Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2013
Publication Date: 3/21/2014
Publication URL: http://handle.nal.usda.gov/10113/58613
Citation: Bjorneberg, D.L., King, B.A. 2014. Groundwater use on southern Idaho dairies. Applied Engineering in Agriculture. 30(1):41-45.
Interpretive Summary: Dairy production has expanded in irrigated areas of the western and southwestern US, potentially competing for limited water supplies. Groundwater withdrawal was measured for two years on six dairy farms in southern Idaho with 660 to 6400 milk cows. Average groundwater withdrawal for each dairy varied from 140 to 280 L/day/milk cow, with an overall average of 220 L/day/milk cow. Annual groundwater withdrawal on an area basis varied from 180 to 880 mm for the six dairies and averaged 530 mm. These values were similar or less than the estimated irrigation requirements for typical crops grown in the area. Wastewater produced was measured on three of the six dairies. Assuming wastewater offset irrigation water, net groundwater use varied from 290 to 370 mm/year (320 mm/year average). The average net water use was 35% of the estimated irrigation requirement for alfalfa, 54% of corn, and 63% of spring small grain in southern Idaho. This study demonstrated that groundwater used by southern Idaho dairies was similar or less than water used for irrigated crops.
Technical Abstract: Dairy production has expanded in irrigated areas of the western and southwestern US, potentially competing for limited water supplies. Groundwater withdrawal was measured for two years on six dairy farms with 660 to 6400 milk cows in southern Idaho. Groundwater withdrawal was calculated on an equivalent cow basis to account for relative differences in the numbers of milk cows, dry cows, heifers and calves on each farm. Average groundwater withdrawal from each dairy varied from 110 to 250 L/d/eq. cow with an overall average of 190 L/d/eq. cow for the six farms. On an area basis, groundwater withdrawal varied from 180 to 880 mm/y on each farm with a mean of 530 mm/y. Estimated annual irrigation requirements in southern Idaho are 510 mm for spring barley, 590 for corn, and 920 for alfalfa. Wastewater that was available for irrigation was only measured on three farms and varied from 21 to 150 L/d/eq. cow, with the highest amounts from a freestall dairy. Assuming that wastewater replaced a portion of groundwater used for irrigation, the net groundwater used on these three dairies was 290 to 370 mm/y. Data from these six dairies indicated that groundwater withdrawal by dairy farms was similar or less than the amount of water required to meet evapotranspiration needs of irrigated crops in southern Idaho, especially if wastewater is used to offset irrigation and is not applied in addition to irrigation.