Abstract:
Grazing cattle usually have access to streams as a
source of drinking water. A model was developed for the
personal computer to predict the bacterial quality of
these streams. The model estimates the number of
organisms that enter the stream by the direct deposit of
feces and by runoff from rainfall or melting snow. The
model also predicts the fate of these organisms upon
entering the stream. The stream discharge rates can be
calculated by the model or input by the user. The
bacterial water quality is determined by the number of
organisms suspended in the stream per volume of discharge.
The model results were compared with bacterial levels
measured in four different research projects and found to
be within an order of magnitude in most cases. These
results demonstrate that the model can predict bacterial
concentrations with sufficient accuracy to make management
decisions to insure a predetermined level of water
quality. These results also demonstrate that the model is
a better predictive tool for stream bacterial counts than
traditional water sampling programs due to the model's
ability to predict bacterial levels given a wide variety
of grazing and hydrologic conditions.
The model was developed and tested using the most
current research in rangeland water quality. As with any
model, the accuracy of the results depend upon the
accuracy of the input data. Future research can improve
the usefulness of the model to better predict the
bacterial counts in extended stream reaches.
