| Land use may result in runoff to surface waters, and with increased urbanization, the proportion of rainfall and snowmelt occurring as runoff is increased by impervious surfaces. Fecal matter from companion animals may enter waterways and cause microbial contamination in drinking and recreational waters. This research included two studies, a field study at Lake Tahoe that examined the links between a heavily used dog exercise area and microbial water quality, and a laboratory study that looked at effects of evaporation on indicator organism populations losses through time. The 14 month field study measured fecal accumulation and distribution on land and E. coli levels in a creek passing through the site. This study utilized Inverse Distance Weighting to estimate fecal loading on site, and membrane filtration to test microbial water quality. Results showed localized loading with an estimated 45.4 kg dry mass accumulation over the study period. Results also showed lower E. coli levels downstream from the park than upstream, with a one-sided Wilcoxon Signed-Rank test (P = .000+), presumably due to an on-line sedimentation basin on the creek in the park.;Based on results of the field study, a laboratory study examined survival of indicator organisms in feces, specifically the relationship of evaporation to microbial survival. Canine feces were used to make a standardized sterile matrix, which was inoculated with E. coli, ATCC strain 25922. An environmental chamber study examining fecal bacteria degradation in canine feces evaluated bacterial degradation rates at evaporation conditions of 0.08, 0.21, and 0.29 in/day. With the data fitted to Chick's law, estimates of decay coefficients corresponded to results of -.07, -.22 and -.23/hr, respectively. Linear regression analysis gave R2 values of 0.69, 0.82, and 0.83, respectively (P = .000+). High and medium rate studies were not statistically different from one another, but significantly different from the low rate study. Control studies showed that high temperatures add to bacterial degradation rates, and that E. coli survival in feces is mostly limited by water potential. We measured changing water potential with water content losses and created a moisture release curve for canine feces. The data corresponded to previous research stating E. coli would not survive conditions below ∼ -22.4 MPa water potential. |
