SANTOS-ROMA´ N, D., G. S. WARNER, AND F. SCATENA. 2003.
Multivariate analysis of water quality and physical
characteristics of selected watersheds in Puerto Rico.
Journal of the American Water Resources Association 39:
829–839.
Abstract:
Multivariate analyses were used to develop equations
that could predict certain water quality (WQ) conditions for unmonitored
watersheds in Puerto Rico based on their physical characteristics.
Long term WQ data were used to represent the WQ of 15
watersheds in Puerto Rico. A factor analysis (FA) was performed to
reduce the number of chemical constituents. Cluster analysis (CA)
was used to group watersheds with similar WQ characteristics.
Finally, a discriminant analysis (DA) was performed to relate the
WQ clusters to different physical parameters and generate predicting
equations. The FA identified six factors (77 percent of variation
explained): nutrients, dissolved ions, sodium and chloride, silicacious
geology, redox conditions, and discharge. From the FA, specific
conductance, sodium, phosphorous, silica, and dissolved oxygen
were selected to represent the WQ characteristics in the CA. The
CA determined five groups of watersheds (forested, urban polluted,
mixed urban/rural, forested plutonic, and limestone) with similar
WQ properties. From the five WQ clusters, two categories can be
observed: forested and urban watersheds. The DA found that
changes in forest cover, percent of limestone, mean annual rainfall,
and watershed shape factor were the most important physical features
affecting the WQ of watersheds in Puerto Rico.