Large livestock operations are becoming the dominant form of livestock operations globally. Their impact on surface water quality occurs in the form of increased nutrient loading. The claim has been made that it is difficult to separate the impacts of these facilities on surface water from general, non-point source impacts, especially in agricultural watersheds over which livestock manure is widely applied. The study investigated two streams and measured different geochemical and biochemical parameters upstream and downstream of two large livestock facilities in two separate watersheds. Nutrient loading attributable to the large livestock facilities resulted in significantly higher (p < 0.05) nutrient concentrations (particularly NH3-N and soluble reactive phosphorus - PO4) downstream as compared with upstream sampling sites. Several simple chemical analysis and assessment tools proved useful in uniquely identifying large livestock facility impacts to surface water. In particular, we found that Soluble Reactive Phosphorus (SRP) and Ammonia Nitrogen (NH3-N) were directly and uniquely linked to these large livestock impacts. This is the first time that direct links between these two parameters have been used to identify livestock-specific impacts. These parameters may be strong indicators of nutrient inputs from large livestock facilities, separate and distinct from other agricultural sources.

As Concentrated Animal Feeding Operations (CAFOs) become increasingly more common in this country, water quality and environmental health researchers are turning their attention towards examining the water and air quality effects of these intensified agricultural practices as they relate to human health (Arnold and Meister, 1999; Cole et al., 2000; Kirkhorn, 2002; Townsend et al., 2003; Barrett, 2006; and Gibbs et al., 2006). One of the most important impacts of intensified agriculture on surface water is nutrient loading (Mallin et al., 1997; Mallin et al., 1998; Mallin and Cahoon, 2003; and Diesel et al., 2004). In fact, as early as 1990, the US EPA determined nutrient loading to be the single-most important surface water impact from agriculture, due in large part to such industrialized agriculture (Smith et al., 1999).

A comprehensive study by Carpenter et al. (1998) concluded that identifying the sources of nutrient loading in surface water and soil is problematic as they are due to diverse agricultural activities, often spread over wide land areas, over various time scales, and all subject to the variable effects of weather. Indeed, in a statement to the US Senate, the AFBF (American Farm Bureau Federation, 1999) made the argument that it is difficult if not impossible, to identify large livestock operation source(s) of nutrient loading in the nation's surface water.