No abstract

Sixteen largely agricultural watersheds in the upper portion of the North Bosque River of central Texas were instrumented to collect storm event samples for nutrient analysis. Flow‐weighted storm‐event mean concentrations were averaged across storm events to characterize the water quality at each site for storms sampled between November 1992 and August 1995. Nutrient concentrations were related to land uses above sampling sites using correlation and regression analysis to indicate major sources of nutrient nonpoint source pollution to the upper North Bosque River. Consistently, N and P concentrations increased as the proportion of land area used for dairy waste application fields (or milking cow densities) increased in the drainage basins above sampling sites. The proportion of total P (TP) in runoff represented by soluble reactive P (SRP) also increased as the percent of dairy waste application fields above a sampling site increased; likely as a response to the common practice of surface application of manure to permanent pasture. This increase in SRP is of particular importance because SRP is readily bioavailable in aquatic systems, thus increasing the potential for accelerated eutrophication in receiving waterbodies. The results of these analyses indicate a strong association between in‐stream nutrient concentrations during storm events and the percent of dairy waste application fields comprising a drainage area. This indicates a need to manage the movement of nutrients, particularly soluble P, from manure application fields in areas where in‐stream nutrient levels are considered a nonpoint source pollution problem.

Over a three-year period, flow and nutrients were monitored at 13 sites in the upper North Bosque River watershed in Texas. Drainage areas above sampling sites differed in percent of dairy waste application fields, forage fields, wood/range, and urban land area. A multiple regression approach was used to develop total phosphorus (TP) and total nitrogen (TN) export coefficients for the major land uses in these heterogeneous drainage areas. The largest export coefficients were associated with dairy waste application fields followed by urban, forage fields, and wood/range. An empirical model was then established to assess nutrient contribution by major sources using developed export coefficients and point source loadings from municipal wastewater treatment. This model was verified by comparison of estimated loadings to measured in-stream data. Monte Carlo simulation techniques were applied to provide an uncertainty analysis for nutrient loads by source, based on the variance associated with each export coefficient. The largest sources of nutrients contributing to the upper North Bosque River were associated with dairy waste application fields and forage fields, while the greatest relative uncertainty in source contribution was associated with loadings from urban and wood/range land uses.(KEY TERMS: nonpoint source pollution; water quality; export coefficients; nutrient loads; nitrogen; phosphorus; animal waste; uncertainty analysis)

No abstract

The village of Ban Pong in northeastern Thailand was studied from January through December 1981 to determine the importance of flies as a source of enteric pathogens. The number of flies (predominantly Musca domestica) increased in kitchens and animal pens in the hot dry spring, when the incidence of diarrhea was highest in the village. Enterotoxigenic Escherichia coli, Shigella spp., non-O1 Vibrio cholerae, and Vibrio fluvalis were isolated from fly pools in yards (69%), animal pens (38%), bathrooms (35%), and kitchens (8%). Enterotoxigenic E. coli was isolated from one fly pool in May and from another in June, when the incidence of such infections was highest in the village. Flies often carry and presumably disseminate enteric pathogens in rural Thailand.