Water Budgets for Dairy Farms*

Because of concern that limitations might be placed on water use on dairies in the future without adequate information, several extension and research scientists put their heads together and tried to construct tentative water budgets that might be appropriate for many of Florida dairy farms. This summary is now available as Florida Extension Circular 1091. The following were uses of water on dairies which were considered:

Drinking by dairy cattle

Cleaning of dairy cows before milking

Cleaning of dairy equipment

Sprinkling cows for evaporative cooling

Flushing manure

Irrigation of crops grown to recycle nutrients from manure

Irrigation of additional crops

Units

1 gallon of water = 8,346 lb

1 cubic ft of water = 7.48 gallons

1 acre = 43,560 sq ft

1 acre-inch of water = 27,152 gallons

Developing A Water Budget for the Dairy Farm

If the dairy waste management system was designed to utilize flushed manure nutrients through cropping systems grown under irrigation, the water used at the dairy should be reused through irrigation. If water amounts are small in relation to irrigation needs for crop production, liberal use of water for cow washing, cow cooling, and manure flushing is not a use problem. Costs for construction of storage structures for holding wastewater until used for irrigation may warrant consideration. The example water use budgets shown in Table 1 illustrate that water usage on dairies is probably small in comparison to irrigation needs when there are 30 acres of sprayfield/100 cows and crop needs are 1.75 inches of water per week. Conversely, the amounts used in most Florida dairy systems would be large and unmanageable if application through irrigation is not an option or if less acreage for irrigation is available than needed for application of all manure nutrients.

Strategies to Minimize Water Usage

If a dairy does not have acreage available close by to utilize manure nutrients and water through an environmentally accountable sprayfield application system, it will be necessary to exclude as much water as possible from the manure management system. Table 1 presents one column indicating a theoretical minimum amount of water use on a dairy. This system implies that cows are clean enough and cool enough that sprinkler washes are not needed to clean and cool cows while being held for milking. Also, it is assumed that all of the manure is scraped and hauled to manure disposal fields or transported off the dairy in some other fashion.

* Reprinted from "Dairy Production Water" - Spring 1993. Although this water budget was developed for Florida farms, it is applicable as well to Texas farms.

Intermediate steps that might be taken to minimize water usage include:

1. Scraping and hauling manure from high use areas such as the feeding barn so that this manure can be managed off the dairy.

2. Using wastewater rather than fresh water to flush feeding areas and freestall barns.

3. Using a housing system that will keep cows clean enough so that cow washers are not needed to clean cows before milking.

If flushing of heavy use areas is desired, these areas could be flushed with recycled water after scraping. This would reduce total nutrient loads retained in wastewater and reduce the size of the sprayfield needed for water and manure nutrient recycling.

Table 1. Estimated water budgets for three example dairies. All values are gallons unless otherwise noted.