Calculating an estimate of the nonpoint source (NPS) pollution that arises from agricultural land use requires information about the location and numbers of farm animals by animal type. This need makes tracking farm animal locations and concentrations, as well as collecting information on the storage and use of farm animal manure, important to programs such as Total Maximum Daily Load (TMDL) analysis, Nutrient Management, NPS Water Quality Assessment, Chesapeake Bay Program and Agricultural Incentives.
When farm animals are concentrated, the manure they generate must be properly managed so that it provides nutrient benefits without creating excess nutrient NPS pollution. Storage or field application of manure too close to a stream can cause excess nutrients and fecal coliform to enter water bodies through stormwater runoff.
There are several sources of information about farm animals that are useful for geospatially ascertaining the potential for farm animal induced NPS pollution. A few are noted here.
One of the more significant sources is the U.S. Census of Agriculture. Based on surveys, it reports estimated inventories and sales of various farm animals by jurisdiction on a five-year cycle (2007, 2002, 1997, 1992, etc.). Click here to view published results that are available from the USDA.
Another source of information about farm animals in Virginia is DCR's Animal Feeding Operations (AFO) database. AFOs are lots or facilities (other than aquatic animal production facilities) where the following conditions are met:
The AFO database contains the numbers by type of confined and, where available, unconfined farm animals by hydrologic unit. It can be queried by animal type (dairy, beef, swine, sheep, chickens, turkeys and horses), geographic area (jurisdiction, hydrologic unit, river basin, etc.) or both measures. A link to the AFO metadata is on the AFO database web page. The AFO database is currently on an annual update schedule.
Please note that to maintain consistent terminology that conforms to Federal regulations, these operations are no longer referred to as “confined” animal feeding operations. The acronym CAFO now refers to concentrated animal feeding operations. The DEQ’s AFO webpage contains information on and links to the regulations and permit requirements for both AFOs and CAFOs.
A database that DCR uses to track farm-specific nutrient management plans is yet another source of farm animal information. Following a well-designed nutrient management plan that details proper storage and application of manure can provide an economical source of nutrients for crops, pasture or hay lands and reduce the potential nutrient load.
The animal related records in this database are one of the sources of information used to maintain the AFO database. Refer to DCR’s nutrient management web page for more information about these plans and the process.
DCR uses the Census of Agriculture and the AFO database to model the geospatial occurrence of farm animals in Virginia for the biennial NPS Assessment portion of the Commonwealth’s Water Quality (305b) Report. The modeling process includes the following:
Results are used to modify the land use and land cover tables developed for the NPS pollution load modeling process. The model uses these tables to calculate NPS pollutant loads by hydrologic unit. Although modeled farm animal numbers are not reported, mapped concentrations of swine, poultry, dairy cows, and beef cattle in Virginia by hydrologic unit (as produced for the 2006 NPS Assessment) can be viewed by choosing the appropriate link. Concentrations were mapped because it is the hydrologic unit, not occurrences within a hydrologic unit, that is ranked in the NPS Assessment.
Based on established and accepted equivalent animal units determinations between all farm animals as used in NPS modeling (i.e. five swine equal one beef cattle), an animal units concentration by hydrologic unit was calculated and also mapped. Although there is a variance in the calculated concentrations, this map shows little spatial variance due to the extraordinary concentrations in parts of the Shenandoah River Basin. Please refer to the Notes on this map for the animal equivalencies used.