Aj. Cannon et Ph. Whitfield, Modeling transient pH depressions in coastal streams of British Columbia using neural networks, J AM WAT RE, 37(1), 2001, pp. 73-89
Citations number
29
Categorie Soggetti
Environment/Ecology
Journal title
JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION
Transient events in water chemistry in small coastal watersheds, particular
ly pH depressions, are largely driven by inputs of precipitation. While the
response of each watershed depends upon both the nature of the precipitati
on event and the season of the year, how the response changes over time can
provide insight into landscape changes. Neural network models for an urban
watershed and a rural-suburban watershed were developed in an attempt to d
etect changes in system response resulting from changes in the landscape. S
eparate models for describing pH depressions for wet season and dry season
conditions were developed for a seven year period at each watershed. The ne
ural network models allowed separation of the effects of precipitation vari
ations and changes in watershed response. The ability to detect trends in p
H depression magnitudes was improved by analyzing neural network residuals
rather than the raw data. Examination of sensitivity plots of the models in
dicated how the neural networks were affected by different inputs. There we
re large differences in effects between seasons in the rural-suburban water
shed whereas effects in the urban watershed were consistent between seasons
. During the study period, the urban watershed showed no change in pH depre
ssion response, while the rural-suburban watershed showed a significant inc
rease in the magnitude of pH depressions, likely the result of increased ur
banization.