |
| Walnuts | 37.0/-- /-- | 2.8 /2.7 /2.6 | 2.0 / 1.4 | 75-85 | ||
| Wheat | 15.3/16.3/14.5 | 4.0 /3.8 /3.6 | 0.3 / 0.2 | 70-85 |
Last Updated January 2002