Overland and shallow subsurface hydrologic transport of pathogenic Cryptosporidium parvum oocysts from cattle feces into surface drinking water supplies is a major concern on annual grasslands in California's central and southern Sierra Nevada foothills. Soil boxes (0.5 m wide × 1.1 m long × 0.3 m deep) were used to evaluate the ability of grass vegetated buffer strips to retain 2 × 108 spiked C. parvum oocysts in 200-g fecal deposits during simulated rainfall intensities of 30 to 47.5 mm/h over 2 h. Buffers were comprised of Ahwahnee sandy loam (coarse-loamy, mixed, active, thermic Mollic Haploxeralfs; 78:18:4 sand to silt to clay ratio; dry bulk density = 1.4 g/cm3) set at 5 to 20% land slope, and ≥95% grass cover (grass stubble height = 10 cm; biomass = 900 kg/ha dry weight). Total number of oocysts discharged from each soil box (combined overland and subsurface flow) during the 120-min simulation ranged from 1.5 × 10 6 to 23.9 × 106 oocysts. Observed overall mean log10 reduction of total C. parvum flux per meter of vegetated buffer was 1.44, 1.19, and 1.18 for buffers at 5, 12, and 20% land slope, respectively. Rainfall application rate (mm/h) was strongly associated with oocyst flux from these vegetated buffers, resulting in a decrease of 2 to 4% in the log10 reduction per meter buffer for every additional mm/h applied to the soil box. These results support the use of strategically placed vegetated buffers as one of several management strategies that can reduce the risk of water-borne C. parvum attributable to extensive cattle grazing on annual grassland watersheds.
|Original language||English (US)|
|Number of pages||9|
|Journal||Journal of Environmental Quality|
|State||Published - Nov 2004|
ASJC Scopus subject areas
- Environmental Science(all)
- Environmental Chemistry