## 3 Results and Discussions
### Empirical Orthogonal Functions
enterica_ across monitoring sites may be related to differences in surrounding land use at these sampling sites. Cropland (barley/soybeans, corn, soybeans, and winter wheat) covered approximately 60% of the land near MA04. The dominant land use type (65%) in MA05 is deciduous and evergreen forests (Table S1). The dominant forest area land cover may account for the high prevalence and levels of _L. monocytogenes_ at MA05 compared to other sampling sites. The forested area (deciduous and evergreen forests) surrounding MA05 is about six times greater than the forested areas around MA04 (65.4% vs. 11.38%, Table S1). The physical canopy created by the trees in the forest may help maintain reduced water temperature values at MA05 compared to other sites by shielding the water from sunlight, leading to colder water temperature, and promoting the higher prevalence and levels of _L. monocytogenes_[28; 36]. Forested areas may also support more wildlife (deer) reported as a reservoir for _L. monocytogenes_[41]. Proximity to forest, pasture, scrublands, water, and wetlands were significantly associated with _Listeria_-positive samples by univariable analysis [42]. The MA05 site was located in an area partially covered with wetlands. Such environments had areas with high soil water contents, which was found to be conducive to _L. monocytogenes_ prevalence [43; 44; 45]. The values of the explained variance for EOF1 and EOF2 for S. _enterica_ were essentially equivalent, indicating that a dominant factor shaping S. _enterica_ distribution was not evident in the data analyzed. Other work characterizing _Salmonella_ in a stream watershed showed an association between volume of flow and _Salmonella_ prevalence, indicating that factors beyond land use and rainfall type may influence S. _enterica_ prevalence [46]. Prevalence of _Salmonella_ was reported in four different watersheds in the eastern part of North Carolina forming part of the White Oak River Basin [47]; the prevalence was highest in residential or industrial areas (58.8%), followed by forests (57.1%) and crop agriculture (50%) [47]. _Salmonella enterica_ levels in water may be affected by agricultural practices such as using untreated manure as organic fertilizer, contributing to contaminated runoff to water bodies [48]. Other reports have shown that soil runoff containing organic fertilizers (heat-treated poultry pellets) can support _Salmonella_ growth in water [49], and that soils amended with synthetic and heat-treated or compost organic fertilizers were contaminated with _Salmonella_ as well [50]. In addition to the agricultural land use proximate to MA05, there was also relatively high wetlands land cover (17.7%), which may support wildlife (including avian, amphibian, and reptile populations), and these animals are known contributors to the S. _enterica_ burden in this stream [51; 52]. As in any study, the analysis of the data we present here is limited by the number of sampling sites and the frequency of microbial analysis from the sampling sites. However, the application of EOF shows that the survival patterns of pathogens can be characterized by a single method for a better understanding of the likelihood of contamination.