Version 1.02: Release Notes * For mobile users, the tab button on the top right is only visible in landscape mode.

Overview:

The purpose of this tool is to create an estimate of how much water is needed for a given agricultural operation in a year. This tool is strictly meant as a preliminary estimate. Water budget numbers provided here are not guaranteed to be feasible for your area, and actual water demands will vary based on real conditions. There are two tabs, which focus on different aspects of an operation

Irrigation

This tab focuses on water needs for irrigating a field. The estimate is based on several inputs:

  • Monthly evapotranspiration (ET), in inches/month
  • Precipitation, in inches/month
  • An estimate of how much rain is left after runoff (Effective Rainfall), in inches/month
  • The ET Adjustment factor, or how much water a specific crop will use throughout the growing season
  • Acreage to be irrigated

All of these inputs are used to calculate an estimate of the total water needed each month. The monthly ET and precipitation are automatically filled in based on the county you select. These represent long term averages and may not be accurate to present conditions. The ET adjustment factor is also generated based on the selected crop. The factor is based on three stages of development, initial, mid, and final, the water use changing as it grows. The growing season was assumed to be generally from April-September, you are encouraged to update these values for your schedule. All input fields are editable if there is data specific to your site you would like to use. You can double click a column to enter values. To save the edits, press "Ctrl + Enter".

Calculation:
((ET Monthly x ET Adjustment Factor) - Effective Rainfall) x Irrigated Acreage x 27,154

The estimated water needs are determined by multiplying the monthly ET with the adjustment factor for that crop in that month, representing its water needs. The effective rainfall is then subtracted out, as that is water the plant is already recieving. For many months, the effective rainfall may be higher than the adjusted ET, in these cases the water needs are shown as 0. This total is then multiplied by the acreage needed and 27,154, a conversion factor to gallons (1 inch of water across one acre = 27,154 gallons).

Livestock Use

This tab estimates the water consumption of livestock. This is based on a simple calculation of the number of heads x the average water use of that animal. You can select the type of animal from a dropdown list, and add additional rows to select multiple animals to be included in the total (displayed at the top). The consumption/head values represent averages across Virginia in the summer. Actual livestock consumption will vary throughout the year as the seasons change.

Data Sources:

  • Precip by county: https://www.ncei.noaa.gov/pub/data/cirs/climdiv
  • Crop ET Adjustment factors: https://www.pubs.ext.vt.edu/BSE/BSE-239/BSE-239.html
  • ET by month: https://www.sciencebase.gov/catalog/item/64135576d34eb496d1ce3d2e
  • Grass ET Adjustment factor: https://www.usga.org/content/usga/home-page/course-care/green-section-record/63/issue-17/dynamic-water-use-models-for-improved-irrigation-scheduling.html

Water Budget for Crop Irrigation

This tab provides an estimate for the water needs for irrigating a field. To use this sheet, select a county (under 'Inputs'), this will automatically update the Precipitation and ET Monthly columns. Then select the type of crop, this will update the ET adjustment factor column. Lastly, enter the acreage of the field in the 'Set acreage for all months' textbox. This will fill in the irrigated acreage column. The last column, Estimated Water Use, provides the estimated irrigation need for that month.

If you have specific site data you would like to use instead of the county/crop averages, you can double click on the column you want to edit. This will let you edit all months for that column. After typing your values, press 'Ctrl-Enter' to save the changes (you may have to click inside one of the white boxes first, then press 'Ctrl-Enter')

Export
Inputs

Inputs

Inputs

Select the type of animal, then the number of heads and it will provide the water use (based on average water use per day).
Export

Terms of Use

No responsibility is assumed for damages or other liabilities due to the accuracy, availability, use or misuse of the information herein provided. There is no warranty, express or implied, nor does the fact of distribution constitute such a warranty.

This information is in the public domain and may be copied without permission; citation of the source is suggested. The information made available through this tool is for reference purposes only and is not to be construed or used as a "legal description” or for legal purposes. All data is provided by DEQ "as is." This information is believed to be accurate, but accuracy is not guaranteed. Information drawn from this application must be used in consultation with appropriate federal, state or local resource management officials. Any errors or omissions should be reported to DEQ via email or phone. By using these applications/data made available by DEQ, you are agreeing to the terms and conditions listed above.

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